Genetic Dilated Cardiomyopathy Research Articles

Clinical Features and Outcomes of Pediatric MYH7-Related Dilated Cardiomyopathy.

Although genetic variants in MYH7 are the most frequent cause of pediatric genetic dilated cardiomyopathy (DCM), there are no studies available describing this entity. We sought to describe clinical features, analyze variant location, and explore predictors of bad prognosis in pediatric MYH7-related DCM. We evaluated clinical records from 44 patients (24 men; median age at diagnosis, 0.54 [interquartile range, 0.01-10.8] years) with pathogenic/likely pathogenic variants in MYH7 diagnosed with DCM at pediatric age (<18 years) followed at 13 international centers. We also explored risk factors associated with a composite end point of end-stage heart failure defined as heart transplantation or heart failure-related death. Twenty-two patients (50%) were diagnosed at age <6 months, including 7 (16%) at birth. Left ventricular (LV) hypertrabeculation features were present in 15 (38%), particularly among patients with genetic variants in the head domain. After a median follow-up of 6.1 years (interquartile range, 1.9-13.4), 15 patients (36%) required a heart transplant (n=14) or died due to end-stage heart failure (n=1), 15 patients (36%) persisted with systolic dysfunction despite treatment, 12 (29%) had a significant increase in LV ejection fraction, and 2 were lost to follow-up. Overall, end-stage heart failure event rate was 25% at 5 years. New York Heart Association class III to IV (hazard ratio [HR], 7.67 [95% CI, 2.16-27.2]; P=0.002) and LV ejection fraction ≤35% (HR, 4.00 [95% CI, 1.11-14.4]; P=0.03) were the best predictors of bad prognosis. Pediatric MYH7-related DCM is characterized by early onset, frequent LV hypertrabeculation, and poor prognosis. Advanced New York Heart Association class and low LV ejection fraction emerged as predictors of end-stage heart failure.

A systematic review and meta-analysis to determine the biological sex ratio in monogenic genetic and non-genetic dilated cardiomyopathy

Abstract Background Dilated cardiomyopathy (DCM) is characterised by left ventricular or biventricular systolic dysfunction and dilatation, in the absence of abnormal loading conditions or coronary artery disease (1). Up to 30% of cases have an identified monogenic cause, usually with autosomal dominant (AD) inheritance (2). The disease appears to be twice as common in males, suggesting either a sex specific penetrance or a potential difference in expressivity. This sex ratio has not been systematically evaluated for genetic forms of DCM. Purpose To assess the sex ratio in patients with all-cause DCM compared to genetic (monogenic) and gene-elusive subtypes, defined by the presence or absence of a pathogenic variant in DCM-associated genes. Methods A literature search was conducted to identify cohorts of DCM patients with identifiable sex ratios. Exclusion criteria were patients with syndromic, X-linked, mitochondrial, or autosomal recessive (AR) DCM. Studies with a small cohort size (n&amp;lt;100), a paediatric population, unidentifiable sex ratio, or ischaemic and peripartum DCM were excluded. 98 studies with a total of 36,662 participants were included in this study. A random-effects meta-analysis generated a pooled proportion of female participants with a 95% confidence interval (95% CI) for an overall DCM cohort as well as for the subtypes – all genetic DCM, individual gene level for 10 key DCM genes (including titin, TTN, and lamin, LMNA), and gene elusive DCM. Results The overall DCM cohort had a 0.30 female proportion (95% CI: 0.28-0.32; Figure 1). This corresponds to a male:female (M:F) ratio of 2.38:1. This ratio did not significantly change in patients with an identified causative DCM variant (0.31 [95% CI 0.26-0.36]; M:F ratio of 2.22:1; p=0.563). There was also no significant difference when compared to patients who had been genetically tested with no identified variant (0.30 [95% CI 0.24-0.37]; M:F ratio of 2.29:1; p=0.814). Furthermore, the ratio within participants with AD gene variants was not significantly different for the specific genes of TTN (0.28 [95% CI 0.22-0.36]; M:F ratio of 2.51:1) and LMNA (0.35 [95% CI 0.27-0.44]; M:F ratio of 1.84:1). Overall, the sex ratio amongst patients with these AD gene variants was similar to the all-cause group (0.34 [95% CI 0.28-0.40]; M:F ratio of 1.98:1; p=0.18); Figure 2. Conclusions This meta-analysis suggests that DCM is twice as prevalent in males than females, even in pooled monogenic genetic subtypes with an equally prevalent genetic risk factor, indicating a difference in penetrance between the sexes. Further studies are required to determine the drivers of this sex specific penetrance.Forest plots: overall DCM cohortForest plots: gene-specific DCM cohort

