Calcium Upregulation by Percutaneous Administration of Gene Therapy in Cardiac Disease (CUPID): a phase 2 trial of intracoronary gene therapy of sarcoplasmic reticulum Ca2+-ATPase in patients with advanced heart failure

Gene Therapy Cargoes Based on Viral Vector Delivery

Viral vectors have been proven useful in a broad spectrum of gene therapy applications due to their possibility to accommodate foreign genetic material for both local and systemic delivery. The wide range of viral vectors has enabled gene therapy applications for both acute and chronic diseases. Cancer gene therapy has been addressed by the delivery of viral vectors expressing anti-tumor, toxic, and suicide genes for the destruction of tumors. Delivery of immunostimulatory genes such as cytokines and chemokines has also been applied for cancer therapy. Moreover, oncolytic viruses specifically replicating in and killing tumor cells have been used as such for tumor eradication or in combination with tumor killing or immunostimulatory genes. In a broad meaning, vaccines against infectious diseases and various cancers can be considered gene therapy, which has been highly successful, not the least for the development of effective COVID-19 vaccines. Viral vector-based gene therapy has also demonstrated encouraging and promising results for chronic diseases such as severe combined immunodeficiency (SCID), muscular dystrophy, and hemophilia. Preclinical gene therapy studies in animal models have demonstrated proof-of-concept for a wide range of disease indications. Clinical evaluation of drugs and vaccines in humans has showed high safety levels, good tolerance, and therapeutic efficacy. Several gene therapy drugs such as the adenovirus-based drug Gendicine® for non-small-cell lung cancer, the reovirus-based drug Reolysin® for ovarian cancer, lentivirus-based treatment of SCID-X1 disease, and the rhabdovirus-based vaccine Ervebo against Ebola virus disease, and adenovirus-based vaccines against COVID-19 have been developed.

AAV capsid engineering identified two novel variants with improved in vivo tropism for cardiomyocytes

AAV vectors are promising delivery tools for human gene therapy. However, broad tissue tropism and pre-existing immunity against natural serotypes limit their clinical use. We identified two AAV capsid variants, AAV2-THGTPAD and AAV2-NLPGSGD, by in vivo AAV2 peptide display library screening in a murine model of pressure overload-induced cardiac hypertrophy. Both variants showed significantly improved efficacy in in vivo cardiomyocyte transduction compared with the parental serotype AAV2 as indicated by a higher number of AAV vector episomes in the nucleus and significant improved transduction efficiency. Both variants also outcompeted the reference serotype AAV9 regarding cardiomyocyte tropism, reaching comparable cardiac transduction efficiencies accompanied with liver de-targeting and decreased transduction efficiency of non-cardiac cells. Capsid modification influenced immunogenicity as sera of mice treated with AAV2-THGTPAD and AAV2-NLPGSGD demonstrated a poor neutralization capacity for the parental serotype and the novel variants. In a therapeutic setting, using the long non-coding RNA H19 in low vector dose conditions, novel AAV variants mediated superior anti-hypertrophic effects and revealed a further improved target-to-noise ratio, i.e., cardiomyocyte tropism. In conclusion, AAV2-THGTPAD and AAV2-NLPGSGD are promising novel tools for cardiac-directed gene therapy outperforming AAV9 regarding the specificity and therapeutic efficiency of in vivo cardiomyocyte transduction.

Reduced sarcoplasmic reticulum Ca2+ pump activity is antiarrhythmic in ischemic cardiomyopathy

BACKGROUND

We have described an arrhythmic mechanism seen only in cardiomyopathy that involves increased mitochondrial Ca²⁺ handling and selective transfer of Ca²⁺ to the sarcoplasmic reticulum (SR). Modeling suggested that mitochondrial Ca²⁺ transfer to the SR via type 2a sarco/endoplasmic reticulum Ca²⁺-ATPase (SERCA2a) is a crucial element of this arrhythmic mechanism.

OBJECTIVE

We tested the role of SERCA2a in arrhythmias during ischemic cardiomyopathy.

METHODS

Myocardial infarction (MI) was induced in wild-type (Wt) and SERCA2a heterozygous knockdown (SERCA^+/-) mice.

