Deep venous thrombosis (DVT) and secondary pulmonary embolism affect 0.1-0.2% of the population and cause 60,000-100,000 deaths annually, an incidence and mortality similar to that of myocardial infarction. In 1856 the pathologist Rudolph Virchow implicated changes in venous blood flow in DVT pathogenesis, but a molecular and genetic basis for how hemodynamic changes drive DVT pathogenesis has not been identified, and present therapy is restricted to prophylactic measures to augment venous blood flow and systemic anticoagulation. We have recently demonstrated that the endothelial GATA2-FOXC2-PROX1 transcriptional pathway is activated by oscillatory or reversing flow and required to stimulate the formation of venous and lymphatic valves. Our preliminary studies demonstrate that endothelial cells around venous valves that experience similar oscillatory flow express the GATA2-FOXC2-PROX1 transcriptional program in association with a strong anti-coagulant phenotype marked by low vWF, high EPCR, high TM, and high TFPI expression. Loss of this transcriptional program conferred by altered venous flow or genetic deletion in peri-valvular ECs results in clot formation around the venous valve. We hypothesize that endothelial GATA2-FOXC2- PROX1 expression stimulated by oscillatory flow maintains an anticoagulant endothelial phenotype required to prevent DVT formation. This proposal will test this hypothesis using a combination of genetic approaches to specifically delete the GATA2/FOXC2/PROX1 pathway in mouse peri-valvular endothelial cells, surgical approaches to reduce venous flow in the mouse, and histologic and physiologic studies of human venous valves to test whether this mechanism is conserved in humans and lost during DVT pathogenesis. These studies are expected to establish a genetic and molecular mechanism for DVT pathogenesis that will serve as the foundation for novel mechanical and molecular therapies.
Our central question is how changes in blood flow in the veins leads to the formation of clots. An important clue to answering this question comes from work we have done demonstrating that oscillatory blood flow triggers the formation of venous and lymphatic valves through control of gene expression in the cells lining the vessel wall. We now propose that the same program is used after valves are formed to prevent blood clot formation in leg veins. We will test this idea by examining vascular cell responses to flow both inside and outside the body, by using mice to examine clot formation and the role of specific genes in that process, and by examining human veins in the setting of health and disease.