There appear to be very few data on the exact mechanisms of a selective progesterone receptor modulator action in myomas. The aim of the study was to assess the effects of ulipristal acetate (UPA) on fibroids, especially on estrogen receptor (ER) and progesterone receptor (PR) immunoexpression, proliferation, apoptosis and tissue fibrosis, and to compare the above parameters in untreated (surgical attention only) and UPA-treated leiomyomas. UPA-treated patients were divided into three groups: (1) good response (≥25% reduction in volume of fibroid), (2) weak response (insignificant volume reduction) and (3) no response to treatment (no decrease or increase in fibroid volume). The study observed a significant decrease in the percentage of collagen volume fraction and ER and PR immunoexpression in the good response group, in the percentage of proliferating cell nuclear antigen (PCNA)- and Ki67-positive cells in the groups with good and weak reactions vs. control group; significantly higher apoptotic index (terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL)-positive cells) in the good reaction group vs. control group. The results of the study indicate that a good response to UPA, manifested by a volume reduction of myoma, may be associated with a decrease in fibrosis, ER/PR and PCNA and Ki67 immunoexpression and an increase in cell apoptosis within the myoma.
Keywords: apoptosis; estrogen receptor; fibrosis; progesterone receptor; proliferation; ulipristal acetate; uterine myoma.