RESULTS

Compared with Wt MI mice, SERCA2a heterozygous knockdown (SERCA^+/-) MI mice had a substantially lower mortality after 3 weeks of MI without a significant change in MI area. Aside from a significant delay of the cytoplasmic Ca²⁺ transient decay existed in SERCA^+/- compared with Wt, SERCA^+/- did not affect cardiac systolic and diastolic function at the whole organ or single cell levels either before or after MI. After MI, SERCA^+/- mice had reduced SERCA2a expression in the MI border zone compared with Wt MI mice. SERCA^+/- mice had significantly decreased corrected QT intervals and less ventricular tachycardia compared with Wt MI mice. SERCA^+/- cardiomyocytes from MI mice showed a reduced action potential duration and reduced triggered activity compared with Wt MI cardiomyocytes. Reduction in arrhythmic risk was accompanied by reduced diastolic SR Ca²⁺ sparks, reduced SR Ca²⁺ content, reduced oxidized ryanodine receptor, and increased calsequestrin 2 in SERCA^+/- MI mice.

CONCLUSION

SERCA2a knockdown was antiarrhythmic after MI without affecting overall systolic performance. Possible antiarrhythmic mechanisms included reduced SR free Ca²⁺ and reduced diastolic SR Ca²⁺ release.

A Large-Scale High-Throughput Screen for Modulators of SERCA Activity

The sarco/endoplasmic reticulum Ca-ATPase (SERCA) is a P-type ion pump that transports Ca²⁺ from the cytosol into the endoplasmic/sarcoplasmic reticulum (ER/SR) in most mammalian cells. It is critically important in muscle, facilitating relaxation and enabling subsequent contraction. Increasing SERCA expression or specific activity can alleviate muscle dysfunction, most notably in the heart, and we seek to develop small-molecule drug candidates that activate SERCA. Therefore, we adapted an NADH-coupled assay, measuring Ca-dependent ATPase activity of SERCA, to high-throughput screening (HTS) format, and screened a 46,000-compound library of diverse chemical scaffolds. This HTS platform yielded numerous hits that reproducibly alter SERCA Ca-ATPase activity, with few false positives. The top 19 activating hits were further tested for effects on both Ca-ATPase and Ca²⁺ transport, in both cardiac and skeletal SR. Nearly all hits increased Ca²⁺ uptake in both cardiac and skeletal SR, with some showing isoform specificity. Furthermore, dual analysis of both activities identified compounds with a range of effects on Ca²⁺-uptake and ATPase, which fit into distinct classifications. Further study will be needed to identify which classifications are best suited for therapeutic use. These results reinforce the need for robust secondary assays and criteria for selection of lead compounds, before undergoing HTS on a larger scale.

Beta-3 adrenergic receptor overexpression reverses aortic stenosis-induced heart failure and restores balanced mitochondrial dynamics

Aortic stenosis (AS) is associated with left ventricular (LV) hypertrophy and heart failure (HF). There is a lack of therapies able to prevent/revert AS-induced HF. Beta3 adrenergic receptor (β3AR) signaling is beneficial in several forms of HF. Here, we studied the potential beneficial effect of β3AR overexpression on AS-induced HF. Selective β3AR stimulation had a positive inotropic effect. Transgenic mice constitutively overexpressing human β3AR in the heart (c-hβ3tg) were protected from the development of HF in response to induced AS, and against cardiomyocyte mitochondrial dysfunction (fragmented mitochondria with remodeled cristae and metabolic reprogramming featuring altered substrate use). Similar beneficial effects were observed in wild-type mice inoculated with adeno-associated virus (AAV9) inducing cardiac-specific overexpression of human β3AR before AS induction. Moreover, AAV9-hβ3AR injection into wild-type mice at late disease stages, when cardiac hypertrophy and metabolic reprogramming are already advanced, reversed the HF phenotype and restored balanced mitochondrial dynamics, demonstrating the potential of gene-therapy-mediated β3AR overexpression in AS. Mice with cardiac specific ablation of Yme1l (cYKO), characterized by fragmented mitochondria, showed an increased mortality upon AS challenge. AAV9-hβ3AR injection in these mice before AS induction reverted the fragmented mitochondria phenotype and rescued them from death. In conclusion, our results step out that β3AR overexpression might have translational potential as a therapeutic strategy in AS-induced HF.

mRNA therapy for myocardial infarction: A review of targets and delivery vehicles