Exercise training improves cardiovascular fitness in dilated cardiomyopathy caused by truncating titin variants

BackgroundParticipation in regular exercise activities is recommended for patients with chronic heart failure. However, less is known about the effect of exercise in patients with genetic dilated cardiomyopathy (DCM). We...

Abstract We103: Integration of deep learning assisted high-content screening and deep tissue-phenotyping to identify cardioprotective compounds in dilated cardiomyopathy

With a prevalence of 4:10,000, dilated cardiomyopathy (DCM) is the most common hereditary heart disease, characterized by dilatation of one or both ventricles and impaired systolic and diastolic function. Numerous mutations have been identified to cause DCM. TITIN-truncating variants (TTNtv) are commonly observed in 20% of the genetic DCM cases. Progress in drug discovery for DCM has been hampered by the lack of robust high-throughput/high-content analysis pipelines of disease-specific cell and tissue platforms for deep structural and functional phenotyping. To address this challenge, we have developed a two-tiered human induced pluripotent stem cell (iPSC)-based screening approach, comprised of high-content cardiomyocyte imaging with artificial intelligence (AI)-driven image and data analyses as well as deep tissue phenotyping in engineered heart muscle (EHM) models. As a DCM use case, we have developed several isogenic human iPSC-lines with and without a previously reported and pathologically relevant A-band-TTNtv mutation (c.70692_70693insAT; p.T23565SfsX5; Gerull et al. 11788824, Gramlich et al. 25759365, Fomin et al. 34731013) Using fixed weights from a convolutional deep neural network trained on ImageNet, we generated unbiased deep embeddings from each 2D cell model and applied these to train machine learning (ML) models to detect morphological disease phenotypes. Our ML model is able to confidently separate healthy controls from TTNtv cells with high accuracy (&gt;93%), specificity (WT &gt;79%) across different batches/plate layouts and generate concentration-response curves, demonstrating platform robustness and sensitivity. Building upon this work, we will present our latest efforts applying the platform technology for a chemogenomic screening campaign to identify novel cardioprotective drugs using a library of 7,100 bioactive compounds and validation assays, including measuring functional changes in EHMs. The phenotypic profiling platform, as presented here, can be readily adapted to other disease-relevant cell types and pathologies. Our results demonstrate the power of combining iPSC-CMs with cytological profiling and deep learning as well as tissue-level phenotyping to accelerate drug discovery for patients with DCM.

Prevalence of Genetically Associated Dilated Cardiomyopathy: A Systematic Literature Review and Meta-Analysis.

Dilated cardiomyopathy (DCM) is a leading cause of heart failure and cardiac transplantation globally. Disease-associated genetic variants play a significant role in the development of DCM. Accurately determining the prevalence of genetically associated DCM (genetic DCM) is important for developing targeted prevention strategies. This review synthesized published literature on the global prevalence of genetic DCM across various populations, focusing on two of the most common variants: titin (TTN) and myosin heavy chain 7 (MYH7). MEDLINE® and Embase were searched from database inception to September 19, 2022 for English-language studies reporting the prevalence of genetic DCM within any population. Studies using family history as a proxy for genetic DCM were excluded. Of 2,736 abstracts, 57 studies were included. Among the global adult or mixed (mostly adults with few pediatric patients) DCM population, median prevalence was 20.2% (interquartile range (IQR): 16.3-36.0%) for overall genetic DCM, 11.4% (IQR: 8.2-17.8%) for TTN-associated DCM, and 3.2% (IQR: 1.8-5.2%) for MYH7-associated DCM. Global prevalence of overall pediatric genetic DCM within the DCM population was similar (weighted mean: 21.3%). Few studies reported data on the prevalence of genetic DCM within the general population. Our study identified variable prevalence estimates of genetic DCM across different populations and geographic locations. The current evidence may underestimate the genetic contributions due to limited screening and detection of potential DCM patients. Epidemiological studies using long-read whole genome sequencing to identify structural variants or non-coding variants are needed, as well as large cohort datasets with genotype-phenotype correlation analyses.

