Neuro-immune interaction following systemic neural stem cell transplantation in experimental disease models.
1. Introduction
Regenerative processes occurring under physiological (
The transplantation of undifferentiated exogenous NPCs very efficiently protects the CNS from experimental chronic degeneration induced by inflammation both in small rodents (mice and rats) [10-14] as well as in non-human primates [15]. Specific homing of systemically injected NPCs is shown, so far, in experimental models of multiple sclerosis (MS), ischemic/haemorrhagic stroke, SCI and TBI, and epilepsy. I
NPC-based therapies have been therefore considered a plausible alternative strategy for the treatment of neurological inflammatory disorders. However, some urgent and still unclear questions have to be solved prior to straightforwardly translate most of these exciting experimental observations into clinical medicines, such as: (i) the ideal stem cell source, whether it has to be derived from pluripotent or multipotent sources; (ii) the ideal route of cell administration, whether it has to be focal or systemic; (iii) the optimal time point for cell administration, depending on the disease characteristics; (iv) the ideal balance between differentiation and persistence of stem cells into the targeted tissue and (v) the ideal mechanism of tissue repair to foster, whether it has to be cell replacement or tissue protection/healing. Further, while some encouraging efforts are being devoted towards the development of guidelines and establishment of explorative phase I clinical trials, still one of the major constraints to the easy translation into human medicines is represented by the immunogenicity of allogeneic stem cells, and the modest expandability of somatic human NPCs
In this chapter we will describe the most recent evidence of the remarkable therapeutic plasticity of transplanted NPCs, when injected systemically in inflammation-driven CNS degeneration experimental models. We will first focus on the evidence that inspired the modern stem cell experimental therapies and then elaborate on the mechanisms regulating the cross talk between somatic NPCs and the dysfunctional microenvironment, both at the outer and inner endothelial sides, and their clinico-pathological impact. Finally, we will discuss the rationale of the most recent explorative trials that are bringing neural stem cell therapies into the clinic.
2. Adult neural stem cells
2.1. A change in the dogma
Stem cells (SCs) possess the unique ability to self-renew and differentiate into different cell types in the body. Their contribution is essential during embryonic and early post-natal life, where they regulate morphogenesis and development by properly balancing proliferation and differentiation. Though their number is destined to decrease with time, their presence in adult organisms is still required to ensure
2.2. Adult neurogenesis in physiological conditions
Today it is widely accepted that in the adult mammalian brain, newly generated cells derive from NSCs residing in two regions [29], the ventricular-subventricular zone (V-SVZ) of the forebrain lateral ventricles [2, 27, 30] and the subgranular zone (SGZ) of the dentate gyrus (DG) of the hippocampus [1, 31, 32] (Figure 1). Because of the peculiar cellular organization and exclusive microenvironment, these neurogenic regions are commonly referred to as
2.2.1. Defining the cellular composition of the V-SVZ
The V-SVZ is situated in proximity of the lateral ventricles and contains slow-cycling SCs with astroglial properties that express glial-fibrillary acidic protein (GFAP), called type B1 cells. These cells give rise to intermediate progenitor cells (IPCs) or type C cells, which lose GFAP immunoreactivity and acquire the expression of the distal-less homeobox (Dlx)-2. These cells finally give origin to a pool of neuroblasts (type A cells) expressing the polysialylated form of neural cell adhesion molecule (PSA-NCAM) and the early neuronal marker doublecourtin (DCX) [38]. Within rodent’s brain these neuroblasts form chains of migration along the rostral migratory stream (RMS) to reach the olfactory bulb (OB), where they terminally differentiate into at least six different subtypes of OB interneurons, depending on their origin along the axes of the V-SVZ [39-41]. The V-SVZ niche (Figure 1 A-B) can be divided in three differently organized domains where self-renewing B1 cells receive different signals:
2.2.2. Defining the cellular composition of the SGZ
The second putative progenitor cell compartment is located in the SGZ of the DG of the hippocampus (Figure 1C-D), namely the region of the brain involved in learning and memory [1, 31, 32]. In this area, NSCs residing at the interface of the hilus and dentate gyrus are called type-1 progenitors or radial astrocytes (RAs) [59] and they mainly correspond to astroglial cells [60]. They mature in dentate granule cells and migrate towards the granule cell layer (GCL) to finally integrate into hippocampal circuitry [59]. RAs, unlike B1 cells of the V-SVZ, are found deeper into the brain parenchyma, surrounded by neurons, neighbouring RAs and other glial cells but without any chance to contact the CSF [37]. However, B1 cells and RAs share some key features: they both express astroglial markers, have ultrastructural characteristics of astrocytes [41] and possess long processes reaching different compartments of the niche far away from where the cell bodies reside [37]. RAs function as the primary precursors for the generation of new dentate granule neurons, either directly or via the generation of IPC1 (type 2a cells) and IPC2 (type 2b cells) [61]. Similarly to the V-SVZ, also the SGZ can be subdivided in a proximal, intermediate and distal domain along which RAs, with their polarized structure (apical-basal), span from the hilus interface (proximal domain) to the inner molecular layer (IML, distal domain) [37]. The proximal domain contains the primary cilium (important for Sonic hedgehog (Shh) signalling), which sense the hilus microenvironment, and lateral processes contacting other RAs and IPCs and, importantly, blood vessels. Here ECs release vascular endothelial growth factor (VEGF), IGF and brain-derived neurotrophic factor (BDNF) responsible for the regulation of the balance between proliferation and differentiation. RAs have their cell bodies in the SGZ and extend their main shaft along the GCL, which compose the intermediate domain. In this area astrocytes receive inputs from their progeny, including immature and mature granule neurons, IPCs and different neuronal and glial (e.g. microglia) cell types. Type 2a cells expressing Achaete-scute homolog (Ascl)-1 (also known as Mash-1) - a transcription factor important for neuronal commitment - are likely to originate in the proximal domain and then rapidly migrate into the intermediate one, where they divide once before differentiating into type 2b cells that will express DCX [62]. Similarly to V-SVZ, feedback mechanisms from the progeny, such as canonical and non-canonical Notch signalling are responsible for the quiescence of RAs or their transition to IPCs [63, 64]. In the IML, RAs terminate with an elaborate and branched structure contacting glial cells, neuronal processes and synapses. Although the contacts taking place in this area are still not completely understood, it seems probable that the GABAergic and glutamatergic inputs coming from interneurons and mossy cells, are important for the regulation of NSCs [65]. These astrocyte-like cells of CNS germinal areas work as real pacemakers of adult neurogenesis, as they receive internal and external inputs from their main shaft as well as from the end-foot of their radial processes that contact ECs in the V-SVZ [42], or embedded into the molecular layer in the SGZ [41]. However, despite the relatively high rate of neurogenesis, only a minority of new born cells eventually survive, mature and integrate within the existing circuitries at the level of the GCL of the hippocampus [66]. In parallel, postnatal SGZ neurogenesis in the human brain has been demonstrated to occur across the lifespan [55]. Although the role of new born neurons generating in the SGZ is not yet fully understood, increasing evidence suggest a possible role in learning and memory function [55].
3. CNS inflammation effects on endogenous adult NSC niches
3.1. Switching from an immune-privileged to an immune-specialized state
Protection and homeostasis are fundamental keystones for the proper maintenance of the CNS. Hence, brain and spinal cord must be kept under an extreme security state to ensure their fully functionality and, ultimately, the survival of an organism. However, in the past the CNS has been often regarded as an immune
3.2. Effects of inflammation on neurogenesis
Studies conducted over the last decade have extensively proved that the immune and nervous systems interact by engaging an active bidirectional crosstalk. Indeed, the expression of receptors able to recognize inflammatory mediators released by activated immune cells allows endogenous progenitor cells to increase their proliferation rate and specifically home to the site of inflammation after a trauma. As a consequence, both acute [69, 70] and chronic CNS inflammation [6, 71] has been shown to perturb the anatomical architecture and functional activity of adult germinal niches.
Work on EAE mice, the most widely accepted model of MS, has shown that chronic CNS inflammation in myelin oligodendrocyte glycoprotein (MOG)35-55-immunized mice causes a transient decrease in the proliferation rate of both C and B1 type cells and a contemporary increased accumulation of neuroblasts within the V-SVZ [6]. This effect, observed during the peak of the disease, was attributed to cell non-autonomous factors, such as pro-inflammatory (Th1) cytokines [e.g. interferon (IFN)- and its intracellular effector Stat-1]. However, these data contrast with other studies showing how inflammatory demyelination in MOG+/- mice immunized with purified mouse myelin increased proliferation and mobilization of neural progenitor cells from the V-SVZ of adult mice. Surprisingly, while new born cells generated at the level of V-SVZ commonly intended to differentiate into neurons, in response to EAE, these cells were able to generate astrocytes and oligodendrocytes as well, thus suggesting that inflammation can diverge (at least partially) their intrinsic nature [4]. Increased proliferation, measured in terms of BrdU-positive cells, has been found also at the level of the hippocampus both during the acute and chronic phases of the disease in MOG35-55 immunized mice. Similarly to the observed accumulation of neuroblasts in the V-SVZ, autoimmune inflammation leads to increased numbers of immature DCX-positive cells in the DG of the hippocampus [72]. Even though some alterations in the Notch, Wnt/β-catenin, Shh, and BDNF signalling pathways have been observed, their real contribution to the deregulation of hippocampal neurogenesis in the course of chronic autoimmune neuroinflammation needs to be further confirmed [72]. In addition, magnetic resonance imaging (MRI) techniques revealed structural alterations in the hippocampus, evidencing marked hippocampal atrophy [73], which may correlate with deficits in attention, information processing capacity and long-term memory observed in the majority of MS patients. Enhanced proliferation during the acute phase of the disease has been observed in proteolipid protein (PLP)139-151-induced relapsing EAE in SJL mice. However, during both the relapsing and chronic phase of the disease, the number of SVZ progenitors cells decreased, without changes in the ultrastructural features of the type B, C or A cells, but accompanied by an impaired maturation of oligodendrocyte progenitor cells (OPCs). This suggests that the chronic activation of glial cells (namely microglia and astrocytes) might be deleterious for the repair potential of endogenous brain stem/progenitor cells. Indeed, minocycline-induced inactivation of microglia during the chronic phase in relapsing-remitting EAE mice was associated with an improvement in the number of proliferating Sox2/Bromodeoxyuridine (BrdU)+ neural stem cells [74]. Finally, models of targeted focal EAE, obtained by stereotactic injection of cytokines [e.g. tumor necrosis factor (TNF)-α and INF-γ] in rodents pre-immunized with a sub-clinical amount of myelin peptides, allowed to better analyse the time course effect of auto-immune inflammation in the neurogenic areas. In this experimental model a decreased proliferation in the proximity of the V-SVZ was observed at 3 days, followed by an increase at 7 days after the injection of the cytokines, suggesting a regenerative attempt at the level of the V-SVZ area. Interestingly, the concomitant death of neuroblasts, the decreased type C cell proliferation, and the reduction of type A migrating cells, during the initial phase, might explain the impaired long-term olfactory memory observed by means of behavioural analysis [75]. Altogether, these findings suggest the existence of a compensatory mechanism of the injured brain in its attempt to counteract neuronal injury and disturbed conductivity resulting from T cell attack to the myelin sheaths wrapping the axons, which is among the most accepted causes of EAE and MS [76].
In agreement with what described in animal models, SVZ activation and expansion have been found at the level of periventricular active and chronic active lesions in MS patients, thus suggesting that the repetitive exposure to inflammatory insults does not completely exhaust the proliferative potential of the SVZ [77]. V-SVZ from post-mortem brains shows an altered balance between neurogenesis and gliogenesis, likely related to these inflammation effects within the neurogenic niche of MS patients [78]. Interestingly, the majority of MS patients show deficits in attention, information processing capacity and long-term memory, thus suggesting that neuronal damage in MS can result not only in motor and sensory deficits but also cognitive impairment. In support of these MRI techniques revealed structural alterations in the hippocampus, evidencing marked hippocampal atrophy [73].
Acute events, occurring in non-autoimmune diseases such as stroke, have been similarly proved of giving rise to increased proliferation of endogenous NSCs in the V-SVZ. These cells migrate from the neurogenic niche towards the ischemic boundary regions of the striatum and cerebral cortex, where they differentiate into mature striatal neurons [79-81]. During this (injury-reactive) site-specific homing, newly generated neuroblasts form chain-like structures in association with reactive astrocytes and blood vessels in the striatum, a reminiscence of the embryonic migration of type A cells along the RMS [82, 83]. Initially, this potential self-repair mechanism was supposed to happen only during the acute post-stroke phase. However, subsequent studies showed that stroke-induced neurogenesis is an extensive and long-lasting (up to 2 weeks) event, with continuous production of mature striatal neurons for several months after the insult [84]. Unfortunately, the vast majority of migrating new born neurons die within few weeks after the ischemia, and only few damaged cells (about 0.1%) are replaced by newly generated neurons [85]. Similar evidence of stroke-induced neurogenesis has been reported in post-mortem brains, where new born neurons are present in the ischemic penumbra surrounding cerebral cortical infarcts, preferentially localized in the vicinity of blood vessels [80]. The identification of those factors able to influence NSCs proliferation, homing and survival after stroke may have a great therapeutic impact. Several cytokines and growth factors that may be released by injured cells are thought to play a substantial role in promoting the observed neurogenic response after stroke. Among these, ciliary neurotrophic factor (CNTF) [86], transforming growth factor (TGF)-α [87], VEGF [88], fibroblast growth factor (FGF)-2 [89] and erythropoietin (Epo) [90] have been proposed.
Much less is known about the presence of adult neurogenesis after SCI. Most likely, this can be ascribed to a more diffuse scepticism concerning the existence of stem cells within the spinal cord. Indeed, even if the spinal cord is generally considered a non-neurogenic tissue, multipotent precursors can be isolated and propagated
3.3. The double face of inflammation
According to what described, it is suggestive that the CNS is able to start a beneficial, though limited, process of self-repair. However, most of the new born cells generated following injury are destined to die within few weeks, maybe due to a failure in their integration or due to the inflammatory milieu. Even if these cells have been shown to fully differentiate into mature neurons [82], the very low rate of occurrence imposes logical concerns regarding the therapeutic value of this regenerative response to brain injury [81, 108]. Because of the rearrangements occurring in the neurogenic niches after an inflammatory event, the immune system has been accredited as one of the major responsible of this failure. This assumption is further corroborated by the observation that the increasing complexity of the immune system over the evolutionary process has been accompanied by a concomitant loss of regenerative capacity [109]. Also, several findings link inflammation to the pathogenesis of neurodegenerative disorders and anti-inflammatory drugs seem to be promising candidates for their treatment. Recent studies suggest that inflammation may indeed have a neuroprotective effect [110]. Nevertheless, the real effect of inflammation in several of these pathologies still needs to be completely clarified.
The early (acute) post-traumatic phase of a neuroinflammatory process involves the action of resident microglial cells. These cells of myeloid origin are usually present in a resting but dynamic state, ready to shift their activity and undergo morphological and functional transformations in response to any kind of brain damage or injury [111, 112]. While on one side the selective ablation of microglia has been shown to exacerbate the ischemic injury in a mouse model of focal cerebral ischemia [113], on the other side mounting evidence indicates that chronic microglial activation may also contribute to the development and progression of neurodegenerative disorders, mainly through the release of pro-inflammatory cytokines such as interleukin (IL)-1, IL-6, and TNF-α [114]. As an example, infiltrating blood-derived macrophages have been shown to exert a beneficial role in an experimental model of SCI, where they contribute to limit the action of activated resident microglia, whose prolonged presence would finally lead to detrimental consequences [115]. Indeed, when the activity of microglia is not properly contained, their action may lead to a prolonged (chronic) inflammation eventually culminating in the formation of fibrotic tissue.
