1.Introduction
Type 1 diabetes mellitus is a classical autoimmune disease that results from immune-mediated destruction of pancreatic β-cells, primarily by T cells specific for β-cell antigens, leading to an absolute loss of insulin production(Gillard and Mathieu et al., 2011, van Belle et al. 2011). While the disease can become clinically apparent at any age, it commonly starts during childhood, and may appear later in adulthood in approximately 30-40% of affected individuals (Fändrich and Ungefroren, 2010, Knip, 1997). A combination of a genetic predisposition and autoimmune processes contribute to its development resulting in the gradual destruction of the insulin-producing β-cells. Daily insulin delivery by injection or pumpto manage hyperglycemia by no means represents a cure, often resulting in hypoglycemic episodes(Leitão et al.,2008, Noguchi, 2009).Current strategies to prevent or reverse diabetes are broadly based on the concepts of β-cell regeneration, replacementor protection from T-cell-mediated autoimmune destruction. While transplantation of both, whole pancreas as well as islets of Langerhans, is able to restore endocrine function and glucose homeostasis, islet transplantation offers added advantage in terms of being minimally invasive, preventing the incidence of severe hypoglycemic episodes and significantly lowering hypoglycemic unawareness, thereby improving the quality of life of the transplant recipients (Bretzel et al, 2007, Langer, 2010, Noguchi et al, 2009). Furthermore, manipulation of islets
2. Endocrine pancreas plasticityin physiological conditions
Although the formation of new islets in adults has primarily been demonstrated in response to pancreatic injury (eg. pancreatic duct ligation (PDL),β-cell ablation, partial pancreactomy etc.) and metabolic stress, there is ample evidence that β-cell replication from existing cells occurs throughout adulthood (Brennand et al, 2007, Dor et al., 2004, Levetan, 2010, Nir et al.,2007, Teta et al., 2007).This has been observed in several physiologic situations including amongst others,late pregnancy and obesity (Bernard-Kargar and Ktorza, 2001).In both these cases, increases in β-cell mass have been observed in response to insulin resistance and contribute to insulin oversecretion. Several studies have demonstrated a doubling of β-cell mass by the end of pregnancy that decreased progressively after parturition, a good illustration of the plasticity of the endocrine pancreas (Karnik et al., 2007, Rieck &Kaestner, 2010, Scaglia et al., 1995). As in pregnancy, euglycemia is maintained in obesity by increased insulin secretion, due not only to enhanced individual β-cell activity but alsoto β-cell growth.This increase in β-cell mass approximates 50% in obese, non-diabetic humans and seems consigned to β-cells, with α, and PP cell mass remaining unchanged(Bernard-Kargar &Ktorza, 2001). In addition to β-cell expansion based on self-duplication, there is evidence indicating the contribution of stem cell differentiation towards pancreatic β-cell maintenance (Bonner-Weir et al.,2004, 2006, 2010). The mechanism of islet regeneration remains controversial, making identification of β-cell progenitors and the in-depth understanding of the underlying mechanisms that trigger β-cell regeneration and expansion absolutely critical in order to apply this strategy in a clinical scenario.
2.1. β-cell progenitors within the pancreas
The exocrine tissue of the pancreas consists of acinar cells that secrete digestive enzymes into a branched ductal network that drains into the gastrointestinal tract. The endocrine cells consist of α, β, δ, ε, and PP cells that are grouped into islets of Langerhans and secrete insulin and other polypeptide hormones into the bloodstream. Numerous studies propose that in addition to replication of pre-existing β-cells, new β-cells can be produced from differentiated adult cells by interconversions amongst different pancreatic cell compartments as well as neogenesis from ductal and circulating progenitors and putative pancreatic stem cells (Bonner-Weir et al., 2004, 2006 , Gao et al., 2003, 2005, Granger and Kushner, 2009, Juhl et al., 2010, Kikugawa et al.,2009, Pittenger et al., 2009). However, while these strategies demonstrate the generation of insulin-producing cells, the major challenge encountered is the inability to generate sufficient amounts of ‘glucose-responsive’ β-cells to normalize hyperglycemia. True mature β-cells are defined by the ability to store large amounts of insulin and secrete it in a regulated manner in response to glucose challenge. This inability to mature into ‘glucose responsive’ β-cells may indicate an underlying inability to dedifferentiate completely to a progenitor state or to efficiently redifferentiate/transdifferentiate into β-cells. Therefore, while these studies outline the therapeutic potential of various regenerative strategies for β-cell expansion, they also highlight the importance of elucidating the underlying mechanisms required to form islets that perform similar to primary islets used in clinical applications.
2.1.1. Can β-cells be derived from the exocrine pancreas - the plasticity of the pancreatic acinar cell.
The exocrine tissue consisting of acinar and ductal cells, comprises approximately 95% of the adult pancreas and shares a common progenitor with endocrine cells, namely, pancreatic and duodenal homeobox 1(Pdx1)-expressing cells (Gu et al, 2002). Several studies indicate the capability of acinar cells to transdifferentiate into insulin positive cells (IPCs) either directly (Minami et al., 2005, Minami and Seino S, 2008) or via a ductal intermediate (Means et al., 2005), usually accompanied by a corresponding increase in functional β-cell mass. However, other studies using cultured, genetically marked, murine acinar cells indicate that these cells are only able to rapidly transdifferentiate into a amylase-negative, keratin 19- and mucin- antigens positive ductal phenotype and not into functional β-cells (Blaine et al., 2010). Using a mouse model that develops hyperplastic ducts containing IPCs in response to the transforming growth factor (TGF-α), Blaine et al. performed genetic lineage tracing experiments and demonstrated that hyperplastic ductal cells arose largely from acinar cells that transdifferentiated into ductal cells, while IPCs adjacent to acinar-derived ductal cells arose from pre-existing IPCs, suggesting that islet endocrine cells can intercalate into hyperplastic ducts as they develop. Thus, the apparent pancreatic plasticity resulted from both, the ability of acinar cells to transdifferentiate and of endocrine cells to reorganize in association with duct structures. Enthusiasm was further curbed by a Cre/loxP-based lineage tracing study suggesting that transdifferentiationof acinar to β-cells was unlikely a part ofthe normal β-cell turnover, even after injury such aspancreatectomy, ductal ligation, or pancreatitis (Desai et al., 2007).A recent time-specific lineage tracing study indicated that in mice containing genetically marked ductal and acinar cells carrying the mucin gene Muc1, theMuc1 positive cells only gave rise to β-cells and otherislet cells
2.1.2. The feasibility of β-cell regeneration through neogenesis from pancreatic ductal cells
Morphological observations of islet-ductal complexes comprising IPCs within or near adult pancreatic ducts in instances such as pregnancy or obesity, damageor disease, supported by various lineage-tracing studies in both human and rodent pancreata, suggest that differentiated pancreatic ductal cells act as
2.1.3. Replication of pre-existing β-cells: contribution to β-cell growth and regeneration
Following stimuli such as pregnancy, obesity, glucose infusion, manipulating growth-hormone expression, toxigene-mediated β-cell ablation and partial pancreatectomy, self-renewal by β-cell replication has emerged as a dominant mechanism for homeostatic maintenance of β-cell mass postnatally. This was elegantly demonstrated in a study by Melton and coworkers wherein, using lineage-tracing highly specific for β-cells (double transgenic mice bearing a tamoxifen-dependent Cre-recombinase construct under the control of a rat insulin promoter together with a reporter Z/AP gene) they showed that pre-existing terminally differentiated β-cells, rather than pluripotent stem cells, were the major source of new β-cells retaining significant proliferative capacity
2.1.4. Intra-Islet cells: role of α and δ cells inβ-cell regeneration
Several studies using the streptozotocin (STZ)-induced diabetic model have indicated the presence of intra-islet precursorcells with the potential to differentiate into neo islets/pancreatic β-cells upon appropriate stimulation (Banerjee & Bhonde, 2003, Guz et al., 2001, Kodama et al., 2005). While some studies indicate that administration of betacellulin improved STZ-induced hyperglycemia by promoting neoformation of β-cells mainly from somatostatin-positive islet cells (Li et al., 2003), others suggested that differentiation of multipotent nestin-positive stem cells isolated from adult pancreatic islets resulted in pancreatic endocrine, exocrine, and hepatic phenotypes
3. Stem cellsstrategies for β-cell regeneration
Obtaining a large source of β-cells for cellular therapy is a major challenge in the treatment of diabetes.While efforts thus far are based on deriving maximal utilization of all the unwanted tissue from the donor organ, the insignificant yield of differentiated β-cells, diminished function and insignificant amounts of insulin secreted both
3.1. Potential stem/progenitor cell sources for regeneration of insulin-producingβ-cells
3.1.1. Regeneration of β-cellsfrom embryonic stem cells
ESCs are pluripotent with high self-renewal potential and a limitless capacity of proliferation. There are several elegant strategies to induce β-cell generation from ESCs, based on sequential exposure of human ESCs to epigenetic signals that mimic
3.1.2. Islet-derived stem/precursor cells as a sourcefor insulin-producingβ-cell regeneration
While ESCshave tremendous potential in tissue engineering, their use is hampered by ethical, legal and scientific considerations. On the contrary, non-embryonic adult stem cells are multipotent and can be derived from several sources including bone marrow, umbilical cord tissue, amniotic fluid, fat tissue, skin, retina and central nervous system (Chhabra et al., 2009). The existence of putative pancreatic stem cells that express low amounts of insulin mRNA
3.1.3. Mesenchymal stem cells: stopping immune destruction and promoting β-cell regeneration
Whole bone marrowcontains a mixture of multiple types of stem cells, including BM-HSCs, BM-MSCs, endothelial progenitor cells (EPCs), multipotent adult progenitor cells and side population (SP) cells. BM-MSCs are plastic-adherent cells, typically expressing surface markers such as CD90, CD73, CD105, CD44 and CD29. They lack hematopoietic lineage markers such as CD34, CD45, CD14 and HLA-DR and can differentiate into cells of connective tissue lineages, including bone, fat, cartilage and muscle (Volarevik et al., 2011). These multipotent cells can be isolated and expanded with high efficiency in culture, are non-immunogenic and display immunosuppressive properties, for eg. inhibitingthe proliferation and function of major immune cell populations, including T cells, B cells and natural killer (NK) cells as well as modulating the activities of dendritic cells (DCs) and inducing regulatory T cells (Tregs) both
3.1.4. Umbilical cord blood (UCB)-derived stem cells: Potential therapeutic tool in β-cell regeneration
Human UCB-derivedstem cells represent a readily available source of MSCs and blood stem cells, both of which are potential sources of IPCs.hUCB-derived mononuclear cells (MNCs
3.1.5. Generation of insulin producing β-cells from induced pluripotent stem cells
Efforts to create pluripotent stem cells (iPSCs) that are molecularly and functionally similar to ES cells by reprogramming somatic cells have tremendous therapeutic potential.Fibroblasts, B lymphocytes, liver, stomach epithelial cells, UCBs, human fetal and newborn epithelia etc. have all been dedifferentiated by the stable genomic integration and overexpression of various combinations of defined transcription factors that participate in determining pluripotency in cells, for instance, oct3/4
3.2. Identifying stem cells with insulin-generating capability and tracking differentiated β-cells - the necessity for cellular markers.
