Canonical Wnt/ β‐catenin Signaling Pathway mediates Shear Stress‐Activated Angiopoeitin‐2 expression and vasculogenesis

Abstract

It is well known that fluid shear stress is intimately involved in vascular stability and differentiation. In particular, low or oscillatory shear stress (OSS) upregulates Angiopoietin‐2 (Ang‐2) in human aortic endothelia cells (HAEC) via VEGF‐dependent mechanism. We hypothesized that Wnt signaling is implicated in shear stress activated vasculogenesis via modulating Ang‐2. Activation of Wnt signaling was assessed with TOPflash lentivirus reporter. After 8 hours of oscillatory flow, HAECs infected with lentivirus of Wnt reporter demonstrated markedly increased luciferase activity compared to cells under static condition, suggesting an activation of canonical Wnt signaling pathway with OSS. We further demonstrated that Wnt3a, a Wnt activator, upregulated Ang‐2 mRNA expression, whereas DKK‐1, a Wnt inhibitor, inhibited Ang‐2 expression in both HAEC cell lines and Tg(hsp70:dkk1‐GFP) zebrafish embryos 72 hours post‐fertilization (hpf). Knock‐down of Ang‐2 by siRNA in HUVEC resulted in impaired tube formation. Similarly, Ang‐2 knock‐down with morpholino oligomers in 72 hpf Tg(flk1:GFP) zebrafish embryos caused impaired systematic vasculature development. Taken together, our findings suggest that Wnt/β‐catenin signaling pathway mediates shear stress‐activated endothelial Ang‐2 and regulates vasculogenesis. These studies were supported by NIH HL083015 and HD069305.Grant Funding Source: NIH