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Neuromuscular diseases (NMDs) are primarily caused by progressive degeneration of motor neurons that leads to skeletal muscle denervation. The physiological complexity and cellular heterogeneity of individual motor units make understanding the underlying pathological mechanisms of NMDs difficult. Moreover, the demonstrable species specificity of neuromuscular synapse structure and function underscores the need to develop reliable human models of neuromuscular physiology with which to study disease etiology and test the efficacy of novel therapeutics. In this regard, human-induced pluripotent stem cells (hiPSCs) represent a valuable tool for developing such models. However, the lack of cellular diversity and transcriptomic immaturity of motor neurons derived from iPSCs has so far limited their downstream applications. To address this shortcoming, biomaterials such as 3D biopolymer scaffolds and biocompatible nanoparticles have been investigated for their ability to improve current neuronal differentiation protocols. In this review, we summarize current efforts and limitations associated with the use of functional biomaterials to increase the physiological relevance of stem cell-derived motor neurons. We also suggest potential future directions for research using biomaterials to overcome outstanding issues related to stem cell-based neuromuscular tissue production for use in NMD modeling applications.
Ulsan National Institute of Science and Technology (UNIST), South Korea
Changho Chun
University of Washington, Seattle, USA
Alec S.T. Smith
University of Washington, Seattle, USA
Jinmyoung Joo*
Ulsan National Institute of Science and Technology (UNIST), South Korea
David L. Mack*
University of Washington, Seattle, USA
*Address all correspondence to: dmack21@uw.edu and jjoo@unist.ac.kr
1. Introduction
Neuromuscular diseases (NMDs) refer to a set of conditions that affect motor units, which are functional units comprising individual spinal motor neurons, their axons, the axon’s terminal nerve branches, neuromuscular junctions (NMJ), and the skeletal muscle fibers connected to these junctions (Figure 1). One of the most the well-known NMDs is amyotrophic lateral sclerosis (ALS) (Figure 2). ALS is a neurodegenerative disorder characterized by the degeneration of upper and lower motor neurons, leading to a progressive loss of motor function and ultimately resulting in death, often due to respiratory failure [1, 2]. Unfortunately, the disease is generally fatal within 3 to 5 years after diagnosis [3]. It typically appears in mid-adulthood, with the average age of onset being 55 years, although it can begin as early as the first or second decade of life or even develop later in life [4, 5]. ALS has an annual diagnosis rate of 1–2 individuals per 100,000 in most countries [1, 2]. In the United States and the United Kingdom, ALS is responsible for more than 1 in 500 deaths in adults, indicating that over 15 million people currently alive may eventually succumb to this disease [1]. Another significant motor neuron disease that is typically classified as an NMD is spinal muscular atrophy (SMA). The global occurrence of SMA is approximately 1 in 40–60 [6, 7]. SMA involves the disruption of the motor unit, leading to the degeneration of proximal motor axons, loss of synaptic inputs to cell bodies, and, ultimately, the death of motor neuron cell bodies [6].
Figure 1.
Motor unit. Motor units are composed of lower motor neurons, neuromuscular junctions (NMJs), and skeletal muscle fiber.
Figure 2.
Neuromuscular disease (NMD). NMDs encompass cellular disorders of the motor unit. Each unique disorder affects different aspect of the motor unit.
ALS and SMA share a common symptom, and current approaches to managing these NMDs is centered around addressing symptoms, such as preserving weakened muscle function, rather than tackling the root cause of the disease. The paucity of effective treatments for NMDs such as ALS and SMA has led to a recent effort to develop more predictive preclinical models with which to model these conditions and evaluate novel therapeutic efficacy.
Historically, the in vitro study of motor neurons has relied on sourcing cells from spinal cord tissue derived from embryonic chicks and rodents [8, 9, 10, 11, 12, 13, 14]. Such neurons are more similar to human cells than to worm-like animals and arthropods, but they still have different developmental patterns and morphologies compared to humans, particularly in the distribution of motor nerve terminals and their size and conformation [15]. Animal models are the current “gold standard” preclinical method for evaluating the efficacy of novel ALS therapeutics. However, the last 20 years have seen rigorous animal tests on multiple ALS-targeted drugs that prolonged life in the animal but failed to elicit a therapeutic benefit in humans [16]. This has fueled a recent interest in developing alternative, human-based preclinical assays to better inform patient responses to compound exposure. The establishment of such assays is dependent on the establishment of robust models of human motor neurons.
