Seizure induces activation of multiple subtypes of neural progenitors and growth factors in hippocampus with neuronal maturation confined to dentate gyrus.

Adult hippocampal neurogenesis is altered in response to different physiological and pathological stimuli. GFAP(+ve)/nestin(+ve) radial glial like Type-1 progenitors are considered to be the resident stem cell population in adult hippocampus. During neurogenesis these Type-1 progenitors matures to GFAP(-ve)/nestin(+ve) Type-2 progenitors and then to Type-3 neuroblasts and finally differentiates into granule cell neurons. In our study, using pilocarpine-induced seizure model, we showed that seizure initiated activation of multiple progenitors in the entire hippocampal area such as DG, CA1 and CA3. Seizure induction resulted in activation of two subtypes of Type-1 progenitors, Type-1a (GFAP(+ve)/nestin(+ve)/BrdU(+ve)) and Type-1b (GFAP(+ve)/nestin(+ve)/BrdU(-ve)). We showed that majority of Type-1b progenitors were undergoing only a transition from a state of dormancy to activated form immediately after seizures rather than proliferating, whereas Type-1a showed maximum proliferation by 3 days post-seizure induction. Type-2 (GFAP(-ve)/nestin(+ve)/BrdU(+ve)) progenitors were few compared to Type-1. Type-3 (DCX(+ve)) progenitors showed increased expression of immature neurons only in DG region by 3 days after seizure induction indicating maturation of progenitors happens only in microenvironment of DG even though progenitors are activated in CA1 and CA3 regions of hippocampus. Also parallel increase in growth factors expression after seizure induction suggests that microenvironmental niche has a profound effect on stimulation of adult neural progenitors.

In vitro differentiation of retinal ganglion-like cells from embryonic stem cell derived neural progenitors.

ES cells have been reported to serve as an excellent source for obtaining various specialized cell types and could be used in cell replacement therapy. Here, we demonstrate the potential of ES cells to differentiate along retinal ganglion cell (RGC) lineage. FGF2-induced ES cell derived neural progenitors (ES-NPs) were able to generate RGC-like cells in vitro upon differentiation. These cells expressed RGC regulators and markers such as, Ath5, Brn3b, RPF-1, Thy-1 and Islet-1, confirming their potential to differentiate into RGCs. The generation of RGCs from ES-NPs was enhanced with the exposure of FGF2 and Sonic hedgehog (Shh), although Shh treatment alone did not affect RGC differentiation significantly. ES-NPs, after exposure to FGF2, were capable of integrating and differentiating into RGCs in vivo upon transplantation. Thus, our study suggests that ES cells can serve an excellent renewable source for generating RGCs that can be used to treat neurodegenerative diseases like glaucoma.