Objective
To characterize the efficacy of mifepristone treatment on extracellular matrix (ECM) production in leiomyomas. Design: Laboratory study. Setting: University research laboratory. Patient(s): None. Intervention(s): Treatment of human immortalized two-dimensional (2D) and three-dimensional (3D) leiomyoma and myometrial cells with mifepristone and the progestin promegestone (R5020). Main outcome measure(s): Expression of COL1A1, fibronectin, versican variant V0, and dermatopontin in treated leiomyoma cells by Western blot analysis and confirmatory immunohistochemistry staining of treated 3D cultures. Result(s): Treatment with progestin stimulated production of COL1A1, fibronectin, versican, and dermatopontin. Mifepristone treatment inhibited protein production of these genes, most notably with versican expression. Combination treatment with both the agonist and antagonist further inhibited protein expression of these genes. Immunohistochemistry performed on 3D cultures demonstrated generalized inhibition of ECM protein concentration.