Plasma CCL3 predicts adverse heart failure outcomes in patients with arrhythmogenic cardiomyopathy

Background: Fibro-fatty replacement of the myocardium plays a key role in the pathogenesis of arrhythmogenic cardiomyopathy (ACM) and may be associated with progressive heart failure (HF). We aimed to investigate the characteristic of the fibro-fatty tissues of ACM patients and the plasma chemokines levels according to HF burden. Methods: The expression level of markers for brown, beige, and white fat of fibro-fatty tissues was determined using a quantitative real-time polymerase chain reaction. Lipidomics analysis of fibro-fatty tissues (n = 10 for normal control NC; n = 24 for ACM patients) was conducted using LC-MS. Single-cell RNA sequencing (n = 2 for NC; n = 6 for ACM patients) was used to compare the immune environment in the myocardium. Immunostaining and enzyme-linked immunosorbent assay were used to examine the expression of CCL3 in the myocardium and plasma samples, respectively. Results: The expression level of beige (TBX1 and TMEM26) and brown (TNFRSF9) fat markers were higher in the fibro-fatty tissues of ACM patients compared to NC. The fibro-fatty tissues revealed a significant increased level of saturated triglycerides (TGs) in ACM patients compared with NC. Single-cell RNA sequencing revealed the obvious accumulation of proinflammatory macrophages and a high expression level of proinflammatory markers in the myocardium of ACM patients compared to NC. The expression of CCL3 in the fibro-fatty tissues was positively correlated with HF progression in patients with ACM. Plasma CCL3 levels were significantly higher in patients with ACM compared to healthy volunteer. A total of 102 patients with ACM have been followed for a median of 7.8 years, indicating that plasma CCL3 levels could successfully predict the incidence of HF and heart transplantation (HTx)/death in patients with ACM (hazard ratio = 3.122 95% confidence interval, 1.556-6.264). The ROC curve analysis revealed the AUC value reached 0.814 for HF and 0.756 for HTx/death. Conclusions: The increased level of saturated TGs and CCL3 in the fibro-fatty tissues might promote HF progression in ACM patients. Plasma CCL3 levels are useful for predicting HF-related adverse events in patients with ACM, but requiring further validation in larger and independent cohorts.