Augmented production of soluble CD93 in patients with systemic sclerosis and clinical association with severity of skin sclerosis

Background The cell surface protein CD93, expressed on endothelial and myeloid cells, mediates phagocytosis, inflammation and cell adhesion. A soluble form of CD93 (sCD93) is released during inflammation. Objectives To determine the serum sCD93 level and its association with clinical parameters in patients with systemic sclerosis (SSc). Methods Serum sCD93 levels were examined by enzyme-linked immunosorbent assay in 59 patients with SSc, 24 patients with systemic lupus erythematosus and 47 healthy individuals. The expression of CD93 in skin tissues was examined immunohistochemically. In a retrospective longitudinal study, sera from 11 patients with SSc were analysed. Results Serum sCD93 levels were increased in patients with SSc compared with healthy individuals (P < 0.001). Patients with diffuse cutaneous SSc showed greater levels of sCD93 than those with limited cutaneous SSc (P < 0.01) or systemic lupus erythematosus (P < 0.01). Serum sCD93 levels correlated positively with the severity of skin sclerosis. Strong CD93 immunostaining was observed on endothelial cells in lesional skin tissues. In the longitudinal study, sCD93 levels decreased in parallel with improvement in skin sclerosis. Conclusions Serum sCD93 levels are increased in patients with SSc and correlate with the severity and activity of skin sclerosis. CD93 may contribute to the development of skin fibrosis in SSc.