Abstract 313: TGF-beta Signaling Mediates Endothelial-to-mesenchymal Transition During Arteriovenous Fistula Remodeling In The Chronic Kidney Disease Environment

Objectives: Arteriovenous fistulae (AVF) are the optimal conduit for hemodialysis access in patients with end-stage chronic kidney disease (CKD); however, AVF have high rates of failure due to aggressive neointimal hyperplasia(NIH). NIH in the CKD environment is characterized by endothelial-to-mesenchymal transition (EndMT). We hypothesized that endothelial TGF-β signaling promotes EndMT to cause AVF failure. Methods: Aortocaval AVF were created in C57BL/6J mice, with control mice having sham procedures. 3 weeks prior to AVF, CKD was created via 5/6 nephrectomy (Nx); five groups were tested, including sham, sham+5/6Nx, AVF+0/6Nx, AVF+3/6Nx, AVF+5/6Nx. Endothelial cell (EC)-and smooth muscle cell (SMC)-specific TGFβRI II knockout mice were treated with tamoxifen 2 weeks prior to AVF; Ultrasound was used to determine AVF diameter and patency at postoperative days 7, 14, and 21. AVF were harvested at days 7 or 21 and examined with histology, Immunofluorescence and Western blot. Results: There was no difference between mice treated with 0/6Nx or 3/6Nx regarding AVF diameter, AVF wall thickness and accumulation of extracellular matrix (ECM) components fibronectin, collagen1, and collagen3; however, AVF diameter was significantly decreased in mice treated with 5/6Nx compared with 0/6Nx or 3/6Nx, whereas there was increased AVF wall thickness as well as immunoreactivity of fibronectin (p=0.031), collagen1 (p=0.022), collagen3 (p=0.005), and TGF-β1 (p=0.022), compared with 0/6Nx. Endothelial cells in the AVF of mice treated with 5/6Nx had significantly increased immunoreactivity of the mesenchymal markers notch3 (p<0.0001), vimentin (p<0.0001) and FSP-1 (p=0.02) compared to 0/6Nx. However, blocking TGFβ signaling using either EC-KO or SMC-KO mice had significantly decreased immunoreactivity of mesenchymal markers and wall thickness (p<0.0001), consistent with reduced EndMT, and increased diameter (p=0.035). Interestingly, the AVF wall thickness in EC-KO mice was thinner than in SMC-KO mice. Conclusion: Both EC- and SMC-specific TGF-β signaling promote EndMT and wall thickening during venous remodeling in the CKD environment. These data suggest that the TGF-β signaling pathway may be a potential therapeutic target to prevent AVF failure.