Objective
Cell-based therapy is a promising strategy for spinal cord injury (SCI) repair, but faced the challenges to direct the neuronal differentiation of appropriate neuron subtypes for achieving the neuronal replacement. We investigated whether allogeneic beforehand in vitro differentiated neural stem cells (NSCs) could relieve the adverse effects of regeneration inhibitory niche and promote motor functional recovery by accomplishing neuronal replacement after transplant into SCI rats.
Methods
Collagen scaffold combined with digested NSCs, NSC sphere, differentiated neurons, and sphere of differentiated neurons were transplanted into completely transected SCI in rats and therapeutic outcomes were investigated. Next, we enriched complex of neurotrophic factors secreted from culture medium of NSCs, neurons, and sphere of neurons and a total of 2 mg total enriched protein combined with collagen scaffold were transplanted into SCI to further assay whether allogeneic NSCs transplant promotes the recovery of SCI predominantly by secreting neurotrophic factors.
Results
NSCs differentiated into neurons in density-dependent manner in vitro and sphere of NSCs could counteract myelin-induced inhibition of neuronal differentiation. Collagen scaffold combined with digested NSCs, NSC sphere, differentiated neurons, and sphere of differentiated neurons were transplanted into completely transected SCI in rats. Overall the cell treatment groups had a much better locomotor recovery, tissue remodeling, and newborn neuron formation than alone collagen scaffold treatment, compared with alone collagen material transplant and control group. However, unexpectedly, the differentiated cell treatment (differentiated neurons and sphere of differentiated neurons transplants) did not present striking better locomotor recovery than the undifferentiated NSCs and sphere of NSCs treatments, only sphere of neurons showed a slight increase in BBB score compared to other cell treatments. Next, we enriched complex of neurotrophic factors secreted from culture medium of NSCs, neurons, and sphere of neurons. BBB score analysis showed that the secreted neurotrophic factors from NSCs, neurons, and sphere of neurons would promote functional recovery of SCI to the same extent.
Conclusion
Allogeneic NSCs transplant promotes functional recovery of SCI predominantly by secreting neurotrophic factors, not direct neuronal replacement of differentiated neurons from transplanted cells.