The inhibitory effects of recombinant human erythropoietin (rhEPO) were examined against (1) the progression of renal fibrosis in mice with complete unilateral ureteral obstruction and (2) the TGF-β1-induced epithelial-to-mesenchymal transition (EMT) in MDCK cells. Unilateral ureteral obstruction was induced in BALB/c mice and rhEPO (100 or 1000 U/kg, intraperitoneally, every other day) or vehicle was administered from day 3 to day 14. Immunoblotting and immunohistochemistry revealed increased expressions of TGF-β1, α-smooth muscle actin (α-SMA), and fibronectin and decreased expression of E-cadherin in the obstructed kidneys. In contrast, rhEPO treatment significantly attenuated the upregulation of TGF-β1 and α-SMA and the downregulation of E-cadherin. MDCK cells were treated with TGF-β1 (5 ng/ml) for 48 h to induce EMT, and the cells were then co-treated with TGF-β1 and rhEPO for another 48 h. Increased expressions of α-SMA and vimentin and decreased expressions of zona occludens-1 and E-cadherin were observed after TGF-β1 treatment, and these changes were markedly attenuated by rhEPO co-treatment. TGF-β1 increased phosphorylated Smad-2 expression in MDCK cells, which was decreased by rhEPO co-treatment. In conclusion, rhEPO treatment inhibits the progression of renal fibrosis in obstructed kidney and attenuates the TGF-β1-induced EMT. It is suggested that the renoprotective effects of rhEPO could be mediated, at least partly, by inhibition of TGF-β1-induced EMT.
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