Endogenous T cells are key components of the protective immunity process. As such, physiological trafficking of lymphocytes through the CNS is required to support the essential function of immune surveillance [116]. Cellular composition analysis of the CSF of healthy patients has revealed that up to 80% of the total number of cells is represented by central memory and effector memory T-cells. This atypical composition, which is very different from the one of the blood, also suggests a major role for the CSF in the defence of the CNS [117]. Indeed, the CSF drains the interstitial fluid of the CNS and brings CNS antigens to the cervical lymph nodes, thus supplying for the absence of a proper lymphatic drainage [118, 119]. Following the seminal observation that self-specific T-cells recognizing myelin basic protein were able to protect injured CNS neurons from secondary degeneration in a rat model of optic nerve crash injury [120], several studies further supported the idea that T cell-dependent autoimmunity might promote recovery from CNS injuries [121, 122]. These studies finally culminated with the idea that boosting T-cell response to CNS antigens by means of immunization with CNS myelin-associated self-antigens could have enhanced this therapeutic potential [123-125]. Also, myelin-reactive T-cells possess neuroprotective effects, which may be essentially attributed to their ability to release neurotrophic factors such as BDNF, nerve growth factor (NGF) and CNTF [126]. Importantly though, auto-reactive T-cells showing this protective effect may turn out to be harmful if escaping the control exerted by the immune system, finally resulting into the development of autoimmune diseases such as MS. Therefore, a strict control is required to finely tune the balance between the
To further complicate the scene, several inflammatory mediators, such as TNF-α, TGF-β, IL-1, IL-6, IL-10 and IL-12 may have contrasting effects (e.g neuroprotective
As described in this paragraph, the CNS is able to regulate the proliferation rate within the adult neurogenic niches as an extreme attempt to respond to damages in both primary and secondary inflammatory neurodegenerative diseases. Nevertheless, this process is not robust enough to effectively re-establish the complex functionality of the CNS. Therefore, protocols aiming at pharmacological manipulation of endogenous precursors from germinal niche(s),
4. Exogenous NPC-based therapies: The systemic administration
4.1. Systemic injection and functional recovery
Following the seminal observation that systemically delivered NPCs were able to target an intracranial tumour in rodent (both mice and rats) model of experimental brain tumours [135], numerous studies started to investigate the validity of this administration route in a variety of CNS disorders. Over the last decade, data have been provided on the feasibility of systemic NPC transplants via either intravenous (i.v.) cell injection into the blood stream, or interacerebroventricular (i.c.v.)/intrathecal (i.t.) into the CSF, in experimental CNS disease models [10-13, 16, 136-138]. Adult somatic mouse NPCs, administered 22 days post immunization (dpi) greatly reduced the functional impairment observed in chronic MOG35-55-immunized EAE mice [11]. Also, rat NPC neurospheres, administered i.c.v. or i.t. in rats affected by acute EAE, attenuate the clinical symptoms when administered at the same day of disease induction (0 dpi) [136]. Intravenous injected mouse NPCs were proved to be efficacious in PLP139-151 immunized relapsing EAE mice [16]. Indeed, mice, treated with NPCs at the disease onset or at the time of the first relapse, recovered faster and showed a decrease in the relapse rate compared to controls. At the end of the follow-up (90 dpi) both treatments resulted in a lower relapsing remitting EAE cumulative score [16]. Finally, MOG35-55-immunized chronic EAE mice receiving either mouse neurospheres (i.c.v) or single cell NPCs (i.v.), at 6 and 8 dpi respectively also showed significant clinical amelioration [20, 139].
The therapeutic efficacy of systemically administered NPCs has been later observed in a different pathological context, such as stroke. Mouse somatic NPCs, systemically transplanted 3 days after middle cerebral artery occlusion (MCAo), resulted in a better recovery, significantly improving the neurological severity score starting from 18 days post transplantation (dpt) until the end of the follow-up (30 dpt) [140]. Similar neurological improvements were observed in rats subjected to MCAo and common carotid artery occlusion (CCAo) after i.t. transplantation (7 days after stroke) of rat NPCs [141]. Significant locomotor recovery was also observed after acute systemic NPC transplant in mice suffering from contusion SCI [13].
Similarly to rodent cells, human NPCs have been proved to be therapeutically efficacious. Foetal NPCs administered either i.v. or i.t. at the disease onset, reduced the severity of MOG1-125-induced chronic EAE in common marmosets [15]. Further, human embryonic stem cell (ESC)-derived NPCs have been shown to reduce disease severity of chronic EAE mice [142]. Human immortalized NPCs have been widely enrolled in stroke models. The systemic injection of the HB1.F3 NPC line resulted in neurological improvements of rats treated 1 day after MCAo or intracerebral hemorrhage (ICH) stroke models [12, 137, 138]. The same line resulted therapeutically effective also in quinolinic acid-induced experimental HD in rats, where NPCs administered intravenously at 7 days after disease induction, significantly ameliorated the behavioural outcome [14].
All these evidences showing behavioural recovery upon systemic injection of NPCs in different CNS inflammatory models, led to the investigation of the molecular mechanisms standing behind, since this capacity bears the hope of developing less invasive surgical techniques to implant therapeutic adult human stem cells into patients affected by highly debilitating CNS disorders, such as MS, stroke, SCI, epilepsy, PD, AD and HD.
4.2. Homing capacity: NPCs breach the CNS barriers
Brain and spinal cord are protected by a complex control system, composed by tight barriers shielding the action of a unique troop of immune cells. Indeed, to access the brain and spinal cord parenchyma, circulating cells have to breach through all the barriers that closely seal the CNS from the surrounding environment. Namely, these are the blood-brain barrier (BBB) at the level of parenchymal capillaries and post-capillary venules, the blood-cerebrospinal fluid barrier (BCSFB) at the level of the choroid plexus in the brain ventricles, and the blood-leptomeningeal barrier (BLMB) at the level of the leptomeningeal/subarachnoid space. The main role of these barriers is to maintain the chemical composition of the CNS microenvironment, thus ensuring the proper functionality of neuronal circuits, synaptic transmission and remodelling, angiogenesis, and neurogenesis in the adult brain, while their rupture is involved in many neuroinflammatory disorders [143]. Because of the existence of such barriers, the access of systemically injected NPCs to the CNS parenchyma seems quite unlikely.
Structurally, the main component of the BBB is represented by specialized ECs characterized by the absence of fenestrae, low pinocytotic activity and by the presence of intercellular tight junctions (TJs) [144]. This clutched arrangement prevents the free passage of molecules, while the transport of nutrients into the CNS and the discard of toxic molecules into the circulation is ensured by active mechanisms, thus guarantying a proper neuronal activity [145]. Moreover, the BBB is an essential constituent of the so-called
Most of the knowledge about the mechanisms that allow circulating cells to breach the barrier(s) [117, 153, 154] and move into the CNS parenchyma comes from observations conducted with models of CNS inflammation. Initial studies showed how intravenously injected radioactively labelled encephalitogenic T cells were able to cross the BBB of healthy recipients [153]. It was also shown that, while activation is mandatory for T-cells to cross the endothelial barrier and reach perivascular spaces, antigen specificity is dispensable to further cross the glia limitans and invade the CNS parenchyma after having encountered the appropriate APCs [155].
The extravasation of specific T cells requires a multistep process [156]. The first step, known as
The following step requires the
A very similar sequential process has been shown being recapitulated when systemically injected NPCs specifically home to the site of damage. In fact, NPCs posses the ability to reach the cerebral parenchyma where they eventually induce recovery in animal models of neurodegenerative diseases such as EAE [10, 11] stroke [12, 166], SCI [167, 168], epilepsy [138, 169], HD [14], other than glioblastoma [135, 170]. The first studies showing the extravasation capacity of NPCs [10-12] clearly demonstrated that this capacity was strictly related to the activation of the ECs by an inflammation process occurring within the brain. NPCs administered either i.c.v. or i.v. to healthy animals were, in fact, never observed inside the CNS, while mainly accumulating in peripheral organs, or remaining confined in the ventricles or subarachnoid space. Only after activation of endothelial cells, exogenous NPCs were observed to accumulate into the CNS. Systemically injected NPCs are, in fact, able to follow a gradient of chemoattractants (e.g. pro-inflammatory cytokines and chemokines) released by the inflammatory lesions into the blood stream and CSF. Following these signals, NPCs rapidly reach the source of pro-inflammatory molecules within and interact with the activated endothelial/ependymal cells around inflamed CNS tissues. At this level, NPCs and endothelial cells start an organized sequence of events resembling those described for T cell extravasation that allow the selective entrance and specific
Similarly, also immortalized human NPC lines express CD44 [175] and CXCR4 [173]. However, in a recent study, human NPCs were shown to interact with activated ECs through integrins α2, α6 and β1 rather than CXCR4 [177]. Further, human NPCs express the receptors CXCR1 and CXCR5, which mediate their
All these evidences suggest that systemically injected mouse and human NPCs share the expression of a variety of functional immune-like receptors, such as functional cell adhesion molecules (e.g. CD44 and VLA-4) and inflammatory chemokine receptors (e.g. CCR2, CCR5 and CXCR4), giving them a unique leukocyte-like molecular signature. This characteristic, allowing NPC interaction with activated endothelial and ependymal cells, represents an essential requirement in the therapeutic paradigm of systemic delivery. Therefore, the discovery of the specific homing ability of NPCs across the BBB opened new frontiers for the treatment of CNS diseases, in particular for those diseases characterized by disseminated damage.
4.3. NPC interaction with the dysfunctional CNS microenvironment: The establishment of ectopic niches
Consistent data exists reporting the ability of i.v. injected NPCs to cross the BBB and accumulate into the CNS. Here, exogenous NPCs co-exist with different host components, such as ECs, infiltrating inflammatory cells, activated macrophages/microglia and reactive astrocytes [19]. In this context, the intimate association with ECs, the physical proximity to the vasculature and the enhanced expression of stem cell regulators and growth factors involved both in angiogenesis and neurogenesis has been described to play a major role in defining a molecular architecture reminiscent of prototypical germinal stem cell niches [16]. Within these
Correlative evidence suggest that, depending on local inflammatory milieu, transplanted NPCs may either remain in the niche while maintaining an undifferentiated state, or move out from the niche, finally acquiring a terminally differentiated phenotype [16]. When systemically injected in chronic EAE mice, syngenic NPCs were found almost exclusively in areas of CNS damage, mainly within the submeningeal space in close proximity to subpial inflammatory foci (after i.t. stem cell injection), or around post-capillary venules (after i.v. stem cell injection) [11]. Ten days after transplantation, relatively few cells were found in the CNS parenchyma and at 30 dpi many of the surviving donor cells were localized deeply within the brain parenchyma and displayed a marked distribution pattern: most of them were confined within areas of demyelination and axonal loss, and only very few cells were found within regions where the myelin architecture was preserved [11]. Similar results were obtained after i.c.v NPC injection at the peak of EAE in rats: cells entered into the brain or spinal cord parenchyma and mostly accumulated at sites of inflamed white matter but not into adjacent grey matter regions. In line with the previous study, after 2 weeks cells had migrated into distant white matter tracts but, on the contrary, most of them had acquired specific markers of the astroglial and oligodendroglial lineages [184]. Mouse NPC transplants in rodents affected by EAE are also associated with significantly reduced glial scar formation [11] and an increased survival and recruitment of endogenous neural cells participating to the naturally occurring brain reparative response upon myelin damage [10, 15, 16, 185, 186].
Human NPCs have shown a higher rate of cell integration after being administered in different animal models. In particular, the HB1.F3 immortalized cell line, i.v. injected in a model of ischemic stroke, were shown to enter the ischemic area and differentiate into neurons and astrocytes, similarly to what observed with focal injected cells [12, 187]. Transplanted cells seemed to adapt their fate accordingly to the region of engraftment, showing the appropriate neuronal and glial markers. NeuN+ and NF+ cells were identified primarily in the CA1 area of the hippocampus and in the dentate gyrus, mixed with GFAP+ cells. Vimentin, GFAP and NF markers showed a progressive expression during the first 2-3 weeks after transplantation, suggesting a step-by-step maturation of the cells [187]. The very same line of cells, injected in a rat model of ICH [137], was observed to infiltrate the brain, survive and migrate towards the peri-hematomal areas. The cells were found mainly differentiating into GFAP+ and NeuN+ cells. However, the rapid behavioural recovery observed in ICH rats as soon as 2 weeks after transplantation, suggested that the NPC therapeutic effect was mainly related to neuroprotection, rather than to integration into neuronal circuitry [137, 187], since the latter would require longer time to produce clinical ameliorations. A similar trend towards human NPC differentiation has been observed in animal models of SCI, SE and HD. HB1.F3 hNPCs administered in mice subjected to compression SCI, were observed to differentiate into βIII-tubulin+ neurons at 21 days after transplantation [167]. GABA-immunoreactive interneurons were, instead, observed originating from HB1.F3 when systemically administered the day after lithium-pilocarpine induction of experimental SE in rats [138]. Further, HB1.F3 cells injected 7 days after unilateral quinolinic acid (QA)-induced model of HD in rats were found to stay confined around blood vessels, mostly in the damaged hemisphere and only partially differentiating in GFAP+ and NeuN+ cells at 3 weeks post transplantation [14]
Despite these evidences showing the ability of exogenous NPCs to survive and differentiate into multiple derivatives according to local cues, the majority of the data provided has substantially failed to show convincing relevant differentiation and integration of transplanted NPCs
4.3.1. Tissue trophic effects
NPCs may exert their neuroprotective effect by increasing
Mouse NPCs systemically injected in mice affected by middle cerebral artery occlusion (MCAo) were observed to mostly maintain an undifferentiated phenotype, while accumulating at the boundaries of the lesioned area [140, 141]. Tissue survival was associated with a down regulation of inflammation, glial scar formation and neuronal apoptotic cell death at both mRNA and protein levels [140]. Increased levels of BDNF, NGF and neurotrophin (NT)-3 were found in the CSF of stroke-affected rats after intra-cisterna magna administration of NPCs. In addition, immunohistochemical analysis of the injured brain revealed an increase of MHC class I levels in treated rats [141]. Interestingly, this neuroprotective effect in the ischemic microenvironment seems to start very soon after the systemic administration of cells. In fact, data have been provided showing an increase in the gene expression levels of IGF-1, VEGF, TGF-1β, BDNF and CXCL12/SDF1-α in the NPC-transplanted MCAo brain, as soon as 24 hours after the acute i.c.v. injection [189]. Further, NPCs have been proved to increase
More recently, adult mouse NPCs systemically injected in mice (3 injections few hours after the injury) suffering from acute contusion SCI, showed an undifferentiated morphology (similarly to what observed in EAE) at the level of the damaged CNS.
All these evidences suggested that the underlying molecular mechanisms by which transplanted NPCs instruct tissue protection effects are partly related to increased
4.3.2. Regulation of the immune system
Considerable evidence of the immune modulatory capacity of NPCs has derived from transplantation studies through different routes in the EAE model. As mentioned, transplanted NPCs are consistently found around inflamed blood vessels, in close contact with both endogenous neural cells (e.g. astrocytes and neurons) and CNS-infiltrating blood-borne CD45+ immune cells [185]. Also, i.c.v. administered NPCs were found to attenuate brain inflammation primarily through a reduction of perivascular infiltrates and CD3+ T cells with a concomitant increase of CD25+ and CD25+/CD62L+ regulatory T cells [136]. Interestingly, i.v. injection of NPCs also protects against chronic neural tissue loss as well as disease-related disability in EAE, via induction of apoptosis of blood-borne CNS-infiltrating encephalitogenic T cells [185]
NPCs have been shown to possess immune modulatory capacity also in models of stroke, where T cells do not have a major role in the disease pathology. Irrespectively of the route of administration (systemically
While the inhibition of the T cell responses by NPCs is a quite established concept [208], the effect of the interaction between transplanted NPCs and microglia/macrophages is still controversial, mainly because of the non-univocal data regarding the role sustained by professional phagocytes under CNS inflammatory conditions.