Risk Assessment and Personalized Treatment Options in Inherited Dilated Cardiomyopathies: A Narrative Review.

Considering the worldwide impact of heart failure, it is crucial to develop approaches that can help us comprehend its root cause and make accurate predictions about its outcome. This is essential for lowering the suffering and death rates connected with this widespread illness. Cardiomyopathies frequently result from genetic factors, and the study of heart failure genetics is advancing quickly. Dilated cardiomyopathy (DCM) is the most prevalent kind of cardiomyopathy, encompassing both genetic and nongenetic abnormalities. It is distinguished by the enlargement of the left ventricle or both ventricles, accompanied by reduced contractility. The discovery of the molecular origins and subsequent awareness of the molecular mechanism is broadening our knowledge of DCM development. Additionally, it emphasizes the complicated nature of DCM and the necessity to formulate several different strategies to address the diverse underlying factors contributing to this disease. Genetic variants that can be transmitted from one generation to another can be a significant contributor to causing family or sporadic hereditary DCM. Genetic variants also play a significant role in determining susceptibility for acquired triggers for DCM. The genetic causes of DCM can have a large range of phenotypic expressions. It is crucial to select patients who are most probable to gain advantages from genetic testing. The purpose of this research is to emphasize the significance of identifying genetic DCM, the relationships between genotype and phenotype, risk assessment, and personalized therapy for both those affected and their relatives. This approach is expected to gain importance once treatment is guided by genotype-specific advice and disease-modifying medications.

In vivo rescue of genetic dilated cardiomyopathy by systemic delivery of nexilin

BackgroundDilated cardiomyopathy (DCM) is one of the most common causes of heart failure. Multiple identified mutations in nexilin (NEXN) have been suggested to be linked with severe DCM. However, the exact association between multiple mutations of Nexn and DCM remains unclear. Moreover, it is critical for the development of precise and effective therapeutics in treatments of DCM.ResultsIn our study, Nexn global knockout mice and mice carrying human equivalent G645del mutation are studied using functional gene rescue assays. AAV-mediated gene delivery is conducted through systemic intravenous injections at the neonatal stage. Heart tissues are analyzed by immunoblots, and functions are assessed by echocardiography. Here, we identify functional components of Nexilin and demonstrate that exogenous introduction could rescue the cardiac function and extend the lifespan of Nexn knockout mouse models. Similar therapeutic effects are also obtained in G645del mice, providing a promising intervention for future clinical therapeutics.ConclusionsIn summary, we demonstrated that a single injection of AAV-Nexn was capable to restore the functions of cardiomyocytes and extended the lifespan of Nexn knockout and G645del mice. Our study represented a long-term gene replacement therapy for DCM that potentially covers all forms of loss-of-function mutations in NEXN.