Nestin, which is detected at low levels in human pancreatic tissue
As necessary as it is to have markers that identify progenitor cells amenable to the islet pathway, it is of equal importance to have makers that can rapidly identify the small number of successfully differentiated cells.With an aim to improve the efficiency of analyzing and sorting β-like insulin-producing cells from undifferentiated cells, Fukazawa
4. Role of transcription factors, growth factors and other cellular targets in enhancing β-cell differentiation and proliferation
Pancreatic development includes the generation of endoderm/gut endothelium, pancreatic differentiation, endocrine specification, and ultimately β-cell differentiation. Therefore,in order to efficiently promote β-cell differentiation and expansion, it is of vital importance to understand the factors that contribute to islet development. A number of signaling molecules and transcriptional regulators including Wnt, TGF-β, FGF, Notch and Hedgehog control various aspects of pancreas and endocrine cell development, proliferation and differentiation (Evans-Molina et al., 2009, Jun et al.,2010, Mishra et al., 2010). During development, it is the definitive endoderm that gives rise to the pancreas and genes such asWnt/β -catenin, Nodal, GATA4/6, FoxA, Sox17 and Mixamongst others participate in its formation. Pdx1 represents a marker of all pancreatic lineages (endocrine, exocrine and ductal), mediating β-cell function, growth, and proliferation and its inactivation prevents both islet and acinar cell differentiation. Pdx1 regulation is mediated by the IRS2/Akt/FoxO1 pathway, maintaining the ability of β-cells to proliferate and function properly. The notch signaling pathway in turn regulates the expansion and differentiation of the pancreatic progenitor cells by the expression of the ‘pro-endocrine’ gene, Ngn3. Transcription factors such as Pdx-1, Isl1, Ngn-3, Nkx2.2, Nkx6.1, NeuroD, Hlxβ9, Pax-4, MafA and Pax-6 all participate in islet differentiation with Ngn-3 acting as a key transcription factor required for islet cell development. Amongst these transcription factors, Pdx-1 is the most extensively utilized factor, driving both β-cell neogenesis as well as transdifferentation of pancreatic and extra-pancreatic cells into insulin-producing β-cells.
Various factors such as pregnancy, diabetogenic stimuli, growth factors such as HGF, a combination of epidermal growth factor (EGF) and gastrin, clonophylline, betacellulin, GLP-1or its long-lasting homolog exendin-4, members of the regenerating protein family such as Reg protein and INGAP can stimulate replication and proliferation of β-cells Jun et al.,2010, Mishra et al., 2010). Herein, we describe a few of the candidates that are used to attain maximal β-cell expansion by targeting pathways that augment mature β-cell proliferation, inhibit apoptosis, or simultaneously target both. Betacellulin is a member of the EGF family, and is known to increase the rate of nativeβ-cell self-duplication and enhance Pdx1-positive progenitor differentiation. It also induces proliferation and differentiation of insulinoma cells as well as converts an exocrine pancreatic cell line (AR42J) into an insulin-expressing phenotype when combined with activin A. This combined treatment potentiates β-cellself-duplication, ductal cell proliferation and δ-cell transdifferentation into new β-cells(Li et al., 2004).Similarly, activin promotes regeneration and differentiation of newly formed β-cells and together with growth differentiation factors participates in endocrine and exocrine lineage specification (Mishra et al., 2010). The incretin GLP-1 is produced from gut endocrine cells and has been shown to stimulate β-cell proliferation and neogenesis, inhibit β-cell apoptosisand have a profound effect on stimulating the release of insulin and suppression of glucagon from the pancreas. Rapid degradation by dipeptidyl peptidase IV (DPPIV) is responsible for its short biological half life. To overcome this, exenatide/Exendin-4 (AC2993), a long acting GLP-1 receptor (GLP-1R) agonistand other such stable GLP-1 analogsthat are resistant to degradation (liraglutide) and inhibitors of DPPIV(sitagliptin, vidaglitpin) are being investigated for treatment of diabetes (Geelhoed-Duijvestijn, 2007). Injections of GLP-1 or exendin-4, have been shown to increase the β-cell mass and improve hyperglycemia. Combination of GLP-1 and gastrin or EGF with gastrin restores β-cell massand inhibits autoimmune destruction of islet cells(Suarez-Pinzon et al., 2005, 2008). Administration of GLP-1 and gastrin restores normoglycemia by expanding β-cell mass and by downregulating immune response in autoimmune diabetic NOD mice. Diabetic immunodeficient NOD
β-cell proliferation is not only affected by factors that that induce expansion and differentiation, but is also tightly regulated by factors that impede/inhibit proliferation. Modulation of these factors therefore represents another alternative to enhance β-cell proliferation. For instancedeletion of p27Kip1, a key cell cycle inhibitor,increased the frequency of cellular replication and proliferationduring β-cell development and in the early neonatal period (Rachdi et al., 2006). Improved glucose tolerance and hyperinsulinemia associated with increased islet mass and proliferation was observed in p27-deficient mice, while induction of p27 expression resulted in severe glucose intolerance and reduced β-cell mass.Additionally, p27(-/-) mice showed decreased susceptibility to develop STZ-induced diabetes compared to controls that displayed elevated blood glucose levels(Georgia & Bhushan, 2006).In mice that developed STZ-induced diabetes,β-cells retained the ability to reenter the cell cycle at a far greater frequency in the p27(-/-) mice than in wild-type littermates. These studies establish the role of p27 in maintaining the quiescent state of newly differentiated β-cells generated during embryogenesis and indicatep27 as a key regulator in the establishment ofβ-cell mass and thus as an important target in regenerative therapies for diabetes. The success of this therapy however would depend on the ability of the cell to reactivate p27 to stop uncontrolled proliferation when metabolic demands for insulin are met. Apart from the risk of tumorigenesis, another drawback is the dedifferentiation and loss of insulin secretion commonly observed with repeated cell division of β-cells. Another key regulator of β-cell replication and expansion is glycogen synthase kinase-3 (GSK3), known tonegatively regulate insulin-mediated glycogen synthesis and glucose homeostasis (Rayasam et al 2009). Islet β-cell growth is controlled by endogenous GSK-3β activity via feedback inhibition of the insulin receptor/PI3K/Akt signalling pathway (Liu et al., 2010). In fact, glucose regulates steady-state levels of Pdx1 via the reciprocal actions of GSK3 and AKT kinases. Glucose-stimulated activation of AKT and inhibition of GSK3 decreased Pdx1 phosphorylation and delayed Pdx1 degradation demonstrating the important role of AKT-GSK3 axis in glucose modulation of Pdx1 stability (Humphrey et al., 2010). Similarly, direct pharmacologic inhibition of AKT destabilized, while inhibition of GSK3 increased Pdx1 protein stability.Increased expression and activity of GSK3 has been reported in type II diabetics and obese animal models and consequently, inhibitors of GSK3 have been demonstrated to have anti-diabetic effects
5. Prolonging long term survival, growth and function of β-cells in vitro
Despite the promising results of β-cell regenerative strategies, maintaining functional islet cells in long-term cultures with persistent insulin-secreting capabilities has proven challenging. The efficacy of various cell culture medium supplements in prolonging the survival and function of newly generated β-cells and enhancing their survival in long-term cultures for optimal expansion has been investigated. For e.g. human islets were cultured
insulin-secreting capabilities and transdifferentiation of β-cells. The efficacy of supplementing culture medium with growth hormone (GH) and prolactin (PRL) as well as co-culturing islets with fibroblastson stimulating long term cell proliferation as well as maintenance of insulin-synthesizing and -secreting capacity has also been investigated (
Gartner et al., 2006
). The supportive role of FGF2 in maintaining functional β-cells in culture has been previously demonstrated (Hardikar et al, 2003). FGF2, acting as a paracrine chemoattractant, stimulates clustering ofhuman islet-derived precursor cells, leading to islet-like cell aggregate formation necessary for the early stages of islet cell differentiation. An impressive protocol that combined bFGF, leukemia inhibitory factor (LIF), and bone morphogenetic protein-4 (BMP-4) proved that islet progenitor-like cells can be derived from islet-enriched fractions under serum-free defined culture conditions and induced to stably express high levels of Pdx1 and Notch pathway-associated genes, characteristic of embryonic pancreatic progenitor cells, for more than 6 months and maintain endodermal and pancreatic phenotypes.Unfortunately, insulin expression remained minimal.Based on the hypothesis that loss of the trophic support provided by surrounding non-endocrine pancreatic cell populations underlies the decline in β-cell mass and insulin secretory function observed in human islets following isolation and culture, the effect of co-culturing islets with ductal epithelial cells on islet structural integrity, β-cell mass and insulin secretory capacity was investigated (Murray et al., 2009).Ten days following isolation, the results showed that co-culturing islets with ductal epithelial cells led to preserved islet morphology and sustained β-cell function, with the presence of ductal epithelial cells beneficial for maintenance of β-cell mass. While reinforcing the possibility of maintaining islets in long-term cultures under appropriate cell culture conditions, the study highlights the necessity for further characterization of regulatory influences in order to realize the promise of its therapeutic potential.The importance of a three-dimensional (3D)environment incorporating extracellular matrix (ECM) components in providing favorable conditions to preserve human islets in long-term culture has also been demonstrated (Daoud et al., 2010). The loss of the ECM basement membrane during isolation contributes to eventual apoptosis
6. Hepatocytes and Xenogeneic islets - prospects and barriers as alternative sources
Reprogramming adult mammalian cells is an attractive approach for generating β-cells for replacement therapy. The common embryonic origin of liver and pancreas, the similarity of glucose-sensing systems, the large group of mutually expressed, specific transcription factors and the high level of developmental plasticity exhibited by adult human liver cells suggest that liver stem cells/hepatocytes are a potential source of pancreatic progenitor tissue. For instance, persistent expression of the Pdx1or its super-active form Pdx1-VP16 fusion protein in hepatic cells reprograms these cells into pancreatic β-cell precursors under condition of hyperglycemia or hepatic regeneration(Yang et al., 2006). Also, most hepatocytes of Ad-pdx-1-infected mice demonstrated positivity for Pdx-1 expression but expressed insulin and somatostatin only in STZ-treated or in STZ-treated plus partial hepatectomy mice vs. nontreated mice. A corresponding amelioration of hyperglycemia and along with expression of otherβ-cell markers like Glut2 glucokinasewas also observed(Kim etal., 2007). Similarly
Xenotransplantation using porcine cells, tissues, or organs may offer a potential solution for the shortage of allogeneic human organs (Denner et al., 2009). However, prior to their clinical use the hurdles of immunologic rejectionand risk of transmission of porcine pathogens needs to be overcome. Immunologic rejection in pig to primate xenotransplants consists of hyperacute rejection, acute humoral xenograft rejection (AHXR), acute cellular rejection and chronic rejection (Elliott et al., 2011). Hyperacute rejection results from the activation of the complement cascade that converts graft endothelial cells from an anticoagulant to a procoagulant phenotype.Apart from old world primates and man, all animals possess a cell surface antigen containing the epitope – Galα1–3Galβ1–4GlcNAc-R (‘α-gal’) to which humans have complement fixing antibodies that cause immediate rejection of animal cells when transplanted into humans.This can be prevented by reducing or inhibiting functional ‘α-gal’ activity using knock-out or knock-in procedures involving human alpha-1, 2-Ft or GnT-111 gene expression as well as by depletion of anti-pig antibodies or complement from serum. Adult porcine islets do not express Gal,reducing the antibody-mediated response to them after transplantation. However, fetal and neonatal islets do, and therefore the use GT knockout (α1,3-galactosyltransferase gene-knockout [GTKO]) pigs as the as the sources of all islets (fetal,neonatal and adult) is likely to be advantageous. Similarly, genetically-engineered pigs expressing thrombomodulin, tissue factor (TF) pathway inhibitor, CD39 or other mechanisms that prevent the coagulation dysfunction; or expressing human complement-regulatory proteins, CD46 [membrane cofactor protein] or CD55 [human decayacceleratingfactor] or CD59 or all three in pig islets (Ekser & Cooper, 2010); or expressing anticoagulant and antiplatelet molecules within the graft, may afford some protection (Cowan & d'Apice, 2008). Recombinant antithrombin III may also ameliorate both early graft damage and the development of systemic coagulation disorders in pig-to-human xenotransplantation. This strategy, in parallel with physical methods such as encasing islets in a protective layer, holds promise for reducing the thrombogenicity of pig islet xenografts. Ideally, genetically engineered GTKO/CD46pigs whose organs and cells are protected from the coagulation dysregulation that include modifications that prevent tissue factor activity on the graft and as well as activation of recipient platelets to express TF and initiate consumptive coagulopathy are required.AHXRor delayed xenograft rejection results from vascular endothelial cell activation and injury caused by the complement and cellular components of the innate immune system. There is increasing evidence that primate neutrophils, natural killer (NK) cells and macrophages play a role in AHXR, particularly seen following