To address this need, researchers have turned to human-induced pluripotent stem cell (iPSC) technology to derive motor neurons that more accurately reflect the cells present in patients. The advantage of human iPSC-derived motor neurons is that they have unlimited expansion potential and can generate large homogeneous populations of neurons for downstream studies. This makes them suitable for studies requiring a large number of neurons for repetitive tasks, such as drug screening, proteomics, and biochemistry [17]. Additionally, human iPSC-derived motor neurons retain patient-specific gene mutations, making it possible to study individual patient genotype–phenotype relationships in vitro [18].
Despite those efforts, a significant challenge in using human iPSC-derived motor neurons is their relative immaturity compared to primary motor neurons. This is because the culture process typically used to differentiate human iPSCs into motor neurons does not encapsulate the complexity of the developing spinal cord in vivo and is conducted on a timescale (days to weeks) that is far more rapid than native embryogenesis and subsequent postnatal development (months to years). As such, some concerns remain that human iPSC-derived motor neurons may not exhibit all of the same physiological properties as primary motor neurons.
As a result, it is essential to improve the maturity of human iPSC-derived motor neurons to increase their suitability for use in next-generation disease modeling and/or drug screening applications. This maturation process is crucial for ensuring that the findings obtained using human iPSC-derived motor neurons are reliable and accurately represent the relevant biological processes as they occur in vivo. Achieving more mature cultured human motor neurons is particularly important to the endeavors to model NMDs such as ALS that exhibit symptomatic onset at stages of life that are far later than embryogenesis and early postnatal development.
2. Unaddressed problems in current motor neuron differentiation strategies using induced pluripotent stem cells (iPSCs)
The development of induced pluripotent stem cells (iPSCs) has enabled researchers to study many human diseases, including congenital neurodegenerative diseases, from a developmental perspective. Established somatic reprogramming techniques, using only four transcription factors (Oct4, Sox2, Klf4, and c-Myc), enable scientist to generate patient-derived stem cell lines harboring specific patient mutations. Advances in genetic editing strategies have also facilitated the establishment of isogenic controls from these mutants and comparison of cells derived from these paired iPSC population allow analysis of how a specific patient mutation alters the phenotype of cells that otherwise harbor identical genotypes [19]. Despite their enormous potential to replace or augment animal disease models, current neuronal iPSC models come with critical shortcomings that have been a major roadblock for their wider adoption in biomedical applications. Although iPSCs show similar transcriptomic profiles with those of embryonic stem cells (ESC), especially for the genes governing pluripotency, even state-of-the-art differentiation strategies for generating human neurons from iPSCs are far from perfect in terms of their capacity to produce cells that accurately reflect their in vivo counterparts [20, 21, 22, 23]. Populations obtained from 20 to 50 days of in vitro neuronal differentiation often contain a mixture of various unknown subtypes of neurons, and glial cells. Even cells from outside the neuroglial lineage are often observed, and these cells tend to outcompete the postmitotic neuronal populations over time [22, 23, 24, 25]. Moreover, commonly used differentiation protocols often lack reproducibility, which can result in the production of transcriptionally and functionally inconsistent neuronal populations from one batch to the next. Thus, it is reasonable to posit that such shortcomings in iPSC differentiation methods will have a negative impact on the accuracy and reproducibility of downstream research results when iPSC-derived neurons are used as predictors of human neural responses to chemical or pathological challenges. In addition to the disparity between in vivo human neurons and iPSC-derived neurons, a more challenging issue lies in the fact that we do not know how to reliably promote the maturation of iPSC-derived neurons toward an adult phenotype, which is critical for the study of late-onset neurodegenerative disorders such as ALS and Parkinson’s disease (PD) [18, 26, 27, 28, 29, 30].
