Base editing correction of hypertrophic cardiomyopathy in human cardiomyocytes and humanized mice

Mechanisms of pathogenicity in the hypertrophic cardiomyopathy-associated TNNI3 c.235C > T variant

BACKGROUND

Hypertrophic cardiomyopathy (HCM) is typically manifested as a hereditary disorder, with 30 %-60 % of cases linked to cardiac sarcomere gene mutations. Despite numerous identified TNNI3 mutations associated with HCM, their severity, prevalence, and disease progression vary. The link between TNNI3 variants and phenotypes remains largely unexplored. This study aims to elucidate the impact of the TNNI3 c.235C > T mutation on HCM through clinical research and cell experiments and to explore its mechanism in HCM development.

METHODS

We screened an HCM family for pathogenic gene mutations using gene sequencing. The proband and family members were assessed through electrocardiography, echocardiography, and cardiac MRI, and a pedigree map was created for disease prediction analysis. Mutant plasmids were constructed with the TNNI3 c.235C > T mutation and transfected into the AC16 human cardiomyocyte cell line to investigate the mutation's effects.

RESULTS

The TNNI3 c.235C > T mutation was identified as the disease-causing variant in the family. This mutation led to the upregulation of hypertrophy-associated genes ANP, BNP, and MYH7, increased cardiomyocyte size, and activation of the ERK signaling pathway. Further investigations revealed that the TNNI3 c.235C > T mutation impaired mitochondrial function, disrupted cardiomyocyte metabolism, and increased cellular autophagy and apoptosis.

CONCLUSIONS

The TNNI3 c.235C > T gene mutation may be a pathogenic factor for HCM, showing heterogeneous features and clinical phenotypes. This mutation induces myocardial hypertrophy, activates the ERK signaling pathway, and exacerbates mitochondrial dysfunction, apoptosis, and autophagy in cardiomyocytes. These findings provide insights into the mechanism of HCM caused by gene mutations and may inform HCM treatment strategies.

From bench to bedside: cutting-edge applications of base editing and prime editing in precision medicine

CRISPR-based gene editing technology theoretically allows for precise manipulation of any genetic target within living cells, achieving the desired sequence modifications. This revolutionary advancement has fundamentally transformed the field of biomedicine, offering immense clinical potential for treating and correcting genetic disorders. In the treatment of most genetic diseases, precise genome editing that avoids the generation of mixed editing byproducts is considered the ideal approach. This article reviews the current progress of base editors and prime editors, elaborating on specific examples of their applications in the therapeutic field, and highlights opportunities for improvement. Furthermore, we discuss the specific performance of these technologies in terms of safety and efficacy in clinical applications, and analyze the latest advancements and potential directions that could influence the future development of genome editing technologies. Our goal is to outline the clinical relevance of this rapidly evolving scientific field and preview a roadmap for successful DNA base editing therapies for the treatment of hereditary or idiopathic diseases.

AAV-mediated gene therapies by miniature gene editing tools

The advent of CRISPR-Cas has revolutionized precise gene editing. While pioneering CRISPR nucleases like Cas9 and Cas12 generate targeted DNA double-strand breaks (DSB) for knockout or homology-directed repair, next generation CRISPR technologies enable gene editing without DNA DSB. Base editors directly convert bases, prime editors make diverse alterations, and dead Cas-regulator fusions allow nuanced control of gene expression, avoiding potentially risks like translocations. Meanwhile, the discovery of diminutive Cas12 orthologs and Obligate Mobile Element-Guided Activity (OMEGA) nucleases has overcome cargo limitations of adeno-associated viral vectors, expanding prospects for in vivo therapeutic delivery. Here, we review the ever-evolving landscape of cutting-edge gene editing tools, focusing on miniature Cas12 orthologs and OMEGA effectors amenable to single AAV packaging. We also summarize CRISPR therapies delivered using AAV vectors, discuss challenges such as efficiency and specificity, and look to the future of this transformative field of in vivo gene editing enabled by AAV vectors delivery.

Long-term therapeutic efficacy and safety profiles of hpCas13d RNA editing in treating early-onset hypertrophic cardiomyopathy

AIMS

Through evolving a precise RNA nuclease, hpCas13d, we have successfully inhibited hypertrophic cardiomyopathy in a compound heterozygous model. However, further investigation is needed to assess the long-term therapeutic effects and safety profiles of hpCas13d treatment.

MATERIALS AND METHODS

AAV-hpCas13d[RQ] was subcutaneously injected into neonatal Myh6RH/RQ mice. Sequential echocardiography analyses were conducted at 4 months and 12 months to evaluate the sustained therapeutic effects of hpCas13d. Electrocardiography was employed to assess cardiac arrhythmias, and mice were euthanized at 12 months. Quantification of Myh6RQ degradation induced by hpCas13d[RQ] was performed using digital droplet PCR and cDNA sequencing. Histological analysis, RNA sequencing, and proteomic analyses were utilized to examine the inhibitory effects on pathological phenotypes and downstream signaling pathways. Biodistribution, tissue damage, and host immune response to AAV-hpCas13d[RQ] were assessed to evaluate long-term safety profiles.

KEY FINDINGS

The allele-specific RNA degradation persisted for 12 months in AAV-hpCas13d[RQ]-treated Myh6RH/RQ mice. Partial degradation of pathogenic Myh6RQ transcripts proved adequate for the long-term inhibition of cardiac hypertrophy, arrhythmias, fibrosis, and cellular apoptosis in Myh6RH/RQ mice. RNA sequencing and proteomic analyses revealed that hpCas13d[RQ] treatment impeded hypertrophy and fibrosis, mitochondrial dysfunction, and abnormalities in ion channels downstream of mutant Myh6. Prolonged treatment with AAV-hpCas13d from the neonatal stage did not induce significant tissue damage, liver toxicity, humoral responses, or cellular immune reactions against the AAV9 capsid and bacterial hpCas13d.

SIGNIFICANCE

These results underscore the promising translational potential of AAV-hpCas13d in treating cardiovascular diseases and advancing in vivo gene therapy.

Amelioration of metabolic and behavioral defects through base editing in the PahR408W phenylketonuria mouse model

Phenylketonuria (PKU) is a liver metabolic disorder mainly caused by a deficiency of the hepatic phenylalanine hydroxylase (PAH) enzyme activity, often leading to severe brain function impairment in patients if untreated or if treatment is delayed. In this study, we utilized dual-AAV8 vectors to deliver a near PAM-less adenine base editor variant, known as ABE8e-SpRY, to treat the PahR408W PKU mouse model carrying a frequent R408W mutation in the Pah gene. Our findings revealed that a single intravenous injection in adult mice and a single intraperitoneal injection in neonatal mice resulted in 19.1%-34.6% A-to-G editing efficiency at the pathogenic mutation site with minimal bystander edits. Furthermore, the dual-AAV8-treated mice exhibited reduced blood Phe levels to below the therapeutic threshold of 360 μmol L-1 and restored weight and fur color to normal levels. Importantly, the brain function of the mice was restored after the treatment, particularly when administered during the neonatal stage, as levels of monoamine neurotransmitters and metabolites in the brain returned to normal and near-normal levels. Our study demonstrated that ABE8e-SpRY-based base editing could effectively correct the point mutation in the PahR408W PKU mouse model, indicating potential clinical applications for PKU and other genetic diseases.

