Desmosomal Genes Research Articles

Disruption of TUFT1, a Desmosome-Associated Protein, Causes Skin Fragility, Woolly Hair, and Palmoplantar Keratoderma

Desmosomes are dynamic complex protein structures involved in cellular adhesion. Disruption of these structures by loss-of-function variants in desmosomal genes leads to a variety of skin- and heart-related phenotypes. In this study, we report TUFT1 as a desmosome-associated protein, implicated in epidermal integrity. In two siblings with mild skin fragility, woolly hair, and mild palmoplantar keratoderma but without a cardiac phenotype, we identified a homozygous splice-site variant in the TUFT1 gene, leading to aberrant mRNA splicing and loss of TUFT1 protein. Patients' skin and keratinocytes showed acantholysis, perinuclear retraction of intermediate filaments, and reduced mechanical stress resistance. Immunolabeling and transfection studies showed that TUFT1 is positioned within the desmosome and that its location is dependent on the presence of the desmoplakin carboxy-terminal tail. A Tuft1-knockout mouse model mimicked the patients' phenotypes. Altogether, this study reveals TUFT1 as a desmosome-associated protein, whose absence causes skin fragility, woolly hair, and palmoplantar keratoderma.

Exercise does not influence development of phenotype in PLN p.(Arg14del) cardiomyopathy.

Endurance and frequent exercise are associated with earlier onset of arrhythmogenic right ventricular cardiomyopathy (ARVC) and ventricular arrhythmias (VA) in desmosomal gene variant carriers. Individuals with the pathogenic c.40_42del; p.(Arg14del) variant in the PLN gene are frequently diagnosed with ARVC or dilated cardiomyopathy (DCM). The aim of this study was to evaluate the effect of exercise in PLN p.(Arg14del) carriers. In total, 207 adult PLN p.(Arg14del) carriers (39.1% male; mean age 53 ± 15years) were interviewed on their regular physical activity since the age of 10years. The association of exercise with diagnosis of ARVC, DCM, sustained VA and hospitalisation for heart failure (HF) was studied. Individuals participated in regular physical activities with amedian of 1661 metabolic equivalent of task (MET) hours per year (31.9MET-hours per week) until clinical presentation. The 50% most and least active individuals had asimilar frequency of sustained VA (18.3% vs 18.4%; p = 0.974) and hospitalisation for HF (9.6% vs 8.7%; p = 0.827). There was no relationship between exercise and survival free from (incident) sustained VA (p = 0.65), hospitalisation for HF (p = 0.81), diagnosis of ARVC (p = 0.67) or DCM (p = 0.39) during follow-up. In multivariate analyses, exercise was not associated with sustained VA or HF hospitalisation during follow-up in this relatively not-active cohort. There was no association between the amount of exercise and the susceptibility to develop ARVC, DCM, VA or HF in PLN p.(Arg14del) carriers. This suggested unaffected PLN p.(Arg14del) carriers can safely perform mild-moderate exercise, in contrast to desmosomal variant carriers and ARVC patients.

A Systematic Analysis of the Clinical Outcome Associated with Multiple Reclassified Desmosomal Gene Variants in Arrhythmogenic Right Ventricular Cardiomyopathy Patients

The presence of multiple pathogenic variants in desmosomal genes (DSC2, DSG2, DSP, JUP, and PKP2) in patients with arrhythmogenic right ventricular cardiomyopathy (ARVC) has been linked to a severe phenotype. However, the pathogenicity of variants is reclassified frequently, which may result in a changed clinical risk prediction. Here, we present the collection, reclassification, and clinical outcome correlation for the largest series of ARVC patients carrying multiple desmosomal pathogenic variants to date (n = 331). After reclassification, only 29% of patients remained carriers of two (likely) pathogenic variants. They reached the composite endpoint (ventricular arrhythmias, heart failure, and death) significantly earlier than patients with one or no remaining reclassified variant (hazard ratios of 1.9 and 1.8, respectively). Periodic reclassification of variants contributes to more accurate risk stratification and subsequent clinical management strategy.Graphical