Most current motor neuron differentiation protocols rely on small molecule treatments to sequentially induce ectoderm, neuroectoderm, ventral spinal neuron progenitors, and finally a mixture of premature motor neurons and interneurons. This is often then followed by treatment with trophic factors to induce further maturation of those early-stage neurons [31, 32, 33, 34]. In the majority of these protocols, undifferentiated iPSCs are initially treated with dual-SMAD inhibitors (SB431542 and LDN193189) to inhibit TGF-beta and BMP signaling pathways, which drives pluripotent stem cells toward the ectoderm lineage. Du et al. found that additional treatment of CHIR99021, which turns on the Wnt pathway, significantly enriches early-stage cultures with proliferative neural progenitors and this, in turn, results in the formation of a greater number of so-called “neural rosettes” around 10 days post-induction. A critically important small molecule that most protocols use to provide a caudalization cue to the developing neural progenitors is retinoic acid (RA) [35]. RA is a pivotal molecule regulating embryonic patterning and development. It is a metabolic product of vitamin A (retinol) synthesized by the paraxial mesoderm. RA mediates the expression of HOX genes that are sequentially activated during embryonic development and is responsible for regulating the regional patterning of neuronal subtypes vertically along the spinal cord (Figure 3). The timing of RA expression dictates when colinear HOX gene expression is stopped, thereby controlling the regional patterning of neurons as well as promoting the transition from neuromesoderm into neuroectoderm [36, 37]. Given the importance of RA physiology in spinal motor neuron development, it has been a major target of research to improve motor neuron differentiation protocols. However, our understanding of RA-mediated motor neuron differentiation has not progressed far beyond the initial findings regarding limited aspects of its mechanism of action, leaving an important knowledge gap in terms of our understanding of spinal motor neuron development.
Figure 3.
Schematic illustration of the spinal cord development in vivo. (A) In the early stages of development, a process called gastrulation occurs, which leads to the differentiation of cells in the inner cell mass (ICM) into three germ layers: Ectoderm, endoderm, and mesoderm. The dorsal part of the ectoderm undergoes further specialization into the neuroectoderm by inhibiting BMP and activin signaling while enhancing FGF and Wnt signaling, particularly in higher organisms. Neuralization progresses as a neural plate form and subsequently folds to create neural folds, which then fuse to form the neural tube. The neural tube is organized along the anterior-posterior axis (rostral-caudal) through the presence of a retinoic acid (RA) gradient, primarily regulated by Raldh2. RA plays a crucial role in establishing the initial boundaries between the spinal cord and hindbrain versus forebrain and hindbrain. Fgfs and Gdf11 counteract the effects of RA and contribute to the specification of more caudal spinal cord cell types. (B) the schematic illustrates key signaling factors that play a crucial role in organizing the anterior–posterior (rostral–caudal) and dorsal–ventral axes of the developing nervous system during embryonic development. It specifically focuses on a coronal section through the developing telencephalon. (fibroblast growth factor: FGF, bone morphogenetic protein: BMP, retinoic acid: RA, sonic hedgehog: Shh).
Once a caudal phenotype is established by RA, sonic hedgehog (SHH) or its agonist (e.g., purmorphamine with or without SAG (Smo agonist) supplementation) is then typically used to derive progenitors toward a ventral spinal identity. SHH is a vertebrate homolog of the Drosophila protein hedgehog and is expressed by the notochord and floor plate in the developing spinal cord. It provides signals necessary for positional patterning in the spinal cord. The concentration gradient of SHH determines whether the unpatterned progenitor cells have dorsal or ventral identity during the course of spinal neuron development. Despite the present understanding and detailed knowledge on the spinal neuron development and the cues necessary to drive the adoption of a motor neuron phenotype, the cells obtained from these protocols typically result in the adoption of an embryonic or neonatal phenotype. The use of particular biomaterials that exhibit various functionality upon applications is one of the promising strategic methods to achieve greater levels of maturation in these cells in vitro. Motor neuron differentiation of iPSCs using such functional biomaterials to improve the physiological relevance in vitro culture is discussed in detail below.
3. The use of biomaterials to improve the physiological relevance of iPSC-derived human neurons
Variety of biomaterials, as forms of hydrogels, nanoparticles, scaffolds and mesh, and so forth, have been recognized as attractive resources in the field of regenerative medicine and tissue engineering due to their physical and chemical tunability as well as their biocompatibility with most human stem cells (Figure 4). In particular, the development of biocompatible materials that can support functional tissue generation has gained significant interest in recent years.
Figure 4.
Characteristics of biomaterials in scaffolds. Each class of biomaterials has numerous advantages and disadvantages in terms of its suitability as an engineered neural scaffold.
For example, a hydrogel is a hydrophilic polymer resembling human tissue with high biocompatibility. Various monomeric compounds have been studied to form the hydrogel by modulating the degree of cross-linking to control the mechanical strength and releasing kinetics of embedded payloads such as growth factors [38]. Gelatin is one of the natural polymers that is a precursor of collagen. Both collagen and gelatin have high biocompatibility and low toxicity, but there are some issues regarding complex purification and modifying short degradation rates [39]. Both of them are often used to form an extracellular matrix (ECM). Also, serum albumin is a natural polymer used to construct ECM [40]. It has long a half-life compared to other natural polymers [40, 41, 42]. A carbon nanotube is also used to make ECM because it is a tunable material that possesses mechanical and electrical properies [43] and it is easy to modify its surface. Moreover, it has biocompatibility and high cell attachment. Those features can be adjusted to mimic ECM.
