Objective: To investigate the regulation of perimenstrual MMP-1 expression in human endometrium.
Design: In vitro study utilizing epithelial-stromal co-cultures.
Setting: Cell Biology Unit, International Institute of Cellular and Molecular Pathology, and Departments of Pathology and Gynecology, Saint-Luc University Clinics, Louvain University Medical School, Brussels, Belgium.
Methods: Contact-dependent and contact-independent co-cultures were established and resulting MMP-1 gene and protein expression was analyzed by RNase protection assays and soluble-collagen assays.
Results: MMP-1 expression in endometrial fibroblasts is markedly stimulated by epithelial cell-conditioned medium. This stimulation can be prevented by antibodies directed against interleukin 1 alpha (IL-1 alpha). Ovarian steroids inhibit MMP-1 production by IL-1 alpha-stimulated fibroblasts in vitro.
Conclusion: Taken together, our results suggest that epithelium-derived IL-1 alpha is the most important paracrine induced of MMP-1 in endometrial fibroblasts. However, IL-1 alpha-stimulated MMP-1 production in the human endometrium is effectively blocked by ovarian steroids. We believe that this mechanism responsible for the MMP-1 repression that occurs when systemic sex steroid concentrations are high and the MMP-1 production and activity during the perimenstrual phase when estrogen and progesterone concentrations are low.