Generation of two edited iPSCs lines by CRISPR/Cas9 with point mutations in PKP2 gene for arrhythmogenic cardiomyopathy in vitro modeling

The arrhythmogenic cardiomyopathy (ACM) is an inherited heart muscle disease characterized by the progressive replacement of contractile myocardium by fibro-fatty adipose tissue, that generates ventricular arrhythmias and sudden death in patients. The ACM has a genetic origin with alterations in desmosomal genes with the most commonly mutated being the PKP2 gene. We generated two CRISPR/Cas9 edited iPSCs lines, one iPSC line with a point mutation in PKP2 reported in patients with ACM and another iPSC line with a premature stop codon to knock-out the same gene.

Diagnostic yield and predictive value on left ventricular remodelling of genetic testing in dilated cardiomyopathy.

We assessed the diagnostic yield of genetic testing and the relationship of left ventricular (LV) reverse remodelling (LVRR) with the presence of DNA pathogenic (P) or likely pathogenic (LP) variants in patients with dilated cardiomyopathy (DCM). From 680 outpatients followed at the Heart Failure Outpatient Clinic of our institution, we selected subjects with a diagnosis of DCM as defined by LV ejection fraction (LVEF) ≤40% and LV dilatation not explained by coronary artery disease or other causes. All patients were offered genetic investigation of 42 disease-associated DCM genes with next-generation sequencing. Seventy patients fulfilled the definition of DCM and 66 underwent genetic investigation. We identified 18 P/LP variants in 16 patients, with a diagnostic yield of 24%. The most common variants were truncating TTN variants (n=7), followed by LMNA (n=3), cytoskeleton Z-disc (n=3), ion channel (n=2), motor sarcomeric (n=2), and desmosomal (n=1) genes. After a median follow-up of 53months (inter-quartile range 20-111), patients without P/LP variants exhibited higher systolic and diastolic blood pressure, lower plasma brain natriuretic peptide levels, and a larger extent of LVRR, as reflected by the increase in LVEF (+14% vs. +1%, P=0.0008) and decrease in indexed LV end-diastolic diameter (-6.5 vs. -2mm/m2 , P=0.03) compared with patients with P/LP variants. Our results confirm the high diagnostic yield of genetic testing in selected DCM patients and suggest that identification of P/LP variants in DCM portends poorer LVRR in response to guideline-directed medical therapy.

Modern view on genetic aspects of arrhythmogenic cardiomyopathy

Arrhythmogenic cardiomyopathy (ACM) is a genetically determined disease with a high risk of sudden cardiac death (SCD). The spectrum of genetic causes of this disease is quite wide and includes mutations in both desmosomal and non-desmosomal genes. A positive result of a genetic examination is used as a diagnostic tool in patients with ACM, so its correct interpretation is one of the key factors in a personalized approach to managing a patient with this pathology. The review presents generalized modern ideas about the genetic nature of ACM.

Cardiac Inflammation As an Underlying Trigger for the Pathological Deficits Associated with Arrhythmogenic Right Ventricular Cardiomyopathy