In addition to synthetic biomaterials, such as polyethylene glycol (PEG), polylactide-co-glycolic acid (PLGA) has been widely demonstrated to stem cell differentiation and tissue regeneration because of its tunable physical and chemical properties that provide beneficial effects to construct functional human tissues in vivo. The central hypothesis of applying such biomaterials to neural tissue engineering is that the physiological relevance of differentiating neurons will be readily improved by providing an extracellular microenvironment that more closely recapitulates the native spatiotemporal niche where these cells occupy in developing embryos. Specifically, researchers have attempted to recapitulate the extracellular microenvironment during neural development by taking into account factors such as the cell–matrix interaction, intracellular interactions within the given environment, the physical and mechanical characteristics of the matrix surrounding the neural tube, the topographical status of extracellular proteins, and the oxygen and nutrient provision capabilities of the matrix. In the following section, we summarized the advances and limitations of the biomaterials that have been used so far to recreate the surrounding environment of nervous tissue during the developmental stages. 3D scaffolds are widely used as a means of structural cues that are responsible for physical and mechanical properties of tissue microenvironment such as matrix stiffness, adhesion, and migration during neuronal differentiation. On the other hand, micro- and nanoparticles are utilized to control the biological cues through spatiotemporal release of active ingredients to differentiate the neurons. Importantly, we discuss ideas that may help to recapitulate the two critical characteristics of native spinal cord development: (1) the exquisite spatiotemporal control of inductive cues secreted around the neural tube, which are the main drivers of neuronal differentiation and specialization throughout the course of normal spinal cord development and (2) the dramatic conversion from flattened neural plate to 3D neural tube during early phases of spinal cord development. We believe that these issues constitute a root cause of the disparity between spinal neurons developed in vitro versus in vivo, and addressing these issues may help disentangle the remaining issues still plaguing iPSC-derived neuronal development in vitro.
4. 3D scaffolds: providing structural cues to iPSCs differentiation neurons
Conventional cell culture experiments, conducted on flat plastic surfaces, have provided us with a wealth of basic cell biology knowledge for decades. However, 2D culture schemes do not accurately recreate the physical cues, such as matrix stiffness, topology, and interaction between cells and matrix, which are present in the extracellular environment during native 3D tissue development in vivo. Additionally, neural differentiation on 2D surfaces often suffers from issues caused by neural sheet delamination, which results in poor longevity of cultured cell populations and batch-to-batch inconsistencies in differentiated populations. This becomes even more of a critical issue when it comes to generating multicellular tissues such as spinal cord that are required to have a continuous intracellular interactions and consistent delivery of differentiating cues from the surrounding microenvironments [44]. To address this issue, various biomaterials have been used to generate 3D scaffolds that provide a physiologically similar, material-permeable environment for exchanging morphogens, oxygen, and nutrients essential for each step of tissue development. Moreover, many studies have shown that 3D scaffold-mediated neural differentiation enables more complex interactions to develop between neural precursors and between cells and ECM proteins. Furthermore, such scaffolds provide better spatial organization of cells, which mimics the native environment during neurogenesis more closely.
Scaffolds can come in various shapes and geometries, such as fibrillar morphologies (3D structures composed of long, fibrous protein chains) with respect to length, thickness, surface structure (smooth vs. rugged), and overall shape (straight vs. curly), which can be modified to impact cell-to-cell and cell-to-matrix interactions. There are three categories of scaffolds to address the structural cues: surface property, mechanical property, and electrical property (Table 1). The surface properties of scaffolds can often be changed by modulating pH or using surfactants to affect material properties such as water uptake, compressive moduli, and cross-linking. Modulation of any of these properties could potentially affect the modality of neural differentiation within such structures. Therefore, it has been important to find a scaffold condition that promotes neurodevelopment that includes robust formation of axons and dendrites as well as the expression of neuron-specific proteins for synaptic transmission and electrophysiological function.
Structural cues derived by 3D scaffolds used in neuronal differentiation.