Gene therapy for cardiac diseases: methods, challenges, and future directions

Gene therapy is advancing at an unprecedented pace, and the recent success of clinical trials reinforces optimism and trust among the scientific community. Recently, the cardiac gene therapy pipeline, which had progressed more slowly than in other fields, has begun to advance, overcoming biological and technical challenges, particularly in treating genetic heart pathologies. The primary rationale behind the focus on monogenic cardiac diseases is the well-defined molecular mechanisms driving their phenotypes, directly linked to the pathogenicity of single genetic mutations. This aspect makes these conditions a remarkable example of 'genetically druggable' diseases. Unfortunately, current treatments for these life-threatening disorders are few and often poorly effective, underscoring the need to develop therapies to modulate or correct their molecular substrates. In this review we examine the latest advancements in cardiac gene therapy, discussing the pros and cons of different molecular approaches and delivery vectors, with a focus on their therapeutic application in cardiac inherited diseases. Additionally, we highlight the key factors that may enhance clinical translation, drawing insights from previous trials and the current prospects of cardiac gene therapy.

In vivo Treatment of a Severe Vascular Disease via a Bespoke CRISPR-Cas9 Base Editor

Genetic vascular disorders are prevalent diseases that have diverse etiologies and few treatment options. Pathogenic missense mutations in the alpha actin isotype 2 gene (ACTA2) primarily affect smooth muscle cell (SMC) function and cause multisystemic smooth muscle dysfunction syndrome (MSMDS), a genetic vasculopathy that is associated with stroke, aortic dissection, and death in childhood. Here, we explored genome editing to correct the most common MSMDS-causative mutation ACTA2 R179H. In a first-in-kind approach, we performed mutation-specific protein engineering to develop a bespoke CRISPR-Cas9 enzyme with enhanced on-target activity against the R179H sequence. To directly correct the R179H mutation, we screened dozens of configurations of base editors (comprised of Cas9 enzymes, deaminases, and gRNAs) to develop a highly precise corrective A-to-G edit with minimal deleterious bystander editing that is otherwise prevalent when using wild-type SpCas9 base editors. We then created a murine model of MSMDS that exhibits phenotypes consistent with human patients, including vasculopathy and premature death, to explore the in vivo therapeutic potential of this base editing strategy. Delivery of the customized base editor via an engineered SMC-tropic adeno-associated virus (AAV-PR) vector substantially prolonged survival and rescued systemic phenotypes across the lifespan of MSMDS mice, including in the vasculature, aorta, and brain. Together, our optimization of a customized base editor highlights how bespoke CRISPR-Cas enzymes can enhance on-target correction while minimizing bystander edits, culminating in a precise editing approach that may enable a long-lasting treatment for patients with MSMDS.

Integrating Prime Editing and Cellular Reprogramming as Novel Strategies for Genetic Cardiac Disease Modeling and Treatment

PURPOSE OF REVIEW

This review aims to evaluate the potential of CRISPR-based gene editing tools, particularly prime editors (PE), in treating genetic cardiac diseases. It seeks to answer how these tools can overcome current therapeutic limitations and explore the synergy between PE and induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) for personalized medicine.

RECENT FINDINGS

Recent advancements in CRISPR technology, including CRISPR-Cas9, base editors, and PE, have demonstrated precise genome correction capabilities. Notably, PE has shown exceptional precision in correcting genetic mutations. Combining PE with iPSC-CMs has emerged as a robust platform for disease modeling and developing innovative treatments for genetic cardiac diseases. The review finds that PE, when combined with iPSC-CMs, holds significant promise for treating genetic cardiac diseases by addressing their root causes. This approach could revolutionize personalized medicine, offering more effective and precise treatments. Future research should focus on refining these technologies and their clinical applications.

Treatment options for hypertrophic obstructive cardiomyopathy: a patient-centric review

INTRODUCTION

Hypertrophic cardiomyopathy (HCM) is defined by an increased left ventricular wall thickness not solely explainable by abnormal loading conditions. Estimated prevalence is 1:200-500 with roughly 60% of cases showing a familiar trait. Medical treatment and surgical interventions significantly altered prognosis in HCM. Recently, new therapies have been introduced in clinical practice and a patient-centric approach is key to HCM optimal management. This review aims to summarize the current HCM therapies focusing on the importance of personalized care and delineate therapeutic approaches under investigation.

AREAS COVERED

The review summarizes and critically evaluates the available data on currently available pharmacological and non-pharmacological therapies for HCM. The evidence in support of the use of beta-blockers, non-dihydropyridine calcium channel blockers, disopyramide, and cardiac myosin inhibitors is discussed. Furthermore, data and controversies on sudden death prevention, surgical and non-surgical septal reduction therapies are reported. Finally, future perspectives in HCM management such as new drugs and gene therapies are explored.

EXPERT OPINION

The authors stress the need for a personalized and tailored approach to managing patients with HCM, which is not only based on phenotypes and risk stratification, but also patients' preferences, needs, and beliefs.

Emerging CRISPR Therapies for Precision Gene Editing and Modulation in the Cardiovascular Clinic

PURPOSE OF REVIEW

Outline the growing suite of novel genome editing tools powered by CRISPR-Cas9 technology that are rapidly advancing towards the clinic for the treatment of cardiovascular disorders.

RECENT FINDINGS

A diversity of new genome editors and modulators are being developed for therapies across myriad human diseases. Recent breakthroughs have improved the efficacy, safety, specificity, and delivery of CRISPR-mediated therapies that could impact heart disease in the next decade, though several challenges remain. Many iterations of the original CRISPR system have been developed seeking to leverage its vast therapeutic potential. As examples, nuclease-free editing, precision single-nucleotide editing, gene expression regulation, and epigenomic modifications are now feasible with the current CRISPR-mediated suite of enzymes. These emerging tools will be indispensable for the development of novel cardiovascular therapeutics as demonstrated by recent successes in both basic research laboratories and pre-clinical models. Here, we provide an overview of current and emerging CRISPR-mediated technologies as they pertain to the cardiovascular system, highlighting successful implementations and future challenges.

