Cell turnover in normal cycling human ovary

We investigated cell proliferation and apoptosis in 37 normal cycling human ovaries to determine cell turnover in the various stages of follicular and luteal development. We examined cell proliferation by immunostaining for both Ki67 and proliferative cell nuclear antigen (PCNA) and by silver staining of nucleolar organizer regions (AgNORs). Apoptosis was examined by 3'-hydroxy nick-end labeling and by immunostaining of an apoptosis-related antigen, Ley. The labeling indexes of Ki67, PCNA, and AgNORs were significantly increased in antral follicles. However, there were no significant differences in the labeling index of Ki67, PCNA, and AgNORs between dominant and nondominant follicles, including nonovulated follicles in the luteal phase. These results indicate that the transformation of granulosa cells from quiescence to active growth is important in early folliculogenesis. Immunoreactivity for Ki67 and PCNA were observed predominantly in the functioning corpus luteum, but not in the degenerating corpus luteum, indicating proliferation only during the luteal phase. Immunoreactivity for Ley and nick end-labeling reactive cells were not observed in the follicular and luteal phases, except for scattered cells in the degenerating corpus luteum. This may be because of the relatively long process of human follicular growth and atresia.