Human NPCs have been proved to suppress the proliferation and alter the cytokine secretion profiles of activated T cells on both xenogeneic antigen-specific T cells derived from EAE induced non-human primates (common marmosets), and allogeneic mitogen-activated T cells. Co-culture of human NPCs with T cells, revealed their immune modulatory capacity through both direct cell-to-cell contacts as well as via the release of soluble mediators into the culture medium [15]. Notably, in contrast to the mouse counterpart, human NPCs have a limited cytotoxicity against T cells
4.4. NPC interactions with the dysfunctional non-CNS microenvironment
In parallel to the observed immune modulation and neuroprotection into the CNS, other studies have shown that systemically injected cells may act also outside the injured CNS. Different studies, in fact, have reported the capacity of NPCs to target and synergize with immune cells at the level of secondary lymphoid organs (e.g. draining lymph nodes) and the spleen, resulting in the attenuation of the inflammatory response following EAE, stroke and SCI.
It was initially showed
Similarly to what observed in EAE models, i.v. administered human NPCs, in a rat model of ICH, revealed a peripheral therapeutic function in attenuating the inflammatory response to the insult [22]. In line with previous studies, cells were rarely observed into the injured brain while the majority of NPCs were found distributed within the systemic organs. In particular, few NPCs were observed in mesenteric lymph nodes while large numbers were detected in the spleen, especially in the marginal zone area, which is typically enriched in macrophages. Once again NPCs were found in close contact with immune cells and some of them were establishing cell-to-cell contact interactions with CD11b+ spleen macrophages. This result was probably due to the existence of a link between brain and spleen inflammation, called “brain-spleen inflammatory coupling”. Remarkably, splenectomy prior to ICH has been shown to reduce the initial cerebral oedema and inflammatory cell infiltration caused by stroke [22]. NPC accumulation into the spleen, in this case, modulated brain inflammation by reducing the level of major inflammatory mediators in stroke, such as TNF-α, IL-6 and nuclear factor-kappa B (NF-κB), and consequently improved neurologic outcome.
It has been recently shown that mouse NPCs (from fully mismatched C57BL/6 mice) co-transplanted with pancreatic islet under the kidney capsule of Balb/c diabetic mice prevents acute islet allograft rejection. This effect was related to a significant reduction of CD4+ T cells and with a concomitant enrichment of CD4+/CD25+/FoxP3+ regulatory T cells in the spleen, inducing active tolerance. These data suggest that the peripheral immune-modulation exerted by NPCs could alleviate the immune reaction leading to organ rejection. Unfortunately this condition appeared strictly associated with the development of NPC-derived tumours mainly sustained by insulin secretion from the co-transplanted islets [218].
Whether most of the immune regulatory effects of systemically injected NPCs act mainly into the CNS or in the periphery is still under debate. Peripheral lymphoid organs have been demonstrated to play an important role in the regulation of the immune responses to myelin antigens in EAE and a very sophisticated modulation of T-cell self-reactivity is known to take place [219-221]. A very recent study proposes a molecular mechanism sustaining NPCs immune modulation capacity in EAE. The preventive (0 dpi) or therapeutic (10 dpi) i.v. administration of NPCs resulted in their accumulation in lymph nodes and spleen, with rare cells observed into the CNS and without any evidence of myelin repair. Nevertheless, treated mice showed partial clinical recovery. Remarkably, the authors achieved the same results even transplanting NPC conditioned-medium or minimally irradiated NPCs (unable to differentiate but capable of secreting cytokines and neurotrophins), evidence sustaining a true peripheral function of NPCs. In particular, the observed clinical amelioration seem to be related to the selective inhibition of encephalitogenic Th17 cell differentiation through secreted factors. LIF has been identified as the key factor responsible for the observed inhibition of Th17 cell differentiation and the authors elucidated the signalling pathway behind this novel mechanism of action, where LIF antagonizes IL-6-induced Th17 cell differentiation through ERK-dependent inhibition of STAT3 phosphorylation [23]. Further studies will be needed to establish the absolute relevance of these pre-clinical data in EAE, where peripheral lymphoid organs play an important role in the regulation of the immune responses to myelin antigens, and their potential for future applications in MS. All the preclinical data describing NPC therapeutic effect upon systemic administration are summarized in Table 1.
|
|
|
|
|
|
|||||
|
|
|
|
|||||||
|
||||||||||
Acute EAE | Rat | Rat neurospheres | 1.5-2x104 | i.c.v. or i.t. | Disease peak | Cell differentiation (neuronal and glial and tissue trophism | None | [10] | ||
Acute EAE | Rat | Rat neurospheres | 2x104 | i.c.v. | 0 dpi | Immune regulation (central) | None | [136] | ||
Chronic EAE | Mouse | Mouse NPCs | 1x106 | i.v. or i.t. | 22 dpi | (Low) cell differentiation and tissue trophism | Inhibition of reactive gliosis | [11] | ||
Chronic EAE | Mouse | Mouse neurospheres | 2.5x103 | i.c.v. | 6 dpi | Immune regulation (local) | Reduction of CNS inflammatory infiltrates, increase of regulatory T cells | [139] | ||
Chronic EAE Passive EAE |
Mouse | Mouse NPCs | 1x106 | i.v. | 8 dpi | Immune regulation (peripheral) | Suppression of encephalitogenic T cells | [20] | ||
Chronic EAE | Mouse | Human ES cell-derived NPCs | 5x105 | i.c.v. | 7 dpi | Immune regulation (local) | Suppression of encephalitogenic T cells | [142] | ||
Chronic EAE | Mouse | IL-10-transduced mouse NPCs | 1.5x106 | i.v. or i.c.v. | 10, 22 or 30 dpi | Immune regulation (local, peripheral) and cell differentiation | Induction of T cell apoptosis, promotion of myelin debris clearance | [213] | ||
Chronic EAE | Mouse | Mouse and human ES cell-derived NPCs | 2x106 | i.v. | 0 or 10 dpi | Immune regulation (peripheral) | LIF-mediated inhibition of Th17 cell differentiation | [23] | ||
Chronic EAE | Mouse | Mouse MSC-derived NPCs | 3.5x104-6.1x106 | i.t. | 21, 28 and 35 dpi | Tissue trophism | None | [258] | ||
Chronic EAE Passive EAE |
Mouse | CCR5-transduced mouse BM-derived NPCs | 1.5x106 | i.v. | 22 dpi (peak) | Immune regulation | None | [259] | ||
Chronic EAE | Common Marmoset | Human NPCs | 2-6x106 | i.t. or i.v. | Disease onset | Immune regulation (central) | Suppression of encephalitogenic T cells, imparment of dendritic cell maturation | [15] | ||
Relapsing EAE | Mouse | Mouse NPCs | 1x106 | i.v. | Disease onset or first relapse | Immune regulation (central) | Induction of T cell apoptosis | [16] | ||
Relapsing EAE | Mouse | Mouse NPCs | 0.5x106 | s.c. | 3 and 10 dpi, or 10 dpi only | Immune regulation (peripheral) | BMP-4-dependent hindrance of dendritic cell maturation | [21] | ||
Relapsing EAE | Mouse | Mouse NPCs and Olig2-transduced NPCs | 1.5x105 | i.c.v. | Disease onset or first relapse | Immune regulation (central) and Tissue trophism | None | [260] | ||
|
||||||||||
MCAo | Rat | Rat NPCs | 1x105 | i.t. | 2 dpi | Cell differentiation (neuronal) | None | [204] | ||
MCAo (10’ or 90’) | Rat | Human NPCs | 5x106 | i.v. | 1 dpi | Cell differentiation (neuronal, glial) | None | [12, 187] | ||
MCAo (180’) | Rat | Rat NPCs | 1x105 | i.t. | 2 dpi | Tissue trophism | Increased angiogenesis | [190] | ||
MCAo (180’ | Rat | Human NPCs | 1x106 | i.v. | 2 dpi | Tissue trophism | None | [261] | ||
CCAo + global hypoxia-ischemia | Mouse | Mouse 17.2 NSCs | 3x105 | i.ca. | 2 dpi | Tissue trophism | Increased angiogenesis | [18] | ||
MCAo (120’) | Rat | GDNF-transduced rat NPCs | 5x105 | i.c.v. | 3 dpi | Tissue trophism, Cell differentiation (neuronal) | None | [198] | ||
MCAo (45’) | Mouse | Mouse NPCs | 1x106 | i.v. | 3 dpi | Immune regulation (local) and Tissue trophism | Reduction of microglial activation and neuronal death | [140] | ||
MCAo and CCAo | Rat | Rat NPCs | 1.5x105 | i.t. | 7 dpi | Immune regulation and tissue trophism | Neuroprotection mediated by NGF and modulation of class I MHC expression | [141] | ||
MCAo (90’) | Rat | HIF-1α-transduced rat NPCs | 1x106 | i.c.v. | 1 dpi | Tissue trophism | Promotion of angiogenesis | [227] | ||
MCAo (45’) | Mouse | TAT-Hsp70-transduced mouse NPCs | 1x106 or 5x105 | i.v. or i.p.c. | Acute | Tissue trophism, reduction of ROS formation and BBB leakage | Neuroprotection and enhanced neurogenesis | [232] | ||
ICH | Rat | Human NPCs | 5x106 | i.v. | 1 dpi | Tissue trophism, Cell differentiation (glial and neuronal) | Neuroprotection and integration in endogenous neuronal circuitries | [137] | ||
|
||||||||||
Contusion (T8) | Mouse | Mouse NPCs | 1x106 or1x105 | i.v. or i.p.c. | Acute | Tissue trophism | Reduction of apoptosis and modulation of TNF-α expression | [13] | ||
Compression (T8) | Mouse | Human NPCs | 1x107 | i.v. | 7 dpi | Cell differentiation (neuronal, glial) | None | [167] | ||
Contusion (T12) | Mouse | Mouse NPCs and MOG35-55 immunization | 5x105 | i.c.v. | 7 dpi | Immune regulation (local) and Tissue trophism | T-cell mediated activation of microglia with a protective phenotype | [226] |
5. Pros and cons of NPC systemic administration
In parallel to the investigation concerning the principal mechanism(s) sustaining NPC therapeutic efficacy, other questions, such as (i) the ideal administration route, (ii) the amount of cells to be transplanted and (iii) the optimal time point for cell delivery need to be answered. Among the different possible routes of cell administration, intravenous cell delivery represents one of the most attractive because of its technical simplicity and clinical practicability. However, i.v. and i.t. administrations result in lower numbers of cells infiltrating the CNS, compared to local stereotaxic-driven intracerebral injections, a reason why local injections of cells are commonly preferred in clinical trials (see next section) despite the higher invasiveness of the procedure. Even though initially investigated for multifocal disorders (e.g. MS), in order to deliver exogenous cells to all the disseminated inflammatory foci, all the previous experimental data suggest that intravenous or intrathecal administration routes could be desirable even for focal damages, such as those occurring in stroke and spinal cord injury [222]. In experimental animal studies, i.p.c [223-225], i.v. [137, 185] i.a. [222], i.t. [204, 226] and i.c.v. [142, 227] protocols have been tested so far. However, only few comparative studies have been conducted, testing pros and cons of the different administration routes. These studies (mainly in animal models of stroke) evidenced the obvious capacity of intraparenchymal injection to deliver higher numbers of cells
Importantly, when evaluating the optimal protocol, we should consider the procedure itself, so that the risk should not outweigh the benefits of the treatment. From this point of view, i.e. cell injection might be accompanied by increased mortality during cell delivery, probably due to further ischemia or thrombosis [233, 234]. By contrast, cell transplantation trough the vertebral artery, into patients affected by SCI, showed no adverse effects [235].
Another important unsolved issue for experimental stem cell therapies is the ideal time point of transplantation. As described, the inflammatory activation of the CNS, characterizing MS, stroke, SCI, epilepsy, AD, PD, HD is necessary for the homing of systemically injected cells. Because of the rapid and dynamic changes occurring into the CNS during these inflammatory conditions, the time of transplantation should be evaluated carefully. In fact, cell death, excitotossicity, reactive oxygen species accumulation, inflammatory cell infiltrations and glial scar formation, cause a rapid evolution in the damaged tissue, while creating an hostile microenvironment for the engraftment of exogenous cells. This is important irrespectively to the route of administration. For example, the acute focal transplantation of cells into the ischemic brain or the injured spinal cord reduces the therapeutic efficacy of the cells, which are subjected to highly inflammatory conditions causing cell death [205, 236]. On the contrary, the sub acute phase (few days after insult, in rodents) of the injury seems to be characterized by better conditions for stem cell survival and a permissive microenvironment for tissue repair/healing [237]. Although higher inflammation generally correlates with higher number of cells infiltrating the CNS, it has been shown that greater numbers of cells accumulated into the spinal cord after i.v. injection at 7 dpi compared to 3 and 10 dpi [167]. However, the optimal time window for cell transplantation is still elusive and depends mainly on the type of pathology and aim of the treatment. While neuroprotection should be addressed in the early stage of the inflammatory disease, just after the initial insult, cell replacement and neuroregeneration should be targeted in a later stage, when the lesion has stabilized. Indeed, administration route, number of cells and time window and seem intimately related and it is not so difficult to envisage a future in which a combination of early i.v. and late i.p.c administration of different stem cell sources will be enrolled for the treatment of so far incurable CNS disorders.
6. Clinical trials
In the last two decades the clinical potential of stem cells in the field of regenerative/restorative medicine has been often matter of debate, mainly because of its inconsistent outcome. As an example, the first attempt to treat a CNS disorder by means of stem cell transplantation took place in the ‘80s: autologous adrenal medulla cells were intracerebrally transplanted into the striatum of PD patients to provide a local source of catecholamine. The study was proved safe although with minimal beneficial effect. Further, the first intrastriatal grafts of human foetal ventral mesencephalic (neuronal preparations) tissue have provided proof-of-concept that cell therapy can work in patients affected by PD [238]. However, subsequent randomized, double-blind, placebo-controlled trials brought to much more sceptical conclusions because of patients showing functional decline (post transplantation) due to dyskinesias (graft-induced involuntary movements), originated by excessive graft function [239, 240].
Prospectively, many factors can be contended to (partially) justify these patchy results. First, it is now clear that different cell types are needed for different diseases. If on one side PD and amyotrophic lateral sclerosis (ALS) patients will require cells with dopaminergic and motor neuron properties respectively, on the other side, cell replacement in AD patients is much more complicated by the necessity to replace a large variety of cell populations lost in different brain areas. Second, even though initially expected and long-term envisaged, neuronal replacement and circuitry integration of transplanted NPCs have been poorly proved. Third, it as to be considered that pre-clinical animal studies only represent models of human conditions, and, as such, they offer an exceptionally homogeneous platform, where the genetic background, age, and environment are all alike. Clearly, this is not the case with patients. Further, even if multiple models have been established to investigate different aspects of a given disease, none of them can faithfully emulate the human pathology in its complexity [241, 242]. This is particularly challenging considering the rate of progression and lack of validated surrogate disease markers typical of many neurodegenerative disorders. While these aspects are most likely destined to remain unsolved pitfalls, others (including the amount of cells to be transplanted, the manipulation protocols used, the time of transplantation, the route of cell delivery and the statistics adopted to analyse the data) need to be ameliorated through the establishment of common guidelines. In particular, the International Society for Stem Cell Research (ISSCR) composed with a group of international experts (scientists, surgeons, ethicists and patient advocates) “The ISSCR Guidelines for the Clinical Translation of Stem Cells” [243] to trace a roadmap guiding the application of experimental stem cell therapeutics in patients. Importantly, when translating into clinical trials, the choice of the “ideal patient” imposes major scientific and ethical constraints. Indeed, if on one side the treatment of the most chronic/severe patients who were not able to respond to previous treatment lowers the blame for a possible ineffectiveness of a therapy, on the other side the scenario offered by such a compromised tissue may hinder the potential effect of the treatment.
