Elevated serum levels of sonic hedgehog are associated with fibrotic and vascular manifestations in systemic sclerosis

Fibrotic tissue remodelling and vascular alterations cause high morbidity and mortality in patients with systemic sclerosis (SSc).1 2 While the pathogenesis of SSc is only partially understood, recent evidence demonstrates a fundamental role of hedgehog signalling in fibrotic disease manifestations. Hedgehog signalling is activated in fibrotic SSc skin, and it induces an SSc-like phenotype in resting fibroblasts.3 Overexpression of sonic hedgehog (SHH) induces skin fibrosis, whereas inhibition of hedgehog signalling ameliorates experimental fibrosis.4 Based on these experimental findings, this European Scleroderma Trials and Research group (EUSTAR) multicentre cooperative study investigates whether circulating SHH may serve as a surrogate marker for a more severe disease phenotype in patients with SSc. We decided to evaluate SHH serum levels rather than total circulating SHH. Measurements of SHH serum levels are easy and robust but may not assess particulated SHH in various different extracellular vesicles. …