Gene editing reverses arrhythmia susceptibility in humanized PLN-R14del mice: modelling a European cardiomyopathy with global impact

In Vivo Approaches to Understand Arrhythmogenic Cardiomyopathy: Perspectives on Animal Models

Arrhythmogenic cardiomyopathy (AC) is a hereditary cardiac disorder characterized by the gradual replacement of cardiomyocytes with fibrous and adipose tissue, leading to ventricular wall thinning, chamber dilation, arrhythmias, and sudden cardiac death. Despite advances in treatment, disease management remains challenging. Animal models, particularly mice and zebrafish, have become invaluable tools for understanding AC's pathophysiology and testing potential therapies. Mice models, although useful for scientific research, cannot fully replicate the complexity of the human AC. However, they have provided valuable insights into gene involvement, signalling pathways, and disease progression. Zebrafish offer a promising alternative to mammalian models, despite the phylogenetic distance, due to their economic and genetic advantages. By combining animal models with in vitro studies, researchers can comprehensively understand AC, paving the way for more effective treatments and interventions for patients and improving their quality of life and prognosis.

Gene editing therapy for cardiovascular diseases

The development of gene editing tools has been a significant area of research in the life sciences for nearly 30 years. These tools have been widely utilized in disease detection and mechanism research. In the new century, they have shown potential in addressing various scientific challenges and saving lives through gene editing therapies, particularly in combating cardiovascular disease (CVD). The rapid advancement of gene editing therapies has provided optimism for CVD patients. The progress of gene editing therapy for CVDs is a comprehensive reflection of the practical implementation of gene editing technology in both clinical and basic research settings, as well as the steady advancement of research and treatment of CVDs. This article provides an overview of the commonly utilized DNA-targeted gene editing tools developed thus far, with a specific focus on the application of these tools, particularly the clustered regularly interspaced short palindromic repeat/CRISPR-associated genes (Cas) (CRISPR/Cas) system, in CVD gene editing therapy. It also delves into the challenges and limitations of current gene editing therapies, while summarizing ongoing research and clinical trials related to CVD. The aim is to facilitate further exploration by relevant researchers by summarizing the successful applications of gene editing tools in the field of CVD.

Exploring the Therapeutic Potential of Gene Therapy in Arrhythmogenic Right Ventricular Cardiomyopathy

Right dominant arrhythmogenic cardiomyopathy, commonly known as Arrhythmogenic Right Ventricular Cardiomyopathy (ARVC), represents a formidable challenge in cardiovascular medicine, as conventional therapies are commonly ineffective in impeding disease progression and the development of end-stage heart failure. Recombinant adeno-associated virus (AAV)-mediated gene therapy presents a promising avenue for targeted therapeutic interventions, potentially revolutionising treatment approaches for ARVC patients. Encouraging results from preclinical studies have sparked optimism about the possibility of curing specific subtypes of ARVC in the near future. This narrative review delves into the dynamic landscape of genetic therapy for ARVC, elucidating its underlying mechanisms and developmental stages, and providing updates on forthcoming trials. Additionally, it examines the hurdles and complexities impeding the successful translation of ARVC genetic therapies into clinical practice. Despite notable scientific advancements, the journey towards implementing genetic therapies for ARVC patients in real-world clinical settings is still in its early phases.

Adeno-associated virus-mediated gene therapy for cardiac tachyarrhythmia: A systematic review and meta-analysis

Cardiac tachyarrhythmia presents a significant health care challenge, causing notable morbidity and mortality. Conventional treatments have limitations and potential risks, resulting in an elevated disease burden. Adeno-associated virus (AAV)-mediated gene therapy holds promise as a potential future treatment option. Therefore, we aimed to provide a measured overview of the latest developments in this rapidly growing field. PubMed and Embase databases were searched up to January 2024. Studies that employed AAV as a vector for delivery of therapeutic agents to treat cardiac tachyarrhythmia were included. Of the 26 studies included, 20 published in the last 5 years. There were 22 novel molecular targets identified. More than 80% of the included studies employed small-animal models or used AAV9. In atrial fibrillation preclinical studies, AAV-mediated gene therapy reduced atrial fibrillation inducibility by 81% (odds ratio, 0.19 [0.08-0.45]; P < .01). Similarly, for acquired and inherited ventricular arrhythmia, animal models receiving gene therapy had less inducible ventricular arrhythmia (odds ratio, 0.06 [0.03-0.11]; P < .01). This review highlights the rapid progress of AAV-mediated gene therapy for cardiac tachyarrhythmia. Although these investigations are currently in the early stages of clinical application, they present promising prospects for gene therapy. (PROSPERO registry: CRD42023479448).