The primary importance of patient’s care dramatically impacts also on the choice of the best route of cell delivery. Indeed, if one side the intravenous injection allows for a less invasive procedure, on the other, the number of cells delivered to the site of interest is lower compared to local injections. Further, the intracerebral transplantation has been widely accepted, by both clinicians and patients, after years of clinical applications and technical improvements. These, together with the relatively limited availability of human NPCs explains why most of the clinical trials started so far have nevertheless favoured the adoption of more invasive procedures, such as intraparenchymal/intracerebroventricular ones (see Table 2). However, as discussed, the correlation between the number of cells entering the CNS and their efficacy still need to be confirmed.
|
|
|
|
|
|
|
|
|
|
|
||||
|
|
|
|
|
||||||||||
StemCells, Inc. at University Hospital Balgrist- Uniklinik Zurich, (Switzerland) | Thoracic spinal cord injuries (SCI) | I/II | 12 | 18-60 | 12 | HuCNS-SC® (Foetal, Brain-derived, Allogeneic, single donor) | 2x107 | Multiple injections, Single dose, Intramedullar | ≥ 3 months | Y (9 months pt) | AR | Armin Curt, MD | NCT01321333 | NA |
ReNeuron, Ltd. at Glasgow Southern General Hospital, Glasgow (UK) |
Stable Ischemic Stroke (PISCES) | I | 12 | 60-85 | 24 | CTX0E303 (Foetal, Brain-derived, c-myc immortalized, Allogeneic, single donor) |
2-20x106 | Single injection, Four Ascending doses, Intracerebral (putamen) | 0.5-5 years | NA | AR | Keith Muir, MD |
NCT01151124 | NA |
Neuralstem, Inc. at Emory University, Atlanta (USA) | Amyotrophic Lateral Sclerosis (ALS) | I | 18 | > 18 | 48 | NSI-566RSC (Foetal, Spinal cord-derived, Allogeneic, single donor) |
0.5-1x106 | Multiple injections, Intraspinal | ≥ 1.5 years | Y (≥ 4 months pt) | AnR | Eva Feldman, MD, PhD | NCT01348451 | [248, 249] |
Azienda Ospedaliera Santa Maria, Terni (Italy) | ALS | I | 18 | 20-75 | 36 | Foetal, Brain-derived, Allogeneic, single donor |
2.5x105/injection | Multiple injections, Single dose, Intraspinal | > 6 months | NA | AR | Angelo Vescovi, PhD | NCT01640067 | NA |
StemCells, Inc. at University of California, San Francisco (USA) |
Pelizaeus Merzbacher disease (PMD) |
I | 4 | 0.5-5 | 12 | HuCNS-SC®
|
3x108 | Multiple injections, Single dose, Intracerebral | NA | Y (9 months pt) | AnR | Stephen Huhn, MD |
NCT01005004 | [250] |
StemCells, Inc. at Oregon Health and Science University, Portland (USA) |
Neuronal Ceroid Lipofuscinosis (NCL) | I | 6 | 1.5-12 | 13 | HuCNS-SC®
|
0.5-1x109 | Multiple injections, Single dose, Intracerebral | NA | Y (12 months pt) | C | Robert Steiner, MD |
NCT00337636 | [247] |
StemCells, Inc. Retina Foundation of the Southwest, Dallas (USA) |
Age-related Macular Degeneration (AMD) | I/II | 16 | > 50 | 12 | HuCNS-SC® | 0.2-1x106 | Single injection, Single dose, Subretinal |
NA | Y (3 months pt) | AR | David Birch, PhD |
NCT01632527 | NA |
Other challenging problems that need to be faced when approaching the clinic, are related to safety, product potency, and manufacturing quality of the cell source. Indeed, principles of good tissue practice (GTP) and good manufacturing practice (GMP) are mandatory requirements, especially when dealing with cells of human origin [244].
Last, but not least, some major issues related to the long-term safety of the cellular product need to be solved. It is important to stress how, differently from the classical drug-therapy, a cell-based treatment cannot be discontinued, since once the cells are within the patient they cannot be removed. Therefore, long-term pre-clinical data need to be collected before translating from the bench to the bed-side to avoid the occurrence of dramatic outcomes, such as the one involving a young patient suffering of Ataxia Telangiectasia who developed a donor-derived brain tumour following neural stem cell transplantation [245].
Nevertheless, translational research did not (and should not) stop. As a matter of fact, the huge amount of data collected so far led to the development of numerous early stage clinical trials. There are currently 1750 studies employing the use of stem cells in interventional clinical trials, among which 280 are testing NPCs. Within the total number of clinical studies, 277 worldwide open trials involve SCs and patients affected by CNS disorders (Figure 2), such as MS, stroke, SCI, epilepsy, ALS, PD, AD, HD, neuronal ceroid lipofuscinose (NCL), Pelizaeus–Merzbacher disease (PMD), age-related macular degeneration (AMD) [246]. Several phase I and II clinical studies with NPCs (9 in highly debilitating CNS disorders, Table 2) have now been started with the primary aim to verify the safety (mainly in terms of toxicity) and feasibility - rather than the efficacy - of the treatment. Further, clinical studies are often accompanied by non-official secondary end-points usually concerning the potential impact in the clinical outcomes. These explorative trials have certainly a key role in stem cell medicine development, as both phase II dose-escalation studies and the inclusion of non-fatal diseases with larger population bases will definitely be facilitated once human safety will be established.
In May 2006 at Oregon Health and Science University (OHSU, Portland, OR, USA) the first human study involving the transplantation of allogeneic NPCs was started on a fatal rare neurometabolic syndrome, such as the NCL Batten’s disease. In this open-label dose-escalating phase I trial, a total of 6 subjects with infantile and late-infantile NCL were transplanted in a single-stage procedure. StemCell, Inc. proprietary, single donor allogeneic free-floating cultured, foetal-derived brain human NPCs (HuCNS- SC®) were directly administered to the cerebral hemispheres and lateral ventricles. Immune suppression was administered for 12 months after transplantation. This study has now been completed with one out of 6 patients died for disease progression, 11 months after treatment. The cell transplantation and combination with prolonged immune suppression were both well tolerated [247].
In September of 2009, NeuralStem, Inc. sponsored a phase I trial in ALS at the Emory University School of Medicine (Atlanta, GA, USA), using proprietary single donor allogeneic, adherent cultured, foetal-derived spinal NPCs (NSI-566RSC). NSI-566 cells were surgically implanted on a total of 12 patients via multiple injections directly into the thoracic spinal cord (either unilateral or bilateral). The clinical assessments demonstrated no evidence of acceleration of disease progression with the planned 18 months post-transplantation follow up [248, 249]. StemCell, Inc. is also sponsoring other two phase I trials with HuCNS-SC® in X chromosome linked connatal leukodistrophy PMD (in which oligodendrocytes cannot myelinate axons) and AMD. With the PMD trial at the University of California, San Francisco (UCSF, San Francisco, CA, USA), HuCNS-SC® were directly delivered through multiple injections into the brain of a total of 4 male patients (clinicaltrials.gov identifier no. NCT01005004). Data regarding this clinical trial has been recently published [250]. The transplantation procedure, the immunosuppression and the cells were well tolerated by all the 4 patients. No adverse effects related to the implant were detected. MRI investigation before and after the transplantation of cells, revealed, after 9 months, a consistent donor cell-derived myelination
In June 2012, the Glasgow Southern General Hospital (Glasgow, Scotland) enrolled the first patient (of 12 total) of the dose-escalating Pilot Investigation of Stem Cells in Stroke (PISCES) phase I trial to be transplanted in a single-stage procedure with direct cerebral (intraparenchymal) delivery of Reneuron, Ltd. proprietary single donor allogeneic adherent cultured, c-myc immortalized foetal-derived brain human NPCs (CTX0E03) (clinicaltrials.gov identifier no. NCT01151124).
In March 2011, the University Hospital Balgrist (Zurich, Switzerland) enrolled the first patient (of 12 total) with chronic thoracic (T2–T11) SCI (3 to 12 months after complete and incomplete cord injuries) to be transplanted with HuCNS-SC® in a further StemCell, Inc. sponsored phase I/II clinical trial estimated to be concluded in March 2016. A single dose (20x106 cells) of HuCNS-SC® has been directly implanted through multiple injections into the thoracic spinal cord, and immune suppression administered for 9 months after transplantation (clinicaltrials.gov identifier no. NCT01321333). In November 2012 started the consequent long-term follow up of the 12 patients subjected to HuCNS-SC® transplantation that will last until March 2018 (clinicaltrials.gov identifier no. NCT01725880).
In June 2012, the Azienda Ospedaliera Santa Maria (Terni, Italy) enrolled the very first of total 18 ALS patients to treat with intraspinally implanted allogeneic free-floating cultured, foetal-derived brain NPCs. (clinicaltrials.gov identifier no. NCT01640067).
Importantly, there are not yet clinical trials with NPCs in MS. However, a consensus paper has recently been produced by a group of experts to define the uniform guidelines on the development of haematopoietic and non-haematopoietic stem cell therapies for MS [9]. All the current clinical trials envolving NPCs for CNS disorders are described in Table 2.
While in this paragraph we offer an overview of the current clinical trials involving solely human NPCs, it has to be said that, in the light of the neuroprotective/immunomodulatory (rather than cell replacement) properties attributed to stem cells, the therapeutic plasticity of cells of non-neural origin are being tested as well. Among these, MSCs are emerging as a good potential candidate, mainly because of their great accessibility and remarkable proliferation. Also, growing evidence suggests that other than giving origin to multiple derivatives of the mesodermal lineage (from which they derive), under particular conditions MSCs seem able to
Since 2006, the advent of induced pluripotent stem cells (iPSCs, [24]) technology has brought new excitement in medical research and clinical therapy, since these cells provide a valuable alternative without being constrained by ethical issues and immunological incompatibility [256]. Although still under debate about their long-term safety, the methods for iPSC generation, reprogramming and differentiation efficiency, iPSCs represent a break-trough for both study of disease mechanisms and investigation of potential new treatments (for a perspective analysis, see [257]).
The potential impact of this technological platform has been further boosted by the scientific stream emerged from iPSC technology that is the “direct reprogramming” from one somatic lineage to another. In fact, the direct conversion of fibroblasts to functional neurons (iN cells) or iNSCs [25, 26], for example, represents one of the most exciting, ultimate technologies for future application in CNS pathologies. Thanks to these next generation techniques, it will be possible to derive virtually unlimited numbers of specific neural/neuronal population bypassing the pluripotent stage, thus likely eliminating the potential presence of unwanted undifferentiated cells. However, many issues, such as the purity of the cell preparation, the use of virus-based technologies and the proper
Abbreviations
AD: Alzheimer’s disease
ALS: Amyotrophic lateral sclerosis
APC: Antigen presenting cell
ASCL1: Achaete-scute homolog 1
BBB: Blood brain barrier
BCSFB: Blood-cerebrospinal fluid barrier
BDNF: Brain-derived neurotrophic factor
BLMB: Blood-leptomeningeal barrier
BMP: Bone morphogenetic protein
BMSC: Bone marrow-derived stem cell
CCAo: Common carotid artery occlusion
CCL: Chemokine (C-C motif) ligand
CCR: C-C chemokine receptor
CNS: Central nervous system
CNTF: Ciliary neurotrophic factor
CSF: Cerebrospinal fluid
CXCR: C-X-C chemokine receptor
DCs: dendritic cells
DCX: Doublecortin
DG: Dentate gyrus
DGC: Dentate granule cell
Dlx: Distal-less homeobox
d.p.t.: days post transplantation
EAE: Experimental autoimmune encephalomyelitis
EC: Endothelial cell
ES cells: Embryonic stem cells
FACS: Fluorescence-activated cell sorting
FGF: Fibroblast growth factor
GABA: Gamma-aminobutyric acid
GCL: Granule cell layer
GDNF: Glial-derived neurotrophic factor
GFAP: Glial-fibrillary acidic protein
GF-CSF: granulocyte macrophage colony stimulating factor
GMP: Good manufacturing practice
GTP: Good tissue practice
HD: Huntington’s disease
hNPC: Human neural stem/precursor cell
Hsp70: Heat shock protein 70
HuCNS-SC: Human CNS stem cell
HVc: hyperstriatum ventrale, pars caudalis
i.a.: Intraartery
i.c.v.: Intracerebroventricular
i.p.c.: Intraparenchyma
i.t.: Intrathecal
i.v.: Intravenous
ICAM: Intercellular adhesion molecule
ICH: Intracerebral hemorrhage
Ig: Immunoglobulin
IGF: Insulin-like growth factor
IL: Interleukin
IML: Inner molecular layer
iN cells: Induced neuronal cells
INF: Interferon
iNOS: inducible nitric oxide synthase
iNSC: Induced neural stem cell
IPC: Intermediate progenitor cell
iPS: Induced pluripotent stem cell
LFA: Leukocyte-function associated antigen
LIF: Leukemia inhibitory factor
LPS: Lipopolysaccharide
MAdCAM: Mucosal addressin cell adhesion molecule
MCAo: Middle cerebral artery occlusion
MCP: Monocyte chemoattractant protein
MHC: Major histocompatibility complex
MMS: Medial migratory stream
MOG: Myelin oligodendrocyte glycoprotein
MPC: Myeloid precursor cell
MRI: Magnetic resonance imaging
MS: Multiple sclerosis
MSC: Mesenchymal stem cell
NCL: Neuronal ceroid lipofuscinose
NeuN: Neuronal nuclei
NF: Neurofilament
NF-kB: Nuclear factor-kB
NGF: Nerve growth factor
NO: Nitric oxide
NPC: Neural stem/precursor cell
NSC: Neural stem cell
OB: Olfactory bulb
OPC: Oligodendrocyte progenitor cells
PD: Parkinson’s disease
PGE2: prostaglandine 2
PLP: Proteolipid protein
PSA-NCAM: Polysialylated neural cell adhesion molecule
PSGL: P-selectin glycoprotein ligand
pt: Post-transplantation
RA: Radial astrocyte
RMS: Rostral migratory stream
s.c.: Subcutaneous
SCF: Stem cell factor
SCI: Spinal cord injury
SC: Stem cell
SDF: Stromal cell-derived factor
SE: Status epilepticus
SGZ: Subgranular zone
Shh: Sonic hedgehog
SIDS: Stroke-induced immune depression syndrome
TCR: T cell receptor
TGF: Transforming growth factor
TJ: Tight junction
TLE: Temporal lobe epilepsy
TLR: Toll-like receptor
TNF: Tumor necrosis factor
V-SVZ: Ventricular-subventricular zone
VCAM: Vascular cell adhesion molecule
VEGF: Vascular endothelial growth factor
VLA: Very late antigen
References
- 1.
Altman J, Das GD. Autoradiographic and histological evidence of postnatal hippocampal neurogenesis in rats. The Journal of comparative neurology. 1965 Jun;124(3):319-35. - 2.
Altman J, Das GD. Autoradiographic and histological studies of postnatal neurogenesis. I. A longitudinal investigation of the kinetics, migration and transformation of cells incorporating tritiated thymidine in neonate rats, with special reference to postnatal neurogenesis in some brain regions. The Journal of comparative neurology. 1966 Mar;126(3):337-89. - 3.
Goldman SA, Nottebohm F. Neuronal production, migration, and differentiation in a vocal control nucleus of the adult female canary brain. Proceedings of the National Academy of Sciences of the United States of America. 1983 Apr;80(8):2390-4. - 4.
Picard-Riera N, Decker L, Delarasse C, Goude K, Nait-Oumesmar B, Liblau R, et al. Experimental autoimmune encephalomyelitis mobilizes neural progenitors from the subventricular zone to undergo oligodendrogenesis in adult mice. Proceedings of the National Academy of Sciences of the United States of America. 2002 Oct 1;99(20):13211-6. - 5.
Pluchino S, Martino G. The therapeutic plasticity of neural stem/precursor cells in multiple sclerosis. Journal of the neurological sciences. 2008 Feb 15;265(1-2):105-10. - 6.
