Identification of circulating inflammatory markers in acute myocarditis

Objective Acute myocarditis is an inflammatory condition with generally favorable short-term outcomes, although some patients may experience fatal complications during hospitalization. This study aims to identify a novel biomarker to distinguish between mild and severe cases of human myocarditis. Methods We enrolled patients with myocarditis and healthy controls, categorizing patients into mild and severe subgroups. Plasma samples were analyzed using the Olink inflammation panel, and principal component analysis was used to assess correlations between immune cell percentages, clinical indicators, and disease states. Differentially expressed proteins (DEPs) were analyzed in relation to clinical indices, and a predictive model was developed based on these markers. To validate the roles of C-C motif chemokine ligand 20 (CCL20) and interleukin 6 (IL-6), enzyme-linked immunosorbent assay (ELISA) and single-cell RNA sequencing (scRNA-seq) of public datasets were performed. Results A total of 23 myocarditis patients (8 mild, 15 severe) and 10 healthy controls were included for Olink analysis. While IL-6 was significantly elevated in severe cases, CCL20, previously unreported in human myocarditis, was also found to be highly expressed in severe cases compared to mild cases and healthy controls. ELISA and scRNA-seq analysis confirmed elevated levels of both CCL20 and IL-6 in patients with severe disease and worse clinical outcomes. Moreover, immunohistochemical staining of LV myocardium indicated CCL20 positive T-lymphocytes. These findings suggest that CCL20, together with IL-6, plays a key role in shaping the myocardial tissue microenvironment by recruiting pathogenic T cells and worsening disease severity. Conclusion This study presents CCL20 as a novel biomarker in human myocarditis, providing new insights into its pathophysiology and offering the potential for early identification of severe cases at the time of admission.