Modulating the resolution of angiogenesis and normalization of the vasculature for therapeutic benefit

Cardiovascular diseases are a leading cause of morbidity and mortality worldwide. Defective vascular repair or insufficient vascularization after disrupted or blocked blood flow often lead to ischemic peripheral artery diseases and other cardiovascular disorders. Treatment options generally aim to re-establish blood flow through affected vascular beds. Angiogenesis, or the formation of new blood vessels from existing vasculature, is fundamental for forming and maintaining the microvascular network and blood vessels that are required for metabolically active tissue growth and repair. Therapeutic angiogenesis is being actively pursued as a treatment to induce, augment and control angiogenic responses and to restore blood supply to ischemic tissues. Most angiogenic therapies have focused on activation of angiogenesis, using stimuli that promote the growth of new blood vessels employing growth factors (e.g. VEGF), stem or progenitor cells, gene delivery and/or extracellular vesicles. Outcomes have been mixed and have had limited therapeutic success. This is largely due to our incomplete understanding of basic mechanisms that regulate the resolution of angiogenesis. Where the angiogenic vasculature does not achieve resolution, the neovasculature is inherently leaky, disorganized, and unresolving, resulting in edema, impaired function, and morbidity. What is poorly understood at this time are the fundamental processes that regulate resolution of angiogenesis, so that more efficacious and specific therapeutic approaches can be devised. We discovered that the membrane-anchored serine protease, testisin, is a novel proteolytic orchestrator of microvascular endothelial cell remodeling during resolution of angiogenesis. Strong preliminary data show that that testisin promotes VE-cadherin inter-junctional adhesions, suppresses a G-protein coupled protease activated receptor-2-dependent proangiogenic signaling pathway and directs the laying down of a provisional fibrin matrix required for directed endothelial cell migration for reparative angiogenesis. These unique activities are unexpected, and reveal a major gap in our understanding of modulators of angiogenic pathways utilized by endothelial cells to repair and normalize vasculature. The proposed research plan will utilize a combination of molecular biology, biochemistry and cell biology techniques, in concert with several in vivo mouse models to address the following specific aims: 1) to define mechanisms by which testisin deficiency impairs resolution of angiogenesis, and 2) to test the therapeutic efficacy of augmenting the testisin pathway to promote resolution of angiogenesis. Augmentation of natural processes that facilitate the normalization of vasculature has potential for treatment of diseases that are perpetuated by unresolving or insufficient angiogenesis, and for enhancing effective delivery of cancer therapeutics.