Serum concentrations of soluble P-selectin glycoprotein ligand-1 are increased in patients with systemic sclerosis: association with lower frequency of pulmonary fibrosis

OBJECTIVE: To determine serum concentrations of soluble P-selectin glycoprotein ligand-1 (sPSGL-1) and its clinical associations in patients with systemic sclerosis. METHODS: Serum sPSGL-1 concentrations from 65 patients with systemic sclerosis were examined by enzyme linked immunosorbent assay. In a retrospective longitudinal study, 177 sera from 35 patients with systemic sclerosis were analysed (follow up 0.3 to 6.3 years) RESULTS: Serum sPSGL-1 was raised in patients with limited cutaneous systemic sclerosis (lSSc) (n = 34) and diffuse cutaneous systemic sclerosis (dSSc) (n = 31) compared with healthy controls (n = 22) and patients with systemic lupus erythematosus (n = 20) or dermatomyositis (n = 20). Patients with systemic sclerosis who had raised sPSGL-1 concentrations less often had pulmonary fibrosis and decreased vital capacity (%VC) than those with normal sPSGL-1 levels. sPSGL-1 concentrations were positively correlated with %VC in patients with systemic sclerosis. In the longitudinal study, patients with systemic sclerosis but without pulmonary fibrosis had consistently increased sPSGL-1 concentrations in the early phase, while those with pulmonary fibrosis had decreased sPSGL-1 throughout the follow up period. CONCLUSIONS: A raised serum sPSGL-1 is associated with a lower frequency and severity of pulmonary fibrosis in systemic sclerosis. sPSGL-1 could be a protective factor against the development of pulmonary fibrosis in this disease and as such would be a possible therapeutic target.