Gene editing in common cardiovascular diseases

Cardiovascular diseases are the leading cause of morbidity and mortality worldwide, highlighting the high socioeconomic impact. Current treatment strategies like compound-based drugs or surgeries are often limited. On the one hand, systemic administration of substances is frequently associated with adverse side effects; on the other hand, they typically provide only short-time effects requiring daily intake. Thus, new therapeutic approaches and concepts are urgently needed. The advent of CRISPR-Cas9 genome editing offers great promise for the correction of disease-causing hereditary mutations. As such mutations are often very rare, gene editing strategies to correct them are not broadly applicable to many patients. Notably, there is recent evidence that gene editing technology can also be deployed to disrupt common pathogenic signaling cascades in a targeted, specific, and efficient manner, which offers a more generalizable approach. However, several challenges remain to be addressed ranging from the optimization of the editing strategy itself to a suitable delivery strategy up to potential immune responses to the editing components. This review article discusses important CRISPR-Cas9-based gene editing approaches with their advantages and drawbacks and outlines opportunities in their application for treatment of cardiovascular diseases.

Comprehensive evaluation and prediction of editing outcomes for near-PAMless adenine and cytosine base editors

Base editors enable the direct conversion of target bases without inducing double-strand breaks, showing great potential for disease modeling and gene therapy. Yet, their applicability has been constrained by the necessity for specific protospacer adjacent motif (PAM). We generate four versions of near-PAMless base editors and systematically evaluate their editing patterns and efficiencies using an sgRNA-target library of 45,747 sequences. Near-PAMless base editors significantly expanded the targeting scope, with both PAM and target flanking sequences as determinants for editing outcomes. We develop BEguider, a deep learning model, to accurately predict editing results for near-PAMless base editors. We also provide experimentally measured editing outcomes of 20,541 ClinVar sites, demonstrating that variants previously inaccessible by NGG PAM base editors can now be precisely generated or corrected. We make our predictive tool and data available online to facilitate development and application of near-PAMless base editors in both research and clinical settings.

Pathophysiology of dilated cardiomyopathy: from mechanisms to precision medicine

Dilated cardiomyopathy (DCM) is a complex disease with multiple causes and various pathogenic mechanisms. Despite improvements in the prognosis of patients with DCM in the past decade, this condition remains a leading cause of heart failure and premature death. Conventional treatment for DCM is based on the foundational therapies for heart failure with reduced ejection fraction. However, increasingly, attention is being directed towards individualized treatments and precision medicine. The ability to confirm genetic causality is gradually being complemented by an increased understanding of genotype-phenotype correlations. Non-genetic factors also influence the onset of DCM, and growing evidence links genetic background with concomitant non-genetic triggers or precipitating factors, increasing the extreme complexity of the pathophysiology of DCM. This Review covers the spectrum of pathophysiological mechanisms in DCM, from monogenic causes to the coexistence of genetic abnormalities and triggering environmental factors (the 'two-hit' hypothesis). The roles of common genetic variants in the general population and of gene modifiers in disease onset and progression are also discussed. Finally, areas for future research are highlighted, particularly novel therapies, such as small molecules, RNA and gene therapy, and measures for the prevention of arrhythmic death.

Feline hypertrophic cardiomyopathy: Does the microRNA-mRNA regulatory network contribute to heart sarcomeric protein remodelling?

Feline primary hypertrophic cardiomyopathy (HCM) is an intrinsic myocardial disease characterized by concentric hypertrophy of the left ventricle. In the present study, we investigated the microRNA-mRNA regulatory network in feline myocardial tissue affected by primary (HCMI) and secondary HCM (HCMII). MRNA expression levels of sarcomeric genes, including, TNNT2, TNNI3, MYH7, MYBPC3, TPM1 and ACTC1 were assessed in the FFPE myocardial tissues. FFPE tissues from healthy cats were sequenced by the NGS, to explore, in the entire non-deposited miRNome, the expression level of microRNAs targeting the complementary sequences of selected sarcomeric mRNAs. The sarcomeric genes TNNT2, MYH7, MYBPC3 and TPM1 showed a statistically significant upregulation in HCMI compared to HCMII (p < .01), except ACTC1 which was downregulated (p < .01); TNNI3 showed no statistically significant difference. In HCMII miR-122-5p, miR-338-3p, miR-484, miR-370-3p, miR-92b-3p, miR-375 and miR-370-3p showed a significant upregulation (p < .01) compared to control. The exception was miR-30a-5p which showed downregulation. Worthy of note is the 4-fold higher expression of miR-370-3p, a key regulator of MYBPC3, in HMCI compared to HMCII. This research does not solve the aetiological mystery of HCM, but it may help to find a way to help diagnose and define the prognosis of HCM in cats.

The Genetic Factors Influencing Cardiomyopathies and Heart Failure across the Allele Frequency Spectrum

Heart failure (HF) remains a major cause of mortality and morbidity worldwide. Understanding the genetic basis of HF allows for the development of disease-modifying therapies, more appropriate risk stratification, and personalised management of patients. The advent of next-generation sequencing has enabled genome-wide association studies; moving beyond rare variants identified in a Mendelian fashion and detecting common DNA variants associated with disease. We summarise the latest GWAS and rare variant data on mixed and refined HF aetiologies, and cardiomyopathies. We describe the recent understanding of the functional impact of titin variants and highlight FHOD3 as a novel cardiomyopathy-associated gene. We describe future directions of research in this field and how genetic data can be leveraged to improve the care of patients with HF.

Emerging trends in virus and virus-like particle gene therapy delivery to the brain

Recent advances in gene therapy and gene-editing techniques offer the very real potential for successful treatment of neurological diseases. However, drug delivery constraints continue to impede viable therapeutic interventions targeting the brain due to its anatomical complexity and highly restrictive microvasculature that is impervious to many molecules. Realizing the therapeutic potential of gene-based therapies requires robust encapsulation and safe and efficient delivery to the target cells. Although viral vectors have been widely used for targeted delivery of gene-based therapies, drawbacks such as host genome integration, prolonged expression, undesired off-target mutations, and immunogenicity have led to the development of alternative strategies. Engineered virus-like particles (eVLPs) are an emerging, promising platform that can be engineered to achieve neurotropism through pseudotyping. This review outlines strategies to improve eVLP neurotropism for therapeutic brain delivery of gene-editing agents.

Genetic therapies for cardiomyopathy: survey of attitudes of the patient community for the CureHeart project

Cardiomyopathies are a group of inherited heart muscle disorders. Expressivity is variable and while sometimes mild, complications can result in sudden cardiac death (SCD) at any age, heart failure and stroke. In around a third of patients a monogenic cause is identifiable, and development of genetic therapies that aim to correct the underlying genetic defect is underway. Here we describe results of a survey designed to understand preliminary views of the patient community about genetic therapies in the context of disease burden. The internet survey was publicized with a bespoke information video via patient support groups in the UK and USA; 634 people responded of whom 96% had a personal and/or family history of cardiomyopathy. Findings show that concern about cardiomyopathy-related issues with a future dimension, such as disease progression, is significantly greater than concern about current issues. A total of 93.6% thought that genetic therapies should be developed for cardiomyopathy. A majority would consider participation in a genetic therapy trial in six scenarios varying by age and clinical situation significantly more in the scenario of an adult with symptomatic disease and evident progression than an asymptomatic adult with SCD risk, or a child. In all scenarios, a majority said that the chance genetic therapy would stop or slow progression, and risk of serious adverse and unintended effects, were important considerations. Qualitative analysis of free-text responses found that concern was often informed by family experience. Patient consideration of genetic therapy is likely to require individualized assessment of the benefits and risks.

