Objective: To determine whether interstitial collagenase (matrix metalloproteinase-1), known to play a pivotal role in the initiation of menstruation, contributes to the pathogenesis of endometriosis.
Design: Serial sections of peritoneal red and black endometriotic lesions, ovarian endometriotic cysts, and rectovaginal adenomyotic nodules were analyzed by in situ hybridization for the expression of matrix metalloproteinase-1 by silver staining for the integrity of the fibrillar extracellular matrix and by immunolabeling for the abundance of sex steroid receptors.
Setting: Academic hospital and research laboratory.
Patient(s): Premenopausal women undergoing laparoscopy for endometriosis.
Intervention(s): Biopsy of endometriotic lesions, combined with endometrium whenever possible.
Main outcome measure(s): Expression of matrix metalloproteinase-1 messenger RNA (mRNA).
Result(s): Matrix metalloproteinase-1 mRNA was expressed focally in red peritoneal and ovarian endometriosis irrespective of the phase of the menstrual cycle but was not detectable in black peritoneal and rectovaginal lesions. Foci of matrix metalloproteinase-1 expression closely correlated with matrix breakdown and with the absence of P receptors in adjacent epithelial cells.
Conclusion(s): Correlation of matrix metalloproteinase-1 expression with activity of endometriotic tissue suggests its involvement in tissue remodeling and bleeding, and possibly in the secondary shedding and reimplantation of endometriotic lesions.