• Ye Zhao, Xi Qiao, Thian Kui Tan, Hong Zhao, Yun Zhang, Lixin Liu, Jianlin Zhang, Lihua Wang, Qi Cao, Yiping Wang, Ya Wang, Yuan Min Wang, Vincent W S Lee, Stephen I Alexander, Harris David C H DCH Centre for Transplant and Renal Research, The Westmead Institute for Medical Research, The University of Sydney, Sydney, NSW, Australia., and Guoping Zheng.
• Centre for Transplant and Renal Research, The Westmead Institute for Medical Research, The University of Sydney, Sydney, NSW, Australia.
• Nephrol. Dial. Transplant. 2017 May 1; 32 (5): 781-791.

BackgroundEndothelial cells are known to contribute to kidney fibrosis via endothelial-mesenchymal transition (EndoMT). Matrix metalloproteinase 9 (MMP-9) is known to be profibrotic. However, whether MMP-9 contributes to kidney fibrosis via EndoMT is unknown.MethodsPrimary mouse renal peritubular endothelial cells (MRPECs) were isolated and treated by recombinant human transforming growth factor beta 1 (rhTGF-β1) with or without MMP-9 inhibitor or by recombinant human MMP-9 (rhMMP-9) alone. Kidney fibrosis was induced by unilateral ureteral obstruction (UUO) in MMP-9 knockout (KO) and wide-type (WT) control mice. The effects of MMP-9 on EndoMT of MRPECs and kidney fibrosis were examined.ResultsWe showed that MRPECs underwent EndoMT after rhTGF-β1 treatment or in UUO kidney as evidenced by decreased expression of endothelial markers, vascular endothelial cadherin (VE-cadherin) and CD31, and increased levels of mesenchymal markers, α-smooth muscle actin (α-SMA) and vimentin. The expression of fibrosis markers was also up-regulated significantly after rhTGF-β1 treatment in MRPECs. The EndoMT and fibrosis markers were significantly less in rhTGF-β1-treated MMP-9 KO MRPECs, whereas MMP-9 alone was sufficient to induce EndoMT in MRPECs. UUO kidney of MMP-9 KO mice showed significantly less interstitial fibrosis and EndoMT in MRPECs. Notch signaling shown by Notch intracellular domain (NICD) was increased, while Notch-1 was decreased in rhTGF-β1-treated MRPECs of MMP-9 WT but not MMP-9 KO mice. Inhibition of MMP-9 or Notch signaling prevented rhTGF-β1- or rhMMP-9-induced α-SMA and NICD upregulation in MRPECs. UUO kidney of MMP-9 KO mice had less staining of Notch signaling transcription factor Hey-1 in VE-cadherin-positive MRPECs than WT controls.ConclusionsOur results demonstrate that MMP-9-dependent Notch signaling plays an important role in kidney fibrosis through EndoMT of MRPECs.© The Author 2016. Published by Oxford University Press on behalf of ERA-EDTA.

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