CHI3L1 and pulmonary fibrosis: First, we compared the levels of different serum biomarkers associated with lung fibrosis (total IGF-1, IGFBP-1, IGFBP-2, IGFBP-3, TGF-β1, YKL-40, and CRP)20,40–42, inflammatory (IL-8 and TNF-α)43,44 and tissue remodeling processes (MMP-7 and MMP-9)45,46 between HS and SSc groups (Fig. 2).