Embarazo en mujeres portadoras de variantes genéticas de miocardiopatía dilatada

Introduction and objectivesLimited information is available on the safety of pregnancy in patients with genetic dilated cardiomyopathy (DCM) and in carriers of DCM-causing genetic variants without the DCM phenotype. We assessed cardiac, obstetric, and fetal or neonatal outcomes in this group of patients. MethodsWe studied 48 women carrying pathogenic or likely pathogenic DCM-associated variants (30 with DCM and 18 without DCM) who had 83 pregnancies. Adverse cardiac events were defined as heart failure (HF), sustained ventricular tachycardia, ventricular assist device implantation, heart transplant, and/or maternal cardiac death during pregnancy, or labor and delivery, and up to the sixth postpartum month. ResultsA total of 15 patients, all with DCM (31% of the total cohort and 50% of women with DCM) experienced adverse cardiac events. Obstetric and fetal or neonatal complications were observed in 14% of pregnancies (10 in DCM patients and 2 in genetic carriers). We analyzed the 30 women who had been evaluated before their first pregnancy (12 with overt DCM and 18 without the phenotype). Five of the 12 (42%) women with DCM had adverse cardiac events despite showing NYHA class I or II before pregnancy. Most of these women had a history of cardiac events before pregnancy (80%). Among the 18 women without phenotype, 3 (17%) developed DCM toward the end of pregnancy. ConclusionsCardiac complications during pregnancy and postpartum were common in patients with genetic DCM and were primarily related to HF. Despite apparently good tolerance of pregnancy in unaffected genetic carriers, pregnancy may act as a trigger for DCM onset in a subset of these women.

Genetic dilated cardiomyopathy with inflammation in an infant that responded to immunosuppressive therapy evaluated using cardiovascular magnetic resonance.

Cardiovascular magnetic resonance T1 and T2 mapping reflects inflammation, fibrosis, and myocardial oedema. However, its application in infants remains uncertain. Herein, we report a three-month-old boy with dilated cardiomyopathy successfully treated with steroids. Cardiovascular magnetic resonance was useful for diagnosis based on the elevated native T1, T2, and extracellular volume and evaluation of response to immunosuppressive therapy in infantile inflammatory dilated cardiomyopathy.

Pregnancy in women with dilated cardiomyopathy genetic variants

Introduction and objectivesLimited information is available on the safety of pregnancy in patients with genetic dilated cardiomyopathy (DCM) and in carriers of DCM-causing genetic variants without the DCM phenotype. We assessed cardiac, obstetric, and fetal or neonatal outcomes in this group of patients. MethodsWe studied 48 women carrying pathogenic or likely pathogenic DCM-associated variants (30 with DCM and 18 without DCM) who had 83 pregnancies. Adverse cardiac events were defined as heart failure (HF), sustained ventricular tachycardia, ventricular assist device implantation, heart transplant, and/or maternal cardiac death during pregnancy, or labor and delivery, and up to the sixth postpartum month. ResultsA total of 15 patients, all with DCM (31% of the total cohort and 50% of women with DCM) experienced adverse cardiac events. Obstetric and fetal or neonatal complications were observed in 14% of pregnancies (10 in DCM patients and 2 in genetic carriers). We analyzed the 30 women who had been evaluated before their first pregnancy (12 with overt DCM and 18 without the phenotype). Five of the 12 (42%) women with DCM had adverse cardiac events despite showing NYHA class I or II before pregnancy. Most of these women had a history of cardiac events before pregnancy (80%). Among the 18 women without phenotype, 3 (17%) developed DCM toward the end of pregnancy. ConclusionsCardiac complications during pregnancy and postpartum were common in patients with genetic DCM and were primarily related to HF. Despite apparently good tolerance of pregnancy in unaffected genetic carriers, pregnancy may act as a trigger for DCM onset in a subset of these women.

Abstract P160: Prevalence of Genetic Dilated Cardiomyopathy: A Systematic Literature Review

