Background: Mouse fetal germ cells have been successfully purified from fetal gonads. However, there are no published reports describing a procedure for deriving mature oocytes from isolated fetal germ cells. The purpose of this present study is to explore whether purified fetal germ cells are able to differentiate into mature oocytes through an in vivo grafting procedure.
Methods and results: First, intact 11.5 and 12.5 days post-coitum (dpc) female gonads with or without the attached mesonephros and the reaggregated female gonad cells were transplanted into the recipient mice. The results demonstrate both the gonad accompanied by mesonephroi and the innate gonad structure are not absolutely required for 11.5 dpc and 12.5 dpc oogonia to generate mature oocytes. Next, oogonia were purified from female gonads, aggregated with different ovarian somatic cells and transplanted into the recipient mice. Purified 12.5 dpc oogonia were able to generate mature oocytes by aggregating with 12.5 dpc ovarian somatic cells, but not with 16.5 dpc or 0 days postpartum ovarian somatic cells. We also tested 12.5 dpc male germ cells but they were unable to undergo oogenesis.
Conclusions: Our study demonstrates that mature oocytes can be derived from purified fetal germ cells through an aggregation and transplantation procedure. It also suggests that the synchronized interactions between oogonia and gonadal somatic cells are important to ensure normal folliculogenesis.