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is an inherited heart muscle disorder that causes cardiomyocyte loss, resulting in myocardial fibro-fatty deposition leading to cardiac dysfunction and sudden cardiac death, particularly in young patients and athletes, with no available treatments. The genetics of ARVC follow an autosomal dominant pattern, although severe cases (especially in pediatric populations) have been reported as recessive. Mutations in genes encoding components of desmosomes (specialized cell-cell junction that act as mechanical anchor between cardiac muscle cells) resulting in loss of desmosomal proteins underlie approximately 40-60% genetic cases of ARVC. Studies highlight that cardiac inflammation may be a critical and early component of ARVC as patients harboring mutations in the desmosomal gene desmoplakin (DSP) present with recurrent myocardial episodes (observed as myocarditis); however, the mechanisms and whether inflammation is a driver of ARVC remain unclear. We hypothesize that desmosomal gene mutations/loss/byproducts alter the acute inflammatory response on the cardiomyocyte cell surface leading to chronic immune intolerance and triggering of ARVC disease. To test our hypothesis, we injected DSP heterozygous deficient mice (harboring 50% loss of DSP without overt signs of ARVC) with a fragment of α-myosin and pertussis toxin to stimulate the immune system to assess its impact on ARVC pathogenesis. We show that DSP heterozygous mice exposed to acute immunological challenge triggered a destructive cardiomyocyte immune response in DSP heterozygous deficient hearts, reminiscent of fulminant myocarditis. Furthermore, we show that this acute immunological challenge was sufficient to trigger classic ARVC disease features in DSP heterozygous deficient mice as exemplified by: (i) enlarged ventricular (mostly right ventricular) chambers and heart size, (ii) fibrotic remodeling, with more clearly striking effects in the right ventricle (RV), (iii) epicardial fat tissue accumulation, (iv) electrophysiological deficits, such as premature ventricular contractions and QRS prolongation as well as (v) right and left ventricular physiological deficits associated with the bi-ventricular form of ARVC, although the RV appeared to be more significantly impacted. Our studies highlight the development of a novel DSP-related model of myocarditis. Using this model, we show that immunological stress is sufficient to lead to loss of cardiomyocyte immune tolerance in DSP heterozygous deficient mice with compromised desmosomal integrity to drive ARVC pathogenesis. More broadly these studies suggest that the immune system maybe an important driver of ARVC pathogenesis in patients with underlying desmosomal gene mutations/heterozygous loss, especially in the setting of autosomal dominant genetics. Work in the laboratory of FS is supported by grants from the NIH (HL142251, HL162369) and industry (LEXEO Therapeutics Inc.). This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Disease modeling of desmosome-related cardiomyopathy using induced pluripotent stem cell-derived cardiomyocytes

Cardiomyopathy is a pathological condition characterized by cardiac pump failure due to myocardial dysfunction and the major cause of advanced heart failure requiring heart transplantation. Although optimized medical therapies have been developed for heart failure during the last few decades, some patients with cardiomyopathy exhibit advanced heart failure and are refractory to medical therapies. Desmosome, which is a dynamic cell-to-cell junctional component, maintains the structural integrity of heart tissues. Genetic mutations in desmosomal genes cause arrhythmogenic cardiomyopathy (AC), a rare inheritable disease, and predispose patients to sudden cardiac death and heart failure. Recent advances in sequencing technologies have elucidated the genetic basis of cardiomyopathies and revealed that desmosome-related cardiomyopathy is concealed in broad cardiomyopathies. Among desmosomal genes, mutations in PKP2 (which encodes PKP2) are most frequently identified in patients with AC. PKP2 deficiency causes various pathological cardiac phenotypes. Human cardiomyocytes differentiated from patient-derived induced pluripotent stem cells (iPSCs) in combination with genome editing, which allows the precise arrangement of the targeted genome, are powerful experimental tools for studying disease. This review summarizes the current issues associated with practical medicine for advanced heart failure and the recent advances in disease modeling using iPSC-derived cardiomyocytes targeting desmosome-related cardiomyopathy caused by PKP2 deficiency.

Desmosomal protein degradation as an underlying cause of arrhythmogenic cardiomyopathy.