Cardiovascular diseases are the leading cause of death in the world. This is partly due to the low regenerative capacity of adult hearts. mRNA therapy is a promising approach under development for cardiac diseases. In mRNA therapy, expression of the target protein is modulated by delivering synthetic mRNA. mRNA therapy benefits cardiac regeneration by increasing cardiomyocyte proliferation, reducing fibrosis, and promoting angiogenesis. Because mRNA is translated in the cytoplasm, the delivery efficiency of mRNA into the cytoplasm and nucleus significantly affects its therapeutic efficacy. To improve delivery efficiency, non-viral vehicles such as lipid nanoparticles have been developed. Non-viral vehicles can protect mRNA from enzymatic degradation and facilitate the cellular internalization of mRNA. In addition to non-viral vehicles, viral vectors have been designed to deliver mRNA templates into cardiac cells. This article reviews lipid nanoparticles, polymer nanoparticles, and viral vectors that have been utilized to deliver mRNA into the heart. Because of the growing interest in lipid nanoparticles, recent advances in lipid nanoparticles designed for cardiac mRNA delivery are discussed. Besides, potential targets of mRNA therapy for myocardial infarction are discussed. Gene therapies that have been investigated in patients with cardiac diseases are analyzed. Reviewing mRNA therapy from a clinically relevant perspective can reveal needs for future investigations.

Vascular smooth muscle cell dysfunction in neurodegeneration

Vascular smooth muscle cells (VSMCs) are the key moderators of cerebrovascular dynamics in response to the brain's oxygen and nutrient demands. Crucially, VSMCs may provide a sensitive biomarker for neurodegenerative pathologies where vasculature is compromised. An increasing body of research suggests that VSMCs have remarkable plasticity and their pathophysiology may play a key role in the complex process of neurodegeneration. Furthermore, extrinsic risk factors, including environmental conditions and traumatic events can impact vascular function through changes in VSMC morphology. VSMC dysfunction can be characterised at the molecular level both preclinically, and clinically ex vivo. However the identification of VSMC dysfunction in living individuals is important to understand changes in vascular function at the onset and progression of neurological disorders such as dementia, Alzheimer's disease, and Parkinson's disease. A promising technique to identify changes in the state of cerebral smooth muscle is cerebrovascular reactivity (CVR) which reflects the intrinsic dynamic response of blood vessels in the brain to vasoactive stimuli in order to modulate regional cerebral blood flow (CBF). In this work, we review the role of VSMCs in the most common neurodegenerative disorders and identify physiological systems that may contribute to VSMC dysfunction. The evidence collected here identifies VSMC dysfunction as a strong candidate for novel therapeutics to combat the development and progression of neurodegeneration, and highlights the need for more research on the role of VSMCs and cerebrovascular dynamics in healthy and diseased states.

Deciphering the Basis of Molecular Biology of Selected Cardiovascular Diseases: A View on Network Medicine

Cardiovascular diseases are the leading cause of death across the world. For decades, researchers have been studying the causes of cardiovascular disease, yet many of them remain undiscovered or poorly understood. Network medicine is a recently expanding, integrative field that attempts to elucidate this issue by conceiving of disease as the result of disruptive links between multiple interconnected biological components. Still in its nascent stages, this revolutionary application of network science facilitated a number of important discoveries in complex disease mechanisms. As methodologies become more advanced, network medicine harbors the potential to expound on the molecular and genetic complexities of disease to differentiate how these intricacies govern disease manifestations, prognosis, and therapy. This is of paramount importance for confronting the incredible challenges of current and future cardiovascular disease research. In this review, we summarize the principal molecular and genetic mechanisms of common cardiac pathophysiologies as well as discuss the existing knowledge on therapeutic strategies to prevent, halt, or reverse these pathologies.

Cell-Based and Selected Cell-Free Therapies for Myocardial Infarction: How Do They Compare to the Current Treatment Options?

