Expression of membrane-type 5 matrix metalloproteinase in human endometrium and endometriosis

Background. The metalloproteinases (MMPs) are a family of proteolytic enzymes involved in tissue remodeling and cell migration. Endometrial tissue remodeling proceeds during the menstrual cycle and requires a temporary and spatially balanced expression of several different MMPs. Various members of the MMPs also seem to play an important role in the invasion process of endometriosis; however, so far only a limited number of studies have focused on membrane-associated MMPs. Methods. The present study investigated the expression of membrane-type 5 metalloproteinase (MT5-MMP) in the human endometrium and endometriotic lesions by microarray hybridization, real-time polymerase chain reaction (PCR) and immunofluorescence. Results. Both the gene chip expression analyses as well as PCR indicated expression of MT5-MMP in normal human endometrium and strongly elevated transcript levels in most peritoneal endometriosis lesions analyzed. Moreover we detected enhanced MT5-MMP expression in the eutopic endometrium from patients suffering from endometriosis, further supporting a role of MT5-MMP in the formation of endometriosis. Immunohistochemical analysis was used to determine the intracellular localization and tissue distribution of MT5-MMP. While the MT5-MMP antigen expression could be clearly attributed to the membrane of epithelial cells, a highly complex differential immunohistochemical staining of MT5-MMP in the various compartments of endometrial tissue was observed. The strongest staining was seen in luminal epithelial cells, whereas endometrial glands frequently showed partial expression of MT5-MMP. Conclusion. Our microarray analysis and real-time PCR of MT5-MMP transcripts may point to an elevated tissue remodeling and cell migration in endometrium from endometriosis patients as implied by the function of related MMPs.