Arrhythmogenic cardiomyopathy (ACM) is an inherited progressive cardiac disease. Many patients with ACM harbor mutations in desmosomal genes, predominantly in plakophilin-2 (PKP2). Although the genetic basis of ACM is well characterized, the underlying disease-driving mechanisms remain unresolved. Explanted hearts from patients with ACM had less PKP2 compared with healthy hearts, which correlated with reduced expression of desmosomal and adherens junction (AJ) proteins. These proteins were also disorganized in areas of fibrotic remodeling. In vitro data from human-induced pluripotent stem cell-derived cardiomyocytes and microtissues carrying the heterozygous PKP2 c.2013delC pathogenic mutation also displayed impaired contractility. Knockin mice carrying the equivalent heterozygous Pkp2 c.1755delA mutation recapitulated changes in desmosomal and AJ proteins and displayed cardiac dysfunction and fibrosis with age. Global proteomics analysis of 4-month-old heterozygous Pkp2 c.1755delA hearts indicated involvement of the ubiquitin-proteasome system (UPS) in ACM pathogenesis. Inhibition of the UPS in mutant mice increased area composita proteins and improved calcium dynamics in isolated cardiomyocytes. Additional proteomics analyses identified lysine ubiquitination sites on the desmosomal proteins, which were more ubiquitinated in mutant mice. In summary, we show that a plakophilin-2 mutation can lead to decreased desmosomal and AJ protein expression through a UPS-dependent mechanism, which preceded cardiac remodeling. These findings suggest that targeting protein degradation and improving desmosomal protein stability may be a potential therapeutic strategy for the treatment of ACM.

Advances in Ion Channel, Non-Desmosomal Variants and Autophagic Mechanisms Implicated in Arrhythmogenic Cardiomyopathy.

Arrhythmogenic cardiomyopathy (ACM) is a heterogeneous disorder characterized by the replacement of cardiac myocytes with fibro-fatty tissues, leading to abnormal excitation-contraction (EC) coupling and a range of malignant events, such as ventricular tachycardia (VT), sudden cardiac death/arrest (SCD/A) and heart failure (HF). The concept of ACM has recently been ex-tended to include right ventricular cardiomyopathy (ARVC), left ventricular cardiomyopathy (ALVC) and biventricular cardiomyopathy. ARVC is generally seen as the most common type of ACM. The pathogenesis of ACM involves mutation variants in desmosomal or non-desmosomal gene loci, as well as various external factors, such as intense exercise, stress and infections. Ion channel alterations, autophagy and non-desmosomal variants are also important components in the development of ACM. As clinical practice enters the era of precision therapy, it is important to review recent studies on these topics to better diagnose and treat the molecular phase of ACM.

Alterations in Calcium Handling Are a Common Feature in an Arrhythmogenic Cardiomyopathy Cell Model Triggered by Desmosome Genes Loss.

Arrhythmogenic cardiomyopathy (ACM) is an inherited cardiac disease characterized by fibrofatty replacement of the myocardium. Deleterious variants in desmosomal genes are the main cause of ACM and lead to common and gene-specific molecular alterations, which are not yet fully understood. This article presents the first systematic in vitro study describing gene and protein expression alterations in desmosomes, electrical conduction-related genes, and genes involved in fibrosis and adipogenesis. Moreover, molecular and functional alterations in calcium handling were also characterized. This study was performed d with HL1 cells with homozygous knockouts of three of the most frequently mutated desmosomal genes in ACM: PKP2, DSG2, and DSC2 (generated by CRISPR/Cas9). Moreover, knockout and N-truncated clones of DSP were also included. Our results showed functional alterations in calcium handling, a slower calcium re-uptake was observed in the absence of PKP2, DSG2, and DSC2, and the DSP knockout clone showed a more rapid re-uptake. We propose that the described functional alterations of the calcium handling genes may be explained by mRNA expression levels of ANK2, CASQ2, ATP2A2, RYR2, and PLN. In conclusion, the loss of desmosomal genes provokes alterations in calcium handling, potentially contributing to the development of arrhythmogenic events in ACM.

The Splicing Factor PTBP1 Represses TP63 γ Isoform Production in Squamous Cell Carcinoma.

