Abstract 13974: Loss of Endothelial Primary Cilia Promotes Thrombus Formation in Mice

Abstract

Introduction: Recent evidence suggest that endothelial cilia may suppress anti-inflammatory signaling and protect against atherosclerosis. Given that atherosclerosis predisposes to thrombosis, we hypothesized that endothelial cilia may also play a fundamental role in thrombogenesis. Hypothesis: We hypothesize that endothelial cilia is important for protection against thrombosis, and that loss of endothelial cilia promotes thrombus formation in mice. Methods: We focused on the intraflagellar transport 88 (IFT88) gene since endothelial deletion of IFT88 has been associated with decreased atherosclerotic lesions in a murine model of atherosclerosis. Key thrombosis-associated molecules were evaluated in IFT88-silenced human umbilical vein endothelial cells (HUVECs). Thrombi formation were monitored in the laser-injured cremasteric arteries of 8 week old male endothelial cell (EC) specific IFT88 knockout (EC-IFT88 -/- ) mice. Results: Compared to scrambled siRNA-treated HUVECs, those exposed to siIFT88 exhibited lower mRNA and protein levels of tissue factor pathway inhibitor (TFPI) and thrombomodulin, two key regulators of blood coagulation (-27% and -20%, respectively; N=3; p < 0.05). We next examined the effect of IFT88 loss on thrombosis in mice. Upon laser-induced injury, we determined, via mean fluorescence intensity, that although the thrombi formed in the cremasteric arteries of EC-IFT88 -/- mice were similar in size to those produced in the wild type (WT) mice (2.2 ± 0.6 and 2.0 ± 0.3 AU, respectively; x10 6 ; N=32 thrombi; p=0.8), the average rate at which thrombi developed was significantly faster in the EC-IFT88 -/- mice relative to that in WT mice (97 ± 11 and 57 ± 3 AU/s, respectively; N=32 thrombi; p<0.001). Conclusions: Loss of endothelial IFT88 results in decreased TFPI mRNA and protein expression in HUVECs. EC-IFT88 -/- mice exhibited earlier thrombi formation in our laser injury model of thrombosis. These results collectively suggest that endothelial cilia intricately regulates thrombus formation in a TFPI-dependent manner and represents a previously unrecognized target to modulate thrombosis susceptibility.