Gender depended potentiality of differentiation of human umbilical cord mesenchymal stem cells into oocyte‐Like cells in vitro

Recent studies have demonstrated that germ-like cells could be differentiated from human umbilical cord mesenchymal stem cells (hUC-MSCs) in vitro. Whether the sexuality of hUC-MSCs affects the formation efficiency of germ-like cells derived from hUC-MSCs is still unclear. To clearly test the formation efficiency of oocyte-like cells from male and female hUC-MSCs, obtained hUC-MSCs were induced by 20% follicular fluid (FF) according to the method that has been proved by our previous studies. Results showed that hUC-MSCs differentiated into oocyte-like structures and expressed germ cell makers. It was noted that the presence of advanced oocyte-like cells in male hUC-MSCs (m-hUC-MSCs) was similar as that in female hUC-MSCs (f-hUC-MSCs); however, the expression of germ cell's specific markers in m-hUC-MSCs was delayed compared with that in f-hUC-MSCs. In addition, immunofluorescence analysis demonstrated that germ cell-specific markers, Oct4, Vasa, Dazl, ZP2, ZP3 and Stra8, were expressed on the 14th day after induction in both f-hUC-MSCs and m-hUC-MSCs. However, the size of oocyte-like cells from f-hUC-MSCs was larger than that in m-hUC-MSCs. The level of secreted oestradiol was significantly higher in f-hUC-MSCs than m-hUC-MSCs. We sought to determine whether critical germ cell's transcription factor-Figlα will promote the development of oocyte-like cells. Some germ cell-specific markers were increased when exogenous Figlα was transfected into hUC-MSCs. This process implied that germ-like cells might be produced by over-expression of exogenous germ cell-specific gene, and this process was similar as that in production of germ cells in induced pluripotent stem cells (iPSCs). Finally, to verify the feasibility that hUC-MSCs differentiate into germ cells, hUC-MSCs were transplanted into seminiferous tubules and kidney capsule of mouse, respectively, and we found the transplanted cells differentiated into germ-like cells in recipient's seminiferous tubules and kidney capsule. This study will provide a simple model to study mammalian germ cell specification using hUC-MSCs in vitro.