Quantifying TP63γ isoforms in patients' tumors could allow for the early detection of patients with HNSCC with an early loss in desmosomal gene expression and poor prognostic. The identification of PTBP1 as a transacting factor controlling TP63γ production may allow to control TP63γ expression.

462 RELATIONSHIP BETWEEN PATIENT GENOTYPE, VENTRICULAR INVOLVEMENT AND SUDDEN CARDIAC DEATH IN PATIENTS WITH ARRHYTHMOGENIC CARDIOMYOPATHY

Abstract Introduction Arrhythmogenic cardiomyopathy (AC) is an important cause of sudden cardiac death (SCD). AC is characterized by areas of fibro-fatty replacement of the myocardium of one or both ventricles, which can be characterized through cardiovascular magnetic resonance (CMR). Several mutations have been associated with the development of AC, most commonly in desmosomal genes. The relationship between the genotype and the disease phenotype (i.e., the extent and severity of myocardial disease and patient outcome) is unclear. Methods We evaluated 280 consecutive patients evaluated in a single CMR laboratory over a 10-year timespan and diagnosed with AC according to the Padua criteria, based on a retrospective evaluation of the electronic health records. All these patients had undergone a genetic testing through Sanger sequencing or Next Generation Sequencing (after 2012). Pathogenic or likely pathogenic mutations and variants of unknown significance were considered. CMR scans performed at diagnosis were examined by an expert blinded to the results of genetic testing to retrieve the location and extent of the areas of fibro-fatty replacement and late gadolinium enhancement (LGE), biventricular volumes and function. Follow-up data were also retrieved. The primary endpoint was SCD or aborted SCD (following successful defibrillator discharge). The secondary endpoint included SCD or aborted SCD plus sustained or non-sustained ventricular tachycardia episodes. Results Patients were more often males (67%), with a mean age of 48±16 years. Gene mutations related to cardiomyopathy were found in 123 patients, and 85 patients harbored mutations in desmosomal genes (DSP, n=41; DSG2, n=16; PKP2, n=16; DSC2, n=6; JUP, n=6), while the other mutations were in genes including TMEM43, LMNA, SCN5A, MYH7, and RYR2. Patients with mutations in desmosomal genes had more often LGE in the left ventricle (LV) than patients with other mutations or with no mutations detected (66% vs. 58% vs. 46%, respectively; p=0.025). Patients with mutations in the DSP gene had a greater LGE extent in terms of number of segments affected (p=0.011), or percent of the LV (p<0.001) compared with patients with other desmosomal mutations or no mutations. No differences between patients with desmosomal or non-desmosomal mutations or no mutations were found in terms of fibro-fatty replacement in the LV (51% vs. 32% vs. 48%; p=0.577), nor in terms of LGE presence or fibro-fatty replacement of the right ventricle (RV; data not shown). Median follow-up duration was 4.4 years (interquartile range 1.8-6.4); 22% of patients underwent defibrillator implantation. Primary endpoint events were recorded in 21 patients (7.5%), with 20 aborted SCD episodes. The secondary endpoint occurred in 58 patients (21%). At Cox regression analysis, the mutation status did not reach statistical significance as univariate predictor of the two endpoints, but LGE in the LV, LGE in ≥2 LV segments, or LGE >9% (considered one at the time) independently predicted both endpoints. Conclusions In patients with AC, mutations in desmosomal genes are found in almost half of patients, and are associated with the presence and a larger extent of LGE in the LV. In turn, the presence and extent of LGE are independent predictor of SCD or aborted SCD.