Background: Dilated cardiomyopathy (DCM) is a leading cause of heart failure and cardiac transplantation worldwide. Many cases of DCM are due to genetic or idiopathic etiology. Two prominent contributors to genetic DCM (gDCM) are the TTN and MYH7 genes, which encode proteins associated with DCM etiology. Purpose: This study aimed to synthesize the published literature on the global prevalence of adult and pediatric gDCM within the clinical DCM population and the general population. Methods: A systematic review was conducted by searching MEDLINE® and Embase from database inception to 09/19/2022. We included observational studies reporting the prevalence of gDCM within any population; prevalence of TTN and MYH7 mutations were also extracted. Excluded were studies using family history as a proxy for gDCM. Median with interquartile range (IQR) or mean with standard deviation (SD) weighted by sample size (in cases of calculations with &lt;10 studies) were used to summarize the data. Results: Of 2,720 identified abstracts, 57 studies were included in the review. Among the adult or mixed (adults and children) DCM population in any country, median prevalence was 21.0% for overall DCM-related genetic mutations, 11.4% for TTN mutations, and 3.2% for MYH7 mutations ( Table ). The prevalence of pediatric gDCM within the DCM population was similar (weighted mean: 21.3%). Data on prevalence of gDCM within the general population were scarce. Conclusion: This study highlights the variable prevalence of gDCM reported across different populations and settings. The current evidence may underestimate the genetic causes due to technical limitations in genetic testing and limited screening. Accurately determining the prevalence of gDCM is critical for identifying high-risk populations, developing targeted prevention strategies for disease complications, and improving outcomes; epidemiological studies using long-read sequencing techniques and large cohort datasets with genotype-phenotype correlation analyses are needed.

Imagenetics for Precision Medicine in Dilated Cardiomyopathy.

Dilated cardiomyopathy (DCM) is a common heart muscle disorder of nonischemic etiology associated with heart failure development and the risk of malignant ventricular arrhythmias and sudden cardiac death. A tailored approach to risk stratification and prevention of sudden cardiac death is required in genetic DCM given its variable presentation and phenotypic severity. Currently, advances in cardiogenetics have shed light on disease mechanisms, the complex genetic architecture of DCM, polygenic contributors to disease susceptibility and the role of environmental triggers. Parallel advances in imaging have also enhanced disease recognition and the identification of the wide spectrum of phenotypes falling under the DCM umbrella. Genotype-phenotype associations have been also established for specific subtypes of DCM, such as DSP (desmoplakin) or FLNC (filamin-C) cardiomyopathy but overall, they remain elusive and not readily identifiable. Also, despite the accumulated knowledge on disease mechanisms, certain aspects remain still unclear, such as which patients with DCM are at risk for disease progression or remission after treatment. Imagenetics, that is, the combination of imaging and genetics, is expected to further advance research in the field and contribute to precision medicine in DCM management and treatment. In the present article, we review the existing literature in the field, summarize the established knowledge and emerging data on the value of genetics and imaging in establishing genotype-phenotype associations in DCM and in clinical decision making for DCM patients.

Cas13b-mediated RNA targeted therapy alleviates genetic dilated cardiomyopathy in mice

BackgroundRecent advances in gene editing technology have opened up new avenues for in vivo gene therapy, which holds great promise as a potential treatment method for dilated cardiomyopathy (DCM). The CRISPR-Cas13 system has been shown to be an effective tool for knocking down RNA expression in mammalian cells. PspCas13b, a type VI-B effector that can be packed into adeno-associated viruses and improve RNA knockdown efficiency, is a potential treatment for diseases characterized by abnormal gene expression.ResultsUsing PspCas13b, we were able to efficiently and specifically knockdown the mutant transcripts in the AC16 cell line carrying the heterozygous human TNNT2R141W (hTNNT2R141W) mutation. We used adeno-associated virus vector serotype 9 to deliver PspCas13b with specific single guide RNA into the hTNNT2R141W transgenic DCM mouse model, effectively knocking down hTNNT2R141W transcript expression. PspCas13b-mediated knockdown significantly increased myofilament sensitivity to Ca2+, improved cardiac function, and reduced myocardial fibrosis in hTNNT2R141W DCM mice.ConclusionsThese findings suggest that targeting genes through Cas13b is a promising approach for in vivo gene therapy for genetic diseases caused by aberrant gene expression. Our study provides further evidence of Cas13b’s application in genetic disease therapy and paves the way for future applicability of genetic therapies for cardiomyopathy.

