Matrix metalloproteinases: expression and regulation in the endometrium during the estrous cycle and at the maternal-conceptus interface during pregnancy in pigs.

Objective: Matrix metalloproteinases (MMPs) are a family of endoproteases produced by various tissues and cells and play important roles in angiogenesis, tissue repair, immune response, and endometrial remodeling. However, the expression and function of MMPs in the pig endometrium during the estrous cycle and pregnancy have not been fully elucidated. Thus, we determined the expression, localization, and regulation of MMP2, MMP8, MMP9, MMP12, and MMP13 in the endometrium throughout the estrous cycle and at the maternal-conceptus interface during pregnancy in pigs.

Methods: Endometrial tissues during the estrous cycle and pregnancy and conceptus and chorioallantoic tissues during pregnancy were obtained and the expression of MMPs was analyzed. The effects of steroid hormones and cytokines on the expression of MMPs were determined in endometrial explant cultures.

Results: Expression levels of MMP12 and MMP13 changed during the estrous cycle, while expression of MMP2, MMP9, MMP12, and MMP13 changed during pregnancy. Expression of MMP2, MMP8, and MMP13 mRNAs was cell type-specific at the maternal-conceptus interface. Gelatin zymography showed that enzymatically active MMP2 was present in endometrial tissues. In endometrial explant cultures, estradiol-17β induced the expression of MMP8 and MMP12, progesterone decreased the expression of MMP12, interleukin-1β increased the expression of MMP2, MMP8, MMP9, and MMP13, and interferon-γ increased the expression of MMP2.

Conclusion: These results suggest that MMPs expressed in response to steroids and cytokines play an important role in the establishment and maintenance of pregnancy by regulating endometrial remodeling and processing bioactive molecules in pigs.