Pluchino S, Muzio L, Imitola J, Deleidi M, Alfaro-Cervello C, Salani G, et al. Persistent inflammation alters the function of the endogenous brain stem cell compartment. Brain. 2008 Oct;131(Pt 10):2564-78. - 7.
Cossetti C, Alfaro-Cervello C, Donega M, Tyzack G, Pluchino S. New perspectives of tissue remodelling with neural stem and progenitor cell-based therapies. Cell and tissue research. 2012 Jul;349(1):321-9. - 8.
Martino G, Pluchino S, Bonfanti L, Schwartz M. Brain regeneration in physiology and pathology: the immune signature driving therapeutic plasticity of neural stem cells. Physiological reviews. 2011 Oct;91(4):1281-304. - 9.
Martino G, Franklin RJ, Van Evercooren AB, Kerr DA. Stem cell transplantation in multiple sclerosis: current status and future prospects. Nat Rev Neurol. 2010 May;6(5):247-55. - 10.
Ben-Hur T, Einstein O, Mizrachi-Kol R, Ben-Menachem O, Reinhartz E, Karussis D, et al. Transplanted multipotential neural precursor cells migrate into the inflamed white matter in response to experimental autoimmune encephalomyelitis. Glia. 2003 Jan;41(1):73-80. - 11.
Pluchino S, Quattrini A, Brambilla E, Gritti A, Salani G, Dina G, et al. Injection of adult neurospheres induces recovery in a chronic model of multiple sclerosis. Nature. 2003 Apr 17;422(6933):688-94. - 12.
Chu K, Kim M, Jeong SW, Kim SU, Yoon BW. Human neural stem cells can migrate, differentiate, and integrate after intravenous transplantation in adult rats with transient forebrain ischemia. Neuroscience letters. 2003 Jun 5;343(2):129-33. - 13.
Bottai D, Madaschi L, Di Giulio AM, Gorio A. Viability-dependent promoting action of adult neural precursors in spinal cord injury. Molecular medicine (Cambridge, Mass. 2008 Sep-Oct;14(9-10):634-44. - 14.
Lee ST, Chu K, Park JE, Lee K, Kang L, Kim SU, et al. Intravenous administration of human neural stem cells induces functional recovery in Huntington's disease rat model. Neuroscience research. 2005 Jul;52(3):243-9. - 15.
Pluchino S, Gritti A, Blezer E, Amadio S, Brambilla E, Borsellino G, et al. Human neural stem cells ameliorate autoimmune encephalomyelitis in non-human primates. Annals of neurology. 2009 Sep;66(3):343-54. - 16.
Pluchino S, Zanotti L, Rossi B, Brambilla E, Ottoboni L, Salani G, et al. Neurosphere-derived multipotent precursors promote neuroprotection by an immunomodulatory mechanism. Nature. 2005 Jul 14;436(7048):266-71. - 17.
van der Meulen AA, Biber K, Lukovac S, Balasubramaniyan V, den Dunnen WF, Boddeke HW, et al. The role of CXC chemokine ligand (CXCL)12-CXC chemokine receptor (CXCR)4 signalling in the migration of neural stem cells towards a brain tumour. Neuropathology and applied neurobiology. 2009 Dec;35(6):579-91. - 18.
Guzman R, De Los Angeles A, Cheshier S, Choi R, Hoang S, Liauw J, et al. Intracarotid injection of fluorescence activated cell-sorted CD49d-positive neural stem cells improves targeted cell delivery and behavior after stroke in a mouse stroke model. Stroke; a journal of cerebral circulation. 2008 Apr;39(4):1300-6. - 19.
Martino G, Pluchino S. The therapeutic potential of neural stem cells. Nature reviews. 2006 May;7(5):395-406. - 20.
Einstein O, Fainstein N, Vaknin I, Mizrachi-Kol R, Reihartz E, Grigoriadis N, et al. Neural precursors attenuate autoimmune encephalomyelitis by peripheral immunosuppression. Annals of neurology. 2007 Mar;61(3):209-18. - 21.
Pluchino S, Zanotti L, Brambilla E, Rovere-Querini P, Capobianco A, Alfaro-Cervello C, et al. Immune regulatory neural stem/precursor cells protect from central nervous system autoimmunity by restraining dendritic cell function. PloS one. 2009;4(6):e5959. - 22.
Lee ST, Chu K, Jung KH, Kim SJ, Kim DH, Kang KM, et al. Anti-inflammatory mechanism of intravascular neural stem cell transplantation in haemorrhagic stroke. Brain. 2008 Mar;131(Pt 3):616-29. - 23.
Cao W, Yang Y, Wang Z, Liu A, Fang L, Wu F, et al. Leukemia inhibitory factor inhibits T helper 17 cell differentiation and confers treatment effects of neural progenitor cell therapy in autoimmune disease. Immunity. 2011 Aug 26;35(2):273-84. - 24.
Takahashi K, Yamanaka S. Induction of pluripotent stem cells from mouse embryonic and adult fibroblast cultures by defined factors. Cell. 2006 Aug 25;126(4):663-76. - 25.
Vierbuchen T, Ostermeier A, Pang ZP, Kokubu Y, Sudhof TC, Wernig M. Direct conversion of fibroblasts to functional neurons by defined factors. Nature. 2010 Feb 25;463(7284):1035-41. - 26.
Thier M, Worsdorfer P, Lakes YB, Gorris R, Herms S, Opitz T, et al. Direct conversion of fibroblasts into stably expandable neural stem cells. Cell stem cell. 2012 Apr 6;10(4):473-9. - 27.
Altman J. Autoradiographic and histological studies of postnatal neurogenesis. 3. Dating the time of production and onset of differentiation of cerebellar microneurons in rats. The Journal of comparative neurology. 1969 Jul;136(3):269-93. - 28.
Ming GL, Song H. Adult neurogenesis in the mammalian central nervous system. Annual review of neuroscience. 2005;28:223-50. - 29.
Gage FH. Mammalian neural stem cells. Science (New York, NY. 2000 Feb 25;287(5457):1433-8. - 30.
Lois C, Alvarez-Buylla A. Proliferating subventricular zone cells in the adult mammalian forebrain can differentiate into neurons and glia. Proceedings of the National Academy of Sciences of the United States of America. 1993 Mar 1;90(5):2074-7. - 31.
Kaplan MS, Bell DH. Mitotic neuroblasts in the 9-day-old and 11-month-old rodent hippocampus. J Neurosci. 1984 Jun;4(6):1429-41. - 32.
Cameron HA, Woolley CS, McEwen BS, Gould E. Differentiation of newly born neurons and glia in the dentate gyrus of the adult rat. Neuroscience. 1993 Sep;56(2):337-44. - 33.
Goldman SA, Chen Z. Perivascular instruction of cell genesis and fate in the adult brain. Nature neuroscience. 2011 Nov;14(11):1382-9. - 34.
Fuchs E, Tumbar T, Guasch G. Socializing with the neighbors: stem cells and their niche. Cell. 2004 Mar 19;116(6):769-78. - 35.
Tavazoie M, Van der Veken L, Silva-Vargas V, Louissaint M, Colonna L, Zaidi B, et al. A specialized vascular niche for adult neural stem cells. Cell stem cell. 2008 Sep 11;3(3):279-88. - 36.
Shen Q, Wang Y, Kokovay E, Lin G, Chuang SM, Goderie SK, et al. Adult SVZ stem cells lie in a vascular niche: a quantitative analysis of niche cell-cell interactions. Cell stem cell. 2008 Sep 11;3(3):289-300. - 37.
Fuentealba LC, Obernier K, Alvarez-Buylla A. Adult neural stem cells bridge their niche. Cell stem cell. 2012 Jun 14;10(6):698-708. - 38.
Alvarez-Buylla A, Garcia-Verdugo JM. Neurogenesis in adult subventricular zone. J Neurosci. 2002 Feb 1;22(3):629-34. - 39.
Merkle FT, Mirzadeh Z, Alvarez-Buylla A. Mosaic organization of neural stem cells in the adult brain. Science (New York, NY. 2007 Jul 20;317(5836):381-4. - 40.
Doetsch F. The glial identity of neural stem cells. Nature neuroscience. 2003 Nov;6(11):1127-34. - 41.
Kriegstein A, Alvarez-Buylla A. The glial nature of embryonic and adult neural stem cells. Annual review of neuroscience. 2009;32:149-84. - 42.
Mirzadeh Z, Merkle FT, Soriano-Navarro M, Garcia-Verdugo JM, Alvarez-Buylla A. Neural stem cells confer unique pinwheel architecture to the ventricular surface in neurogenic regions of the adult brain. Cell stem cell. 2008 Sep 11;3(3):265-78. - 43.
Sawamoto K, Wichterle H, Gonzalez-Perez O, Cholfin JA, Yamada M, Spassky N, et al. New neurons follow the flow of cerebrospinal fluid in the adult brain. Science (New York, NY. 2006 Feb 3;311(5761):629-32. - 44.
Kokovay E, Wang Y, Kusek G, Wurster R, Lederman P, Lowry N, et al. VCAM1 is essential to maintain the structure of the SVZ niche and acts as an environmental sensor to regulate SVZ lineage progression. Cell stem cell. 2012 Aug 3;11(2):220-30. - 45.
Lehtinen MK, Zappaterra MW, Chen X, Yang YJ, Hill AD, Lun M, et al. The cerebrospinal fluid provides a proliferative niche for neural progenitor cells. Neuron. 2011 Mar 10;69(5):893-905. - 46.
Kopan R, Ilagan MX. The canonical Notch signaling pathway: unfolding the activation mechanism. Cell. 2009 Apr 17;137(2):216-33. - 47.
Chapouton P, Jagasia R, Bally-Cuif L. Adult neurogenesis in non-mammalian vertebrates. Bioessays. 2007 Aug;29(8):745-57. - 48.
Fernando RN, Eleuteri B, Abdelhady S, Nussenzweig A, Andang M, Ernfors P. Cell cycle restriction by histone H2AX limits proliferation of adult neural stem cells. Proceedings of the National Academy of Sciences of the United States of America. 2011 Apr 5;108(14):5837-42. - 49.
Villeda SA, Luo J, Mosher KI, Zou B, Britschgi M, Bieri G, et al. The ageing systemic milieu negatively regulates neurogenesis and cognitive function. Nature. 2011 Sep 1;477(7362):90-4. - 50.
Mosher KI, Andres RH, Fukuhara T, Bieri G, Hasegawa-Moriyama M, He Y, et al. Neural progenitor cells regulate microglia functions and activity. Nature neuroscience. 2012 Nov;15(11):1485-7. - 51.
Curtis MA, Kam M, Nannmark U, Anderson MF, Axell MZ, Wikkelso C, et al. Human neuroblasts migrate to the olfactory bulb via a lateral ventricular extension. Science (New York, NY. 2007 Mar 2;315(5816):1243-9. - 52.
Sanai N, Tramontin AD, Quinones-Hinojosa A, Barbaro NM, Gupta N, Kunwar S, et al. Unique astrocyte ribbon in adult human brain contains neural stem cells but lacks chain migration. Nature. 2004 Feb 19;427(6976):740-4. - 53.
Eriksson PS, Perfilieva E, Bjork-Eriksson T, Alborn AM, Nordborg C, Peterson DA, et al. Neurogenesis in the adult human hippocampus. Nature medicine. 1998 Nov;4(11):1313-7. - 54.
Quinones-Hinojosa A, Sanai N, Soriano-Navarro M, Gonzalez-Perez O, Mirzadeh Z, Gil-Perotin S, et al. Cellular composition and cytoarchitecture of the adult human subventricular zone: a niche of neural stem cells. The Journal of comparative neurology. 2006 Jan 20;494(3):415-34. - 55.
Ming GL, Song H. Adult neurogenesis in the mammalian brain: significant answers and significant questions. Neuron. 2011 May 26;70(4):687-702. - 56.
Yang Z, Ming GL, Song H. Postnatal neurogenesis in the human forebrain: from two migratory streams to dribbles. Cell stem cell. 2011 Nov 4;9(5):385-6. - 57.
Guerrero-Cazares H, Gonzalez-Perez O, Soriano-Navarro M, Zamora-Berridi G, Garcia-Verdugo JM, Quinones-Hinojosa A. Cytoarchitecture of the lateral ganglionic eminence and rostral extension of the lateral ventricle in the human fetal brain. The Journal of comparative neurology. 2011 Apr 15;519(6):1165-80. - 58.
Sanai N, Nguyen T, Ihrie RA, Mirzadeh Z, Tsai HH, Wong M, et al. Corridors of migrating neurons in the human brain and their decline during infancy. Nature. 2011 Oct 20;478(7369):382-6. - 59.
Seri B, Garcia-Verdugo JM, McEwen BS, Alvarez-Buylla A. Astrocytes give rise to new neurons in the adult mammalian hippocampus. J Neurosci. 2001 Sep 15;21(18):7153-60. - 60.
Bonaguidi MA, Song J, Ming GL, Song H. A unifying hypothesis on mammalian neural stem cell properties in the adult hippocampus. Current opinion in neurobiology. 2012 Oct;22(5):754-61. - 61.
Seri B, Garcia-Verdugo JM, Collado-Morente L, McEwen BS, Alvarez-Buylla A. Cell types, lineage, and architecture of the germinal zone in the adult dentate gyrus. The Journal of comparative neurology. 2004 Oct 25;478(4):359-78. - 62.
Lugert S, Vogt M, Tchorz JS, Muller M, Giachino C, Taylor V. Homeostatic neurogenesis in the adult hippocampus does not involve amplification of Ascl1(high) intermediate progenitors. Nature communications. 2012;3:670. - 63.
Ehm O, Goritz C, Covic M, Schaffner I, Schwarz TJ, Karaca E, et al. RBPJkappa-dependent signaling is essential for long-term maintenance of neural stem cells in the adult hippocampus. J Neurosci. 2010 Oct 13;30(41):13794-807. - 64.
Lavado A, Lagutin OV, Chow LM, Baker SJ, Oliver G. Prox1 is required for granule cell maturation and intermediate progenitor maintenance during brain neurogenesis. PLoS biology. 2010;8(8). - 65.
Song J, Zhong C, Bonaguidi MA, Sun GJ, Hsu D, Gu Y, et al. Neuronal circuitry mechanism regulating adult quiescent neural stem-cell fate decision. Nature. 2012 Sep 6;489(7414):150-4. - 66.
Dayer AG, Ford AA, Cleaver KM, Yassaee M, Cameron HA. Short-term and long-term survival of new neurons in the rat dentate gyrus. The Journal of comparative neurology. 2003 Jun 9;460(4):563-72. - 67.
Schwartz M, Shechter R. Protective autoimmunity functions by intracranial immunosurveillance to support the mind: The missing link between health and disease. Molecular psychiatry. 2010 Apr;15(4):342-54. - 68.
Ziv Y, Ron N, Butovsky O, Landa G, Sudai E, Greenberg N, et al. Immune cells contribute to the maintenance of neurogenesis and spatial learning abilities in adulthood. Nature neuroscience. 2006 Feb;9(2):268-75. - 69.
Gould E, Tanapat P. Lesion-induced proliferation of neuronal progenitors in the dentate gyrus of the adult rat. Neuroscience. 1997 Sep;80(2):427-36. - 70.
Yang L, Benardo LS, Valsamis H, Ling DS. Acute injury to superficial cortex leads to a decrease in synaptic inhibition and increase in excitation in neocortical layer V pyramidal cells. Journal of neurophysiology. 2007 Jan;97(1):178-87. - 71.
Monje ML, Toda H, Palmer TD. Inflammatory blockade restores adult hippocampal neurogenesis. Science (New York, NY. 2003 Dec 5;302(5651):1760-5. - 72.
Huehnchen P, Prozorovski T, Klaissle P, Lesemann A, Ingwersen J, Wolf SA, et al. Modulation of adult hippocampal neurogenesis during myelin-directed autoimmune neuroinflammation. Glia. 2011 Jan;59(1):132-42. - 73.
