Oocyte growth and ovarian tissue differentiation in organ culture of mouse fetal gonads

Abstract

Mammalian oocytes undergo growth and development through prenatal and postnatal periods. This is an investigation of development in vitro of oocytes and ovarian tissues from fetal gonads of the 12.5 days post coitus. Cultured tissues survived and the oocytes entered the growth phase, subsequently achieving long-term (14-30 days) culture. Growing oocytes were observed in their general morphology and were enclosed within 1-2 layers of granulosa cells, which resembled primary or secondary follicles. However, no follicular structures were also found in the cultures despite the existence of growing oocytes. The oocytes enclosed in very flattened cells were detected as in histological structure on day 18 of culture. The oocyte diameter became approximately 50 μm under culture conditions supplemented with 15% fetal bovine serum or Ehrlich ascites tumor fluid. These results indicate that the maximum culture period for oocyte growth in this organ culture is approximately 3 weeks and that the oocytes can grow in vitro to at least a medium size even if normal follicular structure is not formed.