Preliminary separation and identification of quiescent and activated neural stem cells in mouse embryonic cerebral cortex

AIM To isolate and identify quiescent and activated neural stem cells from mouse embryonic cerebral cortex. METHODS Two cell clusters derived from mouse cerebral cortex on embryonic day 14.5 were separated by flow cytometry. The expression of stem cell marker Pax6 and proliferation marker Ki67 was examined by immunofluorescence. The mRNA expression of stem cell marker genes Pax6, Oct4, Sox2 and Nanog were detected by RT-qPCR. Cell cycle was analyzed by flow cytometry and RT-qPCR. Proliferation ability was investigated by in vitro cell culture. RESULTS In both 2 groups, the cells expressed Pax6. Immunofluorescence staining of Ki67 in the big cell group was positive, while that in small cell group was negative. Cell cycle assay showed that the proportion of G₀/G₁ phase in the small cells was higher than that in the big cells, the G₂/M phase proportion was 0, and the expression of cyclin A and cyclin B was lower than that in the big cells (P<0.05). When cultured in vitro, the number of microspheres formed by the small cells was smaller and the formation speed was slower than those of the big cells. After digestion of microspheres, Pax6 and Ki67 staining of both big and small cells was positive, and the positive rates were not different (P>0.05), indicating that the quiescent neural stem cells were activated. CONCLUSION The 2 cell clusters are quiescent and activated state of neural stem cells. The activated stem cells have strong abilities of self-renewing and proliferation, while these abilities of quiescent stem cells are poor. The quiescent stem cells can translate into activated ones when cultured in vitro for a period.