Skeletal Muscle Involvement in Patients With Truncations of Titin and Familial Dilated Cardiomyopathy

BackgroundGenetic variants in titin (TTN) are associated with dilated cardiomyopathy (DCM) and skeletal myopathy. However, the skeletal muscle phenotype in individuals carrying heterozygous truncating TTN variants (TTNtv), the leading cause of DCM, is understudied. ObjectivesThis study aimed to assess the skeletal muscle phenotype associated with TTNtv. MethodsParticipants with TTNtv were included in a cross-sectional study. Skeletal muscle fat fraction was evaluated by magnetic resonance imaging (compared with healthy controls and controls with non-TTNtv DCM). Muscle strength was evaluated by dynamometry and muscle biopsy specimens were analyzed. ResultsTwenty-five TTNtv participants (11 women, mean age 51 ± 15 years, left ventricular ejection fraction 45% ± 10%) were included (19 had DCM). Compared to healthy controls (n = 25), fat fraction was higher in calf (12.5% vs 9.9%, P = 0.013), thigh (12.2% vs 9.3%, P = 0.004), and paraspinal muscles (18.8% vs 13.9%, P = 0.008) of TTNtv participants. Linear mixed effects modelling found higher fat fractions in TTNtv participants compared to healthy controls (2.5%; 95% CI: 1.4-3.7; P < 0.001) and controls with non-TTNtv genetic DCM (n = 7) (1.5%; 95% CI: 0.2-2.8; P = 0.025). Muscle strength was within 1 SD of normal values. Biopsy specimens from 21 participants found myopathic features in 13 (62%), including central nuclei. Electron microscopy showed well-ordered Z-lines and T-tubuli but uneven and discontinuous M-lines and excessive glycogen depositions flanked by autophagosomes, lysosomes, and abnormal mitochondria with mitophagy. ConclusionsMild skeletal muscle involvement was prevalent in patients with TTNtv. The phenotype was characterized by an increased muscle fat fraction and excessive accumulation of glycogen, possibly due to reduced autophagic flux. These findings indicate an impact of TTNtv beyond the heart.

Does aetiology of dilated cardiomyopathy impact the outcome in Eastern Europe?

Abstract Introduction There are regional variations (West vs. East vs. North vs. South) in aetiology and outcomes in patients with cardiomyopathies according to EORP Registry. However, those preliminary observations have not been systematically verified. Here we report on the large cohort of dilated cardiomyopathy (DCM) patients managed in a tertiary centre in Eastern Europe. Purpose Analysis of all-cause mortality in DCM patients with different aetiology. Methods 500 DCM patients (aged 53.1±13.6 years, 81% male, LVEF 26.6±10.4%, LVEDd 65.9±10.3mm, symptoms duration 38.6±61.2 months) from 2010-2021 with complete baseline and follow-up data were included retrospectively. DCM aetiology was diagnosed according to medical documentation as: idiopathic, inflammatory, toxic: alcohol-induced or other (including chemotherapy and drug-induced), arrhythmic and familial or genetic (ref genetic). After mean follow-up (FU) of 45.6±31.0 months, the all-cause mortality and composite endpoint (all-cause mortality, heart transplant – HTX, left ventricle assist device implantation - LVAD) were assessed. Results Out of 500 DCM patients no clear aetiology was found in 41% of patients (idiopathic DCM). The most common was inflammatory DCM, followed by alcohol-induced, arrhythmic, and genetic DCM (Figure 1-A). The least common was toxic DCM (18 - after chemotherapy, 2 – drug-induced). During FU there were 97 (19%) patients with the following events: 88 (18%) patients died, 7 (1%) had LVAD and 15 (3%) had HTX (Figure 1-B). Statistically, all groups did not differ in terms of events (all p&amp;gt;0.05), however on the Kaplan-Meier plot patients with toxic DCM (chemotherapy or drug-induced) had the worst outcome while patients with inflammatory DCM had the best outcome during 6-years FU (Figure 1-C, 1-D). Conclusion More than one-third of DCM patients were diagnosed with idiopathic DCM. Toxic DCM was the second most prevalent aetiology and was diagnosed in nearly a quarter of patients. Alcohol-induced DCM was present in every fifth of patients. Although statistically no difference in outcome was found, according to Kaplan-Meier curves, patients with inflammatory DCM have the best prognosis and those with chemotherapy- or drug-induced – the worst.Figure 1.

