Regulation of proliferation and differentiation of prostatic stromal cells by oestradiol through prostatic epithelial cells in a paracrine manner

OBJECTIVE To characterize a paracrine effect of prostatic epithelial cells in the presence or absence of oestradiol on the differentiation and proliferation of prostatic stromal cells. MATERIALS AND METHODS Conditioned media (CM) collected from a prostatic epithelial cell line (BPH-1), which was pre-treated with different concentration of oestradiol, were added to cultures of primary prostatic stromal cells. The proliferation rates of stromal cells were determined using a tetrazolium assay. The mRNA level was analysed by real-time reverse transcription-polymerase chain reaction (RT-PCR), and the protein level of smooth muscle myosin heavy chain (SM-MHC), fibronectin and collagen IV were determined with Western blotting, enzyme- linked immunosorbent assay and radioimmunoassay, respectively. The expression of transforming growth factor β1 (TGFβ1) in the BPH-1 cell line was analysed. RESULTS The rate of proliferation of stromal cells increased when they were cultured with CM harvested from oestradiol-treated BPH-1 cells, but there was no remarkable change when they were cultured with CM from untreated cells. The level of smoothelin mRNA and SM-MHC protein increased after treatment with CM from BPH-1. The CM from BPH-1 with oestradiol stimulation was more effective in stimulating smoothelin mRNA and SM-MHC protein level. The protein level of collagen type IV, but not fibronectin, was up-regulated in the supernatants and cell extracts of CM-treated stromal cells. Oestradiol enhanced the expression and secretion of TGFβ1 in BPH-1 cells. TGFβ1-neutralizing antibody abrogated the effect of BPH-1 CM on the synthesis of collagen IV and SM-MHC in stromal cells. CONCLUSION These results suggest that oestradiol-stimulated proliferation and differentiation of prostatic stromal cells could be regulated by factors secreted from prostatic epithelial cells.