BMP-7 fails to attenuate TGF-β1-induced epithelial-to-mesenchymal transition in human proximal tubule epithelial cells

Background. In rodent models of chronic renal disease bone morphogenetic protein-7 (BMP-7) has been shown to halt disease progression and promote recovery. Subsequent studies utilizing immortalized rodent renal cell lines showed that BMP-7 was renoprotective by antagonizing TGF-β1-stimulated epithelial-to-mesenchymal transition(EMT).ThepresentstudysoughttodetermineifBMP7 prevents TGF-β1-induced EMT in primary (RPTEC) andimmortalized(HK-2)humanproximaltubuleepithelial cells. Methods. EMT was determined by quantitative real-time PCR analysis of e-cadherin, vimentin, CTGF and TGF-β1 transcript expression and immunocytochemical analysis of ZO-1 and α-smooth muscle actin (α-SMA) protein expression following TGF-β1 treatment in RPTEC and HK-2 cells. Results. In RPTEC and HK-2 cells, TGF-β1 significantly reduced e-cadherin expression and significantly increased vimentin, CTGF and TGF-β1 expression. TGF-β 1a lso diminished ZO-1 immunoreactivity and increased α-SMA expression in confluent cell monolayers. Co-incubation of TGF-β1 with an anti-TGF-β1 neutralizing antibody substantially reduced the cytokine’s effects, which indicated EMT in these cells was inhibitable. Co-administration of BMP-7 over a broad concentration range (0.01–100 µg/ml) with TGF-β1 failed to attenuate EMT in RPTEC or HK-2 cells,asdemonstratedbynoinhibitionofalterede-cadherin, vimentin, CTGF and TGF-β1 expression and no restoration of ZO-1 immunoreactivity. Furthermore, when BMP-7 was applied to proximal tubule cells alone, it also decreased e-cadherin expression and increased vimentin, CTGF and TGF-β1 expression. Additionally, BMP-7 failed to induce the mesenchymal-to-epithelial transition (MET) in NRK49F rat renal fibroblasts. BMP-7 did however prevent TGFβ1-mediatede-cadherindownregulationinTCMK-1mouse renal tubular epithelial cells. BMP-7 activity was routinely