the development of a T-cell dependent elicited antibody response. Administration of CD39, heme oxygenase, thrombomodulin andTF pathway inhibitor have been used in its treatment (Cowan &d'Apice, 2008).Acute cellular rejectioninvolving T- and B-cell infiltration of the graft, T-cell activation and a T-cell-dependent elicited antibody response is believed to be stronger following xenotransplantation than the alloresponse. However,potent pharmacologic agents can largely prevent acute cellular rejection,which is therefore typically not observed with intense immunosuppressive drug regimens.Ekser et al. have obtained promising results using an immunosuppressive regimen consisting of induction therapy with antithymocyte globulin (ATG), and maintenance with an anti-CD154 monoclonal antibody and Mycophenolate mofetil (MMF) (Ekser & Cooper, 2010). A clinically acceptable regimen of ATG, CTLA4-Ig and MMF has also been found to be particularly effective in preventing T-cell activation in the xenotransplantation setting. Chronic rejection symptomsin the form of chronic vasculopathyhas been observed in pig to primate graft that survived for more than a few weeks, similar to the chronic rejection seen in long-surviving allografts.The risk of development of xenozoonosis in the recipient of a pig graft (particularly with regard to porcine endogenous retroviruses (PERV), is of concern. However, the stable long-term expression of anti-PERV siRNAs has been shown to be effective in knocking down PERV expression in cells.Breeding of designated pathogen-free pigs can prevent transmission of most porcine microbes (Dieckhoff et al., 2008, Ramsoondar et al., 2009).Another hurdle includes sensitization to pig antigens (e.g., swine leukocyte antigens), resulting in an increase in antibodies to HLA. Fortunately current evidence indicates that antibodies that develop after exposure to a pig xenograft are not crossreactive against HLA, and so would not be detrimental to a subsequent allograft (Cooper et al., 2004). However this does not preclude patients with a high level of HLA-reactive antibodies who may still be at greater risk of rejecting a pig xenograft.Clinical attempts to treat type 1 diabetes with implanted porcine islets are underway and showing promising early results. Immune-suppression, sertoli cell co-transplantation and intraperitoneal implantation of micro-encapsulated neonatal islets have been tried in type 1 diabetic humans with some clinical benefit reported from the latter two. In a very recent study by Elliot et al using the microencapsulation technique, transitory insulin independence of several months duration was observed (Elliott et al., 2011). Interestingly, the treatment appeared to significantly decrease severe hypoglycemic episodes and reduce/abolish hypoglycemic unawareness episodes, even in the absence of insulin independence. Evidence of xenosis in the xenotransplants recipients though diligently sought could not befound, given the credentials of the designated pathogen free source herd used. Virus safety in xenotransplantation is a fast-developing field, and new findings may contribute to improved outcomes.
7. The role of gene therapy in enhancing islet function
While not routinely achieving long-term normoglycemia, islet transplantation does afford substantial benefits in the form of reduced incidences of debilitating hypoglycemic episodes and hypoglycemic unawareness, lower daily insulin requirements, a detectable level of c-peptide, andimproved A1c levels.The major limitation of this procedure is the inadequate numbers of donor islets available for transplantation. While we have discussed the various approaches to generate and expand islet β-cells, strategies aimed at increasing the efficiency
of islet function in terms of insulin synthesis and secretionare of equal importance since it would reduce the number of islets required for restoring glucose homeostasis following transplantation. Towards this end, gene therapy has been proposed.A simple conceptual approach to create hyper-functional islets would consist of augmentation of the regulated insulin secretory capacity of an islet graft by insulin gene transfer to the graft before transplantation. Deng etal. demonstrated that Ad-Ins-transduced islets showed superior function in terms of insulin production and secretion as well as GSIS (Deng et al., 2003).The amount of basal insulin secretion and the overall pattern of insulin secretion from the Ad-Ins-transduced islet appeared completely normal and following transplantation, recipients remained normoglycemic for more than 100 days without evidence of deterioration in graft function. Histological examination of the grafts showed normal islet graft morphology and the presence of abundant insulin. Interestingly, although transfer of an exogenous insulin gene under control of a powerful viral promoter forcedβ-cells to produce more insulin, transplantation of a large number of these islets did not result in recipient hypoglycemia, confirming that Ad-Ins-transduced islets secreted insulin in an appropriately regulated manner. Furthermore, only 25% of the previously needed islet mass was required to reverse diabetes suggesting that four times as many transplants could be performed compared to the unmodified islets.The use of insulin promoter instead of the CMV promoter would have further increased insulin secretion from Ad-Ins-transduced islets in response to changes in blood glucose concentrationin a highly regulated manner. Furthermore, the islet gene transfer was carried out using an islet-virus co-culture technique resulting in only partial islet transduction (37% expressing transgene). The authors speculate that Ad-Ins-vector delivery by vascular perfusion of the pancreas, would achieve maximal transgene expression in nearly all islet endocrine cells making it possible to reverse diabetes with islets isolated from only a portion of the perfused pancreas. The consideration of live donors as a source of islets is not unreasonable since laparoscopic-assisted distal pancreatectomy and nephrectomy has been performed successfully in three living donors since December 2007 with minimal peri-operative mortality and acceptable morbidity and the distal pancreas has been used successfully as a segmental vascularised graft (Gruessner et al., 2001, Maruyama et al., 2010, Tan et al., 2005). The uneventful postoperative course and normal functioning of the grafts indicate the technique to be minimally invasive and safe, making the consideration of live related donors for providing islet tissue supply a reasonable solution to the problem of organ shortage until other strategies such as stem-cell derivation of β-cells or xenogeneic sources of islet tissue can be refined. In order to avoid the potential side effects associated with the use of viral vectors, Chen et al. demonstrated targeting of plasmid DNA to the pancreas
8. Increasing post-transplant islet survival - an ummunological approach
From 1999 to 2007, clinical islet transplantation at established centers has resulted in a remarkable reduction in theoccurrence of severe hypoglycemia and a success rate of 70% in achievement of insulin independence persisting for 2 years or more in 50% of those achieving insulin independence, or 35% of all islet alone graft recipients. These results are consistent throughout the 8 years of follow-up included in the Collaborative Islet Transplant Registry (Alejandro et al., 2008). Approximately 60% of transplanted islets are lost in the first 10–14 days post-transplantation (Evgenov et al., 2006) most likely due to local hypoxic injury caused by lack of islet vascularity and the deleterious effects of the innate immune response which induces apoptosis, necrosis, coagulation, and complement fixation (Huang et al., 2008). This non-specific inflammatory response results in the production and release of a number of proinflammatory cytokines (e.g. TNF-α, IL-1β, IFN-γ) thatfurther enhance local inflammatory activity, stimulate adaptive immunity and exert deleterious effects on islet β-cell function by inducing apoptosis and cell death (Donath et al., 2008). Islet cellsthemselves,upon transplantation, possess the ability to receive signals that result in the activation of multiple signaling factors including STAT1, AP-1 and NFkB(Eizirik &Mandrup-Poulsen, 2001). Lisofyllinehas demonstrated significant abilityin down-regulating the systemic inflammatory response by interference with STAT4 signaling resulting in improved islet transplant survival (Yang et al., 2005).Suppression of these pathways has also been attempted through gene therapy approaches(Moore et al., 2006). Currently, islet-directed anti-inflammatory therapy mostly focuses on Toll-like receptor (TLR) signaling pathways within the islets (Huang et al., 2008).Fortifying the β-cell with protection against islet-destructive cytokines represents another avenue to defend against the immune response. For instance, adenoviral transduction of islet cells with a construct expressing IRAP, theinterleukin-1 receptor antagonist protein, resulted in improved islet survival and replication caused mainly due to interference in the activation of the IL-1mediated apoptotic pathway (Tellez et al., 2005). Other strategies that overexpress anti-apoptotic proteins such as the TNF-α inducible transcription factor A20 or bcl-2 demonstrate beneficial effects on islet survival.While immunomodulatory therapies (e.g.monoclonal antibody therapies, CTLA4Ig, anti-thymocyte globulin (ATG), IL-1 receptor antagonist therapy, cellular therapies, etc.) act by either providing immunoregulatory cytokines such as IL-4, IL-10 or TGF-β or by altering the balance between TH1 and TH2 cells,immunosuppressive regimens act by either suppressing the immune response by binding to specific cytoplasmic proteins that inhibit IL-2 secretion and subsequent T cell expansion (Calcineurin inhibitors CNIs; cyclosporine and tacrolimus) or by suppressing IL-2R signaling thereby inactivating T cells (sirolimus) or by suppressing cell division of lymphocytes (Azathioprine) (Winter & Schatz, 2003).Therefore, combinations of CNIs and steroid-sparing or -free regimens with drugs that demonstrate powerful immunosuppressive/anitinflammatory potency in the absence of nephrotoxicity and diabetogenicity are being investigated. A triple therapy approach that combined rapamycin plus agonist IL-2-related and antagonist-type mutant IL-15-related Ig cytolytic fusion proteins(IL-2.Ig and mutIL-15.Ig)demonstrated a striking ability to reverse diabetes and ameliorate inflammation,mainly due to augmentation of the pro-regulatory effects of IL-2 and inhibition of the proinflammatory mediator IL-15, creating a favorable balance between regulation and inflammation (Koulmanda et al., 2007). Currently, targeted antigen specific/non-specific and antibody-specific immunotherapies that readjust the underlying immunologic imbalance in order to stop or reverse the β-cell-specific autoimmune and inflammatory process within islets and maintain immune tolerance are being combined with islet regeneration therapies in a variety of clinical studies and hold great therapeutic promise for islet transplantation outcomes. These include islet transplantation followed with ATG /alemtuzumab (Campath -1H, monoclonal anti CD52 Ab) / hOKT3 γ induction therapy / anti-CD25 (daclizumab) induction therapy along witha sirolimus-based, prednisone-free maintenance regimen in combination with MMF and low Tacrolimus (Bellin et al., 2008, Gillard et al., 2010, Herold et al. 2005, Magliocca & Knechtle, 2006). Short term ATG treatment in T1DM of recent onset has been shown to contribute to the preservation of residual C-peptide production and to lower insulin requirement following diagnosis. Because Tregs strongly suppress the immune response in syngeneic islet transplantation and improve graft survival and function, several approaches are now emerging to induce/increase host Tregs activity in the transplant setting, including amongst others, systemic TGF-β1 therapy (W. Zhang et al., 2010).Otherβ-cell therapies currently in Phase II or III stages of development include Otelixizumab (anti-CD3), Teplizumab(anti-CD3), rituximab(anti-CD20), abatacept (CTLA4Ig), DiapPep 277(heat shock protein) and GAD, Oral Insulin amongst others. Parenteral administration of anti-CD3 mAb for transplantation in humans and for treatment of autoimmune diabetes has been approved.Various combination interventions such as costimulatory blockade with anti-CD4 monoclonal antibodies plus CTLA4Ig and ATG plus CTLA4Ig (Suzuki et al., 2010) as well as combinations of anti-lymphocyte serum (ALS) plus anti-CD3mAb are under investigation. As discussed earlier, GLP-1R agonists like exendin-4 stimulate β-cell proliferation and neogenesis and inhibit β-cell apoptosis while DPPIV inhibitors increase cell insulin content, and therefore are of immense benefit in the above mentioned combination therapies (GLP-1 agonists plus anti-CD3mAB, anti-CD3mAb plus exendin-4, ALS plus exendin-4 etc.) for preserving and expanding β-cell mass following transplantation. Other avenues include encapsulating islets with nanofibre scaffolds or biomatrices synthesized to contain immunosuppressive drugs or drugs that stimulate vasculogenesis/angiogenesis as well as‘bioartificial pancreas’. Stem cells of embryonic, mesenchymal (prochymal), cord blood and haematopoietic (and some neural stem cell) origin, besides their use for regenerative purposes, also possess potent immunomodulatory functions and have great therapeutic potential in increasing post-transplant survival either alone or in combination with the therapies discussed above.Thus, depending on the time of the therapeutic intervention, various immunological approaches may be employed as monotherapy or in combination with short-term tolerance promoting immunoregulatory drugs or drugs promoting preservation, differentiation, expansion or insulin secretion to increase the functional and longitudinal survival of islets post-transplantation. However, while assessing the efficacy of these therapies, it is important to keep in mind that both CNIsas well as corticosteroids contribute toan increased risk of developing post-transplant hyperglycemia and to the differential diagnosis of graft rejection (Cantarovich &Vistoli, 2011, Egidi et al., 2005).Conducting largerandomized trials to establish guidelines that minimize the adverse effects of immunosuppressive regimens for pancreas transplantation will be useful in achieving long-term, functional graft survival.
