Host induction by transplanted neural stem cells in the spinal cord: further evidence for an adult spinal cord neurogenic niche

Aim: To explore the hypothesis that grafts of exogenous stem cells in the spinal cord of athymic rats or rats with transgenic motor neuron disease can induce endogenous stem cells and initiate intrinsic repair mechanisms that can be exploited in amyotrophic lateral sclerosis therapeutics. Materials & methods: Human neural stem cells (NSCs) were transplanted into the lower lumbar spinal cord of healthy rats or rats with transgenic motor neuron disease to explore whether signals related to stem cells can initiate intrinsic repair mechanisms in normal and amyotrophic lateral sclerosis subjects. Patterns of migration and differentiation of NSCs in the gray and white matter, with emphasis on the central canal region and ependymal cell-driven neurogenesis, were analyzed. Results: Findings suggest that there is extensive cross-signaling between transplanted NSCs and a putative neurogenic niche in the ependyma of the lower lumbar cord. The formation of a neuronal cord from NSC-derived cells next to ependyma suggests that this structure may serve a mediating or auxiliary role for ependymal induction. Conclusion: These findings raise the possibility that NSCs may stimulate endogenous neurogenesis and initiate intrinsic repair mechanisms in the lower spinal cord.