Because of cardiomyocyte death or dysfunction frequently caused by myocardial infarction (MI), heart failure is a leading cause of morbidity and mortality in modern society. Paradoxically, only limited and non-curative therapies for heart failure or MI are currently available. As a result, over the past two decades research has focused on developing cell-based approaches promoting the regeneration of infarcted tissue. Cell-based therapies for myocardial regeneration include powerful candidates, such as multipotent stem cells (mesenchymal stem cells (MSCs), bone-marrow-derived stem cells, endothelial progenitor cells, and hematopoietic stem cells) and induced pluripotent stem cells (iPSCs). These possess unique properties, such as potency to differentiate into desired cell types, proliferation capacity, and patient specificity. Preclinical and clinical studies have demonstrated modest improvement in the myocardial regeneration and reduced infarcted areas upon transplantation of pluripotent or multipotent stem cells. Another cell population that need to be considered as a potential source for cardiac regeneration are telocytes found in different organs, including the heart. Their therapeutic effect has been studied in various heart pathologies, such as MI, arrhythmias, or atrial amyloidosis. The most recent cell-free therapeutic tool relies on the cardioprotective effect of complex cargo carried by small membrane-bound vesicles-exosomes-released from stem cells via exocytosis. The MSC/iPSC-derived exosomes could be considered a novel exosome-based therapy for cardiovascular diseases thanks to their unique content. There are also other cell-free approaches, e.g., gene therapy, or acellular cardiac patches. Therefore, our review provides the most recent insights into the novel strategies for myocardial repair based on the regenerative potential of different cell types and cell-free approaches.

Natural Polyphenols as SERCA Activators: Role in the Endoplasmic Reticulum Stress-Related Diseases

Sarco/endoplasmic reticulum Ca²⁺-ATPase (SERCA) is a key protein responsible for transporting Ca²⁺ ions from the cytosol into the lumen of the sarco/endoplasmic reticulum (SR/ER), thus maintaining Ca²⁺ homeostasis within cells. Accumulating evidence suggests that impaired SERCA function is associated with disruption of intracellular Ca²⁺ homeostasis and induction of ER stress, leading to different chronic pathological conditions. Therefore, appropriate strategies to control Ca²⁺ homeostasis via modulation of either SERCA pump activity/expression or relevant signaling pathways may represent a useful approach to combat pathological states associated with ER stress. Natural dietary polyphenolic compounds, such as resveratrol, gingerol, ellagic acid, luteolin, or green tea polyphenols, with a number of health-promoting properties, have been described either to increase SERCA activity/expression directly or to affect Ca²⁺ signaling pathways. In this review, potential Ca²⁺-mediated effects of the most studied polyphenols on SERCA pumps or related Ca²⁺ signaling pathways are summarized, and relevant mechanisms of their action on Ca²⁺ regulation with respect to various ER stress-related states are depicted. All data were collected using scientific search tools (i.e., Science Direct, PubMed, Scopus, and Google Scholar).

Pharmacological Targets in Chronic Heart Failure with Reduced Ejection Fraction

Heart failure management has been repeatedly reviewed over time. This strategy has resulted in improved quality of life, especially in patients with heart failure with reduced ejection fraction (HFrEF). It is for this reason that new mechanisms involved in the development and progression of heart failure, along with specific therapies, have been identified. This review focuses on the most recent guidelines of therapeutic interventions, trials that explore novel therapies, and also new molecules that could improve prognosis of different HFrEF phenotypes.

Evaluating response-adaptive randomization procedures for recurrent events and terminal event data using a composite endpoint

Recurrent event and terminal event data commonly arise in clinical and observational studies. To evaluate the efficacy of a treatment effect for both types of events, a composite endpoint has been used as a possible assessment, particularly when faced with high costs and a longer follow-up study. To model recurrent event processes complicated by the existence of a terminal event, joint frailty modeling has been typically employed. In this study, the objective was to develop some target-driven response adaptive randomization strategies using a composite endpoint based on joint frailty modeling. We first implemented a balanced randomized design and then investigated the response adaptive randomization. The former is intuitively first adopted while the latter is expected to be desirable and ethical in terms of allocating more subjects to the more effective treatment. The results show that the proposed procedures using a composite endpoint are capable of reducing the number of trial participants who receive inferior treatment while simultaneously reaching a desired optimal target as compared to a balanced randomized design. The R shiny application for calculating the sample size and allocation probabilities is also available. Finally, two clinical trials were used as pilot datasets to introduce the proposed procedures.