9. Conclusion
The possibility of transplanting sufficient quantities of functional, viable islets to induce life-long euglycemia depends on the successful outcomes of the various strategies discussed herein, namely regeneration of β-cells utilizing every kind cell from the pancreas, stem cells as well as cells from alternate sources, preserving and expanding their number
References
- 1.
Aguayo-Mazzucato C. Bonner-Weir S. 2010 Stem cell therapy for type 1 diabetes mellitus . ,6 3 139 148 ,1759-5037 - 2.
Agudo J. Ayuso E. Jimenez V. Salavert A. Casellas A. Tafuro S. Haurigot V. Ruberte J. Segovia J. C. Bueren J. Bosch F. 2008 IGF-I mediates regeneration of endocrine pancreas by increasing beta cell replication through cell cycle protein modulation in mice . ,51 10 1862 1872 ,0001-2186 X. - 3.
Alejandro R. Barton F. B. Hering B. J. Wease S. CollaborativeIslet.TransplantRegistry.Investigators 2008 2008 Update from the Collaborative Islet Transplant Registry.,86 12 1783 1788 ,1534-6080 - 4.
Baeyens L. Bouwens L. 2008 ).Can beta-cells be derived from exocrine pancreas?10 Suppl. 4,170 178 ,1463-1326 - 5.
Baeyens L. De Breuck S. Lardon J. Mfopou J. K. Rooman I. Bouwens L. 2005 In vitro generation of insulin-producing beta cells from adult exocrine pancreatic cells.,48 1 49 57 ,0001-2186 X. - 6.
Baharvand H. Jafary H. Massumi M. Ashtiani S. K. 2006 Generation of insulin-secreting cells from human embryonic stem cells.,48 5 No.323-332,0012-1592 - 7.
Baker M. 2009 Stem cells: Fast and furious . ,458 7241 962 965 ,1476-4687 - 8.
Bai M. D. Rong L. Q. Wang L. C. Xu H. Fan R. F. Wang P. Chen X. P. Shi L. B. Peng S. Y. 2008 Experimental study on operative methods of pancreaticojejunostomy with reference to anastomotic patency and postoperative pancreatic exocrine function.,14 3 441 447 ,1007-9327 - 9.
Banerjee M. Bhonde R. R. 2003 Islet generation from intra islet precursor cells of diabetic pancreas: in vitro studies depicting in vivo differentiation.,4 4 137 145 ,1590-8577 - 10.
Baroukh N. Ravier M. A. Loder M. K. Hill E. V. Bounacer A. Scharfmann R. Rutter G. A. Van Obberghen E. 2007 MicroRNA-124a regulates Foxa2 expression and intracellular signaling in pancreatic beta-cell lines.,282 27 19575 19588 ,0021-9258 - 11.
Bellin M. D. Kandaswamy R. Parkey J. Zhang H. J. Liu B. Ihm S. H. Ansite J. D. Witson J. Bansal-Pakala P. Balamurugan A. N. Papas K. K. Sutherland D. E. Moran A. Hering B. J. 2008 ).Prolonged insulin independence after islet allotransplants in recipients with type 1 diabetes. ,8 8 11 2463 2470 ,1600-6143 - 12.
Bernard-Kargar C. Ktorza A. 2001 Endocrine pancreas plasticity under physiological and pathological conditions.50 Suppl.1,S30 S35 ,0012-1797 - 13.
Blaine S. A. Ray K. C. Anunobi R. Gannon M. A. Washington M. K. Means A. L. 2010 Adult pancreatic acinar cells give rise to ducts but not endocrine cells in response to growth factor signaling.,137 14 2289 2296 ,1477-9129 - 14.
Bonner-Weir S. Deery D. Leahy J. L. Weir G. C. 1989 Compensatory growth of pancreatic beta-cells in adult rats after short-term glucose infusion. ,38 1 49 53 ,0012-1797 - 15.
Bonner-Weir S. Inada A. Yatoh S. Li W. C. Aye T. Toschi E. Sharma A. 2008 Transdifferentiation of pancreatic ductal cells to endocrine beta-cells.,36 Pt 3,353 356 ,0300-5127 - 16.
Bonner-Weir S. Li W. C. Ouziel-Yahalom L. Guo L. Weir G. C. Sharma A. 2010 Beta-cell growth and regeneration: replication is only part of the story.,59 10 2340 2348 .0193-9327 X. - 17.
Bonner-Weir S. Sharma A. 2006 Are there pancreatic progenitor cells from which new islets form after birth? ,2 5 240 241 ,1745-8366 - 18.
Bonner-Weir S. Toschi E. Inada A. Reitz P. Fonseca S. Y. Aye T. Sharma A. 2004 The pancreatic ductal epithelium serves as a potential pool of progenitor cells.Pediatr Diabetes,5 Suppl. 2,16 22 ,0139-9543 X. - 19.
Bonner-Weir S. Weir G. C. 2005 New sources of pancreatic beta-cells.,23 7 857 861 ,1087-0156 - 20.
Borowiak M. Maehr R. Chen S. Chen A. E. Tang W. Fox J. L. Schreiber S. L. Melton D. A. 2009 ).Small molecules efficiently direct endodermal differentiation of mouse and human embryonic stem cells.,4 4 4 348 358 ,1875-9777 - 21.
Boumaza I. Srinivasan S. Witt W. T. Feghali-Bostwick C. Dai Y. Garcia-Ocana A. Feili-Hariri M. 2009 Autologous bone marrow-derived rat mesenchymal stem cells promote PDX-1 and insulin expression in the islets, alter T cell cytokine pattern and preserve regulatory T cells in the periphery and induce sustained normoglycemia .,32 1 33 42 ,0896-8411 - 22.
Brennand K. Huangfu D. Melton D. 2007 All beta cells contribute equally to islet growth and maintenance. 5 7 e163 1545-7885 - 23.
Brennand K. Melton D. 2009 Slow and steady is the key to beta-cell replication.,13 3 472 487 ,1582-4934 - 24.
Bretzel R. G. Jahr H. Eckhard M. Martin I. Winter D. Brendel M. D. 2007 Islet cell transplantation today .392 3 239 253 ,1435-2443 - 25.
Butler A. E. Cao-Minh L. Galasso R. Rizza R. A. Corradin A. Cobelli C. Butler P. C. 2010 ).Adaptive changes in pancreatic beta cell fractional area and beta cell turnover in human pregnancy .53 53 10 2167 2176 ,1432-0428 - 26.
Butler A. E. Janson J. Bonner-Weir S. Ritzel R. Rizza R. A. Butler P. C. 2003 Beta-cell deficit and increased beta-cell apoptosis in humans with type 2 diabetes. ,52 1 102 110 ,0012-1797 - 27.
Cantarovich D. Vistoli F. 2009 Minimization protocols in pancreas transplantation.,22 1 61 68 ,0934-0874 - 28.
Carlotti F. Zaldumbide A. Loomans C. J. van Rossenberg E. Engelse M. de Koning E. J. Hoeben R. C. 2010 Isolated human islets contain a distinct population of mesenchymal stem cells. ,2 3 164 173 ,1938-2022 - 29.
Chhabra P. Mirmira R. G. Brayman K. L. 2009 Regenerative medicine and tissue engineering: contribution of stem cells in organ transplantation.14 1 46 50 ,1531-7013 - 30.
Chen B. Z. Yu S. L. Singh S. Kao L. P. Tsai Z. Y. Yang P. C. Chen B. H. Shoei-Lung Li. S. 2011 Identification of microRNAs expressed highly in pancreatic islet-like cell clusters differentiated from human embryonic stem cells.,35 1 29 37 ,1095-8355 - 31.
Chen L. B. Jiang X. B. Yang L. 2004 Differentiation of rat marrow mesenchymal stem cells into pancreatic islet beta-cells.,10 20 3016 3020 ,1007-9327 - 32.
Chen S. Borowiak M. Fox J. L. Maehr R. Osafune K. Davidow L. Lam K. Peng L. F. Schreiber S. L. Rubin L. L. Melton D. 2009 A small molecule that directs differentiation of human ESCs into the pancreatic lineage.,5 4 258 265 ,1552-4469 - 33.
Chen S. Shimoda M. Wang M. Y. Ding J. Noguchi H. Matsumoto S. Grayburn P. A. 2010 Regeneration of pancreatic islets in vivo by ultrasound-targeted gene therapy. ,17 11 1411 1420 ,1476-5462 - 34.
Chung C. H. Hao E. Piran R. Keinan E. Levine F. 2010 Pancreatic beta-cell neogenesis by direct conversion from mature alpha-cells.28 9 1630 1638 ,1549-4918 - 35.
Chung C. H. Levine F. 2010 Adult pancreatic alpha-cells: a new source of cells for beta-cell regeneration.7 2 124 131 ,1614-0575 - 36.
Collombat P. Xu X. Ravassard P. Sosa-Pineda B. Dussaud S. Billestrup N. Madsen O. D. Serup P. Heimberg H. Mansouri A. 2009 The ectopic expression of Pax4 in the mouse pancreas converts progenitor cells into alpha and subsequently beta 138 3 449 462 ,1097-4172 - 37.
Cooper D. K. C., Tseng Y. L., Saidman S. L., 2004 Alloantibody and xenoantibody cross-reactivity in transplantation. ,77 1-5,0041-1337 - 38.
Correa-Medina M. Bravo-Egana V. Rosero S. Ricordi C. Edlund H. Diez J. Pastori R. L. 2009 MicroRNA miR-7 is preferentially expressed in endocrine cells of the developing and adult human pancreas . ,9 4 193 199 ,0156-7133 X. - 39.
Cowan P.J. d’Apice A.J. 2008 )The coagulation barrier in xenotransplantation: incompatibilities and strategies to overcome them . ,13 13 2 178 183 ,1531-7013 - 40.
