Serum CCL24 as a Biomarker of Fibrotic and Vascular Disease Severity in Systemic Sclerosis

Background. Systemic sclerosis (SSc) is a heterogeneous disease, characterized by variable tissue and vascular fibrosis in the context of autoimmune activation. CCL24 (or Eotaxin2) has been shown to promote microangiopathic, proinflammatory, and profibrotic processes in preclinical models of SSc. Here, we study serum CCL24 levels in a real-life cohort of patients with SSc, to determine its distribution across disease features and its value in predicting disease progression and related mortality. Methods. Serum CCL24 was assessed in an observational cohort of consecutively enrolled patients with SSc. A high CCL24 cutoff was defined based on its distribution in a matched cohort of healthy controls. Disease progression and mortality were analyzed from the date of serum assessment. Results. Two-hundred thirteen consecutively enrolled patients with SSc were included in this analysis. Median disease duration was six years (interquartile range 3-14), 28.6% of patients presented with interstitial lung disease (ILD), 46.9% had digital ulcers, and 25.3% showed high CCL24 serum concentration. High-CCL24 patients were more frequently male and positive for anti-scl-70, with a diagnosis of ILD and synovitis (P < 0.05 for all). Notably, high-CCL24 patients had lower diffusion of carbon monoxide and higher prevalence of digital ulcers, telangiectasias, and calcinosis (P < 0.05 for all). In a longitudinal setting, high CCL24 was associated with greater lung function decline and with higher disease-related mortality. Conclusion. Serum CCL24 is a biomarker of disease severity across fibrotic and vascular disease manifestations. These data support the development of therapies targeting CCL24 as a novel comprehensive therapeutic target in SSc.