Differences in the neuronal stem cells survival, neuronal differentiation and neurological improvement after transplantation of neural stem cells between mild and severe experimental traumatic brain injury.

We developed a novel protocol for generation and selective amplification of neural progenitor cells regionally specified to the rostral brain but not the spinal cord from mouse embryonic stem cells (ESCs). The neural progenitors could differentiate in vitro and in vivo into many cholinergic and a few GABAergic neurons but rarely into astrocytes. The transplanted neurospheres could survive in the hippocampus (CA3) of animals with mild traumatic brain injury (TBI). Twelve weeks after transplantation (a week after the behavioral test), we found significant cholinergic differentiation recognized as ChAT immunoreactivity in the eGFP+transplanted cells. Moreover, the grafts contained a few GAD67+cells. However, we barely found GFAP+astrocytes within the grafts. Furthermore, presynaptic formations of graft-derived neurons were recognized by immunohistochemistry of near the grafts around CA3. However, these findings were not observed in severe TBI group. So, we examined NGF, BDNF, and FGF-2 mRNA by RT-PCR in 12 mice including normal, mild TBI and severe TBI group. Increases in the neurotrophic factors' mRNA were evident in the hippocampus on the ipsilateral side in the mild TBI group. Statistical analysis revealed significant differences between the mild and severe TBI groups. The data also revealed significant differences between the mild TBI and normal groups. The transplanted neurospheres could survive in the mild TBI animals, but not in the severe TBI group.