Enriched environment and Mash1 transfection affect neural stem cell differentiation after transplantation into the adult somatosensory cortex

Neural stem cell (NSC) transplantation is a promising therapeutic modality for various nervous-system disorders; however, poor survival and differentiation of the transplanted NSCs limit their therapeutic efficacy. This study elucidated the effect of additive rehabilitative therapy with enriched environment (EE) and of achaete-scute homolog 1 (Mash1) and neurogenin2 (Ngn2) transduction on the fate of NSCs (P28-P35) transplanted into the primary somatosensory cortex (PSC) of mice. NSCs transplanted into the PSC differentiated into neurons and astrocytes and exhibited typical excitatory and synaptic response in mice housed in standard cages or in the EE. After EE exposure, significantly enhanced differentiation of transplanted NSCs into neuronal nuclear antigen-positive neurons was observed, whereas marked inhibition of the differentiation of transplanted NSCs into astrocytes was noted. Additionally, the proportion of GAD+ cells among GFP+/NeuN+ cells decreased following EE exposure. Furthermore, Mash1-transduced NSCs exhibited significantly enhanced populations of glutamic acid decarboxylase-negative neurons, whereas Ngn2-transduced NPCs did not.