Recent Therapeutic Gene Editing Applications to Genetic Disorders

Recent years have witnessed unprecedented progress in therapeutic gene editing, revolutionizing the approach to treating genetic disorders. In this comprehensive review, we discuss the progression of milestones leading to the emergence of the clustered regularly interspaced short palindromic repeats (CRISPR)-based technology as a powerful tool for precise and targeted modifications of the human genome. CRISPR-Cas9 nuclease, base editing, and prime editing have taken center stage, demonstrating remarkable precision and efficacy in targeted ex vivo and in vivo genomic modifications. Enhanced delivery systems, including viral vectors and nanoparticles, have further improved the efficiency and safety of therapeutic gene editing, advancing their clinical translatability. The exploration of CRISPR-Cas systems beyond the commonly used Cas9, such as the development of Cas12 and Cas13 variants, has expanded the repertoire of gene editing tools, enabling more intricate modifications and therapeutic interventions. Outstandingly, prime editing represents a significant leap forward, given its unparalleled versatility and minimization of off-target effects. These innovations have paved the way for therapeutic gene editing in a multitude of previously incurable genetic disorders, ranging from monogenic diseases to complex polygenic conditions. This review highlights the latest innovative studies in the field, emphasizing breakthrough technologies in preclinical and clinical trials, and their applications in the realm of precision medicine. However, challenges such as off-target effects and ethical considerations remain, necessitating continued research to refine safety profiles and ethical frameworks.

Early consequences of the phospholamban mutation PLN-R14del+/- in a transgenic mouse model

AIMS

The heterozygous phospholamban (PLN) mutation R14del (PLN R14del+/- ) is associated with a severe arrhythmogenic cardiomyopathy (ACM) developing in the adult. "Superinhibition" of SERCA2a by PLN R14del is widely assumed to underlie the pathogenesis, but alternative mechanisms such abnormal energy metabolism have also been reported. This work aims to (1) to evaluate Ca2+ dynamics and energy metabolism in a transgenic (TG) mouse model of the mutation prior to cardiomyopathy development; (2) to test whether they are causally connected.

METHODS

Ca2+ dynamics, energy metabolism parameters, reporters of mitochondrial integrity, energy, and redox homeostasis were measured in ventricular myocytes of 8-12 weeks-old, phenotypically silent, TG mice. Mutation effects were compared to pharmacological PLN antagonism and analyzed during modulation of sarcoplasmic reticulum (SR) and cytosolic Ca2+ compartments. Transcripts and proteins of relevant signaling pathways were evaluated.

RESULTS

The mutation was characterized by hyperdynamic Ca2+ handling, compatible with a loss of SERCA2a inhibition by PLN. All components of energy metabolism were depressed; myocyte energy charge was preserved under quiescence but reduced during stimulation. Cytosolic Ca2+ buffering or SERCA2a blockade reduced O2 consumption with larger effect in the mutant. Signaling changes suggest cellular adaptation to perturbed Ca2+ dynamics and response to stress.

CONCLUSIONS

(1) PLN R14del+/- loses its ability to inhibit SERCA2a, which argues against SERCA2a superinhibition as a pathogenetic mechanism; (2) depressed energy metabolism, its enhanced dependency on Ca2+ and activation of signaling responses point to an early involvement of metabolic stress in the pathogenesis of this ACM model.

