Heparan Sulfate Proteoglycans (HSPGs) and Their Degradation in Health and Disease

Heparan sulfate proteoglycans (HSPGs) are essential constituents of the extracellular matrix (ECM) and cell surface, orchestrating a wide range of biological processes, such as cell adhesion, migration, proliferation, and intercellular communication. Through their highly sulfated glycosaminoglycan chains, HSPGs serve as crucial modulators of bioavailability and signaling of growth factors, cytokines, and chemokines, thereby influencing tissue homeostasis. Their dynamic remodeling is mediated by numerous enzymes, with heparanase (HPSE) playing a predominant role as the only known human endo-β-D-glucuronidase that specifically cleaves heparan sulfate chains. Beyond its well-documented enzymatic activity in ECM degradation and the release of HS-bound molecules, HPSE also exerts non-enzymatic functions that regulate intracellular signaling cascades, transcriptional programs, and immune cell behavior. Dysregulated HPSE expression or activity has been implicated in various pathological conditions, including fibrosis, chronic inflammation, cancer progression, angiogenesis, metastasis, and immune evasion, positioning this enzyme as a pivotal driver of ECM plasticity in both health and disease. This review provides an updated overview of HSPG biosynthesis, structure, localization, and functional roles, emphasizing the activity of HPSE and its impact on tissue remodeling and disease pathogenesis. We further explored its involvement in the hallmark processes of cancer, the inflammatory tumor microenvironment, and its contribution to fibrosis. Finally, we summarize current therapeutic strategies targeting HPSE, outlining their potential to restore ECM homeostasis and counteract HPSE-driven pathological mechanisms. A deeper understanding of the HSPG/HPSE axis may pave the way for innovative therapeutic interventions in cancer, inflammatory disorders, and fibrotic diseases.