L-selectin and Skin Damage in Systemic Sclerosis

BACKGROUND: L-selectin ligands are induced on the endothelium of inflammatory sites. L-selectin expression on neutrophils and monocytes may mediate the primary adhesion of these cells at sites of inflammation by mediating the leukocyte-leukocyte interactions that facilitate their recruitment. L-selectin retains functional activity in its soluble form. Levels of soluble L-selectin have been reported as both elevated and lowered in patients with systemic sclerosis (SSc). This preliminary study seeks to discern amongst these disparate results and to discover whether there is an association between L-selectin concentrations in plasma and skin damage in SSc patients. METHODOLOGY AND PRINCIPAL FINDINGS: Nineteen cases with limited systemic sclerosis (lSSc) and 11 cases with diffuse systemic sclerosis (dSSc) were compared on a pairwise basis to age- and sex-matched controls. Criteria of the American College of Rheumatology were used to diagnose SSc. Skin involvement was assessed using the modified Rodnan skin score (mRSS). We find no association between mRSS and plasma L-selectin concentration in lSSc cases (p = 0.9944) but a statistically significant negative correlation in dSSc cases (R(2) = 73.11 per cent, p = 0.0008). The interpretation of the slope for dSSc cases is that for each increase of 100 ng/ml in soluble L-selectin concentration, the mRSS drops 4.22 (95 per cent CI: 2.29, 6.16). There was also a highly statistically significant negative correlation between sL-selectin and disease activity (p = 0.0007) and severity (p = 0.0007) in dSSc cases but not in lSSc cases (p = 0.2596, p = 0.7575, respectively). CONCLUSIONS AND SIGNIFICANCE: No effective treatments exist for skin damage in SSc patients. Nor is there a laboratory alternative to the modified Rodnan skin score as is the case for other organs within the body. Modulation of circulating L-selectin is a promising target for reducing skin damage in dSSc patients. Plasma levels of soluble L-selectin could serve as an outcome measure for dSSc patients in clinical trials.