Blocking phospholamban with VHH intrabodies enhances contractility and relaxation in heart failure

The dysregulated physical interaction between two intracellular membrane proteins, the sarco/endoplasmic reticulum Ca²⁺ ATPase and its reversible inhibitor phospholamban, induces heart failure by inhibiting calcium cycling. While phospholamban is a bona-fide therapeutic target, approaches to selectively inhibit this protein remain elusive. Here, we report the in vivo application of intracellular acting antibodies (intrabodies), derived from the variable domain of camelid heavy-chain antibodies, to modulate the function of phospholamban. Using a synthetic VHH phage-display library, we identify intrabodies with high affinity and specificity for different conformational states of phospholamban. Rapid phenotypic screening, via modified mRNA transfection of primary cells and tissue, efficiently identifies the intrabody with most desirable features. Adeno-associated virus mediated delivery of this intrabody results in improvement of cardiac performance in a murine heart failure model. Our strategy for generating intrabodies to investigate cardiac disease combined with modified mRNA and adeno-associated virus screening could reveal unique future therapeutic opportunities.

Here the authors use modified RNA and VHH libraries to generate intrabodies that target dysregulated interactions between two calcium handling proteins in failing cardiomyocytes. Heart specific expression of the intrabodies in a murine heart failure model results in improved cardiac function.

Adenoviral vectors for cardiovascular gene therapy applications: a clinical and industry perspective

Abstract

Despite the development of novel pharmacological treatments, cardiovascular disease morbidity and mortality remain high indicating an unmet clinical need. Viral gene therapy enables targeted delivery of therapeutic transgenes and represents an attractive platform for tackling acquired and inherited cardiovascular diseases in the future. Current cardiovascular gene therapy trials in humans mainly focus on improving cardiac angiogenesis and function. Encouragingly, local delivery of therapeutic transgenes utilising first-generation human adenovirus serotype (HAd)-5 is safe in the short term and has shown some efficacy in drug refractory angina pectoris and heart failure with reduced ejection fraction. Despite this success, systemic delivery of therapeutic HAd-5 vectors targeting cardiovascular tissues and internal organs is limited by negligible gene transfer to target cells, elimination by the immune system, liver sequestration, off-target effects, and episomal degradation. To circumvent these barriers, cardiovascular gene therapy research has focused on determining the safety and efficacy of rare alternative serotypes and/or genetically engineered adenoviral capsid protein-modified vectors following local or systemic delivery. Pre-clinical studies have identified several vectors including HAd-11, HAd-35, and HAd-20–42-42 as promising platforms for local and systemic targeting of vascular endothelial and smooth muscle cells. In the past, clinical gene therapy trials were often restricted by limited scale-up capabilities of gene therapy medicinal products (GTMPs) and lack of regulatory guidance. However, significant improvement of industrial GTMP scale-up and purification, development of novel producer cell lines, and issuing of GTMP regulatory guidance by national regulatory health agencies have addressed many of these challenges, creating a more robust framework for future adenoviral-based cardiovascular gene therapy. In addition, this has enabled the mass roll out of adenovirus vector-based COVID-19 vaccines.

Key messages

First-generation HAd-5 vectors are widely used in cardiovascular gene therapy.

HAd-5-based gene therapy was shown to lead to cardiac angiogenesis and improved function.

Novel HAd vectors may represent promising transgene carriers for systemic delivery.

Novel methods allow industrial scale-up of rare/genetically altered Ad serotypes.

National regulatory health agencies have issued guidance on GMP for GTMPs.

Calcium cycling as a mediator of thermogenic metabolism in adipose tissue

Canonical non-shivering thermogenesis (NST) in brown and beige fat relies on uncoupling protein 1 (UCP1)-mediated heat generation, although alternative mechanisms of NST have been identified, including sarcoplasmic reticulum (SR)-calcium cycling. Intracellular calcium is a crucial cell signaling molecule for which compartmentalization is tightly regulated, and the sarco-endoplasmic calcium ATPase (SERCA) actively pumps calcium from the cytosol into the SR. In this review, we discuss the capacity of SERCA-mediated calcium cycling as a significant mediator of thermogenesis in both brown and beige adipocytes. Here, we suggest two primary mechanisms of SR calcium mediated thermogenesis. The first mechanism is through direct uncoupling of the ATPase and calcium pump activity of SERCA, resulting in the energy of ATP catalysis being expended as heat in the absence of calcium transport. Regulins, a class of SR membrane proteins, act to decrease the calcium affinity of SERCA and uncouple the calcium transport function from ATPase activity, but remain largely unexplored in adipose tissue thermogenesis. A second mechanism is through futile cycling of SR calcium whereby SERCA-mediated SR calcium influx is equally offset by SR calcium efflux, resulting in ATP consumption without a net change in calcium compartmentalization. A fuller understanding of the functional and mechanistic role of calcium cycling as a mediator of adipose tissue thermogenesis and how manipulation of these pathways can be harnessed for therapeutic gain remains unexplored. Significance Statement Enhancing thermogenic metabolism in brown or beige adipose tissue may be of broad therapeutic utility to reduce obesity and metabolic syndrome. Canonical BAT-mediated thermogenesis occurs via uncoupling protein 1 (UCP1). However, UCP1-independent pathways of thermogenesis, such as sarcoplasmic (SR) calcium cycling, have also been identified, but the regulatory mechanisms and functional significance of these pathways remain largely unexplored. Thus, this mini-review discusses the state of the field with regard to calcium cycling as a thermogenic mediator in adipose tissue.

