A new role for activin in endometrial repair after menses

Abnormal uterine bleeding can severely affect the quality of life for women. After menstruation, the endometrium must adequately repair to limit and stop bleeding. Abnormal uterine bleeding may result from incorrect or inadequate endometrial repair after menstruation. Previous studies have shown an important contribution of activin to skin wound healing, with severely delayed wound repair observed in animals transgenically induced to overexpress activin's natural inhibitor, follistatin. Activin subunits have also been identified within human endometrium; however, their role in endometrial repair is unknown. We assessed the contribution of activin to endometrial repair after menses using a human in vitro cell wounding method and our well-characterized mouse model of endometrial breakdown and repair applied to mice overexpressing follistatin. Endometrial repair after menses is initiated with reepithelialization of the uterine surface. To mimic this repair, we utilized a human endometrial epithelial cell line (ECC-1) and demonstrated significant stimulation of wound closure after activin A administration, and attenuation of this response by addition of follistatin. Immunolocalization of activin subunits, betaA and betaB, in control endometrium from the mouse model demonstrated specific epithelial and stromal localization and some leukocyte staining (betaA) around sites of endometrial repair, suggestive of a role for activin in this process. Follistatin-overexpressing animals had significantly higher circulating follistatin levels than wild-type littermates. There was a significant delay in endometrial repair after breakdown in follistatin transgenic animals compared with control animals. This study demonstrates for the first time a functional role for activin in endometrial repair after menses.