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Arrhythmogenic cardiomyopathy (ACM) is an inherited cardiac disorder that causes sudden cardiac death and progressive heart failure. Besides fibro-fatty replacement and myocyte degenerative changes, inflammatory patchy infiltrates are found in myocardial histological analysis of ACM patients. Inflammatory cells could actively participate in ACM pathogenesis, contributing to the alteration of cardiac microenvironment homeostasis, thus triggering disease evolution. In order to characterize the immune-derived mediators involved in ACM pathogenesis, peripheral blood mononuclear cells from ACM patients were characterized and compared to healthy controls' ones. Flow cytometry analysis revealed a lower frequency of CD4 + T helper type 1 cells, NK cells, and terminally differentiated CD8 + EMRA + T cells in ACM patients compared to age-matched controls. In contrast, a higher proportion of effector/memory FOXP3 + CCR4 + CD45RO + regulatory CD4 + T cells (Treg) were found in ACM patients. Single-cell RNA-seq performed on isolated memory Treg cells (mTreg) from ACM patients and healthy controls identified 6 clusters characterized by specific gene signatures related to tissue repair and immunosuppressive pathways. Notably, interleukin 32 (IL-32) was the most differentially expressed gene in ACM patients mTreg with respect to healthy controls. Treatment of human cardiac mesenchymal stromal cells with recombinant IL-32 in vitro promoted lipid droplet accumulation and collagen deposition, thus identifying IL-32 as a new potential player in the immune-mediated trigger of cardiac fibro-fatty replacement in ACM. Overall, we here provide the first complete characterization of circulating ACM immune cells, revealing an abundance of Treg. The high expression of IL-32 in ACM Treg may contribute to accelerated cardiac remodeling in ACM patients' hearts., Competing Interests: Competing interests: The authors declare no competing interests., (© 2025. The Author(s).)

Arrhythmogenic cardiomyopathy (AC) is an inherited disease characterized by progressive breakdown of heart muscle, myocardial tissue death, and fibrofatty replacement. In most cases of AC, the primary lesion occurs in one of the genes encoding desmosomal proteins, disruption of which increases membrane fragility at the intercalated disc. Disrupted, exposed desmosomal proteins also serve as epitopes that can trigger an autoimmune reaction. Damage to cell membranes and autoimmunity provoke myocardial inflammation, a key feature in early stages of the disease. In several preclinical models, targeting inflammation has been shown to blunt disease progression, but translation to the clinic has been sparse. Here we review current understanding of inflammatory pathways and how they interact with injured tissue and the immune system in AC. We further discuss the potential role of immunomodulatory therapies in AC.

Aims: We previously found that complement components are upregulated in the myocardium of patients with arrhythmogenic right ventricular cardiomyopathy (ARVC), and inhibiting the complement receptor C5aR reduces disease severity in desmin knockout ( Des -/- ) mice, a model for ARVC. Here, we examined the mechanism underlying complement activation in ARVC, revealing a potential new therapeutic target. Methods: First, immunostaining, RT-PCR and western blot were used to detect the expression levels of complement and coagulation factors. Second, we knocked out the central complement component C3 in Des -/- mice (ARVC model) by crossing Des -/- mice with C3 -/- mice to explore whether complement system activation occurs independently of the conventional pathway. Then, we evaluated whether a targeted intervention to coagulation system is effective to reduce myocardium injury. Finally, the plasma sC5b9 level was assessed to investigate the role in predicting adverse cardiac events in the ARVC cohort. Results: The complement system is activated in the myocardium in ARVC. Autoantibodies against myocardial proteins provided a possible mechanism underlying. Moreover, we found increased levels of myocardial C5 and the serum C5a in Des -/- C3 -/- mice compared to wild-type mice, indicating that C5 is activated independently from the conventional pathway, presumably via the coagulation system. Crosstalk between the complement and coagulation systems exacerbated the myocardial injury in ARVC mice, and this injury was reduced by using the thrombin inhibitor lepirudin. In addition, we found significantly elevated plasma levels of sC5b9 and thrombin in patients, and this increase was correlated with all-cause mortality. Conclusions: These results suggest that crosstalk between the coagulation and complement systems plays a pathogenic role in cardiac dysfunction in ARVC. Thus, understanding this crosstalk may have important clinical implications with respect to diagnosing and treating ARVC., Competing Interests: Competing Interests: The authors have declared that no competing interest exists., (© The author(s).)

We present, to our knowledge, the first case of immunosuppressive therapy (IST) application in a 12-year-old child with arrhythmogenic inflammatory cardiomyopathy resulting from the overlap between autoimmune myocarditis and primary arrhythmogenic cardiomyopathy. Indication to off-lable IST was compelling, because of recurrent drug-refractory ventricular arrhythmias (VAs). We show that IST was feasible, safe, and effective on multiple clinical endpoints, including symptoms, VA recurrences, and T-troponin release. Remarkably, all diagnostic and therapeutic strategies were worked out by a dedicated multidisciplinary team, including specialized pediatric immunologists., (© 2020 Wiley Periodicals LLC.)

Aims: Arrhythmogenic right ventricular cardiomyopathy (ARVC) is characterized by right ventricular myocardial replacement and life-threatening ventricular arrhythmias. Desmosomal gene mutations are sometimes identified, but clinical and genetic diagnosis remains challenging. Desmosomal skin disorders can be caused by desmosomal gene mutations or autoantibodies. We sought to determine if anti-desmosome antibodies are present in subjects with ARVC., Methods and Results: We evaluated ARVC subjects and controls for antibodies to cardiac desmosomal cadherin proteins. Desmoglein-2 (DSG2), desmocollin-2, and N-cadherin proteins on western blots were exposed to sera, in primary and validation cohorts of subjects and controls, as well as the naturally occurring Boxer dog model of ARVC. We identified anti-DSG2 antibodies in 12/12 and 25/25 definite ARVC cohorts and 7/8 borderline subjects. Antibody was absent in 11/12, faint in 1/12, and absent in 20/20 of two control cohorts. Anti-DSG2 antibodies were present in 10/10 Boxer dogs with ARVC, and absent in 18/18 without. In humans, the level of anti-DSG2 antibodies correlated with the burden of premature ventricular contractions (r = 0.70), and antibodies caused gap junction dysfunction, a common feature of ARVC, in vitro. Anti-DSG2 antibodies were present in ARVC subjects regardless of whether an underlying mutation was identified, or which mutation was present. A disease-specific DSG2 epitope was identified., Conclusion: Anti-DSG2 antibodies are a sensitive and specific biomarker for ARVC. The development of autoimmunity as a result of target-related mutations is unique. Anti-DSG2 antibodies likely explain the cardiac inflammation that is frequently identified in ARVC and may represent a new therapeutic target.