Directing Induced Pluripotent Stem Cell Derived Neural Stem Cell Fate with a Three-Dimensional Biomimetic Hydrogel for Spinal Cord Injury Repair

Abstract

Current treatment approaches for spinal cord injuries (SCIs) are mainly based on cellular transplantation. Induced pluripotent stem cells (iPSCs) without supply constraints and ethical concerns have emerged as a viable treatment option for repairing neurological disorders. However, the primarily limitations in the neuroregeneration field are uncontrolled cell differentiation, and low cell viability caused by the ischemic environment. The mechanical property of three-dimensional (3D) hydrogel can be easily controlled and shared similar characteristics with nerve tissue, thus promoting cell survival and controlled cell differentiation. We propose the combination of a 3D gelatin methacrylate (GelMA) hydrogel with iPSC-derived NSCs (iNSCs) to promote regeneration after SCI. In vitro, the iNSCs photoencapsulated in the 3D GelMA hydrogel survived and differentiated well, especially in lower-moduli hydrogels. More robust neurite outgrowth and more neuronal differentiation were detected in the soft hydrogel group. To further evaluate the in vivo neuronal regeneration effect of the GelMA hydrogels, a mouse spinal cord transection model was generated. We found that GelMA/iNSC implants significantly promoted functional recovery. Further histological analysis showed that the cavity areas were significantly reduced, and less collagen was deposited in the GelMA/iNSC group. Furthermore, the GelMA and iNSC combined transplantation decreased inflammation by reducing activated macrophages/microglia (CD68-positive cells). Additionally, GelMA/iNSC implantation showed striking therapeutic effects of inhibiting GFAP-positive cells and glial scar formation while simultaneously promoting axonal regeneration. Undoubtedly, use of this 3D hydrogel stem cell-loaded system is a promising therapeutic strategy for SCI repair.

Recent Advances in Photo-Crosslinkable Hydrogels for Biomedical Applications

“…For example, by increasing concentration of Irgacure 2959 from 0.1 to 0.5 (w/v), elastic modulus of GelMA hydrogel was increased from 7 to 10kPa [62,72]. On the other hand, compressive modulus of GelMA hydrogel was increased from 0.68 to 2.03kPa when UV light exposure duration was increased from 15 to 40s (Table 3) [73]. …”

“…It has also been used to develop a liver-on-a-chip platform for drug toxicity assessments (e.g.,acetaminophen toxicity) [80]. Moreover, transplantation of neural stem cells encapsulated in GelMA hydrogel was found to enhance neuronal regeneration and suppress glial scar formation in mouse spinal cord transection models, suggesting the potential therapeutic application of the construct in spinal cord injury [73]. Apart from UV light-crosslinked GelMA hydrogel, visible light-crosslinked GelMA hydrogel has been used to engineer 3D in vitro glioblastoma multiform tissue models for monitoring cancer progression and drug screening [81].…”

Advances in Tissue Engineering and Innovative Fabrication Techniques for 3-D-Structures: Translational Applications in Neurodegenerative Diseases

“…Although iPSCs were 3-D bioprinted and then differentiated into the hydrogel, some evidence suggests that is better to directly bioprint iPSC-derived neural stem cells (NSCs) [ 151 ]. This specific fabrication technique was used, and many phenotypic aspects were investigated, such as the analysis of neurite extension and neural maturation on polyethylene glycol [ 152 ] or 3-D gelatin methacrylate [ 153 ] hydrogels. Moreover, iPSC-derived mature neurons were bioprinted and cultivated on hydrogel scaffolds, and many read-outs were evaluated, such as the expression of integrins, the formation of a complex network, and the expression of synaptophysin along the neurites [ 125 ].…”

Multifunctionalized hydrogels foster hNSC maturation in 3D cultures and neural regeneration in spinal cord injuries

“…Despite many efforts with different cell types, fate of transplanted cells has been typically poorly controlled (19). Indeed, authors agree on the idea that guiding cell fate prior to and after transplantation may be the key to success (20–22). Among these approaches, SAPs can be used as scaffolds providing biomimetic microenvironments tuning the differentiation and favoring the engraftment of cellular transplants (23–27).…”