Apoptosis and Expression of bcl-2, bax in the Cyclic Human Endometrium

Suh, Chang Suk; Moon, Shin Yong

Abstract

OBJECTIVE
To understand the regulatory mechanism of apoptosis by pro- and anti-apoptotic genes in the cyclic human endometrium.
METHODS
Each case of endometrial status was classified by Noyes criteria, and grouped into early proliferative(n=13), late proliferative(n=14), early secretory(n=15), and late secretory phases(n=15). Expression of bcl-2, and bax were assessed by Northern blot and immunohistochemistry in relation to apoptotic index by TUNEL. Results: Apoptotic index showed increasing tendency as progressing to the late secretory phase, which phase showed significantly higher apoptotic index compared to the other phases(p<0.05). The intensity of bcl-2 8.5kb transcript by Northern blot was highest in the late proliferative phase significantly(p<0.05), decreasing to nadir in the late secretory phase. In contrast to bcl-2 expression, bax mRNA expression was highest in the late secretory phase significantly(p<0.05). Both the relative ratio of bcl-2 8.5kb transcript and bcl-2 5.5kb trascript to bax showed that the ratio was higher in the early, and late proliferative phase, but, reversed in the late secretory phase. Both the immunoreactivity of bcl-2 and bax proteins could be detected in the basal, functional, and stromal layers of endometrium. The immunoreactivity of bcl-2 protein was more prominent in the proliferative phase, however, bax protein was more prominent in the secretory phase.
CONCLUSION
This study suggests that apoptosis could be regulated by the relative dominance of bcl-2 or bax expression in the human endometrium. Thus, bcl-2 and bax expressions might be one of the possible mechanism in the regulation of normal menstruation.