Precision Genetic Therapies: Balancing Risk and Benefit in Patients with Heart Failure

PURPOSE OF REVIEW

Precision genetic medicine is evolving at a rapid pace and bears significant implications for clinical cardiology. Herein, we discuss the latest advancements and emerging strategies in gene therapy for cardiomyopathy and heart failure.

RECENT FINDINGS

Elucidating the genetic architecture of heart failure has paved the way for precision therapies in cardiovascular medicine. Recent preclinical studies and early-phase clinical trials have demonstrated encouraging results that support the development of gene therapies for heart failure arising from a variety of etiologies. In addition to the discovery of new therapeutic targets, innovative delivery platforms are being leveraged to improve the safety and efficacy of cardiac gene therapies. Precision genetic therapy represents a potentially safe and effective approach for improving outcomes in patients with heart failure. It holds promise for radically transforming the treatment paradigm for heart failure by directly targeting the underlying etiology. As this new generation of cardiovascular medicines progress to the clinic, it is especially important to carefully evaluate the benefits and risks for patients.

Editing microbes to mitigate enteric methane emissions in livestock

Livestock production significantly contributes to greenhouse gas (GHG) emissions particularly methane (CH4) emissions thereby influencing climate change. To address this issue further, it is crucial to establish strategies that simultaneously increase ruminant productivity while minimizing GHG emissions, particularly from cattle, sheep, and goats. Recent advancements have revealed the potential for modulating the rumen microbial ecosystem through genetic selection to reduce methane (CH4) production, and by microbial genome editing including CRISPR/Cas9, TALENs (Transcription Activator-Like Effector Nucleases), ZFNs (Zinc Finger Nucleases), RNA interference (RNAi), Pime editing, Base editing and double-stranded break-free (DSB-free). These technologies enable precise genetic modifications, offering opportunities to enhance traits that reduce environmental impact and optimize metabolic pathways. Additionally, various nutrition-related measures have shown promise in mitigating methane emissions to varying extents. This review aims to present a future-oriented viewpoint on reducing methane emissions from ruminants by leveraging CRISPR/Cas9 technology to engineer the microbial consortia within the rumen. The ultimate objective is to develop sustainable livestock production methods that effectively decrease methane emissions, while maintaining animal health and productivity.

Studying Pathogenetic Contribution of a Variant of Unknown Significance, p.M659I (c.1977G > A) in MYH7, to the Development of Hypertrophic Cardiomyopathy Using CRISPR/Cas9-Engineered Isogenic Induced Pluripotent Stem Cells

Hypertrophic cardiomyopathy (HCM) is a cardiovascular pathology that is caused by variants in genes encoding sarcomere-associated proteins. However, the clinical significance of numerous variants in HCM-associated genes is still unknown. CRISPR/Cas9 is a tool of nucleotide sequence editing that allows for the unraveling of different biological tasks. In this study, introducing a mutation with CRISPR/Cas9 into induced pluripotent stem cells (iPSCs) of a healthy donor and the directed differentiation of the isogenic iPSC lines into cardiomyocytes were used to assess the pathogenicity of a variant of unknown significance, p.M659I (c.1977G > A) in MYH7, which was found previously in an HCM patient. Using two single-stranded donor oligonucleotides with and without the p.M659I (c.1977G > A) mutation, together with CRISPR/Cas9, an iPSC line heterozygous at the p.M659I (c.1977G > A) variant in MYH7 was generated. No CRISPR/Cas9 off-target activity was observed. The iPSC line with the introduced p.M659I (c.1977G > A) mutation in MYH7 retained its pluripotent state and normal karyotype. Compared to the isogenic control, cardiomyocytes derived from the iPSCs with the introduced p.M659I (c.1977G > A) mutation in MYH7 recapitulated known HCM features: enlarged size, elevated diastolic calcium level, changes in the expression of HCM-related genes, and disrupted energy metabolism. These findings indicate the pathogenicity of the variant.

Humanized-Aquaporin-4-Expressing Rat Created by Gene-Editing Technology and Its Use to Clarify the Pathology of Neuromyelitis Optica Spectrum Disorder

Conventional rodent neuromyelitis optica spectrum disorder (NMOSD) models using patient-derived immunoglobulin G (IgG) are potentially affected by the differences between the human and rodent aquaporin-4 (AQP4) extracellular domains (ECDs). We hypothesized that the humanization of AQP4 ECDs would make the rodent model lesions closer to human NMOSD pathology. Humanized-AQP4-expressing (hAQP4) rats were generated using genome-editing technology, and the human AQP4-specific monoclonal antibody (mAb) or six patient-derived IgGs were introduced intraperitoneally into hAQP4 rats and wild-type Lewis (WT) rats after immunization with myelin basic protein and complete Freund's adjuvant. Human AQP4-specific mAb induced astrocyte loss lesions specifically in hAQP4 rats. The patient-derived IgGs also induced NMOSD-like tissue-destructive lesions with AQP4 loss, demyelination, axonal swelling, complement deposition, and marked neutrophil and macrophage/microglia infiltration in hAQP4 rats; however, the difference in AQP4 loss lesion size and infiltrating cells was not significant between hAQP4 and WT rats. The patient-derived IgGs bound to both human and rat AQP4 M23, suggesting their binding to the shared region of human and rat AQP4 ECDs. Anti-AQP4 titers positively correlated with AQP4 loss lesion size and neutrophil and macrophage/microglia infiltration. Considering that patient-derived IgGs vary in binding sites and affinities and some of them may not bind to rodent AQP4, our hAQP4 rat is expected to reproduce NMOSD-like pathology more accurately than WT rats.

Allele-Specific Suppression of Variant MHC With High-Precision RNA Nuclease CRISPR-Cas13d Prevents Hypertrophic Cardiomyopathy

BACKGROUND

Familial hypertrophic cardiomyopathy has severe clinical complications of heart failure, arrhythmia, and sudden cardiac death. Heterozygous single nucleotide variants (SNVs) of sarcomere genes such as MYH7 are the leading cause of this type of disease. CRISPR-Cas13 (clustered regularly interspaced short palindromic repeats and their associated protein 13) is an emerging gene therapy approach for treating genetic disorders, but its therapeutic potential in genetic cardiomyopathy remains unexplored.