D’Amour K. A. Bang A. G. Eliazer S. Kelly O. G. Agulnick A. D. Smart N. G. Moorman M.A. Kroon E. Carpenter M. K. Baetge E.E. 2006 Production of pancreatic hormone-expressing endocrine cells from human embryonic stem cells.24 11 1392 1401 ,1087-0156 - 41.
Daoud J. T. Petropavlovskaia M. S. Patapas J. M. Degrandpré C. E. Diraddo R. W. Rosenberg L. Tabrizian M. 2011 Long-term in vitro human pancreatic islet culture using three-dimensional microfabricated scaffolds. Biomaterials,32 6 1536 1542 ,1878-5905 - 42.
Daoud J. T. MS Petropavlovskaia Patapas. J. M. CE Degrandpré Diraddo. R. W. Rosenberg L. Tabrizian M. 2011 Long-term in vitro human pancreatic islet culture using three-dimensional microfabricated scaffolds . ,32 6 1536 1542 ,1878-5905 - 43.
Deng S. Vatamaniuk M. Lian M. M. Doliba N. Wang J. Bell E. Wolf B. Raper S. Matschinsky F. M. Markmann J. F. 2003 Insulin gene transfer enhances the function of human islet grafts. Diabetologia,46 3 386 393 ,0001-2186X . - 44.
Denner J. Schuurman H. J. Patience C. 2009 The International Xenotransplantation Association consensus statement on conditions for undertaking clinical trials of porcine islet products in type 1 diabetes--chapter 5: Strategies to prevent transmission of porcine endogenous retroviruses. . ,16 4 239 248 ,1399-3089 - 45.
Desai B. M. Oliver-Krasinski J. De Leon D. D. Farzad C. Hong N. Leach S. D. Stoffers D. A. 2007 Preexisting pancreatic acinar cells contribute to acinar cell, but not islet beta cell, regeneration.J Clin Invest,117 4 971 977 ,0021-9738 - 46.
Dieckhoff B. Petersen B. Kues W. A. Kurth R. Niemann H. Denner J. 2008 Knockdown of porcine endogenous retrovirus (PERV) expression by PERV-specific siRNA in transgenic pigs. ,15 36 45 ,1399-3089 - 47.
Donath M. Y. Størling J. Berchtold L. A. Billestrup N. Mandrup-Poulsen T. 2008 Cytokines and beta-cell biology: from concept to clinical translation. ,3 334 350 ,0016-3769 X. - 48.
Dor Y. Brown J. Martinez O. I. Melton D. A. 2004 Adult pancreatic beta-cells are formed by self-duplication rather than stem-cell differentiation.429 6987 41 46 ,1476-4687 - 49.
Dor Y. Melton D. A. 2004 How important are adult stem cells for tissue maintenance?3 9 1104 1106 ,1551-4005 - 50.
Egidi F. M. 2005 Management of hyperglycaemia after pancreas transplantation: are new immunosuppressants the answer? Drugs,65 2 153 166 ,0012-6667 - 51.
Eizirik D. L. Mandrup-Poulsen T. 2001 A choice of death--the signal-transduction of immune-mediated beta-cell apoptosis.44 12 2115 2133 ,0001-2186 X - 52.
Ekser B. Cooper D. K. 2010 Overcoming the barriers to xenotransplantation: prospects for the future . ,6 2 219 230 ,0174-4666 X. - 53.
Elliott R. B. 2011 Towards Zenotransplantation of pig islets in the clinic.Curr Opin Organ Transplant,16 2 195 200 ,1531-7013 - 54.
Evans-Molina C. Vestermark G. L. Mirmira R. G. 2009 Development of insulin-producing cells from primitive biologic precursors . ,14 1 56 63 ,1531-7013 - 55.
Evgenov N. V. Medarova Z. Pratt J. Pantazopoulos P. Leyting S. Bonner-Weir S. Moore A. 2006 In vivo imaging of immune rejection in transplanted pancreatic islets. ,55 9 2419 2428 ,0012-1797 - 56.
Fan C. G. Zhang Q. J. Zhou J. R. 2011 Therapeutic potentials of mesenchymal stem cells derived from human umbilical cord.Stem Cell Rev,7 1 195 207 ,1558-6804 - 57.
Fändrich F. Ungefroren H. 2010 Customized cell-based treatment options to combat autoimmunity and restore beta-cell function in type 1 diabetes mellitus: current protocols and future perspectives.654 641 665 ,0065-2598 - 58.
Fanjul M. Gmyr V. Sengenès C. Ratovo G. Dufresne M. Lefebvre B. Kerr-Conte J. Hollande E. 2010 Evidence for epithelial-mesenchymal transition in adult human pancreatic exocrine cells.58 9 807 823 ,1551-5044 - 59.
Fiaschi-Taesch N. M. Salim F. Kleinberger J. Troxell R. Cozar-Castellano I. Selk K. Cherok E. Takane K. K. Scott D. K. Stewart A. F. 2010 Induction of human beta-cell proliferation and engraftment using a single G1/S regulatory molecule, cdk6. ,59 8 1926 1936 ,0193-9327 X. - 60.
Figliuzzi M. Cornolti R. Perico N. Rota C. Morigi M. Remuzzi G. Remuzzi A. Benigni A. 2009 Bone marrow-derived mesenchymal stem cells improve islet graft function in diabetic rats.41 5 1797 1800 ,1873-2623 - 61.
Fodor A. Harel C. Fodor L. Armoni M. Salmon P. Trono D. Karnieli E. 2007 Adult rat liver cells transdifferentiated with lentiviral IPF1 vectors reverse diabetes in mice: an ex vivo gene therapy approach . ,50 1 121 130 ,0001-2186 X. - 62.
Fukazawa T. Matsuoka J. Naomoto Y. Nakai T. Durbin M. L. Kojima I. Lakey J. R. Tanaka N. 2006 Development of a novel beta-cell specific promoter system for the identification of insulin-producing cells in in vitro cell cultures.312 17 3404 3412 ,0014-4827 - 63.
Furth M. E. Atala A. 2009 Stem cell sources to treat diabetes.106 4 507 511 ,1097-4644 - 64.
Gao F. Wu D. Q. Hu Y. H. Jin G. X. Li G. D. Sun T. W. Li F. J. (2008 151 6 6 293 302 ,1931-5244 - 65.
Gao R. Ustinov J. Korsgren O. Otonkoski T. 2005 In vitro neogenesis of human islets reflects the plasticity of differentiated human pancreatic cells . ,48 11 2296 2304 ,0001-2186 X. - 66.
Gao F. Wu D. Q. Hu Y. H. Jin G. X. Li G. D. Sun T. W. Li F. J. (2008 151 6 6 293 302 ,1931-5244 - 67.
Gartner W. Koc F. Nabokikh A. Daneva T. Niederle B. Luger A. Wagner L. 2006 Long-term in vitro growth of human insulin-secreting insulinoma cells . ,2 123 130 ,0028-3835 - 68.
Geelhoed-Duijvestijn P. H. 2007 Incretins: a new treatment option for type 2 diabetes? Neth J Med.65 2 60 64 ,0300-2977 - 69.
Gefen-Halevi S. Rachmut I. H. Molakandov K. Berneman D. Mor E. Meivar-Levy I. Ferber S. 2010 NKX6.1 promotes PDX-1-induced liver to pancreatic β-cells reprogramming. ,12 6 655 664 ,2152-4998 - 70.
Georgia S. Bhushan A. 2006 p27 Regulates the transition of beta-cells from quiescence to proliferation. ,55 11 2950 2956 ,0012-1797 - 71.
Gianani R. 2011 Beta cell regeneration in human pancreas . Semin Immunopathol,33 1 23 27 ,1863-2300 - 72.
Gianani R. Putnam A. Still T. Yu L. Miao D. Gill R. G. Beilke J. Supon P. Valentine A. Iveson A. Dunn S. Eisenbarth G. S. Hutton J. Gottlieb P. Wiseman A. 2006 Initial results of screening of nondiabetic organ donors for expression of islet autoantibodies. ,91 5 1855 1861 ,0002-1972 X. - 73.
Gillard P. Keymeulen B. Mathieu C. 2010 Beta-cell transplantation in type 1 diabetic patients: a work in progress to cure.,1-2 ,71 98 ,0302-6469 - 74.
Gillard P. Mathieu C. 2011 ).[Epub ahead of print] Immune and cell therapy in type 1 diabetes: too little too late?1744-7682 - 75.
Giorgetti A. Montserrat N. Rodriguez-Piza I. Azqueta C. Veiga A. Izpisúa Belmonte. J. C. Generation of induced pluripotent stem cells from human cord blood cells with only two factors: Nat Protoc,4 and Sox2.5 4 811 820 ,1750-2799 - 76.
Granger A. Kushner J. A. 2009 Cellular origins of beta-cell regeneration: a legacy view of historical controversies.266 4 325 338 ,1365-2796 - 77.
Gruessner R. W. Kandaswamy R. Denny R. 2001 Laparoscopic simultaneous nephrectomy and distal pancreatectomy from a live donor. ,193 3 333 337 ,1072-7515 - 78.
Gu G. Dubauskaite J. Melton D. A. 2002 Direct evidence for the pancreatic lineage: NGN3+ cells are islet progenitors and are distinct from duct progenitors. 129 10 2447 2457 ,0950-1991 - 79.
Guo T. Hebrok M. 2009 Stem cells to pancreatic beta-cells: new sources for diabetes cell therapy. 30 3 214 227 .1945-7189 - 80.
Guz Y. Nasir I. Teitelman G. 2001 Regeneration of pancreatic beta cells from intra-islet precursor cells in an experimental model of diabetes. ,142 11 4956 4968 ,0013-7227 - 81.
Haller M. J. Viener H. L. Wasserfall C. Brusko T. Atkinson M. A. Schatz D. A. 2008 Autologous umbilical cord blood infusion for type 1 diabetes.Exp. Hematol,36 6 710 715 ,0030-1472 X. - 82.
Hanley S. Rosenberg L. 2009 Islet-derived progenitors as a source of in vitro islet regeneration.482 371-385,1064-3745 - 83.
Hardikar A. A. Marcus-Samuels B. Geras-Raaka E. Raaka B. M. Gershengorn M. C. 2003 Human pancreatic precursor cells secrete FGF2 to stimulate clustering into hormone-expressing islet-like cell aggregates. Proc Natl Acad Sci U S A,100 12 7117 7122 ,0027-8424 - 84.
Herold K. C. Gitelman S. E. Masharani U. Hagopian W. Bisikirska B. Donaldson D. Rother K. Diamond B. Harlan D. M. Bluestone J. A. 2005 A single course of anti-CD3 monoclonal antibody hOKT3gamma1(Ala-Ala) results in improvement in C-peptide responses and clinical parameters for at least 2 years after onset of type 1 diabetes.54 6 1763 1769 ,0012-1797 - 85.
Hochedlinger K. Plath K. 2009 Epigenetic reprogramming and induced Pluripotency . ,136 4 509 523 ,0950-1991 - 86.
Horb M. E. Shen C. N. Tosh D. Slack J. M. 2003 Experimental conversion of liver to pancreas. Curr Biol,13 2 105 115 ,0960-9822 - 87.
Huang X. Moore D. J. Ketchum R. J. Nunemaker C. S. Kovatchev B. Mc Call A. L. Brayman K. L. 2008 Resolving the conundrum of islet transplantation by linking metabolic dysregulation, inflammation, and immune regulation .,29 5 603 630 ,0016-3769X . - 88.
Huangfu D. Osafune K. Maehr R. Guo W. Eijkelenboom A. Chen S. Muhlestein W. Melton D. A. 2008 Induction of pluripotent stem cells from primary human fibroblasts with only Oct4 and Sox2 . ,26 11 1269 1275 ,1546-1696 - 89.
