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

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Abstract
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.