Abstract 240: TGFβ-Activated Kinase 1 is Required for Arteriovenous Fistula Maturation

Abstract

Objectives: Arteriovenous fistulae (AVF) remain the optimal conduit for hemodialysis access but continue to have high rates of primary failure to mature. Transforming growth factor-β-activated kinase 1 (TAK1) plays important roles in regulation of extracellular matrix (ECM) production and deposition as well as inflammatory signaling and prevention of apoptosis; however the function of TAK1 in mechanotransduction in response to hemodynamic changes such as occur during AVF maturation is not well understood. Since deposition of ECM is critical to AVF maturation, we hypothesized that TAK1 is a critical regulator of AVF maturation. Methods: Aortocaval fistulae were created via needle puncture in wild-type (WT) C57BL/6J mice. AVF diameter was serially assessed weekly by duplex ultrasound; AVF were harvested at days 7 or 21 for histological analysis using computerized morphometry, as well as qPCR and Western blot. Some mice were treated with either the TAK1 inhibitor 5Z-7-oxozeaenol (OZ, 0.5mg/kg/day, 7 days) or Lentiviral TAK1 ShRNA (1x 10 8 pfu/ml; adventitial transduction). Mouse lung endothelial cells (MLECs) were exposed to laminar shear stress (3 or 20 dyne/cm 2 , 1h); TAK1 signaling was detected by Western blot and immunofluorescence. Results: TAK1 mRNA expression was increased at days 7 and 21 in AVF (2.0-fold; day 21; p<0.05) compared with sham controls. In AVF treated with OZ there was reduced fistula diameter (p=0.0059) and wall thickness (p=0.031) at day 21, as well as reduced collagen and fibronectin deposition (p<0.05), compared to controls. TAK1 knockdown with ShRNA also showed reduced fistula diameter at day 21 (p<0.05), compared to controls. MLECs exposed to arterial magnitudes of laminar shear stress showed increased TAK1 phosphorylation and downstream signaling (p<0.05) compared to MLECs exposed to venous shear stress or static conditions, which was reduced in cells either pretreated with OZ (p<0.0001) or transfected with TAK1 ShRNA (p<0.05). Conclusions: TAK1 regulates ECM production during AVF maturation. Strategies to alter TAK1 function in vivo may be a novel therapeutic approach to improve AVF maturation.