Genetics of Dilated Cardiomyopathy.

Dilated cardiomyopathy (DCM) is defined as dilation and/or reduced function of one or both ventricles and remains a common disease worldwide. An estimated 40% of cases of familial DCM have an identifiable genetic cause. Accordingly, there is a fast-growing interest in the field of molecular genetics as it pertains to DCM. Many gene mutations have been identified that contribute to phenotypically significant cardiomyopathy. DCM genes can affect a variety of cardiomyocyte functions, and particular genes whose function affects the cell-cell junction and cytoskeleton are associated with increased risk of arrhythmias and sudden cardiac death. Through advancements in next-generation sequencing and cardiac imaging, identification of genetic DCM has improved over the past couple decades, and precision medicine is now at the forefront of treatment for these patients and their families. In addition to standard treatment of heart failure and prevention of arrhythmias and sudden cardiac death, patients with genetic cardiomyopathy stand to benefit from gene mechanism-specific therapies.

Danicamtiv Increases Myosin Recruitment and Alters Cross-Bridge Cycling in Cardiac Muscle.

Modulating myosin function is a novel therapeutic approach in patients with cardiomyopathy. Danicamtiv is a novel myosin activator with promising preclinical data that is currently in clinical trials. While it is known that danicamtiv increases force and cardiomyocyte contractility without affecting calcium levels, detailed mechanistic studies regarding its mode of action are lacking. Permeabilized porcine cardiac tissue and myofibrils were used for X-ray diffraction and mechanical measurements. A mouse model of genetic dilated cardiomyopathy was used to evaluate the ability of danicamtiv to correct the contractile deficient. Danicamtiv increased force and calcium sensitivity via increasing the number of myosins in the on state and slowing cross-bridge turnover. Our detailed analysis showed that inhibition of ADP release results in decreased cross-bridge turnover with cross bridges staying attached longer and prolonging myofibril relaxation. Danicamtiv corrected decreased calcium sensitivity in demembranated tissue, abnormal twitch magnitude and kinetics in intact cardiac tissue, and reduced ejection fraction in the whole organ. As demonstrated by the detailed studies of Danicamtiv, increasing myosin recruitment and altering cross-bridge cycling are 2 mechanisms to increase force and calcium sensitivity in cardiac muscle. Myosin activators such as Danicamtiv can treat the causative hypocontractile phenotype in genetic dilated cardiomyopathy.

Abstract EC.04: The Effects Of Cardiac Troponin Activator CK-358 On Cardiac Contractility In A Mouse Model Of Genetic Dilated Cardiomyopathy

Genetic dilated cardiomyopathy (DCM) is one of the most common causes of heart failure. However, most treatments do not address the underlying contractile deficit caused by the disease. In an effort to create more targeted DCM therapeutics, novel small molecule drugs known as sarcomeric modulators have been of recent interest. In a recent study, a cardiac troponin activator was shown to improve cardiac muscle contractility without adversely affecting energetics or diastolic function. Here, we aim to elucidate the mechanism by which the cardiac troponin activator CK-3827358 (CK-358) is able to recover contractile function in a mouse model of DCM with a mutation at residue 61 of cardiac troponin C (cTnC I61Q). We measured steady state force and k tr , a measure of crossbridge cycling kinetics, in demembranated ventricular tissue from control and cTnC I61Q mice in solutions with increasing concentrations of calcium, ranging from pCa 9 to pCa 4. The cTnC I61Q mutation significantly decreased calcium sensitivity versus control (pCa 50 : 5.48 ± 0.06 vs 5.75 ± 0.01). Compared to controls, CK-358 (1 μM) significantly increased calcium sensitivity (pCa 50 ) in tissue from both cTnC I61Q and control mice (6.03 ± 0.06 and 6.50 ± 0.18, P=0.005) without any change in maximum force. CK-358 also significantly increased k tr , possibly suggesting activation of thin filaments. Next, we used a fluorescently labeled human cardiac troponin C (HcTnC) conjugated to N,N′-dimethyl-N-(iodoacetyl)-N′-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)ethylenediamine (IANBD) combined with subunits T and I to make a full HcTn complex. We performed calcium titrations with the HcTn-IANBD and saw no change in fluorescence in the control protein with and without CK-358. Finally, we performed HcTnC titrations with HcTnI and saw no change in fluorescence at maximum, sub-maximum, and minimum calcium concentrations. Overall, we demonstrate that cardiac troponin activator CK-358 did not alter calcium binding to HcTnC or its interaction with HcTnI. However, it restores the calcium sensitivity of cTnC I61Q DCM ventricular sarcomeres. Future studies will examine the effects of CK-358 on calcium binding in decorated thin filaments and measure activation using stopped flow spectroscopy in this model of DCM.

