Heparan sulfate (HS) is a ubiquitously expressed and highly modifiable glycosaminoglycan implicated in a variety of biological processes, including corneal inflammation and neovascularization. Despite the widespread nature of HS, little is known about how its modifications and cleavage can regulate downstream cellular processes and signal transduction pathways. Our lab has recently become interested in understanding the role of Heparanase-1 (HPSE) in controlling these processes, as it is the only known mammalian protein capable of cleaving HS chains from their proteoglycan bases. The proposed study aims to define the role of human HPSE in driving angiogenesis and inflammation, using herpesvirus infection of corneal cells as a model system. Given the transparency and accessibility of the cornea, we plan to employ established protocols to measure blood vessel growth and immune cell migration in this unique system. Furthermore, HS serves as an attachment receptor for numerous viruses, and we have observed a loss of HS from the cell surface and a coinciding increase in host-encoded HPSE after herpes simplex virus (HSV) infection of human cells. As HS is an important constituent of the extracellular matrix (ECM), increased HPSE action on HS chains would lead to an amplified release of cytokines and growth factors sequestered in this proteoglycan-rich environment, promoting ulceration, neovascularization, and inflammation typical of HSV pathogenesis. We have generated some evidence that HPSE expression is increased via activation of nuclear factor (NF)-kB, and we propose novel proteomics assays to confirm this association and search for other potential regulators. Given recent evidence tying higher HPSE levels with inflammation and angiogenesis, we plan to evaluate amounts of pro- inflammatory and angiogenic factors after HPSE overexpression or knockdown. We will assess corneal neovascularization and opacity as well as immune cell proliferation after modulating HPSE expression levels in a mouse model of corneal infection. With results gathered from these studies, we hope to identify major players controlling HPSE expression, expose key targets in the treatment of ocular inflammation and angiogenesis, and gather valuable information related to many additional human diseases.