Humphrey R. K. Yu S. M. Flores L. E. Jhala U. S. 2010 Glucose regulates steady-state levels of PDX1 via the reciprocal actions of GSK3 and AKT kinases. J Biol Chem,285 5 3406 3416 ,0108-3351X . - 90.
Imai J. Katagiri H. Yamada T. Ishigaki Y. Ogihara T. Uno K. Hasegawa Y. Gao J. Ishihara H. Sasano H. Mizuguchi H. Asano T. Oka Y. 2005 Constitutively active PDX1induced efficient insulin production in adult murine liver326 2 402 409 ,0000-6291 X. - 91.
Inada A. Nienaber C. Katsuta H. Fujitani Y. Levine J. Morita R. Sharma A. Bonner-Weir S. 2008 Carbonic anhydrase II-positive pancreatic cells are progenitors for both endocrine and exocrine pancreas after birth.105 50 19915 19919 .1091-6490 - 92.
Ito T. Itakura S. Todorov I. Rawson J. Asari S. Shintaku J. Nair I. Ferreri K. Kandeel F. Mullen Y. 2010 Mesenchymal stem cell and islet co-transplantation promotes graft revascularization and function .,89 12 1438 1445 ,1534-6080 - 93.
Jeong J. H. Kim S. H. Lee M. Kim W. J. Park T. G. Ko K. S. Kim S. W. 2010 Non-viral systemic delivery of Fas siRNA suppresses cyclophosphamide-induced diabetes in NOD mice . ,143 1 88 94 ,1873-4995 - 94.
Joglekar M. V. Joglekar V. M. Hardikar A. A. 2009 Expression of islet-specific microRNAs during human pancreatic development.Gene Expr Patterns,9 2 109 113 ,0156-7133 X. - 95.
Joglekar M. V. Parekh V. S. Mehta S. Bhonde R. R. Hardikar A. A. 2007 MicroRNA profiling of developing and regenerating pancreas reveal post-transcriptional regulation of neurogenin3.Dev Biol,311 2 603 612 ,0109-5564 X. - 96.
Juhl K. Bonner-Weir S. Sharma A. 2010 Regenerating pancreatic beta-cells: plasticity of adult pancreatic cells and the feasibility of in-vivo neogenesis. 15 1 79 85 ,1531-7013 - 97.
Jun H. S. 2010 In vivo regeneration of insulin-producing beta-cells.Adv Exp Med Biol,654 627 640 ,0065-2598 - 98.
Kadam S. S. Bhonde R. R. 2010 Islet neogenesis from the constitutively nestin expressing human umbilical cord matrix derived mesenchymal stem cells.Islets,2 2 112 120 .1938-2022 - 99.
Kaneto H. Matsuoka T. A. Nakatani Y. Miyatsuka T. Matsuhisa M. Hori M. Yamasaki Y. 2005a A crucial role of MafA as a novel therapeutic target for diabetes280 15 15047 15052 ,0021-9258 - 100.
Kaneto H. Nakatani Y. Miyatsuka T. Matsuoka T. A. Matsuhisa M. Hori M. Yamasaki Y. 2005b PDX-1/VP16 fusion protein, together with NeuroD or Ngn3, markedly induces insulin gene transcription and ameliorates glucose tolerance. ,54 4 1009 1022 ,0012-1797 - 101.
Karnieli O. Izhar-Prato Y. Bulvik S. Efrat S. 2007 Generation of insulin-producing cells from human bone marrow mesenchymal stem cells by genetic manipulation . ,25 11 2837 2844 ,1549-4918 - 102.
Karnik S. K. Chen H. Mc Lean G. W. Heit J. J. Gu X. Zhang A. Y. Fontaine M. Yen M. H. Kim S. K. 2007 Menin controls growth of pancreatic beta-cells in pregnant mice andpromotes gestational diabetes mellitus. ,318 5851 806 809 ,1095-9203 - 103.
Kaung H. L. 1994 Growth dynamics of pancreatic islet cell populations during fetal and neonatal development of the rat.Dev Dyn,200 2 163-175,1058-8388 - 104.
Kayali A. G. Flores L. E. Lopez A. D. Kutlu B. Baetge E. Kitamura R. Hao E. Beattie G. M. Hayek A. 2007 Limited capacity of human adult islets expanded in vitro to redifferentiate into insulin-producing beta-cells.56 3 703 708 ,0012-1797 - 105.
Kikugawa R. Katsuta H. Akashi T. Yatoh S. Weir G. C. Sharma A. Bonner-Weir S. 2009 Differentiation of COPAS-sorted non-endocrine pancreatic cells into insulin-positive cells in the mouse.52 4 645 652 ,1432-0428 - 106.
Kim S. Shin J. S. Kim H. J. Fisher R. C. Lee M. J. Kim C. W. 2007 Streptozotocin-induced diabetes can be reversed by hepatic oval cell activation through hepatic transdifferentiation and pancreatic islet regeneration. Lab Invest,87 7 702 712 ,0023-6837 - 107.
Knip M. 1997 Disease-associated autoimmunity and prevention of insulin-dependent diabetes mellitus . ,29 5 447 451 ,0785-3890 - 108.
Koblas T. Zacharovová K. Berková Z. Leontovic I. Dovolilová E. Zámecník L. Saudek F. 2009 ).In vivo differentiation of human umbilical cord blood-derived cells into insulin-producing beta cells. Folia Biol (Praha),55 55 6 224 232 ,0015-5500 - 109.
Kodama S. Toyonaga T. Kondo T. Matsumoto K. Tsuruzoe K. Kawashima J. Goto H. Kume K. Kume S. Sakakida M. Araki E. 2005 Enhanced expression of PDX-1 and Ngn3 by exendin-4 during beta cell regeneration in STZ-treated mice.327 4 1170 1178 ,0000-6291 X. - 110.
Kogler G. Sensken S. Airey J. A. Trapp T. Muschen M. Feldhahn N. Liedtke S. Sorg R. V. Fischer J. Rosenbaum C. Greschat S. Knipper A. Bender J. Degistirici O. Gao J. Caplan A. I. Colletti E. J. Almeida-Porada G. Müller H. W. Zanjani E. Wernet P. 2004 A new human somatic stem cell from placental cord blood with intrinsic pluripotent differentiation potential.200 2 123 135 ,0022-1007 - 111.
Kojima H. Fujimiya M. Matsumura K. Younan P. Imaeda H. Maeda M. Chan L. 2003 NeuroD-betacellulin gene therapy induces islet neogenesis in the liver and reverses diabetes in mice. 9 5 596 603 ,1078-8956 - 112.
Kopinke D. Murtaugh L. C. 2010 Exocrine-to-endocrine differentiation is detectable only prior to birth in the uninjured mouse pancreas.10 38 0147-1213X . - 113.
Koulmanda M. Budo E. Bonner-Weir S. Qipo A. Putheti P. Degauque N. Shi H. Fan Z. Flier J. S. Auchincloss H. Jr Zheng X. X. Strom T. B. 2007 Modification of adverse inflammation is required to cure new-onset type 1 diabetic hosts. ,104 32 13074 13079 ,0027-8424 - 114.
Koya V. Lu S. Sun Y. P. Purich D. L. Li. S. W. Atkinson M. A. Yang L. J. 2008 Reversal of streptozotocin-induced diabetes in mice by cellular transduction with recombinant pancreatic transcription factor pancreatic duodenal homeobox-1: a novel protein transduction domain-based therap y. ,57 3 757 769 ,0193-9327X . - 115.
Kroon E. Martinson L. A. Kadoya K. Bang A. G. Kelly O. G. Eliazer S. Young H. Richardson M. Smart N. G. Cunningham J. Agulnick A. D. D’Amour K. A. Carpenter M. K. Baetge E.E 2008 Pancreatic endoderm derived from human embryonic stem cells generates glucose-responsive insulin-secreting cells in vivo.26 4 443 452 ,1546-1696 - 116.
Krutzfeldt J. Rajewsky N. Braich R. Rajeev K. G. Tuschl T. Manoharan M. Stoffel M. 2005 Silencing of microRNAs in vivo with’antagomirs’.438 7068 685 689 ,1476-4687 - 117.
Kushner J. A. Weir G. C. Bonner-Weir S. 2010 Ductal origin hypothesis of pancreatic regeneration under attack.Cell Metab.11 1 2 3 ,0932-7420 - 118.
Langer R. M. 2010 Islet transplantation: lessons learned since the Edmonton breakthrough.42 5 1421 1424 ,1873-2623 - 119.
Lardon J. De Breuck S. Rooman I. Van Lommel L. Kruhøffer M. Orntoft T. Schuit F. Bouwens L. 2004 Plasticity in the adult rat pancreas: transdifferentiation of exocrine to hepatocyte-like cells in primary culture.,39 6 1499 1507 ,0270-9139 - 120.
Lechner A. Leech C. A. Abraham E. J. Nolan A. L. Habener J. F. 2002 Nestin-positive progenitor cells derived from adult human pancreatic islets of Langerhans contain side population (SP) cells defined by expression of the ABCG2 (BCRP1) ATP-binding cassette transporter.Biochem Biophys Res Commun,293 2 670 674 ,0000-6291 X. - 121.
Lee R. H. Pulin A. A. Seo M. J. Kota D. J. Ylostalo J. Larson B. L. Semprun-Prieto L. Delafontaine P. Prockop D. J. 2009 Intravenous hMSCs improve myocardial infarction in mice because cells embolized in lung are activated to secrete the anti-inflammatory protein TSG-6.Cell Stem Cell,5 1 54 63 ,1875-9777 - 122.
Lee R. H. Seo M. J. Reger R. L. Spees J. L. Pulin A. A. Olson S. D. Prockop D. J. 2006 Multipotent stromal cells from human marrow home to and promote repair of pancreatic islets and renal glomeruli in diabetic NOD/scid mice.Proc Natl Acad Sci U S A,103 46 17438 17443 ,0027-8424 - 123.
Leitão C. B. Tharavanij T. Cure P. Pileggi A. Baidal D. A. Ricordi C. Alejandro R. 2008 Restoration of hypoglycemia awareness after islet transplantation . ,31 11 2113 2115 ,1935-5548 - 124.
Levetan C. 2010 Distinctions between islet neogenesis and β-cell replication: implications for reversal of Type 1 and 2 diabetes.2 2 76 84 ,1753-0407 - 125.
Li L. Seno M. Yamada H. Kojima I. 2003 Betacellulin improves glucose metabolism by promoting conversion of intraislet precursor cells to beta-cells in streptozotocin-treated mice.285 3 E577 E583 ,0193-1849 - 126.
Li L. Yi Z. Seno M. Kojima I. 2004 Activin A and betacellulin: Effect on regeneration of pancreatic beta-cells in neonatal streptozotocin-treated rats. ,3 608 615 ,0012-1797 - 127.
Li W. C. Horb M. E. Tosh D. Slack J. M. 2005 In vitro transdifferentiation of hepatoma cells into functional pancreatic cells. Mech Dev,122 6 835 847 ,0925-4773 - 128.
Li Y. Song Y. H. Li F. Yang T. Lu Y. W. Geng Y. J. 2009 MicroRNA-221 regulates high glucose-induced endothelial dysfunction.381 1 81 83 ,1090-2104 - 129.
Lipsett M. A. Castellarin M. L. Rosenberg L. 2007 Acinar plasticity: development of a novel in vitro model to study human acinar-to-duct-to-islet differentiation.34 4 452 457 ,1536-4828 - 130.
Liu Y. Tanabe K. Baronnier D. Patel S. Woodgett J. Cras-Méneur C. Permutt M. A. 2010 Conditional ablation of Gsk-3β in islet beta cells results in expanded mass and resistance to fat feeding-induced diabetes in mice. Diabetologia,53 12 2600 2610 ,1432-0428 - 131.