METHODS

We developed a sensitive allelic point mutation reporter system to screen the mutagenic variants of Cas13d. On the basis of Cas13d homology structure, we rationally designed a series of Cas13d variants and obtained a high-precision Cas13d variant (hpCas13d) that specifically cleaves the MYH7 variant RNAs containing 1 allelic SNV. We validated the high precision and low collateral cleavage activity of hpCas13d through various in vitro assays. We generated 2 HCM mouse models bearing distinct MYH7 SNVs and used adenovirus-associated virus serotype 9 to deliver hpCas13d specifically to the cardiomyocytes. We performed a large-scale library screening to assess the potency of hpCas13d in resolving 45 human MYH7 allelic pathogenic SNVs.

RESULTS

Wild-type Cas13d cannot distinguish and specifically cleave the heterozygous MYH7 allele with SNV. hpCas13d, with 3 amino acid substitutions, had minimized collateral RNase activity and was able to resolve various human MYH7 pathological sequence variations that cause hypertrophic cardiomyopathy. In vivo application of hpCas13d to 2 hypertrophic cardiomyopathy models caused by distinct human MYH7 analogous sequence variations specifically suppressed the altered allele and prevented cardiac hypertrophy.

CONCLUSIONS

Our study unveils the great potential of CRISPR-Cas nucleases with high precision in treating inheritable cardiomyopathy and opens a new avenue for therapeutic management of inherited cardiac diseases.

In vivo adenine base editing rescues adrenoleukodystrophy in a humanized mouse model

X-linked adrenoleukodystrophy (ALD), an inherited neurometabolic disorder caused by mutations in ABCD1, which encodes the peroxisomal ABC transporter, mainly affects the brain, spinal cord, adrenal glands, and testes. In ALD patients, very-long-chain fatty acids (VLCFAs) fail to enter the peroxisome and undergo subsequent β-oxidation, resulting in their accumulation in the body. It has not been tested whether in vivo base editing or prime editing can be harnessed to ameliorate ALD. We developed a humanized mouse model of ALD by inserting a human cDNA containing the pathogenic variant into the mouse Abcd1 locus. The humanized ALD model showed increased levels of VLCFAs. To correct the mutation, we tested both base editing and prime editing and found that base editing using ABE8e(V106W) could correct the mutation in patient-derived fibroblasts at an efficiency of 7.4%. Adeno-associated virus (AAV)-mediated systemic delivery of NG-ABE8e(V106W) enabled robust correction of the pathogenic variant in the mouse brain (correction efficiency: ∼5.5%), spinal cord (∼5.1%), and adrenal gland (∼2%), leading to a significant reduction in the plasma levels of C26:0/C22:0. This established humanized mouse model and the successful correction of the pathogenic variant using a base editor serve as a significant step toward treating human ALD disease.

CRISPR-Cas Genome Editing in Ex Vivo Human Lungs to Rewire the Translational Path of Genome-Targeting Therapeutics

The ongoing advancements in CRISPR-Cas technologies can significantly accelerate the preclinical development of both in vivo and ex vivo organ genome-editing therapeutics. One of the promising applications is to genetically modify donor organs prior to implantation. The implantation of optimized donor organs with long-lasting immunomodulatory capacity holds promise for reducing the need for lifelong potent whole-body immunosuppression in recipients. However, assessing genome-targeting interventions in a clinically relevant manner prior to clinical trials remains a major challenge owing to the limited modalities available. This study introduces a novel platform for testing genome editing in human lungs ex vivo, effectively simulating preimplantation genetic engineering of donor organs. We identified gene regulatory elements whose disruption via Cas nucleases led to the upregulation of the immunomodulatory gene interleukin 10 (IL-10). We combined this approach with adenoviral vector-mediated IL-10 delivery to create favorable kinetics for early (immediate postimplantation) graft immunomodulation. Using ex vivo organ machine perfusion and precision-cut tissue slice technology, we demonstrated the feasibility of evaluating CRISPR genome editing in human lungs. To overcome the assessment limitations in ex vivo perfused human organs, we conducted an in vivo rodent study and demonstrated both early gene induction and sustained editing of the lung. Collectively, our findings lay the groundwork for a first-in-human-organ study to overcome the current translational barriers of genome-targeting therapeutics.

Advances in Hypertrophic Cardiomyopathy Disease Modelling Using hiPSC-Derived Cardiomyocytes

The advent of human induced pluripotent stem cells (hiPSCs) and their capacity to be differentiated into beating human cardiomyocytes (CMs) in vitro has revolutionized human disease modelling, genotype-phenotype predictions, and therapeutic testing. Hypertrophic cardiomyopathy (HCM) is a common inherited cardiomyopathy and the leading known cause of sudden cardiac arrest in young adults and athletes. On a molecular level, HCM is often driven by single pathogenic genetic variants, usually in sarcomeric proteins, that can alter the mechanical, electrical, signalling, and transcriptional properties of the cell. A deeper knowledge of these alterations is critical to better understanding HCM manifestation, progression, and treatment. Leveraging hiPSC-CMs to investigate the molecular mechanisms driving HCM presents a unique opportunity to dissect the consequences of genetic variants in a sophisticated and controlled manner. In this review, we summarize the molecular underpinnings of HCM and the role of hiPSC-CM studies in advancing our understanding, and we highlight the advances in hiPSC-CM-based modelling of HCM, including maturation, contractility, multiomics, and genome editing, with the notable exception of electrophysiology, which has been previously covered.

Gene Therapy in Cardiology: Is a Cure for Hypertrophic Cardiomyopathy on the Horizon?

Hypertrophic cardiomyopathy (HCM) is the most common genetic cardiomyopathy worldwide, affecting approximately 1 in 500 individuals. Current therapeutic interventions include lifestyle optimisation, medications, septal reduction therapies, and, rarely, cardiac transplantation. Advances in our understanding of disease-causing genetic variants in HCM and their associated molecular mechanisms have led to the potential for targeted therapeutics and implementation of precision and personalised medicine. Results from preclinical research are promising and raise the question of whether cure of some subtypes of HCM may be possible in the future. This review provides an overview of current genetic therapy platforms, including 1) genome editing, 2) gene replacement, 3) allelic-specific silencing, and 4) signalling pathway modulation. The current applicability of each of these platforms within the paradigm of HCM is examined, with updates on current and emerging trials in each domain. Barriers and limitations within the current landscape are also highlighted. Despite recent advances, translation of genetic therapy for HCM to clinical practice is still in early development. In realising the promises of genetic HCM therapies, ethical and equitable access to safe gene therapy must be prioritised.