Roosendaal SD, Hulst HE, Vrenken H, Feenstra HE, Castelijns JA, Pouwels PJ, et al. Structural and functional hippocampal changes in multiple sclerosis patients with intact memory function. Radiology. 2010 May;255(2):595-604. - 74.
Rasmussen S, Imitola J, Ayuso-Sacido A, Wang Y, Starossom SC, Kivisakk P, et al. Reversible neural stem cell niche dysfunction in a model of multiple sclerosis. Annals of neurology. 2011 May;69(5):878-91. - 75.
Tepavcevic V, Lazarini F, Alfaro-Cervello C, Kerninon C, Yoshikawa K, Garcia-Verdugo JM, et al. Inflammation-induced subventricular zone dysfunction leads to olfactory deficits in a targeted mouse model of multiple sclerosis. The Journal of clinical investigation. 2011 Dec;121(12):4722-34. - 76.
Ransohoff RM. Animal models of multiple sclerosis: the good, the bad and the bottom line. Nature neuroscience. 2012 Aug;15(8):1074-7. - 77.
Nait-Oumesmar B, Picard-Riera N, Kerninon C, Decker L, Seilhean D, Hoglinger GU, et al. Activation of the subventricular zone in multiple sclerosis: evidence for early glial progenitors. Proceedings of the National Academy of Sciences of the United States of America. 2007 Mar 13;104(11):4694-9. - 78.
Zivadinov R, Zorzon M, Monti Bragadin L, Pagliaro G, Cazzato G. Olfactory loss in multiple sclerosis. Journal of the neurological sciences. 1999 Oct 15;168(2):127-30. - 79.
Zhang R, Zhang Z, Zhang C, Zhang L, Robin A, Wang Y, et al. Stroke transiently increases subventricular zone cell division from asymmetric to symmetric and increases neuronal differentiation in the adult rat. J Neurosci. 2004 Jun 23;24(25):5810-5. - 80.
Jin K, Wang X, Xie L, Mao XO, Zhu W, Wang Y, et al. Evidence for stroke-induced neurogenesis in the human brain. Proceedings of the National Academy of Sciences of the United States of America. 2006 Aug 29;103(35):13198-202. - 81.
Arvidsson A, Collin T, Kirik D, Kokaia Z, Lindvall O. Neuronal replacement from endogenous precursors in the adult brain after stroke. Nature medicine. 2002 Sep;8(9):963-70. - 82.
Yamashita T, Ninomiya M, Hernandez Acosta P, Garcia-Verdugo JM, Sunabori T, Sakaguchi M, et al. Subventricular zone-derived neuroblasts migrate and differentiate into mature neurons in the post-stroke adult striatum. J Neurosci. 2006 Jun 14;26(24):6627-36. - 83.
Thored P, Wood J, Arvidsson A, Cammenga J, Kokaia Z, Lindvall O. Long-term neuroblast migration along blood vessels in an area with transient angiogenesis and increased vascularization after stroke. Stroke; a journal of cerebral circulation. 2007 Nov;38(11):3032-9. - 84.
Thored P, Arvidsson A, Cacci E, Ahlenius H, Kallur T, Darsalia V, et al. Persistent production of neurons from adult brain stem cells during recovery after stroke. Stem cells (Dayton, Ohio). 2006 Mar;24(3):739-47. - 85.
Nadareishvili Z, Hallenbeck J. Neuronal regeneration after stroke. The New England journal of medicine. 2003 Jun 5;348(23):2355-6. - 86.
Kang SS, Keasey MP, Arnold SA, Reid R, Geralds J, Hagg T. Endogenous CNTF mediates stroke-induced adult CNS neurogenesis in mice. Neurobiology of disease. 2012 Aug 31;49C:68-78. - 87.
Guerra-Crespo M, Gleason D, Sistos A, Toosky T, Solaroglu I, Zhang JH, et al. Transforming growth factor-alpha induces neurogenesis and behavioral improvement in a chronic stroke model. Neuroscience. 2009 May 5;160(2):470-83. - 88.
Sun Y, Jin K, Xie L, Childs J, Mao XO, Logvinova A, et al. VEGF-induced neuroprotection, neurogenesis, and angiogenesis after focal cerebral ischemia. The Journal of clinical investigation. 2003 Jun;111(12):1843-51. - 89.
Jin K, Mao XO, Sun Y, Xie L, Greenberg DA. Stem cell factor stimulates neurogenesis in vitro and in vivo. The Journal of clinical investigation. 2002 Aug;110(3):311-9. - 90.
Shingo T, Sorokan ST, Shimazaki T, Weiss S. Erythropoietin regulates the in vitro and in vivo production of neuronal progenitors by mammalian forebrain neural stem cells. J Neurosci. 2001 Dec 15;21(24):9733-43. - 91.
Weiss S, Dunne C, Hewson J, Wohl C, Wheatley M, Peterson AC, et al. Multipotent CNS stem cells are present in the adult mammalian spinal cord and ventricular neuroaxis. J Neurosci. 1996 Dec 1;16(23):7599-609. - 92.
Xu R, Wu C, Tao Y, Yi J, Yang Y, Zhang X, et al. Nestin-positive cells in the spinal cord: a potential source of neural stem cells. Int J Dev Neurosci. 2008 Nov;26(7):813-20. - 93.
Ke Y, Chi L, Xu R, Luo C, Gozal D, Liu R. Early response of endogenous adult neural progenitor cells to acute spinal cord injury in mice. Stem cells (Dayton, Ohio). 2006 Apr;24(4):1011-9. - 94.
Vaquero J, Ramiro MJ, Oya S, Cabezudo JM. Ependymal reaction after experimental spinal cord injury. Acta neurochirurgica. 1981;55(3-4):295-302. - 95.
Beattie MS, Bresnahan JC, Komon J, Tovar CA, Van Meter M, Anderson DK, et al. Endogenous repair after spinal cord contusion injuries in the rat. Experimental neurology. 1997 Dec;148(2):453-63. - 96.
Felix MS, Popa N, Djelloul M, Boucraut J, Gauthier P, Bauer S, et al. Alteration of forebrain neurogenesis after cervical spinal cord injury in the adult rat. Frontiers in neuroscience. 2012;6:45. - 97.
Parent JM, Valentin VV, Lowenstein DH. Prolonged seizures increase proliferating neuroblasts in the adult rat subventricular zone-olfactory bulb pathway. J Neurosci. 2002 Apr 15;22(8):3174-88. - 98.
Jessberger S, Romer B, Babu H, Kempermann G. Seizures induce proliferation and dispersion of doublecortin-positive hippocampal progenitor cells. Experimental neurology. 2005 Dec;196(2):342-51. - 99.
Overstreet-Wadiche LS, Bromberg DA, Bensen AL, Westbrook GL. Seizures accelerate functional integration of adult-generated granule cells. J Neurosci. 2006 Apr 12;26(15):4095-103. - 100.
Mathern GW, Leiphart JL, De Vera A, Adelson PD, Seki T, Neder L, et al. Seizures decrease postnatal neurogenesis and granule cell development in the human fascia dentata. Epilepsia. 2002;43 Suppl 5:68-73. - 101.
Haughey NJ, Liu D, Nath A, Borchard AC, Mattson MP. Disruption of neurogenesis in the subventricular zone of adult mice, and in human cortical neuronal precursor cells in culture, by amyloid beta-peptide: implications for the pathogenesis of Alzheimer's disease. Neuromolecular medicine. 2002;1(2):125-35. - 102.
Yu Y, He J, Zhang Y, Luo H, Zhu S, Yang Y, et al. Increased hippocampal neurogenesis in the progressive stage of Alzheimer's disease phenotype in an APP/PS1 double transgenic mouse model. Hippocampus. 2009 Dec;19(12):1247-53. - 103.
Rodriguez JJ, Jones VC, Verkhratsky A. Impaired cell proliferation in the subventricular zone in an Alzheimer's disease model. Neuroreport. 2009 Jul 1;20(10):907-12. - 104.
Ermini FV, Grathwohl S, Radde R, Yamaguchi M, Staufenbiel M, Palmer TD, et al. Neurogenesis and alterations of neural stem cells in mouse models of cerebral amyloidosis. The American journal of pathology. 2008 Jun;172(6):1520-8. - 105.
Zhang C, McNeil E, Dressler L, Siman R. Long-lasting impairment in hippocampal neurogenesis associated with amyloid deposition in a knock-in mouse model of familial Alzheimer's disease. Experimental neurology. 2007 Mar;204(1):77-87. - 106.
Demars M, Hu YS, Gadadhar A, Lazarov O. Impaired neurogenesis is an early event in the etiology of familial Alzheimer's disease in transgenic mice. Journal of neuroscience research. 2010 Aug 1;88(10):2103-17. - 107.
Jin K, Peel AL, Mao XO, Xie L, Cottrell BA, Henshall DC, et al. Increased hippocampal neurogenesis in Alzheimer's disease. Proceedings of the National Academy of Sciences of the United States of America. 2004 Jan 6;101(1):343-7. - 108.
Parent JM, Vexler ZS, Gong C, Derugin N, Ferriero DM. Rat forebrain neurogenesis and striatal neuron replacement after focal stroke. Annals of neurology. 2002 Dec;52(6):802-13. - 109.
Bonfanti L. From hydra regeneration to human brain structural plasticity: a long trip through narrowing roads. TheScientificWorldJournal. 2011;11:1270-99. - 110.
Schwartz M, Shechter R. Systemic inflammatory cells fight off neurodegenerative disease. Nat Rev Neurol. 2010 Jul;6(7):405-10. - 111.
Nimmerjahn A, Kirchhoff F, Helmchen F. Resting microglial cells are highly dynamic surveillants of brain parenchyma in vivo. Science (New York, NY. 2005 May 27;308(5726):1314-8. - 112.
Hanisch UK, Kettenmann H. Microglia: active sensor and versatile effector cells in the normal and pathologic brain. Nature neuroscience. 2007 Nov;10(11):1387-94. - 113.
Lalancette-Hebert M, Gowing G, Simard A, Weng YC, Kriz J. Selective ablation of proliferating microglial cells exacerbates ischemic injury in the brain. J Neurosci. 2007 Mar 7;27(10):2596-605. - 114.
Smith JA, Das A, Ray SK, Banik NL. Role of pro-inflammatory cytokines released from microglia in neurodegenerative diseases. Brain research bulletin. 2012 Jan 4;87(1):10-20. - 115.
Shechter R, London A, Varol C, Raposo C, Cusimano M, Yovel G, et al. Infiltrating blood-derived macrophages are vital cells playing an anti-inflammatory role in recovery from spinal cord injury in mice. PLoS medicine. 2009 Jul;6(7):e1000113. - 116.
Engelhardt B, Ransohoff RM. The ins and outs of T-lymphocyte trafficking to the CNS: anatomical sites and molecular mechanisms. Trends in immunology. 2005 Sep;26(9):485-95. - 117.
Kivisakk P, Imitola J, Rasmussen S, Elyaman W, Zhu B, Ransohoff RM, et al. Localizing central nervous system immune surveillance: meningeal antigen-presenting cells activate T cells during experimental autoimmune encephalomyelitis. Annals of neurology. 2009 Apr;65(4):457-69. - 118.
Weller RO, Kida S, Zhang ET. Pathways of fluid drainage from the brain--morphological aspects and immunological significance in rat and man. Brain pathology (Zurich, Switzerland). 1992 Oct;2(4):277-84. - 119.
Carare RO, Bernardes-Silva M, Newman TA, Page AM, Nicoll JA, Perry VH, et al. Solutes, but not cells, drain from the brain parenchyma along basement membranes of capillaries and arteries: significance for cerebral amyloid angiopathy and neuroimmunology. Neuropathology and applied neurobiology. 2008 Apr;34(2):131-44. - 120.
Moalem G, Leibowitz-Amit R, Yoles E, Mor F, Cohen IR, Schwartz M. Autoimmune T cells protect neurons from secondary degeneration after central nervous system axotomy. Nature medicine. 1999 Jan;5(1):49-55. - 121.
Yoles E, Hauben E, Palgi O, Agranov E, Gothilf A, Cohen A, et al. Protective autoimmunity is a physiological response to CNS trauma. J Neurosci. 2001 Jun 1;21(11):3740-8. - 122.
Kipnis J, Mizrahi T, Yoles E, Ben-Nun A, Schwartz M. Myelin specific Th1 cells are necessary for post-traumatic protective autoimmunity. Journal of neuroimmunology. 2002 Sep;130(1-2):78-85. - 123.
Schwartz M, Hauben E. T cell-based therapeutic vaccination for spinal cord injury. Progress in brain research. 2002;137:401-6. - 124.
Hauben E, Butovsky O, Nevo U, Yoles E, Moalem G, Agranov E, et al. Passive or active immunization with myelin basic protein promotes recovery from spinal cord contusion. J Neurosci. 2000 Sep 1;20(17):6421-30. - 125.
Hauben E, Ibarra A, Mizrahi T, Barouch R, Agranov E, Schwartz M. Vaccination with a Nogo-A-derived peptide after incomplete spinal-cord injury promotes recovery via a T-cell-mediated neuroprotective response: comparison with other myelin antigens. Proceedings of the National Academy of Sciences of the United States of America. 2001 Dec 18;98(26):15173-8. - 126.
Hohlfeld R, Kerschensteiner M, Stadelmann C, Lassmann H, Wekerle H. The neuroprotective effect of inflammation: implications for the therapy of multiple sclerosis. Journal of neuroimmunology. 2000 Jul 24;107(2):161-6. - 127.
Eugster HP, Frei K, Kopf M, Lassmann H, Fontana A. IL-6-deficient mice resist myelin oligodendrocyte glycoprotein-induced autoimmune encephalomyelitis. European journal of immunology. 1998 Jul;28(7):2178-87. - 128.
Lacroix S, Chang L, Rose-John S, Tuszynski MH. Delivery of hyper-interleukin-6 to the injured spinal cord increases neutrophil and macrophage infiltration and inhibits axonal growth. The Journal of comparative neurology. 2002 Dec 16;454(3):213-28. - 129.
Klusman I, Schwab ME. Effects of pro-inflammatory cytokines in experimental spinal cord injury. Brain Res. 1997 Jul 11;762(1-2):173-84. - 130.
Whiteley W, Jackson C, Lewis S, Lowe G, Rumley A, Sandercock P, et al. Inflammatory markers and poor outcome after stroke: a prospective cohort study and systematic review of interleukin-6. PLoS medicine. 2009 Sep;6(9):e1000145. - 131.
Okada S, Nakamura M, Mikami Y, Shimazaki T, Mihara M, Ohsugi Y, et al. Blockade of interleukin-6 receptor suppresses reactive astrogliosis and ameliorates functional recovery in experimental spinal cord injury. Journal of neuroscience research. 2004 Apr 15;76(2):265-76. - 132.
Serada S, Fujimoto M, Mihara M, Koike N, Ohsugi Y, Nomura S, et al. IL-6 blockade inhibits the induction of myelin antigen-specific Th17 cells and Th1 cells in experimental autoimmune encephalomyelitis. Proceedings of the National Academy of Sciences of the United States of America. 2008 Jul 1;105(26):9041-6. - 133.
Gertz K, Kronenberg G, Kalin RE, Baldinger T, Werner C, Balkaya M, et al. Essential role of interleukin-6 in post-stroke angiogenesis. Brain. 2012 Jun;135(Pt 6):1964-80. - 134.
Reynolds BA, Weiss S. Generation of neurons and astrocytes from isolated cells of the adult mammalian central nervous system. Science (New York, NY. 1992 Mar 27;255(5052):1707-10. - 135.
Aboody KS, Brown A, Rainov NG, Bower KA, Liu S, Yang W, et al. Neural stem cells display extensive tropism for pathology in adult brain: evidence from intracranial gliomas. Proceedings of the National Academy of Sciences of the United States of America. 2000 Nov 7;97(23):12846-51. - 136.
