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. Eutopic endometrium from healthy women was transferred to the CAM and cultivated ectopically for up to 3 days. Before transplantation and after 24, 48 and 72 h of culture on the CAM, total RNA was extracted and reverse transcribed. Human MMP-1 (interstitial collagenase) and MMP-2 (gelatinase A) mRNA expression was assessed by competitive PCR. Results were normalized to the content of human glyceraldehyde 3-phosphate dehydrogenase (GAPDH) mRNA. In eutopic endometrium, 0.29 amol MMP-1 mRNA and 0.42 fmol MMP-2 mRNA per fmol GAPDH mRNA were found. Relative MMP-1 mRNA concentrations increased strongly after culture on the CAM, while MMP-2 mRNA levels were nearly unaltered. This differential regulation suggests different roles of these enzymes in the angiogenesis of ectopic endometrial fragments and during the development of endometriosis.