Lovvorn H. N. 3rd Nance M. L. Ferry R. J. Jr Stolte L. Jr Baker L. O’Neill J. A. Schnaufer L. Jr Stanley C. A. Adzick N. S. 1999 Congenital hyperinsulinism and the surgeon: lessons learned over 35 years. J Pediatr Surg.34 5 786 792 ; discussion 792-793,0022-3468 - 132.
Lu J. Herrera P. L. Carreira C. Bonnavion R. Seigne C. Calender A. Bertolino P. Zhang C. X. 2010 Alpha cell-specific Men1 ablation triggers the transdifferentiation of glucagon-expressing cells and insulinoma development.138 5 1954 1965 ,1528-0012 - 133.
Magliocca J. F. Knechtle S. J. (2006 19 19 9 705 714 ,0934-0874 - 134.
Martín J. Hunt S. L. Dubus P. Sotillo R. Néhmé-Pélluard F. Magnuson M. A. Parlow A. F. Malumbres M. Ortega S. Barbacid M. 2003 Genetic rescue of Cdk4 null mice restores pancreatic beta-cell proliferation but not homeostatic cell number.Oncogene,22 34 5261 5269 ,0950-9232 2008 Insulin protein and proliferation in ductal cells in the transplanted pancreas of patients with type 1 diabetes and recurrence of autoimmunity. Diabetologia,10 1803 1813 ,0001-2186 X - 135.
Martin-Pagola A. Sisino G. Allende G. Dominguez-Bendala J. Gianani R. Reijonen H. Nepom G. T. Ricordi C. Ruiz P. Sageshima J. Ciancio G. Burke G. W. Pugliese A. 2008 Insulin protein and proliferation in ductal cells in the transplanted pancreas of patients with type 1 diabetes and recurrence of autoimmunity . ,10 1803 1813 ,0001-2186 X - 136.
Maruyama M. Kenmochi T. Akutsu N. Saigo K. Iwashita C. Otsuki K. Ito T. Asano T. 2010 Laparoscopic-assisted distal pancreatectomy and nephrectomy from a live donor . ,17 2 193 196 ,1868-6982 - 137.
Mc Guckin C. P. Forraz N. Baradez M. O. Navran S. Zhao J. Urban R. Tilton R. Denner L. 2005 Production of stem cells with embryonic characteristics from human umbilical cord blood. .38 4 245 255 ,0960-7722 - 138.
Means A. L. Meszoely I. M. Suzuki K. Miyamoto Y. Rustgi A. K. Coffey R. J. Jr Wright C. V. Stoffers D. A. Leach S. D. 2005 Pancreatic epithelial plasticity mediated by acinar cell transdifferentiation and generation of nestin-positive intermediates.132 16 3767 3377 ,.0950-1991 - 139.
Meier J. J. Butler A. E. Saisho Y. Monchamp T. Galasso R. Bhushan A. Rizza R. A. Butler P. C. 2008 Beta-cell replication is the primary mechanism subserving the postnatal expansion of beta-cell mass in humans.,57 6 1584 1594 ,0193-9327 X. - 140.
Meivar-Levy I. Ferber S. 2006 Regenerative medicine: using liver to generate pancreas for treating diabetes. ,8 6 430 434 ,1565-1088 - 141.
Melkman-Zehavi T. Oren R. Kredo-Russo S. Shapira T. Mandelbaum A. D. Rivkin N. Nir T. Lennox K. A. Behlke M. A. Dor Y. Hornstein E. 2011 miRNAs control insulin content in pancreatic β-cells via downregulation of transcriptional repressors. EMBO J,5 835 845 ,1460-2075 2011 miRNAs control insulin content in pancreatic β-cells via downregulation of transcriptional repressors.5 835 845 ,1460-2075 - 142.
Menge B. A. Tannapfel A. Belyaev O. Drescher R. Müller C. Uhl W. Schmidt W. E. Meier J. J. 2008 Partial pancreatectomy in adult humans does not provoke beta-cell regeneration.Diabetes,57 1 142 149 ,0193-9327 X. - 143.
Milanesi A. Lee J. W. Xu Q. Perin L. Yu J. S. 2011 Differentiation of Nestin-Positive Cells Derived from Bone Marrow into Pancreatic Endocrine and Ductal Cells in vitro.,1479-6805 - 144.
Minami K. Okuno M. Miyawaki K. Okumachi A. Ishizaki K. Oyama K. Kawaguchi M. Ishizuka N. Iwanaga T. Seino S. 2005 Lineage tracing and characterization of insulin-secreting cells generated from adult pancreatic acinar cells.102 42 15116 15121 ,0027-8424 - 145.
Minami K. Seino S. 2008 Pancreatic acinar-to-beta cell transdifferentiation in vitro.13 5824 5837 ,1093-4715 - 146.
Mishra P. K. Singh S. R. Joshua I. G. Tyagi S. C. 2010 Front Biosci,15 461 477 ,1093-4715 - 147.
Miyatsuka T. Kaneto H. Kajimoto Y. et al. 2003 Ectopically expressed PDX-1 in liver initiates endocrine and exocrine pancreas differentiation but causes dysmorphogenesis. 310 3 1017 1025 ,0000-6291 X. - 148.
Montaña E. Bonner-Weir S. Weir G. C. 1994 Transplanted beta cell response to increased metabolic demand. Changes in beta cell replication and mass. ,93 4 1577 1582 , ISSN.0021-9738. - 149.
Moore D. J. Markmann J. F. Deng S. 2006 Avenues for immunomodulation and graftprotection by gene therapy in transplantation. ,6 435 445 ,0934-0874 - 150.
Murray H. E. Paget M. B. Bailey C. J. Downing R. 2009 Sustained insulin secretory response in human islets co-cultured with pancreatic duct-derived epithelial cells within a rotational cell culture system.,52 3 477 485 ,1432-0428 - 151.
Nakagawa M. Koyanagi M. Tanabe K. Takahashi K. Ichisaka T. Aoi T. Okita K. Mochiduki Y. Takizawa N. Yamanaka S. 2008 Generation of induced pluripotent stem cellswithout myc from mouse and human fibroblasts. ,26 1 101 106 ,1546-1696 - 152.
Nir T. Dor Y. 2005 How to make pancreatic beta cells--prospects for cell therapy in diabetes.16 5 524 529 ,0958-1669 - 153.
Nir T. Melton D. A. Dor Y. 2007 Recovery from diabetes in mice by beta cell regeneration. 117,9 2553 2561 ,0021-9738 - 154.
Noguchi H. 2009 Pancreatic islet transplantation .1 1 16 20 ,1948-9366 - 155.
Okuno M. Minami K. Okumachi A. Miyawaki K. Yokoi N. Toyokuni S. Seino S. 2007 Generation of insulin-secreting cells from pancreatic acinar cells of animal models of type 1 diabetes. ,292 1 E158 E165 ,0193-1849 - 156.
Parekh V. S. Joglekar M. V. Hardikar A. A. 2009 Differentiation of human umbilical cord blood-derived mononuclear cells to endocrine pancreatic lineage.Differentiation,78 4 232 240 ,1432-0436 - 157.
Phuc P. V. Nhung T. H. Loan D. T. Chung D. C. Ngoc P. K. 2011 Differentiating of banked human umbilical cord blood-derived mesenchymal stem cells into insulin-secreting cells.In Vitro Cell Dev Biol Anim,47 1 54 63 ,0154-3706 X. - 158.
Pierro A. Nah S. A. 2011 Surgical management of congenital hyperinsulinism of infancy . ,20 1 50 53 ,1532-9453 - 159.
Pittenger G. L. Taylor-Fishwick D. Vinik A. I. 2009 A role for islet neogenesis in curing diabetes . .52 5 735 738 ,1432-0428 - 160.
Poy M. N. Eliasson L. Krutzfeldt J. Kuwajima S. Macdonald X. Ma P. E. Pfeffer S. Tuschl T. Rajewsky N. Rorsman P. Stoffel M. 2004 A pancreatic islet-specific microRNA regulates insulin secretion.Nature,432 7014 226 230 ,1476-4687 - 161.
Poy M. N. Hausser J. Trajkovski M. Braun M. Collins S. Rorsman P. Zavolan M. Stoffel M. 2009 miR-375 maintains normal pancreatic alpha- and beta-cell mass.106 14 5813 5818 ,1091-6490 - 162.
Rachdi L. Balcazar N. Elghazi L. Barker D. J. Krits I. Kiyokawa H. Bernal-Mizrachi E. 2006 Differential effects of p27 in regulation of beta-cell mass during development, neonatal period, and adult life. ,55 12 3520 3528 ,0012-1797 - 163.
Rackham C. L. Chagastelles P. C. Nardi N. B. Hauge-Evans A. C. Jones P. M. King A. J. 2011 Co-transplantation of mesenchymal stem cells maintains islet organisation and morphology in mice.Diabetologia,1432-0428 - 164.
Ramsoondar J. Vaught T. Ball S. et al. 2009 Production of transgenic pigs that express porcine endogenous retrovirus small interfering RNAs . ,16 164 180 ,1399-3089 - 165.
Rane S. G. Dubus P. Mettus R. V. Galbreath E. J. Boden G. Reddy E. P. Barbacid M. 1999 Loss of Cdk4 expression causes insulin-deficient diabetes and Cdk4 activation results in beta-islet cell hyperplasia.22 1 44 52 ,1061-4036 - 166.
Rayasam G. V. Tulasi V. K. Sodhi R. Davis J. A. Ray A. 2009 Glycogen synthase kinase 3: more than a namesake 156 6 885 898 ,1476-5381 - 167.
Rieck S. Kaestner K. H. 2010 Expansion of beta-cell mass in response to pregnancy. 21 3 151 158 ,1879-3061 - 168.
Rooman I. Heremans Y. Heimberg H. Bouwens L. 2000 Modulation of rat pancreatic acinoductal transdifferentiation and expression of PDX-1 in vitro.,43 7 907 914 ,0001-2186X . - 169.
Salpeter S. J. Klein A. M. Huangfu D. Grimsby J. Dor Y. 2010 Glucose and aging control the quiescence period that follows pancreatic beta cell replication.137 19 3205 3213 ,1477-9129 - 170.
Santana A. Ensenat-Waser R. Arribas M. I. Reig J. A. Roche E. 2006 Insulin-producing cells derived from stem cells: recent progress and future directions.10 4 866 883 ,1582-1838 - 171.
Sapir T. Shternhall K. Meivar-Levy I. et al. 2005 From the cover: cell replacement therapy for diabetes. Generating functional insulinproducing tissue from adult human liver cells,102 22 7964 7969 ,0027-8424 - 172.
Scaglia L. Smith F. E. Bonner-Weir S. 1995 Apoptosis contributes to the involution of beta cell mass in the post partum rat pancreas. ,136 12 5461 5468 ,0013-7227 - 173.
Schmied B. M. Ulrich A. Matsuzaki H. Ding X. Ricordi C. Weide L. Moyer M. P. Batra S. K. Adrian T. E. Pour P. M. 2001 Transdifferentiation of human islet cells in a long-term culture. Pancreas.23 2 157 171 ,0885-3177 - 174.
Seaberg R. M. Smukler S. R. Kieffer T. J. Enikolopov G. Asghar Z. Wheeler M. B. Korbutt G. van der Kooy D. 2004 Clonal identification of multipotent precursors from adult mouse pancreas that generate neural and pancreatic lineages.22 9 1115 1124 ,1087-0156 - 175.