Navigating the prime editing strategy to treat cardiovascular genetic disorders in transforming heart health

INTRODUCTION

After understanding the genetic basis of cardiovascular disorders, the discovery of prime editing (PE), has opened new horizons for finding their cures. PE strategy is the most versatile editing tool to change cardiac genetic background for therapeutic interventions. The optimization of elements, prediction of efficiency, and discovery of the involved genes regulating the process have not been completed. The large size of the cargo and multi-elementary structure makes the in vivo heart delivery challenging.

AREAS COVERED

Updated from recent published studies, the fundamentals of the PEs, their application in cardiology, potentials, shortcomings, and the future perspectives for the treatment of cardiac-related genetic disorders will be discussed.

EXPERT OPINION

The ideal PE for the heart should be tissue-specific, regulatable, less immunogenic, high transducing, and safe. However, low efficiency, sup-optimal PE architecture, the large size of required elements, the unclear role of transcriptomics on the process, unpredictable off-target effects, and its context-dependency are subjects that need to be considered. It is also of great importance to see how beneficial or detrimental cell cycle or epigenomic modifier is to bring changes into cardiac cells. The PE delivery is challenging due to the size, multi-component properties of the editors and liver sink.

Comprehensive review on gene mutations contributing to dilated cardiomyopathy

Dilated cardiomyopathy (DCM) is one of the most common primary myocardial diseases. However, to this day, it remains an enigmatic cardiovascular disease (CVD) characterized by ventricular dilatation, which leads to myocardial contractile dysfunction. It is the most common cause of chronic congestive heart failure and the most frequent indication for heart transplantation in young individuals. Genetics and various other factors play significant roles in the progression of dilated cardiomyopathy, and variants in more than 50 genes have been associated with the disease. However, the etiology of a large number of cases remains elusive. Numerous studies have been conducted on the genetic causes of dilated cardiomyopathy. These genetic studies suggest that mutations in genes for fibronectin, cytoskeletal proteins, and myosin in cardiomyocytes play a key role in the development of DCM. In this review, we provide a comprehensive description of the genetic basis, mechanisms, and research advances in genes that have been strongly associated with DCM based on evidence-based medicine. We also emphasize the important role of gene sequencing in therapy for potential early diagnosis and improved clinical management of DCM.

The Many Faces of Arrhythmogenic Cardiomyopathy: An Overview

Arrhythmogenic cardiomyopathy (AC) is a disease that involves electromechanical uncoupling of cardiomyocytes. This leads to characteristic histologic changes that ultimately lead to the arrhythmogenic clinical features of the disease. Initially thought to affect the right ventricle predominantly, more recent data show that it can affect both the ventricles or the left ventricle alone. Throughout the recent era, diagnostic modalities and criteria for AC have continued to evolve and our understanding of its clinical features in different age groups as well as the genotype to the phenotype correlations have improved. In this review, we set out to detail the epidemiology, etiologies, presentations, evaluation, and management of AC across the age continuum.

Application of next generation sequencing in cardiology: current and future precision medicine implications

Inherited cardiovascular diseases are highly heterogeneous conditions with multiple genetic loci involved. The application of advanced molecular tools, such as Next Generation Sequencing, has facilitated the genetic analysis of these disorders. Accurate analysis and variant identification are required to maximize the quality of the sequencing data. Therefore, the application of NGS for clinical purposes should be limited to laboratories with a high level of technological expertise and resources. In addition, appropriate gene selection and variant interpretation can result in the highest possible diagnostic yield. Implementation of genetics in cardiology is imperative for the accurate diagnosis, prognosis and management of several inherited disorders and could eventually lead to the realization of precision medicine in this field. However, genetic testing should also be accompanied by an appropriate genetic counseling procedure that clarifies the significance of the genetic analysis results for the proband and his family. In this regard, a multidisciplinary collaboration among physicians, geneticists, and bioinformaticians is imperative. In the present review, we address the current state of knowledge regarding genetic analysis strategies employed in the field of cardiogenetics. Variant interpretation and reporting guidelines are explored. Additionally, gene selection procedures are accessed, with a particular emphasis on information concerning gene-disease associations collected from international alliances such as the Gene Curation Coalition (GenCC). In this context, a novel approach to gene categorization is proposed. Moreover, a sub-analysis is conducted on the 1,502,769 variation records with submitted interpretations in the Clinical Variation (ClinVar) database, focusing on cardiology-related genes. Finally, the most recent information on genetic analysis's clinical utility is reviewed.

