Does Apoptosis Contribute Follicular Atresia and Luteal Regression in Human Ovary?

We investigated apoptosis in 37 human ovaries from normally cycling women to determine the mechanism of the various stages of follicular atresia and the regression of corpus luteum in human. Apoptosis was examined by 3'-hydroxy nick end-labeling, by immunostaining of an apoptosis-related antigen, Le(y) and by cell death-related genes, bcl-2. Immunoreactivity for Le(y) and nick end-labeling reactive cells were not observed in the follicular and luteal phases, except for scattered cells in the degenerating corpus luteum. On the other hand, immunoreactivity for bcl-2 was observed in the granulosa cells of antral follicles. These results indicated that apoptosis is not obvious through follicular maturation and luteal regression. This may be due to the relatively long process of human follicular growth and atresia.