For the use of biomaterials in neural tissue generation and remodeling, there are preconditions to be satisfied. Scaffolds should have the ability to provide structural support that is tailored to the needs of the embedded stem cells (in terms of stiffness etc.) and provide correct guidance cues to the developing neurons by allowing small molecules in the medium to reach the entire population of cells at desired concentrations and kinetics during tissue formation. Although challenging, researchers have been trying to achieve this goal by modulating the structural parameters of scaffolds such as the pore size, porosity (% of void area relative to the entire surface area of the scaffold), and surface stiffness. Additionally, work has been performed that explores the binding of functional groups on to the scaffold surface to induce biochemical interactions between the matrix and the embedded cells [54, 55]. For example, adjusting surface stiffness and wettability have been shown to impact the number of neurites growing out of individual cells and the number of neuritic branches that develop from these projections, which are both major metrics for assessing neuronal differentiation and maturation in culture (Figure 5) [46, 52, 53, 56, 57]. The mechanical properties of the substrate and the interaction between the matrix structure and cells are also important factors to consider [40, 58, 59, 60, 61, 62]. Nanocomposite materials composed of synthetic polymers and fillers allow bulk and local modulation of physical properties to create a high surface area to volume ratio and control interfacial binding strength, which can enable the release of neurotrophic factors that induce neuronal differentiation [62, 63, 64, 65]. Lastly, electrical properties of the scaffold, such as conductive nanostructures like silver, gold, and carbon, can affect cell adhesion, migration, and orientation by electrical stimulation, which can also impact neuronal differentiation [62, 66, 67].
Figure 5.
Currently studied applications of scaffolds in neuronal differentiation. (A) An example of surface property modulation. Carbon nanotube (CNT) network patterns are utilized to achieve selective growth and polarization-controlled neuronal differentiation of human neural stem cells (hNSCs). CNT roughness promotes the adhesion and longevity of primary neurons. This CNT pattern induces the selective growth and differentiation of hNMSs. Also, the CNT pattern is able to maintain cell-to-cell interaction well. As a result, the CNT pattern is a more stable and versatile platform, with optimal nano-topography and biocompatibility, with which to regulate hNSC growth in vitro [46]. (B) An example of mechanical property modification. Surfactant templating is shown to effectively tune the water uptake and compressive modulus of photo-cross-linked chitosan hydrogels, mitigating property fluctuations with changing pH, enabling greater attachment of iPSCs, and enhancing neuronal differentiation [49]. (C) An example of electrical property modulation. Conductive scaffolds incorporating topographical, biochemical, and electrical stimuli support attachment, proliferation, neuronal differentiation, and maturation of iPSCs, demonstrating their potential for nerve regeneration strategies without the need for growth factor supplementation [42].
5. Nanoparticles: controlling the spatiotemporal supplement of biological cues to iPSCs differentiation to neurons
In addition to the provision of structural guidance using biomaterial-based scaffolds, exposing developing stem cells to molecular cues in a spatiotemporally-controlled manner is another factor that is crucial to establish the mature neurons when attempting to recapitulate the native morphogen supply that is achieved during native spinal cord development. To this end, understanding the molecular supply mechanisms that determine spinal neuron cell fate is important. During spinal cord development, stem cells differentiate into each type of spinal neuron through the exquisite control of several morphogens and growth factors, which creates combinatorial gradients of factors releasing mainly from the notochord and paraxial mesoderm. However, in vitro differentiation schemes lack accuracy in terms of recreating these morphogen gradients, resulting in the formation of an often poorly defined population of neurons and glia at the end of the protocol. The lack of materials to function as a source of controlled morphogen release has been a major reason for this shortcoming in current protocols, exacerbated by our insufficient understanding of native morphogen supply scheme during spinal cord development. Therefore, there is an urgent need to develop material tools, with high cytocompatibility, to more closely mimic the exquisite biomolecule release schemes that exist in vivo and to do so in a tunable manner to be enable optimization of release kinetics for the various factors necessary to induce motor neuron differentiation (e.g., RA, SHH, SAG, etc.).