SERCA2 phosphorylation at serine 663 is a key regulator of Ca2+ homeostasis in heart diseases

Despite advances in cardioprotection, new therapeutic strategies capable of preventing ischemia-reperfusion injury of patients are still needed. Here, we discover that sarcoplasmic/endoplasmic reticulum Ca2+ ATPase (SERCA2) phosphorylation at serine 663 is a clinical and pathophysiological event of cardiac function. Indeed, the phosphorylation level of SERCA2 at serine 663 is increased in ischemic hearts of patients and mouse. Analyses on different human cell lines indicate that preventing serine 663 phosphorylation significantly increases SERCA2 activity and protects against cell death, by counteracting cytosolic and mitochondrial Ca2+ overload. By identifying the phosphorylation level of SERCA2 at serine 663 as an essential regulator of SERCA2 activity, Ca2+ homeostasis and infarct size, these data contribute to a more comprehensive understanding of the excitation/contraction coupling of cardiomyocytes and establish the pathophysiological role and the therapeutic potential of SERCA2 modulation in acute myocardial infarction, based on the hotspot phosphorylation level of SERCA2 at serine 663 residue.

Characterization of Skeletal Muscle Biopsy and Derived Myoblasts in a Patient Carrying Arg14del Mutation in Phospholamban Gene

Phospholamban is involved in the regulation of the activity and storage of calcium in cardiac muscle. Several mutations have been identified in the PLN gene causing cardiac disease associated with arrhythmogenic and dilated cardiomyopathy. The patho-mechanism underlying PLN mutations is not fully understood and a specific therapy is not yet available. PLN mutated patients have been deeply investigated in cardiac muscle, but very little is known about the effect of PLN mutations in skeletal muscle. In this study, we investigated both histological and functional features in skeletal muscle tissue and muscle-derived myoblasts from an Italian patient carrying the Arg14del mutation in PLN. The patient has a cardiac phenotype, but he also reported lower limb fatigability, cramps and fasciculations. The evaluation of a skeletal muscle biopsy showed histological, immunohistochemical and ultrastructural alterations. In particular, we detected an increase in the number of centronucleated fibers and a reduction in the fiber cross sectional area, an alteration in p62, LC3 and VCP proteins and the formation of perinuclear aggresomes. Furthermore, the patient's myoblasts showed a greater propensity to form aggresomes, even more marked after proteasome inhibition compared with control cells. Further genetic and functional studies are necessary to understand whether a definition of PLN myopathy, or cardiomyopathy plus, can be introduced for selected cases with clinical evidence of skeletal muscle involvement. Including skeletal muscle examination in the diagnostic process of PLN-mutated patients can help clarify this issue.

Genome Editing and Cardiac Arrhythmias

This article reviews progress in the field of cardiac genome editing, in particular, its potential utility in treating cardiac arrhythmias. First, we discuss genome editing methods by which DNA can be disrupted, inserted, deleted, or corrected in cardiomyocytes. Second, we provide an overview of in vivo genome editing in preclinical models of heritable and acquired arrhythmias. Third, we discuss recent advancements in cardiac gene transfer, including delivery methods, gene expression optimization, and potential adverse effects associated with therapeutic somatic genome editing. While genome editing for cardiac arrhythmias is still in its infancy, this approach holds great promise, especially for inherited arrhythmia syndromes with a defined genetic defect.

Recent advances in CRISPR-based genome editing technology and its applications in cardiovascular research

The rapid development of genome editing technology has brought major breakthroughs in the fields of life science and medicine. In recent years, the clustered regularly interspaced short palindromic repeats (CRISPR)-based genome editing toolbox has been greatly expanded, not only with emerging CRISPR-associated protein (Cas) nucleases, but also novel applications through combination with diverse effectors. Recently, transposon-associated programmable RNA-guided genome editing systems have been uncovered, adding myriads of potential new tools to the genome editing toolbox. CRISPR-based genome editing technology has also revolutionized cardiovascular research. Here we first summarize the advances involving newly identified Cas orthologs, engineered variants and novel genome editing systems, and then discuss the applications of the CRISPR-Cas systems in precise genome editing, such as base editing and prime editing. We also highlight recent progress in cardiovascular research using CRISPR-based genome editing technologies, including the generation of genetically modified in vitro and animal models of cardiovascular diseases (CVD) as well as the applications in treating different types of CVD. Finally, the current limitations and future prospects of genome editing technologies are discussed.

Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) in Cardiovascular Disease: A Comprehensive Clinical Review on Dilated Cardiomyopathy

Dilated cardiomyopathy (DCM) is one of the most important causes of heart failure in developed and developing countries. Currently, most medical interventions in the treatment of DCM are mainly focused on mitigating the progression of the disease and controlling the symptoms. The vast majority of patients who survive till the late stages of the disease require cardiac transplantation; this is exactly why we need novel therapeutic interventions and hopefully treatments that can reverse the clinical cardiac deterioration in patients with DCM. Clustered regularly interspaced short palindromic repeats (CRISPR) technology is a novel therapeutic intervention with such capacity; it can help us edit the genome of patients with genetic etiology for DCM and potentially cure them permanently. This review provides an overview of studies investigating CRISPR-based gene editing in DCM, including the use of CRISPR in DCM disease models, phenotypic screening, and genotype-specific precision therapies. The review discusses the outcomes of these studies and highlights the potential benefits of CRISPR in developing novel genotype-agnostic therapeutic strategies for the genetic causes of DCM. The databases we used to extract relevant literature include PubMed, Google Scholar, and Cochrane Central. We used the Medical Subject Heading (MeSH) strategy for our literature search in PubMed and relevant search keywords for other databases. We screened all the relevant articles from inception till February 22, 2023. We retained 74 research articles after carefully reviewing each of them. We concluded that CRISPR gene editing has shown promise in developing precise and genotype-specific therapeutic strategies for DCM, but there are challenges and limitations, such as delivering CRISPR-Cas9 to human cardiomyocytes and the potential for unintended gene targeting. This study represents a turning point in our understanding of the mechanisms underlying DCM and paves the way for further investigation into the application of genomic editing for identifying novel therapeutic targets. This study can also act as a potential framework for novel therapeutic interventions in other genetic cardiovascular diseases.

A Crossroads Junction That Leads to Heart Failure (Arrhythmogenic Cardiomyopathy): Hope for Future Therapeutics

Arrhythmogenic cardiomyopathy (ACM) is an inherited multifaceted cardiac disease that causes sudden cardiac death, especially in young adults and athletes [...]

Myofilament Alterations Associated with Human R14del-Phospholamban Cardiomyopathy

Phospholamban (PLN) is a major regulator of cardiac contractility, and human mutations in this gene give rise to inherited cardiomyopathies. The deletion of Arginine 14 is the most-prevalent cardiomyopathy-related mutation, and it has been linked to arrhythmogenesis and early death. Studies in PLN-humanized mutant mice indicated an increased propensity to arrhythmias, but the underlying cellular mechanisms associated with R14del-PLN cardiac dysfunction in the absence of any apparent structural remodeling remain unclear. The present study addressed the specific role of myofilaments in the setting of R14del-PLN and the long-term effects of R14del-PLN in the heart. Maximal force was depressed in skinned cardiomyocytes from both left and right ventricles, but this effect was more pronounced in the right ventricle of R14del-PLN mice. In addition, the Ca2+ sensitivity of myofilaments was increased in both ventricles of mutant mice. However, the depressive effects of R14del-PLN on contractile parameters could be reversed with the positive inotropic drug omecamtiv mecarbil, a myosin activator. At 12 months of age, corresponding to the mean symptomatic age of R14del-PLN patients, contractile parameters and Ca2+ transients were significantly depressed in the right ventricular R14del-PLN cardiomyocytes. Echocardiography did not reveal any alterations in cardiac function or remodeling, although histological and electron microscopy analyses indicated subtle alterations in mutant hearts. These findings suggest that both aberrant myocyte calcium cycling and aberrant contractility remain specific to the right ventricle in the long term. In addition, altered myofilament activity is an early characteristic of R14del-PLN mutant hearts and the positive inotropic drug omecamtiv mecarbil may be beneficial in treating R14del-PLN cardiomyopathy.

