Immunoassay of platelet-derived growth factor in the plasma of patients with scleroderma

It has been postulated that platelet-derived growth factor (PDGF) is responsible for the abnormal fibroblast proliferation observed in scleroderma. In one previous study, plasma samples from patients with scleroderma caused increased mitogenesis in cultured fibroblasts, suggesting that the pathogenesis of scleroderma is related to increased plasma PDGF concentrations. To test this hypothesis, we used a sensitive, monoclonal antibody-based ELISA to measure PDGF in the plasma of 12 scleroderma patients. A rigorous sampling protocol prevented false elevations in plasma PDGF levels from ex vivo platelet degranulation: beta-thromboglobulin concentrations were measured in each plasma sample to monitor platelet lysis. Plasma PDGF concentrations in the scleroderma patients were not statistically different from those observed in age- and sex-matched normal controls, and patients with RA. While it is possible that changes in PDGF activity at a local level alter fibroblast function, we cannot conclude that elevated plasma concentrations of PDGF play a role in the pathogenesis of scleroderma.