INVOLVEMENT OF APOPTOSIS IN OVARIAN FOLLICULAR ATRESIA AND POSTOVULATORY REGRESSION

TLDR

More than 99 % of ovarian follicles are destined to degenerate, with fewer than 400 of over 400 000 at puberty ovulating, and the exact mechanism of follicular atresia remains unknown. Using a sensitive 3‑end DNA labeling technique, the study detected internucleosomal DNA cleavage in atretic follicles of chicken and pig ovaries, indicating apoptosis similar to that seen in embryogenesis and other programmed cell death processes. These results establish a foundation for identifying hormonal signals that trigger follicular atresia during recruitment, reproductive aging, and premature ovarian failure.

Abstract

In the ovary, greater than 99% of the follicles present at birth are destined to degenerate during life. In humans, less than 400 of the more than 400,000 follicles found at puberty will eventually ovulate whereas the overwhelming majority of follicles undergo atresia. Although follicular atresia plays a critical role during the recruitment of follicles for ovulation, the exact mechanism of this process is unknown. In chicken and porcine ovaries, atretic follicles can be morphologically distinguished from their healthy counterparts of the same size. Adapting a sensitive 3’-end labeling method for DNA analysis, we identified internucleosomal cleavage of cellular DNA in atretic (but not normal) follicles of both animal species, resembling that found during programmed cell death in embryogenesis, autoimmune T-cell removal and prostate regression. The present findings provide: a basis for elucidating the hormonal signals involved in the initiation of follicular atresia during follicle recruitment, reproductive aging and premature ovarian failure.