Signaling cascades in the failing heart and emerging therapeutic strategies

Chronic heart failure is the end stage of cardiac diseases. With a high prevalence and a high mortality rate worldwide, chronic heart failure is one of the heaviest health-related burdens. In addition to the standard neurohormonal blockade therapy, several medications have been developed for chronic heart failure treatment, but the population-wide improvement in chronic heart failure prognosis over time has been modest, and novel therapies are still needed. Mechanistic discovery and technical innovation are powerful driving forces for therapeutic development. On the one hand, the past decades have witnessed great progress in understanding the mechanism of chronic heart failure. It is now known that chronic heart failure is not only a matter involving cardiomyocytes. Instead, chronic heart failure involves numerous signaling pathways in noncardiomyocytes, including fibroblasts, immune cells, vascular cells, and lymphatic endothelial cells, and crosstalk among these cells. The complex regulatory network includes protein-protein, protein-RNA, and RNA-RNA interactions. These achievements in mechanistic studies provide novel insights for future therapeutic targets. On the other hand, with the development of modern biological techniques, targeting a protein pharmacologically is no longer the sole option for treating chronic heart failure. Gene therapy can directly manipulate the expression level of genes; gene editing techniques provide hope for curing hereditary cardiomyopathy; cell therapy aims to replace dysfunctional cardiomyocytes; and xenotransplantation may solve the problem of donor heart shortages. In this paper, we reviewed these two aspects in the field of failing heart signaling cascades and emerging therapeutic strategies based on modern biological techniques.

Novel Therapeutics for Anthracycline Induced Cardiotoxicity

Anthracyclines remain an essential component of the treatment of many hematologic and solid organ malignancies, but has important implications on cardiovascular disease. Anthracycline induced cardiotoxicity (AIC) ranges from asymptomatic LV dysfunction to highly morbid end- stage heart failure. As cancer survivorship improves, the detection and treatment of AIC becomes more crucial to improve patient outcomes. Current treatment modalities for AIC have been largely extrapolated from treatment of conventional heart failure, but developing effective therapies specific to AIC is an area of growing research interest. This review summarizes the current evidence behind the use of neurohormonal agents, dexrazoxane, and resynchronization therapy in AIC, evaluates the clinical outcomes of advanced therapy and heart transplantation in AIC, and explores future horizons for treatment utilizing gene therapy, stem cell therapy, and mechanism-specific targets.

Bmi-1-RING1B prevents GATA4-dependent senescence-associated pathological cardiac hypertrophy by promoting autophagic degradation of GATA4

AIMS

Senescence-associated pathological cardiac hypertrophy (SA-PCH) is associated with upregulation of foetal genes, fibrosis, senescence-associated secretory phenotype (SASP), cardiac dysfunction and increased morbidity and mortality. Therefore, we conducted experiments to investigate whether GATA4 accumulation induces SA-PCH, and whether Bmi-1-RING1B promotes GATA4 ubiquitination and its selective autophagic degradation to prevent SA-PCH.

