Differential regulatory effect of progesterone on the proliferation and apoptosis of uterine leiomyoma tissue explants and primary leiomyoma cell cultures

OBJECTIVE: The growth of uterine leiomyomas is regulated by progesterone, although the underlying molecular mechanisms are not fully understood. METHODS: Primary leiomyoma cells were isolated by standard method from 16 samples of uterine leiomyoma tissue. Uterine leiomyoma explants and primary leiomyoma cell cultures were exposed to progesterone in concentrations of 0.01 µg/ml, 0.1 µg/ml and 1 µg/ml for 24 h. Cell apoptosis was assessed with Annexin V assays performed in cell cultures by flow cytometry. The expression of PR-A, PR-B, Ki67, Akt, ERK, PTEN and PPARγ mRNAs was estimated in cultured leiomyoma cells and tissue explants by real time RT-PCR. RESULTS: Treatment with progesterone promoted viability and proliferation of cultured leiomyoma cells in a dose-dependent manner. Low and high doses of progesterone decreased early apoptosis of leiomyoma cells. High concentrations of progesterone increased the number of living cells in Annexin V assays. High doses of progesterone increased the expression of Ki67 mRNA, while low doses increased the expression of PR-A mRNA in cultured leiomyoma cells and tissue explants. In cell cultures, low doses of progesterone increased the expression of PR-B mRNA and the expression of PTEN and PPARγ mRNAs in a dose-dependent manner. Exposure of leiomyoma tissue explants to progesterone led to increased expression of PR-B and ERK mRNAs in a dose-dependent manner. CONCLUSIONS: The effects of progesterone on the apoptosis and proliferation of leiomyoma cells was dose-dependent and different in cell cultures and leiomyoma explants, possibly as a result of impacts derived from the tumor microenvironment.