Navigating the landscape of RNA delivery systems in cardiovascular disease therapeutics

Cardiovascular diseases (CVDs) stand as the leading cause of death worldwide, posing a significant global health challenge. Consequently, the development of innovative therapeutic strategies to enhance CVDs treatment is imperative. RNA-based therapies, encompassing non-coding RNAs, mRNA, aptamers, and CRISPR/Cas9 technology, have emerged as promising tools for addressing CVDs. However, inherent challenges associated with RNA, such as poor cellular uptake, susceptibility to RNase degradation, and capture by the reticuloendothelial system, underscore the necessity of combining these therapies with effective drug delivery systems. Various non-viral delivery systems, including extracellular vesicles, lipid-based carriers, polymeric and inorganic nanoparticles, as well as hydrogels, have shown promise in enhancing the efficacy of RNA therapeutics. In this review, we offer an overview of the most relevant RNA-based therapeutic strategies explored for addressing CVDs and emphasize the pivotal role of delivery systems in augmenting their effectiveness. Additionally, we discuss the current status of these therapies and the challenges that hinder their clinical translation.

Advanced cell and gene therapies in cardiology

We review the evidence for the presence of stem/progenitor cells in the heart and the preclinical and clinical data using diverse cell types for the therapy of cardiac diseases. We highlight the failure of adult stem/progenitor cells to ameliorate heart function in most cardiac diseases, with the possible exception of refractory angina. The use of pluripotent stem cell-derived cardiomyocytes is analysed as a viable alternative therapeutic option but still needs further research at preclinical and clinical stages. We also discuss the use of direct reprogramming of cardiac fibroblasts into cardiomyocytes and the use of extracellular vesicles as therapeutic agents in ischemic and non-ischemic cardiac diseases. Finally, gene therapies and genome editing for the treatment of hereditary cardiac diseases, ablation of genes responsible for atherosclerotic disease, or modulation of gene expression in the heart are discussed.

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.

Strategies for non-viral vectors targeting organs beyond the liver

In recent years, nanoparticles have evolved to a clinical modality to deliver diverse nucleic acids. Rising interest in nanomedicines comes from proven safety and efficacy profiles established by continuous efforts to optimize physicochemical properties and endosomal escape. However, despite their transformative impact on the pharmaceutical industry, the clinical use of non-viral nucleic acid delivery is limited to hepatic diseases and vaccines due to liver accumulation. Overcoming liver tropism of nanoparticles is vital to meet clinical needs in other organs. Understanding the anatomical structure and physiological features of various organs would help to identify potential strategies for fine-tuning nanoparticle characteristics. In this Review, we discuss the source of liver tropism of non-viral vectors, present a brief overview of biological structure, processes and barriers in select organs, highlight approaches available to reach non-liver targets, and discuss techniques to accelerate the discovery of non-hepatic therapies.

State of Gene Therapy for Monogenic Cardiovascular Diseases

Over the past 2 decades, significant efforts have been made to advance gene therapy into clinical practice. Although successful examples exist in other fields, gene therapy for the treatment of monogenic cardiovascular diseases lags behind. In this review, we (1) highlight a brief history of gene therapy, (2) distinguish between gene silencing, gene replacement, and gene editing technologies, (3) discuss vector modalities used in the field with a special focus on adeno-associated viruses, (4) provide examples of gene therapy approaches in cardiomyopathies, channelopathies, and familial hypercholesterolemia, and (5) present current challenges and limitations in the gene therapy field.

Autosomal recessive primary microcephaly type 2 associated with a novel WDR62 splicing variant that disrupts the expression of the functional transcript

Background

Autosomal recessive primary microcephaly (MCPH) is a rare neurodevelopmental disorder characterized primarily by congenital microcephaly and intellectual disability but without extra-central nervous system malformations. This investigation aimed to elucidate the genetic underpinnings of microcephaly in a patient from a Chinese consanguineous family.

Methods

A comprehensive clinical assessment, including brain magnetic resonance imaging (MRI), electroencephalogram (EEG), and genetic analyses, was conducted to evaluate the patient's condition. Whole-exome sequencing (WES) was employed to identify the causative gene, followed by Sanger sequencing, to confirm the mutation and its segregation within the family. Reverse transcript polymerase chain reaction (RT-PCR) was utilized to detect changes in splicing. Western blot was employed to reveal the difference of protein expression level between the wild-type and mutant WDR62 in vitro.

Results

The patient exhibited classic MCPH symptoms, including microcephaly, recurrent epilepsy, delayed psychomotor development, and intellectual disability. Additionally, asymmetrical limb length was noted as a prominent feature. MRI findings indicated reduced brain volume with cortical malformations, while EEG demonstrated heightened sharp wave activity. A molecular analysis uncovered a novel homozygous variant c.4154-6 C > G in the WDR62 intron, and a functional analysis confirmed the pathogenicity of this mutation, resulting in the formation of an abnormal transcript with premature termination codons.

Conclusion

This study enhances our understanding of the genetic heterogeneity associated with MCPH and highlights the pivotal role of genetic testing in the diagnosing and managing of rare neurodevelopmental disorders. Furthermore, it highlights the potential of emerging genetic therapies in treating conditions such as MCPH2.

Current RNA strategies in treating cardiovascular diseases

Cardiovascular disease (CVD) continues to impose a significant global health burden, necessitating the exploration of innovative treatment strategies. Ribonucleic acid (RNA)-based therapeutics have emerged as a promising avenue to address the complex molecular mechanisms underlying CVD pathogenesis. We present a comprehensive review of the current state of RNA therapeutics in the context of CVD, focusing on the diverse modalities that bring about transient or permanent modifications by targeting the different stages of the molecular biology central dogma. Considering the immense potential of RNA therapeutics, we have identified common gene targets that could serve as potential interventions for prevalent Mendelian CVD caused by single gene mutations, as well as acquired CVDs developed over time due to various factors. These gene targets offer opportunities to develop RNA-based treatments tailored to specific genetic and molecular pathways, presenting a novel and precise approach to address the complex pathogenesis of both types of cardiovascular conditions. Additionally, we discuss the challenges and opportunities associated with delivery strategies to achieve targeted delivery of RNA therapeutics to the cardiovascular system. This review highlights the immense potential of RNA-based interventions as a novel and precise approach to combat CVD, paving the way for future advancements in cardiovascular therapeutics.

Efficient Gene Editing for Heart Disease via ELIP-Based CRISPR Delivery System

Liposomes as carriers for CRISPR/Cas9 complexes represent an attractive approach for cardiovascular gene therapy. A critical barrier to this approach remains the efficient delivery of CRISPR-based genetic materials into cardiomyocytes. Echogenic liposomes (ELIP) containing a fluorescein isothiocyanate-labeled decoy oligodeoxynucleotide against nuclear factor kappa B (ELIP-NF-κB-FITC) were used both in vitro on mouse neonatal ventricular myocytes and in vivo on rat hearts to assess gene delivery efficacy with or without ultrasound. In vitro analysis was then repeated with ELIP containing Cas9-sg-IL1RL1 (interleukin 1 receptor-like 1) RNA to determine the efficiency of gene knockdown. ELIP-NF-κB-FITC without ultrasound showed limited gene delivery in vitro and in vivo, but ultrasound combined with ELIP notably improved penetration into heart cells and tissues. When ELIP was used to deliver Cas9-sg-IL1RL1 RNA, gene editing was successful and enhanced by ultrasound. This innovative approach shows promise for heart disease gene therapy using CRISPR technology.

