Matrix metalloproteinases and their tissue inhibitors in antegradely shed menstruum and peritoneal fluid

OBJECTIVE: To investigate the expression of matrix metalloproteinases (MMPs) and their tissue inhibitors (TIMPs) in antegradely shed menstruum and peritoneal fluid. DESIGN: A cell biological and immunohistochemical study. SETTING: Tertiary care university medical center. INTERVENTION(s): Immunohistochemistry was performed on cryostat sections and cultures of menstrual endometrium. Zymography was used to characterize MMP activity in peritoneal fluid, in menstrual serum, and in conditioned medium. Western blot analysis was used to further identify the MMPs in these fluids. MAIN OUTCOME MEASURE(s): Staining of MMPs and TIMPs in cryostat sections and cultures and MMP expression and activity in peritoneal fluid and menstrual blood serum. RESULT(s): Strong staining for MMP-1 and MMP-3 was observed in stroma and for MMP-7 in epithelium. Matrix metalloproteinase-2 and MMP-9 were weakly expressed in stroma. Both TIMP-1 and TIMP-2 were expressed in menstrual endometrium. Menstrual serum showed a pattern of MMP activity on zymography different from peritoneal fluid. Western blot analysis showed the presence of MMP-7 and MMP-9 in menstrual serum. CONCLUSION(s): Antegradely shed menstrual endometrium expresses several MMPs and TIMPs, even after culturing for 24 hours. MMP activity in menstrual serum is different from and more intense than MMP activity in peritoneal fluid. These enzymes may be involved in the early invasion of menstrual endometrium into the extracellular matrix of the peritoneum.