Clinical Insights Into Heritable Cardiomyopathies

Patterns of Cardiomyopathy in Patients Presenting to a Tertiary Care Hospital

BACKGROUND

Cardiomyopathy is a broad category of myocardial conditions that have a substantial effect on heart function. Improving patient treatment requires a knowledge of its epidemiology.

OBJECTIVE

The aim of this study was to determine the pattern of cardiomyopathy in patients presenting to a tertiary care hospital in Peshawar, Pakistan.

METHODOLOGY

This cross-sectional study was conducted at the Department of Cardiology, Northwest General Hospital & Research Centre, Peshawar, from December 14, 2022, to June 14, 2023. There were 79 individuals with cardiomyopathy who were 16 years of age or older. Clinical and demographic information, such as age, gender, BMI, length of illness, and family history, were gathered. Cardiomyopathy patterns were classified using echocardiographic evaluations, and IBM SPSS Statistics for Windows, version 25 (IBM Corp., Armonk, NY) was employed for statistical analysis.

RESULTS

The average age of the 79 participants was 45.72 ± 2.45 years, and 40.5% (n=32) were between the ages of 51 and 60. There were 63.3% male individuals (n=50) and 36.7% female individuals (n=29). With 69.6% (n=55) and 30.4% (n=24) having a duration of symptoms ≤1 month and >1 month, respectively. 38.0% (n=30) had a family history of cardiomyopathy. With dilated, hypertrophic, and peripartum cardiomyopathy each at 15.2%, the most prevalent forms of cardiomyopathy were restrictive (20.3%, n=16), ischemic (17.7%, n=14), and arrhythmogenic right ventricular (16.5%, n=13). BMI (p = 0.000) and illness duration (p = 0.000) were substantially correlated with dilated and hypertrophic cardiomyopathies. Older age groups, especially those between the ages of 51 and 60, had a greater prevalence of cardiomyopathy (p = 0.000). Dilated cardiomyopathy (p = 0.000) and peripartum cardiomyopathy (p = 0.000) were significantly influenced by family history.

CONCLUSION

The research highlights the variety of cardiomyopathy patterns seen in a tertiary care facility, with ischemic and restrictive forms being the most prevalent. This highlights the need for specialized diagnosis and treatment strategies.

Exosomes and non-coding RNAs: Exploring their roles in human myocardial dysfunction

Myocardial dysfunction, characterized by impaired cardiac muscle function, arises from diverse etiologies, including coronary artery disease, myocardial infarction, cardiomyopathies, hypertension, and valvular heart disease. Recent advancements have highlighted the roles of exosomes and non-coding RNAs in the pathophysiology of myocardial dysfunction. Exosomes are small extracellular vesicles released by cardiac and other cells that facilitate intercellular communication through their molecular cargo, including ncRNAs. ncRNAs are known to play critical roles in gene regulation through diverse mechanisms, impacting oxidative stress, fibrosis, and other factors associated with myocardial dysfunction. Dysregulation of these molecules correlates with disease progression, presenting opportunities for therapeutic interventions. This review explores the mechanistic interplay between exosomes and ncRNAs, underscoring their potential as biomarkers and therapeutic agents in myocardial dysfunction. Emerging evidence supports the use of engineered exosomes and modified ncRNAs to enhance cardiac repair by targeting signaling pathways associated with fibrosis, apoptosis, and angiogenesis. Despite promising preclinical results, delivery, stability, and immunogenicity challenges remain. Further research is needed to optimize clinical translation. Understanding these intricate mechanisms may drive the development of innovative strategies for diagnosing and treating myocardial dysfunction, ultimately improving patient outcomes.

An hiPSC-CM approach for electrophysiological phenotyping of a patient-specific case of short-coupled TdP

INTRODUCTION

A healthy young woman, age 26 without prior cardiac complications, experienced an out-of-hospital cardiac arrest caused by ventricular fibrillation (VF), which coincided with a fever. Comprehensive diagnostics including echo, CMR, exercise testing, and genetic sequencing, did not identify any potential cause. This led to the diagnosis of idiopathic VF and installment of an implantable cardioverter defibrillator, which six months later appropriately intervened another VF episode under conditions comparable to the first event. A second diagnostic opinion concluded short-coupled Torsade de Pointes (scTdP), and the patient was started on a verapamil treatment.

