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.