207 RE-DEFINING ARRHYTHMOGENIC CARDIOMYOPATHY: CHARACTERIZATION AND LONG-TERM PROGNOSTIC IMPLICATIONS

Abstract Background Arrhythmogenic dilated cardiomyopathy (AR-DCM) combines phenotypical aspects of dilated cardiomyopathy (DCM) and risk of sudden cardiac death (SCD), typical of the arrhythmogenic form (ACM). However, AR-DCM is often ambiguously defined leaving clinicians uncertain on how to identify these high-risk patients. The aims of the study were to re-define AR-DCM based on outcome related arrhythmic markers and to test the usefulness of the novel AR-DCM definition in identifying arrhythmogenic genotypes (i.e., LMNA, FLNC, RBM20, and desmosomal genes). Materials and methods Consecutive DCM patients with genetic evaluation and Holter ECG monitoring or telemetry in two referral institution were analyzed. The arrhythmic markers tested to define AR-DCM were: SCD or major ventricular arrhythmias (MVA), unexplained syncope, rapid nonsustained ventricular tachycardia (nsTV), ≥1000 premature ventricular contractions/24 hours, or ≥50 ventricular couplets/24 hours. Patients were labeled as Early AR-DCM if criteria were met within 12 months from enrolment. The primary endpoint was a composite of SCD/MVA; the secondary endpoint was a composite of all-cause mortality/heart transplant/LVAD implantation (D/HTx/LVAD). Results Among the 743 DCM patients included, 290 had disease-related variants (39%), 94 (30%) of these carried arrhythmogenic genotype. Early AR-DCM was identified in 429 (58%) patients. During a median follow-up of 7.0 [2.2-13.8] years, among arrhythmic markers the occurrence of syncope and/or nsVT within 12 months from enrolment were the only arrhythmic markers independently associated with SCD/MVA (Figure), while the occurrence of early MVA and/or nsTV emerged as the strongest long-term predictors of D/ HTx/LVAD. Family history of MVA was also independently associated with primary and secondary endpoints, and together with MVA, nsTV or unexplained syncope increased the agreement between AR-DCM and arrhythmogenic genotypes in 1 out 2 patients. Conclusions A combination of early (i.e., within 1 year from diagnosis) MVA or nsVT or unexplained syncope might be proposed as a clinically useful new definition of AR-DCM, especially if associated to family history of MVA. This definition in fact allows clinicians to anticipates worse long-term arrhythmic and global outcomes, and to accurately identify malignant arrhythmogenic genotypes.

80 GENETIC MYOCARDITIS: ADVANCED WORKUP AND TREATMENT

Abstract Background Preclinical data support the rationale for targeting myocardial inflammation in genetic nonischemic cardiomyopathies. However, no consistent clinical reports have been provided so far. Methods We describe a series of patients (n=25) with genetic cardiomyopathy and active myocardial inflammation (AMI) proven by multimodal diagnostic workup. Patient-tailored immunosuppressive therapy was empirically started to target myocardial inflammation whenever feasible. Multiple outcomes were retrospectively assessed by a dedicated multidisciplinary disease unit. Results Patients carrying desmosomal (DGV), cytoskeletal (CGV) and membrane gene variants (MGV), were 12 (48%), 10 (40%), and 3 (12%), respectively. DGV carriers uniformly presented with myocarditis-like chest pain and ventricular arrhythmias, whereas heart failure symptoms were found only in CGV carriers. Dilated cardiomyopathy phenotype and ring-like pattern on cardiac magnetic resonance allowed the best discrimination among genotypes. AMI was proven by endomyocardial biopsy in all cases, and by noninvasive imaging in 21 (83%). IST was started in 17 patients (71%) with no safety issues. By the end of follow-up (median 69 months, range 21-182), signs of AMI were documented in 6/18 IST receivers (33%) and 4/7 untreated cases (57%). For most genotypes, paucity of adverse events was noted while on immunosuppression as compared to the off-treatment period. Conclusion Our preliminary data provide the clinical rationale for the research and targeting of AMI in a spectrum of genetic nonischemic cardiomyopathies.

