The tumour necrosis factor-related apoptosis-inducing ligand-osteoprotegerin system in limited systemic sclerosis: a new disease marker?

OBJECTIVE: To investigate the role of the TNF-related apoptosis-inducing ligand-osteoprotegerin (TRAIL-OPG) system in the pathogenesis of limited SSc (lSSc). METHODS: Circulating levels of TRAIL and of its soluble receptor OPG were measured by ELISA in serum samples obtained from 50 lSSc patients and 50 healthy controls. RESULTS: TRAIL serum levels in lSSc patients were similar to those of healthy controls, whereas the OPG serum levels were significantly increased (P < 0.0001). According to different subgroups of lSSc patients, TRAIL was not statistically different between each group and healthy controls; concerning OPG, the statistically different value was also maintained when comparing each single lSSc group with the whole control population. CONCLUSIONS: OPG serum levels, but not TRAIL, are elevated in lSSc patients. Since OPG binding to TRAIL inhibits TRAIL-TRAIL receptor interaction, the relative concentrations of these two molecules in the local micro-environment has to be considered. In this setting, OPG increase in lSSc patients may produce a detrimental effect by counteracting the vasoprotective activity of TRAIL. The TRAIL : OPG ratio and their relative levels of expression in lSSc patients should be taken into consideration as a possible novel marker of vascular damage.