METHODS

From this patient, human induced pluripotent stem cell cardiomyocyte (hiPSC-CM) lines were generated to study cellular electrophysiology. Without a known genetic pathogenic variation, no isogenic control line could be produced, therefore a healthy age- and sex-matched control hiPSC-CM line was used. Cellular electrophysiology was studied in these cardiomyocytes using calcium- and voltage sensitive fluorescent dyes and measurements were carried out at 37 °C and 39 °C, to mimic the condition of hyperthermia in the patient. mRNA expression of electrophysiologically relevant genes were analyzed to identify a potential underlying mechanism.

RESULTS

Calcium transients measured in patient lines at a physiological temperature indicated the occurrence of early after transients (EATs). Strikingly, at 39 °C the incidence of EATs further increased. Membrane potential data from the patient also revealed shorter action potentials that, combined with the EATs, indicate the premature release of calcium during diastole, which could be responsible for the extrasystoles in the patient. Gene expression profiles were mainly downregulated in the patient but could not clearly aid in unraveling a mechanism behind the occurrence of EATs. Pharmacological screening was performed to evaluate the treatment regimen and to determine a mechanism of action of the EATs. While verapamil, dantrolene, and flecainide did not decrease the incidence of EATs, calcium handling parameters were affected indicating functionality of the drugs.

CONCLUSION

This patient-specific case of electrophysiological phenotyping resulted in a hypothesis of the possible mechanism behind the scTdP arrhythmias, but also accentuates the applicability of patient-specific hiPSC-CM disease modeling and phenotyping.

The power of hybridization capture - Illustrated using an expanded gene panel on 100 post mortem samples, focusing on sudden unexplained death

Sudden unexpected death (SUD) is an unexpected event that in many cases are caused by diseases with an underlying genetic background. Forensic molecular autopsy is an approach that has gained wide-spread attention, in part explained by the rapid progress of DNA sequencing techniques. The approach leverages genetic data in combination with medical autopsy findings in post-mortem samples to explore a potential underlying genetic cause of death. Traditional forensic approaches to molecular autopsy focus on a small panel of genes, say <200 genes, with strong association to heart conditions whereas clinical genetics tend to capture entire exomes while subsequently selecting targeted panels bioinformatically. The drop in price and the increased throughput has promoted wider exome sequencing as a viable method to discover genetic variants. We explore a targeted gene panel consisting of 2422 genes, selected based on their broad association to sudden unexplained death. A hybridization capture approach from Twist Bioscience based on double stranded DNA probes was used to target exons of the included genes. We selected and sequenced a total of 98 post-mortem samples from historical forensic autopsy cases where the cause of death could not be unambiguously determined based on medical findings and that had a previous negative molecular autopsy. In the current study, we focus on the performance of the hybridization capture technology on a 2422 gene panel and explore metrics related to sequencing success using a mid-end NextSeq 550 as well as a MiSeq FGx platform. With the latter we demonstrate that our sequence data benefits from 2×300 bp sequencing increasing coverage, in particular, for difficult regions where shadow coverage, i.e. regions outside the probes, are utilized. The results further illustrate a highly uniform capture across the panel of genes (mean fold80=1.5), in turn minimizing excessive sequencing costs to reach sufficient coverage, i.e. 20X. We outline a stepwise procedure to select genes associated with SUD through virtual bioinformatical panels extracting tier of genes with increasing strength of association to SUD. We propose some prioritization strategies to filter variants with highest potential and show that the number of high priority genetic variant requiring manual inspections is few (0-3 for all tiers of genes) when all filters are applied.

The impact of the European Society of Cardiology guidelines and whole exome sequencing on genetic testing in hereditary cardiac diseases

In the last decade, an incredible improvement has been made in elucidating the genetic bases of cardiomyopathies. Here we report the impact of either the European Society of Cardiology (ESC) guidelines or the use of whole exome sequencing (WES) in terms of a number of variants of uncertain significance (VUS) and missed diagnoses in a series of 260 patients affected by inherited cardiac disorders. Samples were analyzed using a targeted gene panel of 128 cardiac-related genes and/or WES in a subset of patients, with a three-tier approach. Analyzing (i) only a subset of genes related to the clinical presentation, strictly following the ESC guidelines, 20.77% positive test were assessed. The incremental diagnostic rate for (ii) the whole gene panel, and (iii) the WES was 4.71% and 11.67%, respectively. The diverse analytical approaches increased the number of VUSs and incidental findings. Indeed, the use of WES highlights that there is a small percentage of syndromic conditions that standard analysis would not have detected. Moreover, the use of targeted sequencing coupled with "narrow" analytical approach prevents the detection of variants in actionable genes that could allow for preventive treatment. Our data suggest that genetic testing might aid clinicians in the diagnosis of inheritable cardiac disorders.