Sebastiani G. Vendrame F. Dotta F. 2011 MicroRNAs as New Tools for Exploring Type 1 Diabetes: Relevance for Immunomodulation and Transplantation Therapy . ,43 1 330 332 ,1873-2623 - 176.
Shi M. Liu Z. W. Wang F. S. 2011 Immunomodulatory properties and therapeutic application of mesenchymal stem cells.164 1 1 8 ,1365-2249 - 177.
Shi Y. Desponts C. Do J. T. Hahm H. S. Scholer H. R. Ding S. 2008 Induction of pluripotentstem cells from mouse embryonic fibroblasts by Oct4 and Klf4 with small-molecule compounds.3 5 568 574 ,1875-9777 - 178.
Shimajiri Y. Kosaka Y. Scheel D. W. Lynn F. C. Kishimoto N. Wang J. Zhao S. German M.S. 2011 A mouse model for monitoring islet cell genesis and developing therapies for diabetes.4 2 268 276 ,1754-8411 - 179.
Solar M. Cardalda C. Houbracken I. Martín M. Maestro M. A. De Medts N. Xu X. Grau V. Heimberg H. Bouwens L. Ferrer J. 2009 Pancreatic exocrine duct cells give rise to insulin-producing beta cells during embryogenesis but not after birth.Dev Cell,17 6 849 860 ,1878-1551 - 180.
Sordi V. Bertuzzi F. Piemonti L. 2008 Diabetes mellitus: an opportunity for therapy with stem cells?3 3 377 397 ,0174-6076X . - 181.
Stanley E. G. Elefanty A. G. 2008 Building better beta cells.2 4 300 301 ,1875-9777 - 182.
Suarez-Pinzon W. L. Lakey J. R. Brand S. J. Rabinovitch A. 2005 Combination therapy with epidermal growth factor and gastrin induces neogenesis of huan islet {beta}-cells from pancreatic duct cells and an increase in functional {beta}-cell mass.90 6 3401 3409 ,0002-1972 X. - 183.
Suarez-Pinzon W. L. Power R. F. Yan Y. Wasserfall C. Atkinson M. Rabinovitch A. 2008 ).Combination therapy with glucagon-like peptide-1 and gastrin restores normoglycemia in diabetic NOD mice.12 3281 3288 ,0193-9327X . - 184.
Sun Y. Chen L. Hou X. G. Hou W. K. Dong J. J. Sun L. Tang K. X. Wang B. Song J. Li H. Wang K. X. 2007 Differentiation of bone marrow-derived mesenchymal stem cells from diabetic patients into insulin-producing cells in vitro.120 9 771 776 ,0366-6999 - 185.
Suzuki A. Nakauchi H. Taniguchi H. 2004 Prospective isolation of multipotent pancreatic progenitors using flow-cytometric cell sorting. ,53 8 2143 2152 ,0012-1797 - 186.
Suzuki J. Ricordi C. Chen Z. 2010 Immune tolerance induction by integrating innate and adaptive immune regulators .19 3 253 268 ,1555-3892 - 187.
Szymczak P. Wojcik-Stanaszek L. Sypecka J. Sokolowska A. Zalewska T. 2010 Effect of matrix metalloproteinases inhibition on the proliferation and differentiation of HUCB-NSCs cultured in the presence of adhesive substrates . ,70 4 325 336 ,1689-0035 - 188.
Tan M. Kandaswamy R. Sutherland D. E. Gruessner R. W. 2005 Laparoscopic donor distal pancreatectomy for living donor pancreas and pancreas-kidney transplantation . ,5 8 1966 1970 ,1600-6135 - 189.
Tang D. Q. Cao L. Z. Burkhardt B. R. Xia C. Q. Litherland S. A. Atkinson M. A. Yang L. J. 2004 In vivo and in vitro characterization of insulin-producing cells obtained from murine bone marrow.53 7 1721 1732 ,0012-1797 - 190.
Tang D. Q. Lu S. Sun Y. P. Rodrigues E. Chou W. Yang C. Cao L. Z. Chang L. J. Yang L. J. 2006 Reprogramming liver-stem WB cells into functional insulin-producing cells by persistent expression of Pdx1- and Pdx1-VP16 mediated by lentiviral vectors. ,86 1 83 93 ,0023-6837 - 191.
Tang X. Muniappan L. Tang G. Ozcan S. 2009 Identification of glucose-regulated miRNAs from pancreatic {beta} cells reveals a role for miR-30d in insulin transcription.15 2 287 293 .1469-9001 - 192.
Tellez N. Montolio M. Biarnes M. Castano E. Soler J. Montanya E. 2005 Adenoviraloverexpression of interleukin-1 receptor antagonist protein increases beta-cellreplication in rat pancreatic islets,12 2 120 128 ,0969-7128 - 193.
Teta M. Rankin M.M. Long . S. Y. Stein G. M. Kushner J. A. 2007 Growth and regeneration of adult beta cells does not involve specialized progenitors.12 5 817 826 ,1534-5807 - 194.
Thatava T. Nelson T. J. Edukulla R. Sakuma T. Ohmine S. Tonne J. M. Yamada S. Kudva Y. Terzic A. Ikeda Y. 2011 Indolactam V/GLP-1-mediated differentiation of human iPS cells into glucose-responsive insulin-secreting progeny .18 3 283 293 ,0476-5462 - 195.
Thorel F. Népote V. Avril I. Kohno K. Desgraz R. Chera S. Herrera P. L. 2010 Conversion of adult pancreatic alpha-cells to beta-cells after extreme beta-cell loss.464 7292 1149 1154 ,1476-4687 - 196.
Uchida T. Nakamura T. Hashimoto N. Matsuda T. Kotani K. Sakaue H. Kido Y. Hayashi Y. Nakayama K. I. White M. F. Kasuga M. 2005 Deletion of Cdkn1b ameliorates hyperglycemia by maintaining compensatory hyperinsulinemia in diabetic mice.11 2 175 182 ,1078-8956 - 197.
Uccelli A. Benvenuto F. Laroni A. Giunti D. 2011 Neuroprotective features of mesenchymal stem cells . Best Pract Res Clin Haematol.24 1 59 64 ,1532-1924 - 198.
van Belle T.L Coppieters K.T von Herrath M.G. 2011 Type 1 diabetes: etiology, immunology, and therapeutic strategies. 91 1 79 118 ,1522-1210 - 199.
Volarevic V. Arsenijevic N. Lukic M. L. Stojkovic M. 2011 Concise review: Mesenchymal stem cell treatment of the complications of diabetes mellitus .,29 1 5 10 ,1549-4918 - 200.
Wang A. Y. Ehrhardt A. Xu H. Kay M.A. 2007 ).Adenovirus transduction is required for the correction of diabetes using ,1 or neurogenin-3 in the liver.15 2 255 263 ,1525-0016 - 201.
Winter W. E. Schatz D. 2003 Prevention strategies for type 1 diabetes mellitus: current status and future directions. ,17 1 39 64 ,1173-8804 - 202.
Xia B. Zhan X. R. Yi R. Yang B. 2009 Can pancreatic duct-derived progenitors be a source of islet regeneration?383 4 383 385 ,1090-2104 - 203.
Xie Q. P. Huang H. Xu B. Dong X. Gao S. L. Zhang B. Wu Y. L. 2009 Human bone marrow mesenchymal stem cells differentiate into insulin-producing cells upon microenvironmental manipulation in vitro.77 5 483 491 ,1432-0436 - 204.
Xu X. D’Hoker J. Stangé G. Bonné S. De Leu N. Xiao X. Van de Casteele M. Mellitzer G. Ling Z. Pipeleers D. Bouwens L. Scharfmann R. Gradwohl G. Heimberg H. 2008 Beta cells can be generated from endogenous progenitors in injured adult mouse pancreas.132 2 197 207 ,1097-4172 - 205.
Yang L.J. 2006 Liver stem cell-derived beta-cell surrogates for treatment of type 1 diabetes. ,5 6 409 413 ,1568-9972 - 206.
Yang Z. Chen M. Ellett J.D. Carter J. D. Brayman K. L. (Nadler J. 2005 ).Inflammatory blockade improves human pancreatic islet function and viability .,5 5 3 475 483 ,1600-6135 - 207.
Yoshida S. Ishikawa F. Kawano N. Shimoda K. Nagafuchi S. Shimoda S. Yasukawa M. Kanemaru T. Ishibashi H. Shultz L. D. Harada M. 2005 Human cord blood--derived cells generate insulin-producing cells in vivo.23 9 1409 1416 ,1066-5099 - 208.
Zalzman M. Anker-Kitai L. Efrat S. 2005 Differentiation of human liver derived, insulin-producing cells toward the (beta)-cell phenotyp e.,54 9 2568 2575 ,0012-1797 - 209.
Zhang D. Jiang W. Liu M. Sui X. Yin X. Chen S. Shi Y. Deng H. 2009 Highly efficientdifferentiation of human ES cells and iPS cells into mature pancreatic insulin producing cells. ,19 4 429 438 ,1748-7838 - 210.
Zhang L. Hu J. Hong T. P. Liu Y. N. Wu Y. H. Li L. S. 2005 Monoclonal side population progenitors isolated from human fetal pancreas.333 2 603 608 ,0000-6291 X. - 211.
Zhang W. Zhang D. Shen M. Liu Y. Tian Y. Thomson A. W. Lee W. P. Zheng X. X. 2010 ).Combined administration of a mutant TGF-beta1/Fc and rapamycin promotes induction of regulatory T cells and islet allograft tolerance.,185 8 4750-4759,1550-6606 - 212.
Zhang Y. Shen W. Hua J. Lei A. Lv C. Wang H. Yang C. Gao Z. Dou Z. 2010 Pancreatic islet-like clusters from bone marrow mesenchymal stem cells of human first-trimester abortus can cure streptozocin-induced mouse diabetes.13 6 695 706 ,1557-8577 - 213.
Zhao Y. Lin B. Dingeldein M. Guo C. Hwang D. Holterman M.J. 2010 New type of human blood stem cell: a double-edged sword for the treatment of type 1 diabetes..155 5 211 216 ,1878-1810 - 214.
Zhao Y. Wang H. Mazzone T. 2006 Identification of stem cells from human umbilical cord blood with embryonic and hematopoietic characteristics . ,312 13 2454 2464 ,0014-4827 - 215.
Zhao Y. Yin X. Qin H. Zhu F. Liu H. Yang W. Zhang Q. Xiang C. Hou P. Song Z. Liu Y. Yong J. Zhang P. Cai J. Liu M. Li H. Li Y. Qu X. Cui K. Zhang W. Xiang T. Wu Y. Zhao Y. Liu C. Yu C. Yuan K. Lou J. Ding M. Deng H. 2008 Two supporting factors greatlyimprove the efficiency of human iPSC generation. ,3 5 475 479 ,1875-9777 - 216.
Zhou H. Wu S. Joo J. Y. Zhu S. Han D. W. Lin T. Trauger S. Bien G. Yao S. Zhu Y. Siuzdak G. Scholer H. R. Duan L. Ding S. 2009 Generation of induced pluripotent stem cellsusing recombinant proteins Cell,4 5 1875-9777 - 217.
Zhou Q. Brown J. Kanarek A. Rajagopal J. Melton D. A. 2008 In vivo reprogramming of adult pancreatic exocrine cells to beta-cells. ,455 7213 627 632 ,1476-4687 - 218.
Zulewski H. Abraham E. J. Gerlach M. J. Daniel P. B. Moritz W. Müller B. Vallejo M. Thomas M. K. Habener J. F. 2001 Multi-potential nestin-positive stem cells isolated from adult pancreatic islets differentiate ex vivo into pancreatic endocrine, exocrine, andhepatic phenotypes.Diabetes,50 3 521 533 ,0012-1797