Einstein O, Karussis D, Grigoriadis N, Mizrachi-Kol R, Reinhartz E, Abramsky O, et al. Intraventricular transplantation of neural precursor cell spheres attenuates acute experimental allergic encephalomyelitis. Molecular and cellular neurosciences. 2003 Dec;24(4):1074-82. - 137.
Jeong SW, Chu K, Jung KH, Kim SU, Kim M, Roh JK. Human neural stem cell transplantation promotes functional recovery in rats with experimental intracerebral hemorrhage. Stroke; a journal of cerebral circulation. 2003 Sep;34(9):2258-63. - 138.
Chu K, Kim M, Jung KH, Jeon D, Lee ST, Kim J, et al. Human neural stem cell transplantation reduces spontaneous recurrent seizures following pilocarpine-induced status epilepticus in adult rats. Brain Res. 2004 Oct 15;1023(2):213-21. - 139.
Einstein O, Grigoriadis N, Mizrachi-Kol R, Reinhartz E, Polyzoidou E, Lavon I, et al. Transplanted neural precursor cells reduce brain inflammation to attenuate chronic experimental autoimmune encephalomyelitis. Experimental neurology. 2006 Apr;198(2):275-84. - 140.
Bacigaluppi M, Pluchino S, Peruzzotti-Jametti L, Kilic E, Kilic U, Salani G, et al. Delayed post-ischaemic neuroprotection following systemic neural stem cell transplantation involves multiple mechanisms. Brain. 2009 Aug;132(Pt 8):2239-51. - 141.
Sun C, Zhang H, Li J, Huang H, Cheng H, Wang Y, et al. Modulation of the major histocompatibility complex by neural stem cell-derived neurotrophic factors used for regenerative therapy in a rat model of stroke. Journal of translational medicine. 2010;8:77. - 142.
Aharonowiz M, Einstein O, Fainstein N, Lassmann H, Reubinoff B, Ben-Hur T. Neuroprotective effect of transplanted human embryonic stem cell-derived neural precursors in an animal model of multiple sclerosis. PloS one. 2008;3(9):e3145. - 143.
Zlokovic BV. The blood-brain barrier in health and chronic neurodegenerative disorders. Neuron. 2008 Jan 24;57(2):178-201. - 144.
Wolburg H, Lippoldt A. Tight junctions of the blood-brain barrier: development, composition and regulation. Vascular pharmacology. 2002 Jun;38(6):323-37. - 145.
Begley DJ. ABC transporters and the blood-brain barrier. Current pharmaceutical design. 2004;10(12):1295-312. - 146.
Agrawal S, Anderson P, Durbeej M, van Rooijen N, Ivars F, Opdenakker G, et al. Dystroglycan is selectively cleaved at the parenchymal basement membrane at sites of leukocyte extravasation in experimental autoimmune encephalomyelitis. The Journal of experimental medicine. 2006 Apr 17;203(4):1007-19. - 147.
Engelhardt B, Ransohoff RM. Capture, crawl, cross: the T cell code to breach the blood-brain barriers. Trends in immunology. 2012 Aug 24. - 148.
Nag S, Venugopalan R, Stewart DJ. Increased caveolin-1 expression precedes decreased expression of occludin and claudin-5 during blood-brain barrier breakdown. Acta neuropathologica. 2007 Nov;114(5):459-69. - 149.
Readnower RD, Chavko M, Adeeb S, Conroy MD, Pauly JR, McCarron RM, et al. Increase in blood-brain barrier permeability, oxidative stress, and activated microglia in a rat model of blast-induced traumatic brain injury. Journal of neuroscience research. 2010 Dec;88(16):3530-9. - 150.
Jiao H, Wang Z, Liu Y, Wang P, Xue Y. Specific role of tight junction proteins claudin-5, occludin, and ZO-1 of the blood-brain barrier in a focal cerebral ischemic insult. J Mol Neurosci. 2011 Jun;44(2):130-9. - 151.
van Assema DM, Lubberink M, Bauer M, van der Flier WM, Schuit RC, Windhorst AD, et al. Blood-brain barrier P-glycoprotein function in Alzheimer's disease. Brain. 2012 Jan;135(Pt 1):181-9. - 152.
Errede M, Girolamo F, Ferrara G, Strippoli M, Morando S, Boldrin V, et al. Blood-Brain Barrier Alterations in the Cerebral Cortex in Experimental Autoimmune Encephalomyelitis. Journal of neuropathology and experimental neurology. 2012 Oct;71(10):840-54. - 153.
Hickey WF. Migration of hematogenous cells through the blood-brain barrier and the initiation of CNS inflammation. Brain pathology (Zurich, Switzerland). 1991 Jan;1(2):97-105. - 154.
Engelhardt B, Wolburg-Buchholz K, Wolburg H. Involvement of the choroid plexus in central nervous system inflammation. Microscopy research and technique. 2001 Jan 1;52(1):112-29. - 155.
Archambault AS, Sim J, Gimenez MA, Russell JH. Defining antigen-dependent stages of T cell migration from the blood to the central nervous system parenchyma. European journal of immunology. 2005 Apr;35(4):1076-85. - 156.
Butcher EC, Picker LJ. Lymphocyte homing and homeostasis. Science (New York, NY. 1996 Apr 5;272(5258):60-6. - 157.
Steiner O, Coisne C, Cecchelli R, Boscacci R, Deutsch U, Engelhardt B, et al. Differential roles for endothelial ICAM-1, ICAM-2, and VCAM-1 in shear-resistant T cell arrest, polarization, and directed crawling on blood-brain barrier endothelium. J Immunol. 2010 Oct 15;185(8):4846-55. - 158.
Yednock TA, Cannon C, Fritz LC, Sanchez-Madrid F, Steinman L, Karin N. Prevention of experimental autoimmune encephalomyelitis by antibodies against alpha 4 beta 1 integrin. Nature. 1992 Mar 5;356(6364):63-6. - 159.
Coisne C, Mao W, Engelhardt B. Cutting edge: Natalizumab blocks adhesion but not initial contact of human T cells to the blood-brain barrier in vivo in an animal model of multiple sclerosis. J Immunol. 2009 May 15;182(10):5909-13. - 160.
Man S, Tucky B, Cotleur A, Drazba J, Takeshita Y, Ransohoff RM. CXCL12-induced monocyte-endothelial interactions promote lymphocyte transmigration across an in vitro blood-brain barrier. Science translational medicine. 2012 Feb 1;4(119):119ra14. - 161.
Mahad D, Callahan MK, Williams KA, Ubogu EE, Kivisakk P, Tucky B, et al. Modulating CCR2 and CCL2 at the blood-brain barrier: relevance for multiple sclerosis pathogenesis. Brain. 2006 Jan;129(Pt 1):212-23. - 162.
Quandt J, Dorovini-Zis K. The beta chemokines CCL4 and CCL5 enhance adhesion of specific CD4+ T cell subsets to human brain endothelial cells. Journal of neuropathology and experimental neurology. 2004 Apr;63(4):350-62. - 163.
Alt C, Laschinger M, Engelhardt B. Functional expression of the lymphoid chemokines CCL19 (ELC) and CCL 21 (SLC) at the blood-brain barrier suggests their involvement in G-protein-dependent lymphocyte recruitment into the central nervous system during experimental autoimmune encephalomyelitis. European journal of immunology. 2002 Aug;32(8):2133-44. - 164.
Nourshargh S, Hordijk PL, Sixt M. Breaching multiple barriers: leukocyte motility through venular walls and the interstitium. Nat Rev Mol Cell Biol. 2010 May;11(5):366-78. - 165.
Carman CV. Mechanisms for transcellular diapedesis: probing and pathfinding by 'invadosome-like protrusions'. Journal of cell science. 2009 Sep 1;122(Pt 17):3025-35. - 166.
Lindvall O, Kokaia Z. Stem cell research in stroke: how far from the clinic? Stroke; a journal of cerebral circulation. 2011 Aug;42(8):2369-75. - 167.
Takeuchi H, Natsume A, Wakabayashi T, Aoshima C, Shimato S, Ito M, et al. Intravenously transplanted human neural stem cells migrate to the injured spinal cord in adult mice in an SDF-1- and HGF-dependent manner. Neuroscience letters. 2007 Oct 16;426(2):69-74. - 168.
Sandner B, Prang P, Rivera FJ, Aigner L, Blesch A, Weidner N. Neural stem cells for spinal cord repair. Cell and tissue research. 2012 Jul;349(1):349-62. - 169.
Shetty AK. Progress in cell grafting therapy for temporal lobe epilepsy. Neurotherapeutics. 2011 Oct;8(4):721-35. - 170.
Ahmed AU, Lesniak MS. Glioblastoma multiforme: can neural stem cells deliver the therapeutic payload and fulfill the clinical promise? Expert review of neurotherapeutics. 2011 Jun;11(6):775-7. - 171.
Carbajal KS, Schaumburg C, Strieter R, Kane J, Lane TE. Migration of engrafted neural stem cells is mediated by CXCL12 signaling through CXCR4 in a viral model of multiple sclerosis. Proceedings of the National Academy of Sciences of the United States of America. 2010 Jun 15;107(24):11068-73. - 172.
Andres RH, Choi R, Pendharkar AV, Gaeta X, Wang N, Nathan JK, et al. The CCR2/CCL2 interaction mediates the transendothelial recruitment of intravascularly delivered neural stem cells to the ischemic brain. Stroke; a journal of cerebral circulation. 2012 Oct;42(10):2923-31. - 173.
Peng H, Huang Y, Rose J, Erichsen D, Herek S, Fujii N, et al. Stromal cell-derived factor 1-mediated CXCR4 signaling in rat and human cortical neural progenitor cells. Journal of neuroscience research. 2004 Apr 1;76(1):35-50. - 174.
DeGrendele HC, Estess P, Siegelman MH. Requirement for CD44 in activated T cell extravasation into an inflammatory site. Science (New York, NY. 1997 Oct 24;278(5338):672-5. - 175.
Rampon C, Weiss N, Deboux C, Chaverot N, Miller F, Buchet D, et al. Molecular mechanism of systemic delivery of neural precursor cells to the brain: assembly of brain endothelial apical cups and control of transmigration by CD44. Stem cells (Dayton, Ohio). 2008 Jul;26(7):1673-82. - 176.
Carman CV, Springer TA. A transmigratory cup in leukocyte diapedesis both through individual vascular endothelial cells and between them. The Journal of cell biology. 2004 Oct 25;167(2):377-88. - 177.
Mueller A, Mahmoud NG, Strange PG. Diverse signalling by different chemokines through the chemokine receptor CCR5. Biochemical pharmacology. 2006 Sep 14;72(6):739-48. - 178.
Weiss N, Deboux C, Chaverot N, Miller F, Baron-Van Evercooren A, Couraud PO, et al. IL8 and CXCL13 are potent chemokines for the recruitment of human neural precursor cells across brain endothelial cells. Journal of neuroimmunology. 2010 Jun;223(1-2):131-4. - 179.
Jaderstad J, Jaderstad LM, Li J, Chintawar S, Salto C, Pandolfo M, et al. Communication via gap junctions underlies early functional and beneficial interactions between grafted neural stem cells and the host. Proceedings of the National Academy of Sciences of the United States of America. Mar 16;107(11):5184-9. - 180.
Gnecchi M, Zhang Z, Ni A, Dzau VJ. Paracrine mechanisms in adult stem cell signaling and therapy. Circulation research. 2008 Nov 21;103(11):1204-19. - 181.
Gerdes HH, Bukoreshtliev NV, Barroso JF. Tunneling nanotubes: a new route for the exchange of components between animal cells. FEBS letters. 2007 May 22;581(11):2194-201. - 182.
Thery C, Ostrowski M, Segura E. Membrane vesicles as conveyors of immune responses. Nat Rev Immunol. 2009 Aug;9(8):581-93. - 183.
Vultur A, Cao J, Arulanandam R, Turkson J, Jove R, Greer P, et al. Cell-to-cell adhesion modulates Stat3 activity in normal and breast carcinoma cells. Oncogene. 2004 Apr 8;23(15):2600-16. - 184.
Ben-Hur T, Ben-Menachem O, Furer V, Einstein O, Mizrachi-Kol R, Grigoriadis N. Effects of proinflammatory cytokines on the growth, fate, and motility of multipotential neural precursor cells. Molecular and cellular neurosciences. 2003 Nov;24(3):623-31. - 185.
Pluchino S, Zanotti L, Deleidi M, Martino G. Neural stem cells and their use as therapeutic tool in neurological disorders. Brain research. 2005 Apr;48(2):211-9. - 186.
Einstein O, Friedman-Levi Y, Grigoriadis N, Ben-Hur T. Transplanted neural precursors enhance host brain-derived myelin regeneration. J Neurosci. 2009 Dec 16;29(50):15694-702. - 187.
Chu K, Kim M, Park KI, Jeong SW, Park HK, Jung KH, et al. Human neural stem cells improve sensorimotor deficits in the adult rat brain with experimental focal ischemia. Brain Res. 2004 Aug 6;1016(2):145-53. - 188.
Martino G, Pluchino S. Neural stem cells: guardians of the brain. Nature cell biology. 2007 Sep;9(9):1031-4. - 189.
Capone C, Frigerio S, Fumagalli S, Gelati M, Principato MC, Storini C, et al. Neurosphere-derived cells exert a neuroprotective action by changing the ischemic microenvironment. PloS one. 2007;2(4):e373. - 190.
Jiang Q, Zhang ZG, Ding GL, Zhang L, Ewing JR, Wang L, et al. Investigation of neural progenitor cell induced angiogenesis after embolic stroke in rat using MRI. NeuroImage. 2005 Nov 15;28(3):698-707. - 191.
Lu P, Jones LL, Snyder EY, Tuszynski MH. Neural stem cells constitutively secrete neurotrophic factors and promote extensive host axonal growth after spinal cord injury. Experimental neurology. 2003 Jun;181(2):115-29. - 192.
Lee HJ, Kim KS, Park IH, Kim SU. Human neural stem cells over-expressing VEGF provide neuroprotection, angiogenesis and functional recovery in mouse stroke model. PloS one. 2007;2(1):e156. - 193.
Teng YD, Lavik EB, Qu X, Park KI, Ourednik J, Zurakowski D, et al. Functional recovery following traumatic spinal cord injury mediated by a unique polymer scaffold seeded with neural stem cells. Proceedings of the National Academy of Sciences of the United States of America. 2002 Mar 5;99(5):3024-9. - 194.
Kim SU, de Vellis J. Stem cell-based cell therapy in neurological diseases: a review. Journal of neuroscience research. 2009 Aug 1;87(10):2183-200. - 195.
Lin LF, Doherty DH, Lile JD, Bektesh S, Collins F. GDNF: a glial cell line-derived neurotrophic factor for midbrain dopaminergic neurons. Science (New York, NY. 1993 May 21;260(5111):1130-2. - 196.
Zhang WR, Sato K, Iwai M, Nagano I, Manabe Y, Abe K. Therapeutic time window of adenovirus-mediated GDNF gene transfer after transient middle cerebral artery occlusion in rat. Brain Res. 2002 Aug 23;947(1):140-5. - 197.
Kobayashi T, Ahlenius H, Thored P, Kobayashi R, Kokaia Z, Lindvall O. Intracerebral infusion of glial cell line-derived neurotrophic factor promotes striatal neurogenesis after stroke in adult rats. Stroke; a journal of cerebral circulation. 2006 Sep;37(9):2361-7. - 198.
Chen B, Gao XQ, Yang CX, Tan SK, Sun ZL, Yan NH, et al. Neuroprotective effect of grafting GDNF gene-modified neural stem cells on cerebral ischemia in rats. Brain Res. 2009 Aug 11;1284:1-11. - 199.
Nishimura Y, Natsume A, Ito M, Hara M, Motomura K, Fukuyama R, et al. Interferon-beta delivery via human neural stem cell abates glial scar formation in spinal cord injury. Cell transplantation. 2012 Oct 12. - 200.