Phospholamban R14del disease: The past, the present and the future

Arrhythmogenic cardiomyopathy affects significant number of patients worldwide and is characterized by life-threatening ventricular arrhythmias and sudden cardiac death. Mutations in multiple genes with diverse functions have been reported to date including phospholamban (PLN), a key regulator of sarcoplasmic reticulum (SR) Ca²⁺ homeostasis and cardiac contractility. The PLN-R14del variant in specific is recognized as the cause in an increasing number of patients worldwide, and extensive investigations have enabled rapid advances towards the delineation of PLN-R14del disease pathogenesis and discovery of an effective treatment. We provide a critical overview of current knowledge on PLN-R14del disease pathophysiology, including clinical, animal model, cellular and biochemical studies, as well as diverse therapeutic approaches that are being pursued. The milestones achieved in <20 years, since the discovery of the PLN R14del mutation (2006), serve as a paradigm of international scientific collaboration and patient involvement towards finding a cure.

Computational design of custom therapeutic cells to correct failing human cardiomyocytes

Background

Myocardial delivery of non-excitable cells-namely human mesenchymal stem cells (hMSCs) and c-kit⁺ cardiac interstitial cells (hCICs)-remains a promising approach for treating the failing heart. Recent empirical studies attempt to improve such therapies by genetically engineering cells to express specific ion channels, or by creating hybrid cells with combined channel expression. This study uses a computational modeling approach to test the hypothesis that custom hypothetical cells can be rationally designed to restore a healthy phenotype when coupled to human heart failure (HF) cardiomyocytes.

Methods

Candidate custom cells were simulated with a combination of ion channels from non-excitable cells and healthy human cardiomyocytes (hCMs). Using a genetic algorithm-based optimization approach, candidate cells were accepted if a root mean square error (RMSE) of less than 50% relative to healthy hCM was achieved for both action potential and calcium transient waveforms for the cell-treated HF cardiomyocyte, normalized to the untreated HF cardiomyocyte.

Results

Custom cells expressing only non-excitable ion channels were inadequate to restore a healthy cardiac phenotype when coupled to either fibrotic or non-fibrotic HF cardiomyocytes. In contrast, custom cells also expressing cardiac ion channels led to acceptable restoration of a healthy cardiomyocyte phenotype when coupled to fibrotic, but not non-fibrotic, HF cardiomyocytes. Incorporating the cardiomyocyte inward rectifier K⁺ channel was critical to accomplishing this phenotypic rescue while also improving single-cell action potential metrics associated with arrhythmias, namely resting membrane potential and action potential duration. The computational approach also provided insight into the rescue mechanisms, whereby heterocellular coupling enhanced cardiomyocyte L-type calcium current and promoted calcium-induced calcium release. Finally, as a therapeutically translatable strategy, we simulated delivery of hMSCs and hCICs genetically engineered to express the cardiomyocyte inward rectifier K⁺ channel, which decreased action potential and calcium transient RMSEs by at least 24% relative to control hMSCs and hCICs, with more favorable single-cell arrhythmia metrics.

Conclusion

Computational modeling facilitates exploration of customizable engineered cell therapies. Optimized cells expressing cardiac ion channels restored healthy action potential and calcium handling phenotypes in fibrotic HF cardiomyocytes and improved single-cell arrhythmia metrics, warranting further experimental validation studies of the proposed custom therapeutic cells.

