Granzyme B‐dependent Matrix Degradation Generates Anti‐Angiostatic Activity in Scleroderma Patients

Abstract

Introduction Scleroderma is a systemic connective tissue disease with an extensive vascular component of an uncertain etiology that includes an aberrant microvasculature and impaired wound healing. We investigated the possibility that the presence of anti-angiogenic factors may contribute to vascular abnormalities in scleroderma patients. Methods Plasma was obtained from patients with scleroderma (SSc, n=30), rheumatoid arthritis (RA, n=10) and normal control patients (n=14). The samples were analyzed for the plasma ability to affect endothelial cell migration, proliferation, and vascular structure formation and for the presence of anti-angiogenic activity. Results Normal endothelial cells exposed to SSc plasma had a 46 ±14% reduction in migration (p < 0.001), a 30%± 4% reduction in proliferation (p < 0.001), and a 73% ±16% decrease in tube formation (p < 0.001) when compared to plasma from control or RA patients. Plasmin activity in SSc patients was 30% lower than in controls while PAI-1 levels were equivalent in both groups. At the same time, plasma from SSc patients contained 2.4- and 4-fold more plasminogen kringles 1–3 fragments (angiostatin) than control or RA patients respectively. Conclusions Plasminogen conformation in SSc patients enables access to cleavage sites in the kringle domains resulting in production of angiostatin K1-3. Biochemical and co-immunoprecipitation studies suggest that granzyme B is the proteolytic enzyme that cleaves plasminogen into angiostatin in SSc patients.