Angiogenesis extent and expression of matrix metalloproteinase-2 and -9 in ovarian endometriomata.

Abstract

Objective: Angiogenesis and matrix metalloproteinases (MMPs) expression play a central role in development of endometriosis. The purpose of the present study is to study the extent of angiogenesis and MMPs expression in ovarian endometriomata, which represent the highest grade of the disease. Design: Molecular and biological studies in human endometriotic tissue. Materials/Methods: The study has been performed in 44 endometriomata, removed during laparoscopy by stripping technique. Control group was represented by 10 normal parous women, submitted during mid-follicular phase to endometrial biopsy and laparoscopy for infertility. Studies on MMP-2 and -9 expression were performed by in situ hybridization. Angiogenesis was examined by counts of microvessels stained by Factor VIII and CD31 antibodies. The angiogenic capacity of tissues was analyzed by chick embryo chorioallantoic membrane (CAM) system. The significance of changes in microvessels number was assessed by Fisher’s test and Kruskal-Wallis test, corrected by Duncan, Bonferroni and Wilcoxon tests to compare groups two by two. Correlations were examined by linear regression analysis. Results: We described a trend of microvessel counts to increase in endometriotic tissue (both stage 3 and 4) as a whole compared to control tissues (p < 0.001). Simultaneously, there was a trend of vessel count to increase in these tissues together with their higher angiogenic capacity in the CAM. Moreover, we observed a significant increase in the frequency of MMP-2 expression (p < 0.001), MMP-9 expression (p < 0.01) and their co-expression (p < 0.05) over control tissues. In all ovarian endometriomata, MMP-2 was detected in endothelial cells and fibroblasts, whereas MMP-9 was found in a subset of macrophages (evidenced by CD68 staining). In addition, CD31 was more effective than factor VIII in highlighting more immature vessels, thus implying its pivotal role as a prognostic marker in endometriosis. Conclusions: Our data shows that angiogenesis extent, evaluated as microvessel number, and the expression of mRNA for MMP-2 and –9 by ectopic endometrial cells increase in ovarian endometriomata. Since MMP-2 and -9 are also expressed by host stromal cells (microvascular endothelial cells, fibroblasts and macrophages), this suggests that endometriosis gives increased proteolytic and angiogenic activity, therefore there are more opportunities for ovarian endometriomata cells to enter the circulation and spread systemically.