216 ARRHYTHMOGENIC CARDIOMYOPATHY: IS THERE EVIDENCE OF AN INFLAMMATORY MYOCARDIAL DISEASE?

Abstract Background and aim Arrhythmogenic cardiomyopathy (ACM) is a heredo-familiar primary heart muscle disease, mainly due to mutations of desmosomal genes and characterized by progressive myocardial atrophy with fibro-fatty replacement, causing electrical instability at risk of sudden cardiac death (SCD). Since the first anatomopathological descriptions, the hypothesis that myocardial inflammation could have an important role in the onset and evolution of ACM has been advanced. With this work we aim to describe the prevalence of inflammatory cells in ACM and their characterization through histological and immunohistochemical (IHC) analysis in endomyocardial biopsy (EMB) and heart specimens coming from either SCD or heart transplantation (HTx). Material and methods We analysed EMB and whole heart specimens (from juvenile SCD registry – below 40 years of age at the time of death – and HTx) with a diagnosis of ACM, focusing on the presence of inflammatory infiltrates. For the whole hearts, in a subgroup of cases the inflammatory infiltrate was evaluated on 9 myocardial sections by applying a semi-quantitative score according to the number of sections involved (0 = none; 1 = 1 section involved; 2 = 2-5 sections; 3 = >5 sections) and an IHC panel for myocarditis on 1 right ventricular and 1 left ventricular section (CD45, CD3, CD8, CD4, CD68, CD20, CD138 and vimentin- as a control for fibroblast). Results Among the 63 analysed EMB (41 M, mean age 45 years, range 18-71 years), 26 cases (41%) showed foci of inflammation with CD3+ > 7/mm2. In all cases viral genome (DNA and RNA virus) was absent. A total of 106 heart specimens with a diagnosis of ACM were enrolled, including 73 juvenile SCD (49 M, mean age 26 years) and 33 HTx (18 M, mean age 45 years). Inflammation was reported in 95% of SCD an d 67% of HTx. The inflammatory infiltrate was focal or multifocal in all, except one case of juvenile SCD with diffuse myocarditis in the postero-lateral wall of the left ventricle. In the 24 reviewed cases, the inflammation was focal with a mean inflammatory score of 1.75 ±0.9 in the HTx group and 1.5±0.9 in the SD group (p = NS). By IHC we showed that: a) there is no significant difference in the inflammatory score between SD and HTx; b) the inflammation is mostly near-scarring (13 cases); c) inflammatory cells consist prevalently of cytotoxic T lymphocytes CD3+CD8+ (with CD4+<CD8+ both in SD and HTx, p < 0.05). Conclusions Our pathological data confirm that ACM is an inflammatory cardiomyopathy with a higher prevalence of inflammation in SCD cases. The inflammatory infiltrate is mainly composed of cytotoxic T lymphocytes with a variable presence of macrophages. These data, combined with the recent experimental studies demonstrating the role of immune mediators in the evolution of the disease, support the potential application of immunosuppressive therapy in ACM.

Novel view of arrhythmogenic cardiomyopathy as a “multicellular disease” affecting cardiac sympathetic innervation

Arrhythmogenic Cardiomyopathy (AC) is an incurable familial cardiac disease, mainly due to mutations in desmosomal genes, accounting for most cases of stress-related arrhythmic sudden death, in the young and athletes. AC hearts display cardiomyocyte (CM) death and diffuse fibro-fatty lesions, which compromise cardiac contractile performance and generate the substrate for arrhythmias. Correlation between physical/emotional stresses and arrhythmias incriminates sympathetic neurons (SNs), which may be the sought-after killers in disguise.