Isoform changes of action potential regulators in the ventricles of arrhythmogenic phospholamban-R14del humanized mouse hearts

Arrhythmogenic cardiomyopathy (ACM) is characterized by life-threatening ventricular arrhythmias and sudden cardiac death and affects hundreds of thousands of patients worldwide. The deletion of Arginine 14 (p.R14del) in the phospholamban (PLN) gene has been implicated in the pathogenesis of ACM. PLN is a key regulator of sarcoplasmic reticulum (SR) Ca2+ cycling and cardiac contractility. Despite global gene and protein expression studies, the molecular mechanisms of PLN-R14del ACM pathogenesis remain unclear. Using a humanized PLN-R14del mouse model and human induced pluripotent stem cell derived cardiomyocytes (iPSC-CMs), we investigated the transcriptome-wide mRNA splicing changes associated with the R14del mutation. We identified >200 significant alternative splicing (AS) events and distinct AS profiles were observed in the right (RV) and left (LV) ventricles in PLN-R14del compared to WT mouse hearts. Enrichment analysis of the AS events showed that the most affected biological process was associated with "cardiac cell action potential", specifically in the RV. We found that splicing of 2 key genes, Trpm4 and Camk2d, which encode proteins regulating calcium homeostasis in the heart, were altered in PLN-R14del mouse hearts and human iPSC-CMs. Bioinformatical analysis pointed to the tissue-specific splicing factors Srrm4 and Nova1 as likely upstream regulators of the observed splicing changes in the PLN-R14del cardiomyocytes. Our findings suggest that aberrant splicing may affect Ca2+-homeostasis in the heart, contributing to the increased risk of arrythmogenesis in PLN-R14del ACM.

Aberrant PLN-R14del Protein Interactions Intensify SERCA2a Inhibition, Driving Impaired Ca2+ Handling and Arrhythmogenesis

Phospholamban (PLN), a key modulator of Ca2+-homeostasis, inhibits sarcoplasmic reticulum (SR) calcium-ATPase (SERCA2a) and regulates cardiac contractility. The human PLN mutation R14del has been identified in arrhythmogenic cardiomyopathy patients worldwide and is currently extensively investigated. In search of the molecular mechanisms mediating the pathological phenotype, we examined PLN-R14del associations to known PLN-interacting partners. We determined that PLN-R14del interactions to key Ca2+-handling proteins SERCA2a and HS-1-associated protein X-1 (HAX-1) were enhanced, indicating the super-inhibition of SERCA2a’s Ca2+-affinity. Additionally, histidine-rich calcium binding protein (HRC) binding to SERCA2a was increased, suggesting the inhibition of SERCA2a maximal velocity. As phosphorylation relieves the inhibitory effect of PLN on SERCA2a activity, we examined the impact of phosphorylation on the PLN-R14del/SERCA2a interaction. Contrary to PLN-WT, phosphorylation did not affect PLN-R14del binding to SERCA2a, due to a lack of Ser-16 phosphorylation in PLN-R14del. No changes were observed in the subcellular distribution of PLN-R14del or its co-localization to SERCA2a. However, in silico predictions suggest structural perturbations in PLN-R14del that could impact its binding and function. Our findings reveal for the first time that by increased binding to SERCA2a and HAX-1, PLN-R14del acts as an enhanced inhibitor of SERCA2a, causing a cascade of molecular events contributing to impaired Ca2+-homeostasis and arrhythmogenesis. Relieving SERCA2a super-inhibition could offer a promising therapeutic approach for PLN-R14del patients.

Gene therapy to terminate tachyarrhythmias

INTRODUCTION

To date, the treatment option for tachyarrhythmia is classified into drug therapy, catheter ablation, and implantable device therapy. However, the efficacy of the antiarrhythmic drugs is limited. Although the indication of catheter ablation is expanding, several fatal tachyarrhythmias are still refractory to ablation. Implantable cardioverter-defibrillator increases survival, but it is not a curable treatment. Therefore, a novel therapy for tachyarrhythmias refractory to present treatments is desired. Gene therapy is being developed as a promising candidate for this purpose, and basic research and translational research have been accumulated in recent years.

AREAS COVERED

This paper reviews the current state of gene therapy for arrhythmias, including susceptible arrhythmias, the route of administration to the heart, and the type of vector to use. We also discuss the latest progress in the technology of gene delivery and genome editing.

EXPERT OPINION

Gene therapy is one of the most promising technologies for arrhythmia treatment. However, additional technological innovation to achieve safe, localized, homogeneous, and long-lasting gene transfer is required for its clinical application.