The regulation of trophoblast invasion and decidual reaction by matrix metalloproteinase‐2, metalloproteinase‐7, and metalloproteinase‐9 expressions in the rat endometrium

PURPOSE: We aimed to evaluate how matrix metalloproteinases (MMPs) regulate the trophoblast invasion and placentation. METHODS: Female rats were divided into the estrous cycle and early pregnancy day groups. Obtained uterine tissues and implantation sites were processed for immunofluorescence and real‐time PCR examinations. RESULTS: The mRNA expression of MMP‐7 was higher than MMP‐2 and MMP‐9. Immunofluorescence findings confirmed that MMP‐2, MMP‐7, and MMP‐9 were localized in the endometrial stroma, while MMP‐7 was high in glandular and lining epithelial cells throughout the entire estrous cycle. However, their immunolocalizations and mRNA expressions were dramatically changed with the early pregnancy days. The MMP‐7 reached very strong immunostaining in the giant trophoblast cells (GTCs), and the cytoplasm of mature and differentiating decidual cells, whereas MMP‐2 and MMP‐9 were mostly seen in the primary decidual zone (PDZ), GTCs, and the endothelium of blood vessels. CONCLUSIONS: All three MMPs seemed likely to be a key mediator of trophoblast invasion into the decidual region as well as angiogenesis during the placentation process. Due to the strong and wide expression of MMP‐7 in the mature decidua, it could be suggested that MMP‐7 is important for decidual ECM remodeling and it might be used as a new marker of decidual reaction.