Differential induction of matrix metalloproteinase 1 and 2 in ectopic endometrium.

According to the transplantation theory, endometriosis develops from endometrial fragments that are retrogradely menstruated into the peritoneal cavity. In order to develop into endometriotic lesions, they have to connect to the vascular system by angiogenesis, probably involving matrix metalloproteinases (MMP) as key enzymes in extracellular matrix remodelling. A model of endometriosis using the chorioallantoic membrane (CAM) of chick embryos was established.