Nanoparticles are an attractive candidate to fulfill this requirement. Depending on the type of nanoparticle, its surface can be modified for active targeting, penetrating barriers, and releasing molecules through pH-responsive properties while also avoiding clearance by the immune system [68, 69, 70, 71]. To improve neuronal differentiation, researchers have been developing many different types of nanoparticle carriers, such as DNA nanostructures, mesoporous silica nanoparticles (MSN), and polyethyleneimine (PEI) to effectively deliver neurogenic-inductive factors such as signaling ligands, DNA, siRNA, and mRNA into early-stage differentiating neuronal progenitors (Figure 6). In the context of supporting controlled release of morphogens, a study demonstrated that morphogen-loaded nanoparticles could be used as a source of controlled molecule release to provide pivotal molecules for neurogenesis, such as RA. Since RA has a very short half-life (14 minutes in PBS), it is difficult to maintain its active form to induce an effective role for a long-term period of culture in vitro. Using nanoparticles to release RA can facilitate the conversion of stem cells into neural cells by activating neural signaling pathways and minimizing cell cytotoxicity (Table 2) [69, 73, 74, 75, 76]. Such studies demonstrate that nanoparticles have a significant impact on neuronal differentiation from stem cell sources and with minimal effect on cell viability and proliferation. Nanoparticle modification can also provide an intracellular docking system for the simultaneous delivery of multiple factors to facilitate neuronal differentiation (Figures 7–10).
Figure 6.
Characteristics of nanoparticles for use as morphogen carriers. Each class of nanoparticle has numerous advantages and disadvantages regarding cargo and delivery. (poly(lactic-co-glycolic acid): PLGA, Polyethyleminine: PEI, mesoporous silica nanoparticle: MSN, iron oxide nanoparticle: IONP).
Application of nanoparticle for neuronal differentiation: Tetrahedral DNA nanostructure (TDN). The study investigated the effects of TDN on neural stem cells, demonstrating that TDNs promote self-renewal through the Wnt/β-catenin pathway and enhance neuronal differentiation by inhibiting the notch signaling pathway and suggesting their potential for nerve tissue regeneration. Because using TDN increase uptake of cells in stem cells [72].
Figure 8.
Application of nanoparticle for neuronal differentiation: Metal-organic framework (MOF). The study introduces a new platform, called SMENA, which utilizes MOF-embedded nanopit arrays to provide a stable and continuous supply of retinoic acid, promoting enhanced neuronal cell generation and demonstrating potential for various stem cell-based regenerative therapies [73].
Figure 9.
Applications of nanoparticle for neuronal differentiation: Mesoporous silica nanoparticle. This study used MSN as a delivery carrier of RA, which enabled rapid and high-quality neural differentiation of mouse embryonic stem cells, resulting in the successful derivation of stable neurite marker-expressing neural cells [74].
Figure 10.
Applications of nanoparticle for neuronal differentiation: Polyethyleminine (PEI). This study described the synthesis of functional RA-PEI complex nanoparticles with controlled release properties and their effectiveness in inducing neuronal differentiation of embryonic stem (ES) cells, suggesting their potential as a powerful tool for directing murine ES cell fate [75].
In spite of several long-term efforts to employ biomaterials to improve the physiological relevance of stem cell-derived spinal motor neurons in vitro, the resulting cells are still far from representing accurate reflections of their native counterparts in many physiological respects in vivo. We believe the core problem lies in the fact that we do not currently have the necessary tools to enable us to recapitulate the dynamic flux of morphogens continuously occurring near the neural tube during the developmental process. One attractive candidate for helping to achieve this goal is micro- and nanotechnology that generates 3D scaffold with high cavity of reservoir for target morphogen loading with a controllable release rate and concentration for longer period of time in vitro. By virtue of having established production protocols for those biomaterials with highly tunable porous structure and surface properties, we believe such materials have great potential to function as a morphogen-releasing source that facilitates the establishment of in vitro environments corresponding more closely with those of the notochord and paraxial mesoderm.
In conclusion, the use of biocompatible materials has great promise to address a current roadblock in iPSC-neuron research, namely, the accurate recapitulation of native spinal neuron development in culture. Conversion into a 3D culture environment that incorporates materials of similar mechanical and physical properties to those of native extracellular matrices holds great potential to improve current neurodevelopment modeling. More importantly, future efforts to recapitulate the unique morphogen supply schemes present at different stages of spinal cord development in human embryos would help overcome one of the most challenging issues in producing reliable neural tissue models from iPSC-derived spinal neurons.
This work was supported by a grant of the Korea Health Technology R&D Project through the Korea Health Industry Development Institute (KHIDI), funded by the Ministry of Health & Welfare (HI19C1095), and by the National Research Foundation of Korea (NRF) grant funded by the Ministry of Science and ICT (RS-2023-00209822), Republic of Korea.
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Written By
Juyoung Seong, Changho Chun, Alec S.T. Smith, Jinmyoung Joo and David L. Mack
Submitted: 01 August 2023Reviewed: 25 September 2023Published: 24 October 2023
Open access peer-reviewed chapter - ONLINE FIRST
