BMP-7 counteracts TGF0-β1-induced tubular epithelial-myofibroblast transdifferentiation of cultured renal tubular epithelial cells

Objective To study the possible role of bone morphogenetic protein 7(BMP 7) in the TGF β1 induced tubular epithelial myofibroblast transdifferentiation (TEMT) of cultured renal tubular epithelial cells. Methods The normal rat kidney tubular epithelial cell line (HK 2) was cultured for three days on plastic plates in the presence or absence of recombinant TGF β1 and BMP 7. The alterations in the phenotype were assessed by phase contrast microscopy. Transdifferentiation of tubular cells into myofibroblasts was assessed by immunofluorescence, with monoantibodies to alpha smooth muscle actin (α SMA), vimentin and cytokeratin respectively. The expression of α SMA of HK 2 cells was measured by flowcytometry. The expression of α SMA mRNA of HK 2 cells was assessed with reverse transcriptase polymerase chain reaction (RT PCR). Results Treatment of HK 2 cells with BMP 7(50 and 100 ng/ml) for 24～48 hours increased cellular proliferation. The culture of HK 2 cells in the presence of TGF β1 induced a clear fibroblast like morphology, a loss of the epithelial marker cytokeratin and de novo expression of α SMA and vimentin. Immunofluorescence staining showed the addition of various concentrations of BMP 7 to subconfluent cells for 24 and 48 hours, and the expression of α SMA and vimentin was decreased. There was an increase in the percentage of cells expressing α SMA with TGF β1, which was completed inhibited by an addition of BMP 7(P 0 05).Conclusions TGF β1 is a key mediator that regulates the transdifferentiation of tubular epithelial cells into α SMA(+) myofibroblast. The ability of BMP 7 to block TGF β1 induced TEMT indicates that BMP 7 treatments may lead to the design of a new therapeutic strategy for renal fibrosis.