Apoptosis, proliferation, and sex hormone receptors in superficial parts of human endometrium at the end of the secretory phase

Apoptosis with one regulator, Bcl-2, and proliferation with the marker Ki-6 7 were studied in 75 endometrial biopsies representing superficial parts of endometriun from 35 regularly menstruating women premenstrually and menstr ually. Hormonal withdrawal was studied in serum samples and potentiated in epithelium by the decreasing 17 beta-estradiol and progesterone receptor sc ores 4 days premenstrually. The apoptotic index increased 2 days before the onset of menstruation and peaked on the second menstrual day. The high apo ptotic index together with low proliferation in endometrial epithelium at t he end of the menstrual cycle are similar to the involution process seen in other hormone-dependent organs. In stroma, the apoptotic index increased l ater, at the onset of menstruation, and the increase was lower than that in epithelium. The Ki-67 index increased during the last 3 days of the secret ory phase, parallel with an increasing progesterone receptor score and decr easing Bcl-2 staining, and peaked at the onset of menstruation. The finding s in stroma concur with high proliferation at the end of the menstrual cycl e and high cell turnover during menstruation, suggesting the participation of stroma in the renewal process of endometrium.