Precise genome-editing in human diseases: mechanisms, strategies and applications

Precise genome-editing platforms are versatile tools for generating specific, site-directed DNA insertions, deletions, and substitutions. The continuous enhancement of these tools has led to a revolution in the life sciences, which promises to deliver novel therapies for genetic disease. Precise genome-editing can be traced back to the 1950s with the discovery of DNA's double-helix and, after 70 years of development, has evolved from crude in vitro applications to a wide range of sophisticated capabilities, including in vivo applications. Nonetheless, precise genome-editing faces constraints such as modest efficiency, delivery challenges, and off-target effects. In this review, we explore precise genome-editing, with a focus on introduction of the landmark events in its history, various platforms, delivery systems, and applications. First, we discuss the landmark events in the history of precise genome-editing. Second, we describe the current state of precise genome-editing strategies and explain how these techniques offer unprecedented precision and versatility for modifying the human genome. Third, we introduce the current delivery systems used to deploy precise genome-editing components through DNA, RNA, and RNPs. Finally, we summarize the current applications of precise genome-editing in labeling endogenous genes, screening genetic variants, molecular recording, generating disease models, and gene therapy, including ex vivo therapy and in vivo therapy, and discuss potential future advances.

Harnessing human genetics and stem cells for precision cardiovascular medicine

Human induced pluripotent stem cell (iPSC) platforms are valuable for biomedical and pharmaceutical research by providing tissue-specific human cells that retain patients' genetic integrity and display disease phenotypes in a dish. Looking forward, combining iPSC phenotyping platforms with genomic and screening technologies will continue to pave new directions for precision medicine, including genetic prediction, visualization, and treatment of heart disease. This review summarizes the recent use of iPSC technology to unpack the influence of genetic variants in cardiovascular pathology. We focus on various state-of-the-art genomic tools for cardiovascular therapies-including the expansion of genetic toolkits for molecular interrogation, in vitro population studies, and function-based drug screening-and their current applications in patient- and genome-edited iPSC platforms that are heralding new avenues for cardiovascular research.

Medical Treatment Strategies for Hypertrophic Cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is a heterogeneous genetic heart disease inherited in an autosomal dominant pattern with an estimated prevalence of 0.6% in the general population. Clinical manifestations of HCM vary considerably, with symptoms ranging from none or mild exercise intolerance to severe lifestyle-limiting symptoms, advanced heart failure, and sudden cardiac death. Current management options for HCM include lifestyle modifications, familial screening with genetic counseling, pharmacotherapy for symptom control, sudden cardiac death risk stratification with or without defibrillator implantation, septal reduction therapy, and, in some cases, heart transplantation. Only recently have strongly targeted medical therapies for HCM, such as myosin inhibitors, been studied in multicenter randomized controlled trials. In this report, we review the currently available medical treatments for HCM and the future directions of HCM pharmacotherapy, and we highlight important unmet needs in this population.

Current therapies for osteoarthritis and prospects of CRISPR-based genome, epigenome, and RNA editing in osteoarthritis treatment

Osteoarthritis (OA) is one of the most common degenerative joint diseases worldwide, causing pain, disability, and decreased quality of life. The balance between regeneration and inflammation-induced degradation results in multiple etiologies and complex pathogenesis of OA. Currently, there is a lack of effective therapeutic strategies for OA treatment. With the development of CRISPR-based genome, epigenome, and RNA editing tools, OA treatment has been improved by targeting genetic risk factors, activating chondrogenic elements, and modulating inflammatory regulators. Supported by cell therapy and in vivo delivery vectors, genome, epigenome, and RNA editing tools may provide a promising approach for personalized OA therapy. This review summarizes CRISPR-based genome, epigenome, and RNA editing tools that can be applied to the treatment of OA and provides insights into the development of CRISPR-based therapeutics for OA treatment. Moreover, in-depth evaluations of the efficacy and safety of these tools in human OA treatment are needed.

Gene correction and overexpression of TNNI3 improve impaired relaxation in engineered heart tissue model of pediatric restrictive cardiomyopathy

Research on cardiomyopathy models using engineered heart tissue (EHT) created from disease-specific induced pluripotent stem cells (iPSCs) is advancing rapidly. However, the study of restrictive cardiomyopathy (RCM), a rare and intractable cardiomyopathy, remains at the experimental stage because there is currently no established method to replicate the hallmark phenotype of RCM, particularly diastolic dysfunction, in vitro. In this study, we generated iPSCs from a patient with early childhood-onset RCM harboring the TNNI3 R170W mutation (R170W-iPSCs). The properties of R170W-iPSC-derived cardiomyocytes (CMs) and EHTs were evaluated and compared with an isogenic iPSC line in which the mutation was corrected. Our results indicated altered calcium kinetics in R170W-iPSC-CMs, including prolonged tau, and an increased ratio of relaxation force to contractile force in R170W-EHTs. These properties were reversed in the isogenic line, suggesting that our model recapitulates impaired relaxation of RCM, i.e., diastolic dysfunction in clinical practice. Furthermore, overexpression of wild-type TNNI3 in R170W-iPSC-CMs and -EHTs effectively rescued impaired relaxation. These results highlight the potential efficacy of EHT, a modality that can accurately recapitulate diastolic dysfunction in vitro, to elucidate the pathophysiology of RCM, as well as the possible benefits of gene therapies for patients with RCM.

Adenine base editor-based correction of the cardiac pathogenic Lmna c.1621C > T mutation in murine hearts

Base editors are emerging as powerful tools to correct single-nucleotide variants and treat genetic diseases. In particular, the adenine base editors (ABEs) exhibit robust and accurate adenine-to-guanidine editing capacity and have entered the clinical stage for cardiovascular therapy. Despite the tremendous progress using ABEs to treat heart diseases, a standard technical route toward successful ABE-based therapy remains to be fully established. In this study, we harnessed adeno-associated virus (AAV) and a mouse model carrying the cardiomyopathy-causing Lmna c.1621C > T mutation to demonstrate key steps and concerns in designing a cardiac ABE experiment in vivo. We found DeepABE as a reliable deep-learning-based model to predict ABE editing outcomes in the heart. Screening of sgRNAs for a Cas9 mutant with relieved protospacer adjacent motif (PAM) allowed the reduction of bystander editing. The ABE editing efficiency can be significantly enhanced by modifying the TadA and Cas9 variants, which are core components of ABEs. The ABE systems can be delivered into the heart via either dual AAV or all-in-one AAV vectors. Together, this study showcased crucial technical considerations in designing an ABE system for the heart and pointed out major challenges in further improvement of this new technology for gene therapy.