Hypertrophic Cardiomyopathy

PURPOSE OF REVIEW

Hypertrophic cardiomyopathy (HCM) is a common inherited cardiac condition with potential for severe complications including sudden cardiac death. Early diagnosis allows appropriate risk stratification and prompt intervention to minimise the potential for adverse outcomes. The implications of poorly coordinated screening are significant, either missing relatives at high-risk or burdening low-risk individuals with a diagnosis associated with reduced life expectancy. We aim to guide clinicians through the diagnostic pathway through to novel treatment options. Several conditions mimic the condition, and we discuss the phenocopies and how to differentiate from HCM.

RECENT FINDINGS

We summarise the latest developments informing clinical decision making in the modern era of myosin inhibitors and future gene editing therapies. Early identification will enable prompt referral to specialist centres. A diagnostic flowchart is included, to guide the general cardiology and heart failure clinician in important decision making regarding the care of the HCM patient and importantly their relatives at risk. We have highlighted the importance of screening because genotype-positive/phenotype-negative patients are likely to have the most to gain from novel therapies.

Knockdown of SCN5A alters metabolic-associated genes and aggravates hypertrophy in the cardiomyoblast

SCN5A mutations have been reported to cause various cardiomyopathies in humans. Most of the SCN5A mutations causes loss of function and thereby, alters the overall cellular function. Therefore, to understand the loss of SCN5A function in cardiomyocytes, we have knocked down the SCN5A gene (SCN5A-KD) in H9c2 cells and explored the cell phenotype and molecular behaviors in the presence and absence of isoproterenol (ISO), an adrenergic receptor agonist that induces cardiac hypertrophy. Expression of several genes related to hypertrophy, inflammation, fibrosis, and energy metabolism pathways were evaluated. It was found that the mRNA expression of hypertrophy-related gene, brain (B-type) natriuretic peptide (BNP) was significantly increased in SCN5A-KD cells as compared to 'control' H9c2 cells. There was a further increase in the mRNA expressions of BNP and βMHC in SCN5A-KD cells after ISO treatment compared to their respective controls. Pro-inflammatory cytokine, tumor necrosis factor-alpha expression was significantly increased in 'SCN5A-KD' H9c2 cells. Further, metabolism-related genes like glucose transporter type 4, cluster of differentiation 36, peroxisome proliferator-activated receptor alpha, and peroxisome proliferator-activated receptor-gamma were significantly elevated in the SCN5A-KD cells as compared to the control cells. Upregulation of these metabolic genes is associated with increased ATP production. The study revealed that SCN5A knock-down causes alteration of gene expression related to cardiac hypertrophy, inflammation, and energy metabolism pathways, which may promote cardiac remodelling and cardiomyopathy.

Hypertrophic cardiomyopathy: a modern view of the problem

Cardiomyopathy is considered one of the main causes of heart failure and sudden cardiac death, at least in young people. Approximately 50% of patients who die suddenly in childhood or adolescence or undergo heart transplantation suffer from this condition. The purpose of this literature review is to study and highlight the issues of etiology, pathogenesis, clinical features, diagnosis and treatment of hypertrophic cardiomyopathy from the point of view of modern ideas. The search and analysis of domestic and foreign literature materials using the PubMed and eLibrary databases was carried out. Of particular interest is the etiology of primary congenital cardiomyopathies, in respect of which research continues. As a result of the implementation of genetic factors, multiple structural and functional changes in the myocardium develop, which lead to changes in hemodynamics. Cardiomyopathy is a clinically heterogeneous disease, and one of the factors that determine the clinical phenotype is the genotype. In addition to standard laboratory testing, patients with suspected hypertrophic cardiomyopathy are advised to undergo medical genetic counseling to identify the causative mutation, and often to obtain prognostic information. The fundamental imaging method is echocardiography, but the role of magnetic resonance imaging in the diagnosis of the disease is also considered. Patients with symptomatic obstructive hypertrophic cardiomyopathy are usually recommended first-line pharmacotherapy with -blockers or non-dihydropyridine calcium channel blockers. Currently, research on new drugs for the treatment of hypertrophic cardiomyopathy inhibitors of cardiac myosin is ongoing. Surgical methods of treatment are developing progressively, however, methods of conservative treatment require further active research of drugs that have not been used before.

