Secreted Protein Acidic and Rich in Cysteine (SPARC) is a multifunctional secreted glycoprotein found in the extracellular matrix. SPARC is expressed only at sites of tissue remodeling and wound repair. SPARC gene overexpression by cultured dermal fibroblasts from patients with systemic sclerosis has been shown in a cDNA micro-array study. Serum levels of SPARC of 20 patients with limited cutaneous systemic sclerosis, 13 patients with diffuse cutaneous systemic sclerosis, 33 patients with systemic sclerosis, 15 patients with localized scleroderma, 12 patients with dermatomyositis and 15 healthy volunteers were measured with specific enzyme linked immunosorbent assay. The mRNA and protein levels of SPARC were also investigated by real time PCR and immunohistochemistry. The relationships between the clinical manifestations of patients and the expressions of SPARC were analyzed. Serum levels of SPARC were significantly higher in patients with localized scleroderma than those in other groups or healthy individuals. The mRNA levels of SPARC were up regulated in all groups of scleroderma. The SPARC protein were highly expressed in the skin tissue of localized scleroderma. And the patients with elevated serum SPARC levels had significantly larger number of sclerotic lesions and significantly higher serum levels of anti-single strand DNA antibodies than those without. These results suggested that the serum levels of SPARC might be a serological marker for the disease activity and the extent of skin involvement in localized scleroderma.

Secreted Protein Acidic and Rich in Cysteine, a new biomarker of localized scleroderma