Long-Term Survival, Robust Neuronal Differentiation, and Extensive Migration of Human Forebrain Stem/Progenitor Cells Transplanted to the Adult Rat Dorsal Root Ganglion Cavity

Neurons in dorsal root ganglia (DRGs) transmit sensory information from peripheral tissues to the spinal cord. This pathway can be interrupted, for example, as the result of physical violence, traffic accidents, or complications during child delivery. As a consequence, the patient permanently loses sensation and often develops intractable neuropathic pain in the denervated area. Here we investigate whether human neural stem/progenitor cells (hNSPCs) transplanted to the DRG cavity can serve as a source for repairing lost peripheral sensory connections. We found that hNSPCs robustly differentiate to neurons, which survive long-term transplantation. The neuronal population in the transplants was tightly surrounded by astrocytes, suggesting their active role in neuron survival. Furthermore, 3 months after grafting hNSPCs were found in the dorsal root transitional zone (DRTZ) and within the spinal cord. The level of differentiation of transplanted cells was high in the core of the transplants whereas cells that migrated to the DRTZ and spinal cord were undifferentiated, nestin-expressing precursors. These data indicate that peripherally transplanted hNPSCs can be used for repair of dorsal root avulsion or spinal cord injuries; however, additional factors are required to guide their differentiation to the desired type of neurons. Furthermore, hNPSCs that migrate from the DRG cavity graft site to the DRTZ and spinal cord may provide trophic support for regenerating dorsal root axons, thereby allowing them to reenter the host spinal cord.