RagD auto-activating mutations impair MiT/TFE activity in kidney tubulopathy and cardiomyopathy syndrome

Heterozygous mutations in the gene encoding RagD GTPase were shown to cause a novel autosomal dominant condition characterized by kidney tubulopathy and cardiomyopathy. We previously demonstrated that RagD, and its paralogue RagC, mediate a non-canonical mTORC1 signaling pathway that inhibits the activity of TFEB and TFE3, transcription factors of the MiT/TFE family and master regulators of lysosomal biogenesis and autophagy. Here we show that RagD mutations causing kidney tubulopathy and cardiomyopathy are "auto- activating", even in the absence of Folliculin, the GAP responsible for RagC/D activation, and cause constitutive phosphorylation of TFEB and TFE3 by mTORC1, without affecting the phosphorylation of "canonical" mTORC1 substrates, such as S6K. By using HeLa and HK-2 cell lines, human induced pluripotent stem cell-derived cardiomyocytes and patient-derived primary fibroblasts, we show that RRAGD auto-activating mutations lead to inhibition of TFEB and TFE3 nuclear translocation and transcriptional activity, which impairs the response to lysosomal and mitochondrial injury. These data suggest that inhibition of MiT/TFE factors plays a key role in kidney tubulopathy and cardiomyopathy syndrome.

Generation of a heterozygous TPM1-E192K knock-in human induced pluripotent stem cell line using CRISPR/Cas9 system

E192K missense mutation of TPM1 has been found in different types of cardiomyopathies (e.g., hypertrophic cardiomyopathy, dilated cardiomyopathy, and left ventricular non-compaction), leading to systolic dysfunction, diastolic dysfunction, and/or tachyarrhythmias. Here, we generated a heterozygous TPM1-E192K knock-in human induced pluripotent stem cell (iPSC) line using CRISPR/Cas9-based genome editing system. The cells exhibit normal karyotype, typical stem cell morphology, expression of pluripotency markers and differentiation ability into three germ layers. Accordingly, this cell line could provide a useful cell resource for exploring the pathogenic role of TPM1-E192K mutation in different types of cardiomyopathies.

Construction of Immune-Related ceRNA Network in Dilated Cardiomyopathy: Based on Sex Differences

Background: Immune targeted therapy has become an attractive therapeutic approach for patients with dilated cardiomyopathy (DCM) recently. Genetic predisposition and gender play a critical role in immune-related responses of DCM. This study aimed to perform a bioinformatics analysis of molecular differences between male and female samples and identify immune-related ceRNA network in DCM.

Methods: The gene expression microarray and clinical features dataset of GSE19303 was downloaded from the GEO. The raw data were preprocessed, followed by identification of differentially expressed genes (DEGs) between male and female DCM samples. Crucial functions and pathway enrichment analysis of DEGs were investigated through GO analysis and KEGG pathway analysis, respectively. A lncRNA–miRNA–mRNA network was constructed and a central module was extracted from the ceRNA network.

Results: Compared with the female group, the male group benefits more from IA/IgG immunotherapy. Male patients of DCM had a significant positive correlation with the abundance of inflammatory cells (B cells, memory B cells, CD8⁺ Tem cells, and NK cells). Sex difference DEGs had a widespread impact on the signaling transduction, transcriptional regulation, and metabolism in DCM. Subsequently, we constructed an immune-related ceRNA network based on sex differences in DCM, including five lncRNAs, six miRNAs, and 29 mRNAs. Furthermore, we extracted a central module from the ceRNA network, including two lncRNAs (XIST and LINC00632), three miRNAs (miR-1-3p, miR-17-5p, and miR-22-3p), and six mRNAs (CBL, CXCL12, ESR1, IGF1R, IL6ST, and STC1). Among these DEGs, CBL, CXCL12, and IL6ST expression was considered to be associated with inflammatory cell infiltration in DCM.

Conclusions: The identified ceRNA network and their enriched pathways may provide genetic insights into the phenotypic diversity of female and male patients with DCM and may provide a basis for development of sex-related individualization of immunotherapy.

Cardiac Remodeling in Cancer-Induced Cachexia: Functional, Structural, and Metabolic Contributors

Cancer cachexia is a syndrome of progressive weight loss and muscle wasting occurring in many advanced cancer patients. Cachexia significantly impairs quality of life and increases mortality. Cardiac atrophy and dysfunction have been observed in patients with cachexia, which may contribute to cachexia pathophysiology. However, relative to skeletal muscle, little research has been carried out to understand the mechanisms of cardiomyopathy in cachexia. Here, we review what is known clinically about the cardiac changes occurring in cachexia, followed by further discussion of underlying physiological and molecular mechanisms contributing to cachexia-induced cardiomyopathy. Impaired cardiac contractility and relaxation may be explained by a complex interplay of significant heart muscle atrophy and metabolic remodeling, including mitochondrial dysfunction. Because cardiac muscle has fundamental differences compared to skeletal muscle, understanding cardiac-specific effects of cachexia may bring light to unique therapeutic targets and ultimately improve clinical management for patients with cancer cachexia.

