Localization of Bcl-2 in the human fetal müllerian tract.

Objective: To determine if apoptosis is involved in development of the human fetal mullerian tract and regression of the uterine septum and to localize Bcl-2. a protein involved with regulating apoptosis.

Design: Descriptive controlled study.

Setting: Tertiary academic medical center.

Patient(s): Eight human fetal uteri from 12 to 21 weeks' gestation.

Intervention(s): Immunohistochemistry using a monoclonal antibody for Bcl-2.

Main Outcome Measure(s): Immunostaining.

Results: Bcl-2 was localized in endometrial cells, tubal muscularis and epithelium, and myometrial edges. It was absent from the septum of 4 uteri.

Conclusions: The presence of Bcl-2 suggests that development of the human fetal müllerian tract involves apoptosis. Bcl-2 may protect the fetal endometrium from apoptosis as it continues to grow. The superior, inferior, and lateral myometrium as well as the tubal epithelium and muscularis also may represent active growth zones that are protected from apoptosis. The notable absence of staining for Bcl-2 in the embryonal uterine septum may indicate lack of protection from apoptosis in this area. This finding supports our hypothesis that apoptosis may be a mechanism by which the uterine septum regresses.