After activation, MMPs activity is generally controlled by soluble inhibitors (TIMPs) but can also be regulated by endocytosis. Looking at mechanisms of MMPs clearance, we found that RAP, a natural antagonist of the low-density lipoprotein receptor-related protein (LRP-1), causes a strong accumulation of some MMPs in the conditioned medium of endometrial explants. Although LRP-1 mRNA is fairly stable during the menstrual cycle, the protein level of LRP-1 is minimal at menses. Thus, LRP-1-mediated endocytosis of MMPs could represent an additional regulatory mechanism of MMPs activity during the menstrual cycle, in synergy with TIMPS. Current projects aim at investigating the mechanisms of postranslational control of LRP-1.