PROJECT SUMMARY: The cornea is a unique structure that remarkably maintains its optic clarity by remaining completely avascular. Diseases in which the optical clarity of the cornea is lost are the third most common cause of blindness worldwide. Although the etiology of these diseases may be distinct, most converge on a common pathway leading to the growth of pathological vessels in this tissue, a process known as corneal neovascularization (CoNV). CoNV is ultimately a consequence of an imbalance between proangiogenic factors and antiangiogenic factors in the corneal limbus. As vascular and lymphatic vessels grow into the corneal stroma, edema, inflammation, protein and lipid deposition, and scarring can occur, leading to corneal opacities, visual impairment or blindness. It is estimated that 1.4 million people develop CoNV per year, 12% of whom suffer the subsequent significant loss of vision. We have recently described the role of Angiopoeitin-like 4 (ANGPTL4), as a potent pro-angiogenic and vessel hyperpermeability factor in posterior segment diseases, including diabetic retinopathy, proliferative sickle retinopathy, and uveal melanoma. Interestingly, we recently found an additive effect in the induction of vessel hyperpermeability by ANGPTL4 and VEGFA. Furthermore, we found that ANGPTL4 binds Neuropilin (NRP)1 and 2, two plasma membrane isoforms that act as co-receptors for several members of the VEGF family. More recently, we have observed a role for ANGPTL4 in promoting angiogenesis in the anterior segment, leading to the development of CoNV and corneal pterygia. Growing appreciation of the role of lymphangiogenesis in the development of anterior segment pathological angiogenesis prompted us to explore a role for ANGPTL4 in this process. Recently, we have observed that ANGPTL4 potently induces the migration and sprouting of lymphatic endothelial cells (lECs), and this appears to be dependent on ANGPTL4 binding to NRP2. Collectively, these observations suggest that ANGPTL4 could play a central role in the development of CoNV. We propose that a combinatorial therapy targeting VEGFs and ANGPTL4 may be a more effective treatment for CoNV patients. The objective of this proposal is to investigate the role of ANGPTL4/NRPs alone or in combination with VEGFs as regulators of hemangiogenesis and lymphangionesis and thus as important pathways influencing the avascularity of the cornea. The successful completion of these investigations will move us towards a combinational therapy targeting ANGPTL4 and VEGF signaling as a novel alternative for the treatment of CoNV.