Cardiac Inflammation in Adult-Onset Genetic Dilated Cardiomyopathy.

Dilated cardiomyopathy (DCM) has a genetic cause in up to 40% of cases, with differences in disease penetrance and clinical presentation, due to different exogeneous triggers and implicated genes. Cardiac inflammation can be the consequence of an exogeneous trigger, subsequently unveiling a phenotype. The study aimed to determine cardiac inflammation in a cohort of genetic DCM patients and investigate whether it associated with a younger disease onset. The study included 113 DCM patients with a genetic etiology, of which 17 had cardiac inflammation as diagnosed in an endomyocardial biopsy. They had a significant increased cardiac infiltration of white blood, cytotoxic T, and T-helper cells (p < 0.05). Disease expression was at a younger age in those patients with cardiac inflammation, compared to those without inflammation (p = 0.015; 50 years (interquartile range (IQR) 42-53) versus 53 years (IQR 46-61). However, cardiac inflammation was not associated with a higher incidence of all-cause mortality, heart failure hospitalization, or life-threatening arrhythmias (hazard ratio 0.85 [0.35-2.07], p = 0.74). Cardiac inflammation is associated with an earlier disease onset in patients with genetic DCM. This might indicate that myocarditis is an exogeneous trigger unveiling a phenotype at a younger age in patients with a genetic susceptibility, or that cardiac inflammation resembles a 'hot-phase' of early-onset disease.

Abstract 15027: Senescence-Associated Pathway Activation in Cardiac Fibroblasts in Dilated Cardiomyopathy

Introduction: Cardiac fibrosis is a pathologic driver in heart failure (HF) and aging is a major risk factor for HF. Persistence of activated myofibroblasts is a key feature of pathological fibrosis. In an aging model of lung fibrosis, senescent myofibroblasts exhibit apoptosis-resistance, which contributes to the sustained fibrotic response. Therapeutic targeting of NADPH oxidase-4 (NOX4), a primary source of reactive oxygen species (ROS) in myofibroblasts, can inhibit fibrosis development and reverse established lung fibrosis. We sought to understand the role of cellular senescence and NOX4 activation and persistence of cardiac fibroblasts with progression to HF. Methods and Results: Mice carrying a mutation in the phospholamban gene (PLNR9C) develop progressive dilated cardiomyopathy (DCM), extensive cardiac fibrosis and HF. Using the Langendorff hanging heart method and flow cytometry, cardiac fibroblasts were isolated and studied for markers of cellular senescence. Cardiac fibroblasts from PLNR9C mice with DCM display a senescent phenotype, with significantly elevated levels of the senescence markers p16 (2.1-fold, p&lt;0.01, n=3, Figure) and beta-galactosidase (1.7-fold, p&lt;0.01, n=3), along with significantly increased ROS production (Amplex Red assay 2.5-fold, p&lt;0.01, n=3), as compared to fibroblasts from age-matched wild type (WT) mice. Nox4 is upregulated in cardiac fibroblasts from PLNR9C mice (mRNA 8.5-fold, n=4, p&lt;0.01; protein 5.0-fold, p&lt;0.01, n=4, Figure) with HF but not in young PLNR9C mice prior to development of DCM. Conclusions: These data reveal a premature aging phenotype in cardiac fibroblasts from mice with genetic DCM and identify NOX4 as a putative mediator of fibroblast activation and persistence.