Ca2+ dysregulation in cardiac stromal cells sustains fibro-adipose remodeling in Arrhythmogenic Cardiomyopathy and can be modulated by flecainide

BackgroundCardiac mesenchymal stromal cells (C-MSC) were recently shown to differentiate into adipocytes and myofibroblasts to promote the aberrant remodeling of cardiac tissue that characterizes arrhythmogenic cardiomyopathy (ACM). A calcium (Ca2+) signaling dysfunction, mainly demonstrated in mouse models, is recognized as a mechanism impacting arrhythmic risk in ACM cardiomyocytes. Whether similar mechanisms influence ACM C-MSC fate is still unknown.Thus, we aim to ascertain whether intracellular Ca2+ oscillations and the Ca2+ toolkit are altered in human C-MSC obtained from ACM patients, and to assess their link with C-MSC-specific ACM phenotypes.Methods and resultsACM C-MSC show enhanced spontaneous Ca2+ oscillations and concomitant increased Ca2+/Calmodulin dependent kinase II (CaMKII) activation compared to control cells. This is manly linked to a constitutive activation of Store-Operated Ca2+ Entry (SOCE), which leads to enhanced Ca2+ release from the endoplasmic reticulum through inositol-1,4,5-trisphosphate receptors. By targeting the Ca2+ handling machinery or CaMKII activity, we demonstrated a causative link between Ca2+ oscillations and fibro-adipogenic differentiation of ACM C-MSC. Genetic silencing of the desmosomal gene PKP2 mimics the remodelling of the Ca2+ signalling machinery occurring in ACM C-MSC. The anti-arrhythmic drug flecainide inhibits intracellular Ca2+ oscillations and fibro-adipogenic differentiation by selectively targeting SOCE.ConclusionsAltogether, our results extend the knowledge of Ca2+ dysregulation in ACM to the stromal compartment, as an etiologic mechanism of C-MSC-related ACM phenotypes. A new mode of action of flecainide on a novel mechanistic target is unveiled against the fibro-adipose accumulation in ACM.

Adding up the desmosomal genes causing syndromes with hair and skin involvement: identification of TUFT1 by state-of-the-art whole-genome sequencing.

Adding up the desmosomal genes causing syndromes with hair and skin involvement: identification of TUFT1 by state-of-the-art whole-genome sequencing.

Abstract 14888: Arrhythmogenic Right Ventricular Cardiomyopathy-Brugada Syndrome Overlap: A Rare Clinical Entity

Introduction: Arrhythmogenic right ventricular cardiomyopathy (ARVC) and Brugada syndrome (BS) are inherited disorders that predispose individuals to arrhythmic sudden cardiac death. ARVC is a heart muscle disorder of intercellular junctions resulting from mutations of desmosomal (DS) genes, often leading to heart failure, and monomorphic ventricular tachycardia (VT). BS is a channelopathy due to sodium channel mutations, usually presenting as polymorphic VT without cardiomyopathy. Case presentation: A 35-year-old male with history of migraines presented with syncope resulting in a fall. No family history of arrhythmias or sudden cardiac death. Initial EKG showed wide complex monomorphic VT. Repeat EKG (figure 1), revealed coved ST-segment elevations in V1, V2 consistent with Brugada type 1 pattern. Emergent coronary angiography was unremarkable, and echocardiogram showed left ventricular ejection fraction of 55-60%, right ventricle (RV) outflow tract proximal diameter measured 3.5cm and normal RV function. An implantable cardioverter-defibrillator (ICD) was implanted for secondary prevention. Device interrogation on follow-up showed 11 shocks for recurrent episodes of monomorphic VT and patient was started on quinidine maintenance therapy. He remained symptom-free on subsequent visits. Genetic testing was positive for DSC2, DSP, and TMEM43 mutations associated with ARVC, but negative for genes associated with BS. Cardiac MRI results are pending. Discussion: Our patient has overlapping features of ARVC (genotype and monomorphic VT) and BS (EKG with coved ST elevations in V1, V2). Emerging evidence supports the theory that defects in DS proteins may affect the integrity of voltage-gated sodium channels in cardiac intercalated discs, leading to BS like phenotype. Conclusion: ARVC and BS could be related to the same disease spectrum, but further studies are required to understand pathophysiology, to guide treatment decisions.