Kim HM, Hwang DH, Lee JE, Kim SU, Kim BG. Ex vivo VEGF delivery by neural stem cells enhances proliferation of glial progenitors, angiogenesis, and tissue sparing after spinal cord injury. PloS one. 2009;4(3):e4987. - 201.
Lee HJ, Kim KS, Kim EJ, Choi HB, Lee KH, Park IH, et al. Brain transplantation of immortalized human neural stem cells promotes functional recovery in mouse intracerebral hemorrhage stroke model. Stem cells (Dayton, Ohio). 2007 May;25(5):1204-12. - 202.
Lee HJ, Lim IJ, Lee MC, Kim SU. Human neural stem cells genetically modified to overexpress brain-derived neurotrophic factor promote functional recovery and neuroprotection in a mouse stroke model. Journal of neuroscience research. 2010 Nov 15;88(15):3282-94. - 203.
Modo M, Stroemer RP, Tang E, Patel S, Hodges H. Effects of implantation site of stem cell grafts on behavioral recovery from stroke damage. Stroke; a journal of cerebral circulation. 2002 Sep;33(9):2270-8. - 204.
Zhang ZG, Jiang Q, Zhang R, Zhang L, Wang L, Zhang L, et al. Magnetic resonance imaging and neurosphere therapy of stroke in rat. Annals of neurology. 2003 Feb;53(2):259-63. - 205.
Kelly S, Bliss TM, Shah AK, Sun GH, Ma M, Foo WC, et al. Transplanted human fetal neural stem cells survive, migrate, and differentiate in ischemic rat cerebral cortex. Proceedings of the National Academy of Sciences of the United States of America. 2004 Aug 10;101(32):11839-44. - 206.
Roitberg BZ, Mangubat E, Chen EY, Sugaya K, Thulborn KR, Kordower JH, et al. Survival and early differentiation of human neural stem cells transplanted in a nonhuman primate model of stroke. Journal of neurosurgery. 2006 Jul;105(1):96-102. - 207.
Darsalia V, Kallur T, Kokaia Z. Survival, migration and neuronal differentiation of human fetal striatal and cortical neural stem cells grafted in stroke-damaged rat striatum. The European journal of neuroscience. 2007 Aug;26(3):605-14. - 208.
Ben-Hur T. Immunomodulation by neural stem cells. Journal of the neurological sciences. 2008 Feb 15;265(1-2):102-4. - 209.
Iadecola C, Anrather J. The immunology of stroke: from mechanisms to translation. Nature medicine. 2011 Jul;17(7):796-808. - 210.
Molina-Holgado F, Grencis R, Rothwell NJ. Actions of exogenous and endogenous IL-10 on glial responses to bacterial LPS/cytokines. Glia. 2001 Feb;33(2):97-106. - 211.
Croxford JL, Feldmann M, Chernajovsky Y, Baker D. Different therapeutic outcomes in experimental allergic encephalomyelitis dependent upon the mode of delivery of IL-10: a comparison of the effects of protein, adenoviral or retroviral IL-10 delivery into the central nervous system. J Immunol. 2001 Mar 15;166(6):4124-30. - 212.
Boyd ZS, Kriatchko A, Yang J, Agarwal N, Wax MB, Patil RV. Interleukin-10 receptor signaling through STAT-3 regulates the apoptosis of retinal ganglion cells in response to stress. Investigative ophthalmology & visual science. 2003 Dec;44(12):5206-11. - 213.
Yang J, Jiang Z, Fitzgerald DC, Ma C, Yu S, Li H, et al. Adult neural stem cells expressing IL-10 confer potent immunomodulation and remyelination in experimental autoimmune encephalitis. The Journal of clinical investigation. 2009 Dec;119(12):3678-91. - 214.
Fainstein N, Vaknin I, Einstein O, Zisman P, Ben Sasson SZ, Baniyash M, et al. Neural precursor cells inhibit multiple inflammatory signals. Molecular and cellular neurosciences. 2008 Nov;39(3):335-41. - 215.
Knight JC, Scharf EL, Mao-Draayer Y. Fas activation increases neural progenitor cell survival. Journal of neuroscience research. 2010 Mar;88(4):746-57. - 216.
Wang L, Shi J, van Ginkel FW, Lan L, Niemeyer G, Martin DR, et al. Neural stem/progenitor cells modulate immune responses by suppressing T lymphocytes with nitric oxide and prostaglandin E2. Experimental neurology. 2009 Mar;216(1):177-83. - 217.
Ricci-Vitiani L, Casalbore P, Petrucci G, Lauretti L, Montano N, Larocca LM, et al. Influence of local environment on the differentiation of neural stem cells engrafted onto the injured spinal cord. Neurological research. 2006 Jul;28(5):488-92. - 218.
Melzi R, Antonioli B, Mercalli A, Battaglia M, Valle A, Pluchino S, et al. Co-graft of allogeneic immune regulatory neural stem cells (NPC) and pancreatic islets mediates tolerance, while inducing NPC-derived tumors in mice. PloS one. 2010;5(4):e10357. - 219.
Flugel A, Berkowicz T, Ritter T, Labeur M, Jenne DE, Li Z, et al. Migratory activity and functional changes of green fluorescent effector cells before and during experimental autoimmune encephalomyelitis. Immunity. 2001 May;14(5):547-60. - 220.
de Vos AF, van Meurs M, Brok HP, Boven LA, Hintzen RQ, van der Valk P, et al. Transfer of central nervous system autoantigens and presentation in secondary lymphoid organs. J Immunol. 2002 Nov 15;169(10):5415-23. - 221.
Mohindru M, Kang B, Kim BS. Functional maturation of proteolipid protein(139-151)-specific Th1 cells in the central nervous system in experimental autoimmune encephalomyelitis. Journal of neuroimmunology. 2004 Oct;155(1-2):127-35. - 222.
Guzman R, Choi R, Gera A, De Los Angeles A, Andres RH, Steinberg GK. Intravascular cell replacement therapy for stroke. Neurosurgical focus. 2008;24(3-4):E15. - 223.
Takahashi K, Yasuhara T, Shingo T, Muraoka K, Kameda M, Takeuchi A, et al. Embryonic neural stem cells transplanted in middle cerebral artery occlusion model of rats demonstrated potent therapeutic effects, compared to adult neural stem cells. Brain Res. 2008 Oct 9;1234:172-82. - 224.
Karimi-Abdolrezaee S, Eftekharpour E, Wang J, Schut D, Fehlings MG. Synergistic effects of transplanted adult neural stem/progenitor cells, chondroitinase, and growth factors promote functional repair and plasticity of the chronically injured spinal cord. J Neurosci. 2010 Feb 3;30(5):1657-76. - 225.
Zhang P, Li J, Liu Y, Chen X, Lu H, Kang Q, et al. Human embryonic neural stem cell transplantation increases subventricular zone cell proliferation and promotes peri-infarct angiogenesis after focal cerebral ischemia. Neuropathology. 2011 Aug;31(4):384-91. - 226.
Ziv Y, Avidan H, Pluchino S, Martino G, Schwartz M. Synergy between immune cells and adult neural stem/progenitor cells promotes functional recovery from spinal cord injury. Proceedings of the National Academy of Sciences of the United States of America. 2006 Aug 29;103(35):13174-9. - 227.
Wu W, Chen X, Hu C, Li J, Yu Z, Cai W. Transplantation of neural stem cells expressing hypoxia-inducible factor-1alpha (HIF-1alpha) improves behavioral recovery in a rat stroke model. J Clin Neurosci. 2010 Jan;17(1):92-5. - 228.
Jin K, Sun Y, Xie L, Mao XO, Childs J, Peel A, et al. Comparison of ischemia-directed migration of neural precursor cells after intrastriatal, intraventricular, or intravenous transplantation in the rat. Neurobiology of disease. 2005 Mar;18(2):366-74. - 229.
Lundberg J, Le Blanc K, Soderman M, Andersson T, Holmin S. Endovascular transplantation of stem cells to the injured rat CNS. Neuroradiology. 2009 Oct;51(10):661-7. - 230.
Chu K, Park KI, Lee ST, Jung KH, Ko SY, Kang L, et al. Combined treatment of vascular endothelial growth factor and human neural stem cells in experimental focal cerebral ischemia. Neuroscience research. 2005 Dec;53(4):384-90. - 231.
Vendrame M, Cassady J, Newcomb J, Butler T, Pennypacker KR, Zigova T, et al. Infusion of human umbilical cord blood cells in a rat model of stroke dose-dependently rescues behavioral deficits and reduces infarct volume. Stroke; a journal of cerebral circulation. 2004 Oct;35(10):2390-5. - 232.
Doeppner TR, Ewert TA, Tonges L, Herz J, Zechariah A, ElAli A, et al. Transduction of neural precursor cells with TAT-heat shock protein 70 chaperone: therapeutic potential against ischemic stroke after intrastriatal and systemic transplantation. Stem cells (Dayton, Ohio). Jun;30(6):1297-310. - 233.
Walczak P, Zhang J, Gilad AA, Kedziorek DA, Ruiz-Cabello J, Young RG, et al. Dual-modality monitoring of targeted intraarterial delivery of mesenchymal stem cells after transient ischemia. Stroke; a journal of cerebral circulation. 2008 May;39(5):1569-74. - 234.
Li L, Jiang Q, Ding G, Zhang L, Zhang ZG, Li Q, et al. Effects of administration route on migration and distribution of neural progenitor cells transplanted into rats with focal cerebral ischemia, an MRI study. J Cereb Blood Flow Metab. Mar;30(3):653-62. - 235.
Sykova E, Homola A, Mazanec R, Lachmann H, Konradova SL, Kobylka P, et al. Autologous bone marrow transplantation in patients with subacute and chronic spinal cord injury. Cell transplantation. 2006;15(8-9):675-87. - 236.
Parr AM, Kulbatski I, Tator CH. Transplantation of adult rat spinal cord stem/progenitor cells for spinal cord injury. Journal of neurotrauma. 2007 May;24(5):835-45. - 237.
Cusimano M, Biziato D, Brambilla E, Donega M, Alfaro-Cervello C, Snider S, et al. Transplanted neural stem/precursor cells instruct phagocytes and reduce secondary tissue damage in the injured spinal cord. Brain. 2012 Feb;135(Pt 2):447-60. - 238.
Brundin P, Strecker RE, Londos E, Bjorklund A. Dopamine neurons grafted unilaterally to the nucleus accumbens affect drug-induced circling and locomotion. Experimental brain research Experimentelle Hirnforschung. 1987;69(1):183-94. - 239.
Freed CR, Greene PE, Breeze RE, Tsai WY, DuMouchel W, Kao R, et al. Transplantation of embryonic dopamine neurons for severe Parkinson's disease. The New England journal of medicine. 2001 Mar 8;344(10):710-9. - 240.
Olanow CW, Goetz CG, Kordower JH, Stoessl AJ, Sossi V, Brin MF, et al. A double-blind controlled trial of bilateral fetal nigral transplantation in Parkinson's disease. Annals of neurology. 2003 Sep;54(3):403-14. - 241.
Lindvall O. Why is it taking so long to develop clinically competitive stem cell therapies for CNS disorders? Cell stem cell. 2012 Jun 14;10(6):660-2. - 242.
Daley GQ. The promise and perils of stem cell therapeutics. Cell stem cell. 2012 Jun 14;10(6):740-9. - 243.
Hyun I, Lindvall O, Ahrlund-Richter L, Cattaneo E, Cavazzana-Calvo M, Cossu G, et al. New ISSCR guidelines underscore major principles for responsible translational stem cell research. Cell stem cell. 2008 Dec 4;3(6):607-9. - 244.
Aboody K, Capela A, Niazi N, Stern JH, Temple S. Translating stem cell studies to the clinic for CNS repair: current state of the art and the need for a Rosetta stone. Neuron. 2011 May 26;70(4):597-613. - 245.
Amariglio N, Hirshberg A, Scheithauer BW, Cohen Y, Loewenthal R, Trakhtenbrot L, et al. Donor-derived brain tumor following neural stem cell transplantation in an ataxia telangiectasia patient. PLoS medicine. 2009 Feb 17;6(2):e1000029. - 246.
Feng Z, Gao F. Stem cell challenges in the treatment of neurodegenerative disease. CNS neuroscience & therapeutics. 2012 Feb;18(2):142-8. - 247.
Steiner R, Huhn, S., Koch, T., Al-Uzri, A., Guillaime, D., Sutcliffe, T., Vogel, H., and Selden, N. CNS transplantation of purified human neural stem cells in infantile and late-infantile neuronal ceroid lipofuscinoses: Summary of the Phase I trial. Mol Genet Metab. 2010;99(S35). - 248.
Glass JD, Boulis NM, Johe K, Rutkove SB, Federici T, Polak M, et al. Lumbar intraspinal injection of neural stem cells in patients with amyotrophic lateral sclerosis: results of a phase I trial in 12 patients. Stem cells (Dayton, Ohio). 2012 Jun;30(6):1144-51. - 249.
Riley J, Federici T, Polak M, Kelly C, Glass J, Raore B, et al. Intraspinal stem cell transplantation in amyotrophic lateral sclerosis: a phase I safety trial, technical note, and lumbar safety outcomes. Neurosurgery. 2012 Aug;71(2):405-16; discussion 16. - 250.
Gupta N, Henry RG, Strober J, Kang SM, Lim DA, Bucci M, et al. Neural stem cell engraftment and myelination in the human brain. Science translational medicine. 2012 Oct 10;4(155):155ra37. - 251.
Pittenger MF, Mackay AM, Beck SC, Jaiswal RK, Douglas R, Mosca JD, et al. Multilineage potential of adult human mesenchymal stem cells. Science (New York, NY. 1999 Apr 2;284(5411):143-7. - 252.
Brazelton TR, Rossi FM, Keshet GI, Blau HM. From marrow to brain: expression of neuronal phenotypes in adult mice. Science (New York, NY. 2000 Dec 1;290(5497):1775-9. - 253.
Woodbury D, Schwarz EJ, Prockop DJ, Black IB. Adult rat and human bone marrow stromal cells differentiate into neurons. Journal of neuroscience research. 2000 Aug 15;61(4):364-70. - 254.
Sanchez-Ramos J, Song S, Cardozo-Pelaez F, Hazzi C, Stedeford T, Willing A, et al. Adult bone marrow stromal cells differentiate into neural cells in vitro. Experimental neurology. 2000 Aug;164(2):247-56. - 255.
Joyce N, Annett G, Wirthlin L, Olson S, Bauer G, Nolta JA. Mesenchymal stem cells for the treatment of neurodegenerative disease. Regenerative medicine. 2010 Nov;5(6):933-46. - 256.
Gao A, Peng Y, Deng Y, Qing H. Potential therapeutic applications of differentiated induced pluripotent stem cells (iPSCs) in the treatment of neurodegenerative diseases. Neuroscience. 2012 Oct 13. - 257.
Yamanaka S. Induced pluripotent stem cells: past, present, and future. Cell stem cell. 2012 Jun 14;10(6):678-84. - 258.
Harris VK, Yan QJ, Vyshkina T, Sahabi S, Liu X, Sadiq SA. Clinical and pathological effects of intrathecal injection of mesenchymal stem cell-derived neural progenitors in an experimental model of multiple sclerosis. Journal of the neurological sciences. 2012 Feb 15;313(1-2):167-77. - 259.
Yang J, Yan Y, Ma CG, Kang T, Zhang N, Gran B, et al. Accelerated and enhanced effect of CCR5-transduced bone marrow neural stem cells on autoimmune encephalomyelitis. Acta neuropathologica. 2012 Oct;124(4):491-503. - 260.
Sher F, Amor S, Gerritsen W, Baker D, Jackson SL, Boddeke E, et al. Intraventricularly injected Olig2-NSCs attenuate established relapsing-remitting EAE in mice. Cell transplantation. 2012 Mar 28. - 261.
Jiang Q, Zhang ZG, Ding GL, Silver B, Zhang L, Meng H, et al. MRI detects white matter reorganization after neural progenitor cell treatment of stroke. NeuroImage. 2006 Sep;32(3):1080-9.