Abstract
Protease system is an essential mechanism for human body which contains various molecule including its inhibitors. In human pregnancy, this system takes an important role on trophoblast invasion, spiral artery remodeling and the maintenance of the course of pregnancy. In this review, we describe roles of proteases (matrix metalloproteinases, plasminogen activators and inhibitors) in early pregnancy, especially on placentation. A radical switch of the placentation process from invasive trophoblast invasion (until 10w GA) to spiral artery remodeling (12 to 15w GA, which now regarded as a key pathophysiology of the complicated human pregnancy if it failed) is considered to be owe to the protease system alteration on invasive trophoblast and uterine natural killer cells. Further research into protease system in human reproduction is needed for understanding of mysterious establishment of early human pregnancy.