Applications of Gene Therapy in Cardiomyopathies

Gene therapy is defined by the introduction of new genes or the genetic modification of existing genes and/or their regulatory portions via gene replacement and gene editing strategies, respectively. The genetic material is usually delivered though cardiotropic vectors such as adeno-associated virus 9 or engineered capsids. The enthusiasm for gene therapy has been hampered somewhat by adverse events observed in clinical trials, including dose-dependent immunologic reactions such as hepatotoxicity, acquired hemolytic uremic syndrome and myocarditis. Notably, gene therapy for Duchenne muscular dystrophy has recently been approved and pivotal clinical trials are testing gene therapy approaches in rare myocardial conditions such as Danon disease and Fabry disease. Furthermore, promising results have been shown in animal models of gene therapy in hypertrophic cardiomyopathy and arrhythmogenic cardiomyopathy. This review summarizes the gene therapy techniques, the toxicity risk associated with adeno-associated virus delivery, the ongoing clinical trials, and future targets.

In Vivo Base Editing of Scn5a Rescues Type 3 Long QT Syndrome in Mice

BACKGROUND

Pathogenic variants in SCN5A can result in long QT syndrome type 3, a life-threatening genetic disease. Adenine base editors can convert targeted A T base pairs to G C base pairs, offering a promising tool to correct pathogenic variants.

METHODS

We generated a long QT syndrome type 3 mouse model by introducing the T1307M pathogenic variant into the Scn5a gene. The adenine base editor was split into 2 smaller parts and delivered into the heart by adeno-associated virus serotype 9 (AAV9-ABEmax) to correct the T1307M pathogenic variant.

RESULTS

Both homozygous and heterozygous T1307M mice showed significant QT prolongation. Carbachol administration induced Torsades de Pointes or ventricular tachycardia for homozygous T1307M mice (20%) but not for heterozygous or wild-type mice. A single intraperitoneal injection of AAV9-ABEmax at postnatal day 14 resulted in up to 99.20% Scn5a transcripts corrected in T1307M mice. Scn5a mRNA correction rate >60% eliminated QT prolongation; Scn5a mRNA correction rate <60% alleviated QT prolongation. Partial Scn5a correction resulted in cardiomyocytes heterogeneity, which did not induce severe arrhythmias. We did not detect off-target DNA or RNA editing events in ABEmax-treated mouse hearts.

CONCLUSIONS

These findings show that in vivo AAV9-ABEmax editing can correct the variant Scn5a allele, effectively ameliorating arrhythmia phenotypes. Our results offer a proof of concept for the treatment of hereditary arrhythmias.

CRISPR-Cas9 base editing of pathogenic CaMKIIδ improves cardiac function in a humanized mouse model

Cardiovascular diseases are the most common cause of worldwide morbidity and mortality, highlighting the necessity for advanced therapeutic strategies. Ca2+/calmodulin-dependent protein kinase IIδ (CaMKIIδ) is a prominent inducer of various cardiac disorders, which is mediated by 2 oxidation-sensitive methionine residues within the regulatory domain. We have previously shown that ablation of CaMKIIδ oxidation by CRISPR-Cas9 base editing enables the heart to recover function from otherwise severe damage following ischemia/reperfusion (IR) injury. Here, we extended this therapeutic concept toward potential clinical translation. We generated a humanized CAMK2D knockin mouse model in which the genomic sequence encoding the entire regulatory domain was replaced with the human sequence. This enabled comparison and optimization of two different editing strategies for the human genome in mice. To edit CAMK2D in vivo, we packaged the optimized editing components into an engineered myotropic adeno-associated virus (MyoAAV 2A), which enabled efficient delivery at a very low AAV dose into the humanized mice at the time of IR injury. CAMK2D-edited mice recovered cardiac function, showed improved exercise performance, and were protected from myocardial fibrosis, which was otherwise observed in injured control mice after IR. Our findings identify a potentially effective strategy for cardioprotection in response to oxidative damage.

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.

Inhibition of miR-199a-3p in a murine hypertrophic cardiomyopathy (HCM) model attenuates fibrotic remodeling

Background

Hypertrophic cardiomyopathy (HCM) is an autosomal dominant genetic disorder, characterized by cardiomyocyte hypertrophy, cardiomyocyte disarray and fibrosis, which has a prevalence of ∼1: 200-500 and predisposes individuals to heart failure and sudden death. The mechanisms through which diverse HCM-causing mutations cause cardiac dysfunction remain mostly unknown and their identification may reveal new therapeutic avenues. MicroRNAs (miRNAs) have emerged as critical regulators of gene expression and disease phenotype in various pathologies. We explored whether miRNAs could play a role in HCM pathogenesis and offer potential therapeutic targets.

Methods and results

Using high-throughput miRNA expression profiling and qPCR analysis in two distinct mouse models of HCM, we found that miR-199a-3p expression levels are upregulated in mutant mice compared to age- and treatment-matched wild-type mice. We also found that miR-199a-3p expression is enriched in cardiac non-myocytes compared to cardiomyocytes. When we expressed miR-199a-3p mimic in cultured murine primary cardiac fibroblasts and analyzed the conditioned media by proteomics, we found that several extracellular matrix (ECM) proteins (e.g., TSP2, FBLN3, COL11A1, LYOX) were differentially secreted (data are available via ProteomeXchange with identifier PXD042904). We confirmed our proteomics findings by qPCR analysis of selected mRNAs and demonstrated that miR-199a-3p mimic expression in cardiac fibroblasts drives upregulation of ECM gene expression, including Tsp2, Fbln3, Pcoc1, Col1a1 and Col3a1. To examine the role of miR-199a-3p in vivo, we inhibited its function using lock-nucleic acid (LNA)-based inhibitors (antimiR-199a-3p) in an HCM mouse model. Our results revealed that progression of cardiac fibrosis is attenuated when miR-199a-3p function is inhibited in mild-to-moderate HCM. Finally, guided by computational target prediction algorithms, we identified mRNAs Cd151 and Itga3 as direct targets of miR-199a-3p and have shown that miR-199a-3p mimic expression negatively regulates AKT activation in cardiac fibroblasts.

Conclusions

Altogether, our results suggest that miR-199a-3p may contribute to cardiac fibrosis in HCM through its actions in cardiac fibroblasts. Thus, inhibition of miR-199a-3p in mild-to-moderate HCM may offer therapeutic benefit in combination with complementary approaches that target the primary defect in cardiac myocytes.

Gene therapy for heart failure and cardiomyopathies

Gene therapy strategies encompass a range of approaches, including gene replacement and gene editing. Gene replacement involves providing a functional copy of a modified gene, while gene editing allows for the correction of existing genetic mutations. Gene therapy has already received approval for treating genetic disorders like Leber's congenital amaurosis and spinal muscular atrophy. Currently, research is being conducted to explore its potential use in cardiology. This review aims to summarize the mechanisms behind different gene therapy strategies, the available delivery systems, the primary risks associated with gene therapy, ongoing clinical trials, and future targets, with a particular emphasis on cardiomyopathies.