Apoptosis in human endometrial and endometriotic tissues

Apoptosis has recently been proposed to represent programmed cell death. Several investigations have revealed that uterine endometrium in mammals can be regulated by apoptosis. However, apoptosis may be less likely to occur in human eutopic endometrium. On the other hand, immunoreactivity of Bcl-2 that may serve a regulatory function in protecting from undergoing apoptosis was observed in uterine endometrial glandular cells in the proliferative phase through to the early secretory phase. In endometriotic tissues, although apoptosis was detected in all the samples from ovarian endometriosis, it was indicated in only a few tissues from adenomyosis. Bcl-2 was negative in almost all samples from ovarian endometriosis, whereas it was positive in all adenomyotic tissues from cases in the proliferative phase, but in none of tissues from cases in the secretory phase. Thus, ovarian endometriosis can be discriminated from adenomyosis based on the existence of apoptosis though both represent a type of ectopic endometrial tissue, and the pathogenesis or condition of the cells may be different between ovarian endometriosis and adenomyosis.