Dilated cardiomyopathy is a part of the ARV1-associated phenotype: a case report

Background

ACAT-related enzyme 2 required for viability 1 (ARV1) encodes a transmembrane lipid transporter of the endoplasmic reticulum, which is presented in all eukaryotes and in plants. Deficiency of ARV1 is clinically presented as autosomal recessive developmental and epileptic encephalopathy 38 (DEE38) in humans and in mice. So far, three different homozygous and two compound heterozygous ARV1 mutations in humans have been reported in 15 children.

Case presentation

In this case report we present a novel homozygous in-frame ARV1-deletion (c.554_556delTAT, p.L185del) in a 21-year old Caucasian man with developmental delay, intellectual disability, seizures, walking and speech impairments, as well as with a dilated cardiomyopathy (DCM), which has not yet been firmly related to the ARV1-associated phenotype. Interestingly, this novel variant lies in the proximity of the p.G189R mutation, which was previously described in two brothers with DEE38 and dilated cardiomyopathy.

Conclusion

The finding of dilated cardiomyopathy in the presented as well as in three previously reported patients from two different families indicates that dilated cardiomyopathy is a part of the ARV1-induced DEE38 phenotype. However, more data are needed to make this conclusion definitive.

Discerning the Ambiguous Role of Missense TTN Variants in Inherited Arrhythmogenic Syndromes

The titin gene (TTN) is associated with several diseases, including inherited arrhythmias. Most of these diagnoses are attributed to rare TTN variants encoding truncated forms, but missense variants represent a diagnostic challenge for clinical genetics. The proper interpretation of genetic data is critical for translation into the clinical setting. Notably, many TTN variants were classified before 2015, when the American College of Medical Genetics and Genomics (ACMG) published recommendations to accurately classify genetic variants. Our aim was to perform an exhaustive reanalysis of rare missense TTN variants that were classified before 2015, and that have ambiguous roles in inherited arrhythmogenic syndromes. Rare missense TTN variants classified before 2015 were updated following the ACMG recommendations and according to all the currently available data. Our cohort included 193 individuals definitively diagnosed with an inherited arrhythmogenic syndrome before 2015. Our analysis resulted in the reclassification of 36.8% of the missense variants from unknown to benign/likely benign. Of all the remaining variants, currently classified as of unknown significance, 38.3% showed a potential, but not confirmed, deleterious role. Most of these rare missense TTN variants with a suspected deleterious role were identified in patients diagnosed with hypertrophic cardiomyopathy. More than 35% of the rare missense TTN variants previously classified as ambiguous were reclassified as not deleterious, mainly because of improved population frequencies. Despite being inconclusive, almost 40% of the variants showed a potentially deleterious role in inherited arrhythmogenic syndromes. Our results highlight the importance of the periodical reclassification of rare missense TTN variants to improve genetic diagnoses and help increase the accuracy of personalized medicine.

Integration of Cardiac Actin Mutants Causing Hypertrophic (p.A295S) and Dilated Cardiomyopathy (p.R312H and p.E361G) into Cellular Structures

The human mutant cardiac α-actins p.A295S or p.R312H and p.E361G, correlated with hypertrophic or dilated cardiomyopathy, respectively, were expressed by the baculovirus/Sf21 insect cell system and purified to homogeneity. The purified cardiac actins maintained their native state but showed differences in Ca²⁺-sensitivity to stimulate the myosin-subfragment1 ATPase. Here we analyzed the interactions of these c-actins with actin-binding and -modifying proteins implicated in cardiomyocyte differentiation. We demonstrate that Arp2/3 complex and the formin mDia3 stimulated the polymerization rate and extent of the c-actins, albeit to different degrees. In addition, we tested the effect of the MICAL-1 monooxygenase, which modifies the supramolecular actin organization during development and adaptive processes. MICAL-1 oxidized these c-actin variants and induced their de-polymerization, albeit at different rates. Transfection experiments using MDCK cells demonstrated the preferable incorporation of wild type and p.A295S c-actins into their microfilament system but of p.R312H and p.E361G actins into the submembranous actin network. Transduction of neonatal rat cardiomyocytes with adenoviral constructs coding HA-tagged c-actin variants showed their incorporation into microfilaments after one day in culture and thereafter into thin filaments of nascent sarcomeric structures at their plus ends (Z-lines) except the p.E361G mutant, which preferentially incorporated at the minus ends.