METHODS AND RESULTS

Bmi-1-deficient (Bmi-1-/- ), transgenic Bmi-1 overexpressing (Bmi-1Tg ) and wild-type (WT) mice were infused with angiotensin II (Ang II) to stimulate the development of SA-PCH. Through bioinformatics analysis with RNA sequencing data from cardiac tissues, we found that Bmi-1-RING1B and autophagy are negatively related to SA-PCH. Bmi-1 deficiency promoted GATA4-dependent SA-PCH by increasing GATA4 protein and hypertrophy-related molecules transcribed by GATA4 such as ANP and BNP. Bmi-1 deficiency stimulated NF-κB-p65-dependent SASP, leading to cardiac dysfunction, cardiomyocyte hypertrophy and senescence. Bmi-1 overexpression repressed GATA4-dependent SA-PCH. GATA4 degraded by Bmi-1 was mainly dependent on autophagy rather than proteasome. In human myocardium, p16 positively correlated with ANP and GATA4 and negatively correlated with LC3B, Bmi-1 and RING1B; GATA4 positively correlated with p62 and negatively correlated with Bmi-1 and LC3B. With increased p16 protein levels, ANP-, BNP- and GATA4-positive cells or areas increased; however, LC3B-positive cells or areas decreased in human myocardium. GATA4 is ubiquitinated after combining with Bmi-1-RING1B, which is then recognised by p62, is translocated to autophagosomes to form autophagolysosomes and degraded. Downregulated GATA4 ameliorated SA-PCH and cardiac dysfunction by reducing GATA4-dependent hypertrophy and SASP-related molecules. Bmi-1 combined with RING1B (residues 1-179) and C-terminus of GATA4 (residues 206-443 including zinc finger domains) through residues 1-95, including a RING-HC-finger. RING1B combined with C-terminus of GATA4 through the C-terminus (residues 180-336). Adeno-associated viral vector serotype 9 (AAV9)-cytomegalovirus (CMV)-Bmi-1-RING1B treatment significantly attenuated GATA4-dependent SA-PCH through promoting GATA4 autophagic degradation.

CONCLUSIONS

Bmi-1-RING1B maintained cardiac function and prevented SA-PCH by promoting selective autophagy for degrading GATA4.

TRANSLATIONAL PERSPECTIVE

AAV9-CMV-Bmi-1-RING1B could be used for translational gene therapy to ubiquitinate GATA4 and prevent GATA4-dependent SA-PCH. Also, the combined domains between Bmi-1-RING1B and GATA4 in aging cardiomyocytes could be therapeutic targets for identifying stapled peptides in clinical applications to promote the combination of Bmi-1-RING1B with GATA4 and the ubiquitination of GATA4 to prevent SA-PCH and heart failure. We found that degradation of cardiac GATA4 by Bmi-1 was mainly dependent on autophagy rather than proteasome, and autophagy agonists metformin and rapamycin could ameliorate the SA-PCH, suggesting that activation of autophagy with metformin or rapamycin could also be a promising method to prevent SA-PCH.

Cas9/AAV9-Mediated Somatic Mutagenesis Uncovered the Cell-Autonomous Role of Sarcoplasmic/Endoplasmic Reticulum Calcium ATPase 2 in Murine Cardiomyocyte Maturation

Sarcoplasmic/endoplasmic reticulum calcium ATPase 2 (SERCA2) is a key player in cardiomyocyte calcium handling and also a classic target in the gene therapy for heart failure. SERCA2 expression dramatically increases during cardiomyocyte maturation in the postnatal phase of heart development, which is essential for the heart to acquire its full function in adults. However, whether and how SERCA2 regulates cardiomyocyte maturation remains unclear. Here, we performed Cas9/AAV9-mediated somatic mutagenesis (CASAAV) in mice and achieved cardiomyocyte-specific knockout of Atp2a2, the gene coding SERCA2. Through a cardiac genetic mosaic analysis, we demonstrated the cell-autonomous role of SERCA2 in building key ultrastructures of mature ventricular cardiomyocytes, including transverse-tubules and sarcomeres. SERCA2 also exerts a profound impact on oxidative respiration gene expression and sarcomere isoform switching from Myh7/Tnni1 to Myh6/Tnni3, which are transcriptional hallmarks of cardiomyocyte maturation. Together, this study uncovered a pivotal role of SERCA2 in heart development and provided new insights about SERCA2-based cardiac gene therapy.

Type 2 Diabetes Complicated With Heart Failure: Research on Therapeutic Mechanism and Potential Drug Development Based on Insulin Signaling Pathway

Type 2 diabetes mellitus (T2DM) and heart failure (HF) are diseases characterized by high morbidity and mortality. They often occur simultaneously and increase the risk of each other. T2DM complicated with HF, as one of the most dangerous disease combinations in modern medicine, is more common in middle-aged and elderly people, making the treatment more difficult. At present, the combination of blood glucose control and anti-heart failure is a common therapy for patients with T2DM complicated with HF, but their effect is not ideal, and many hypoglycemic drugs have the risk of heart failure. Abnormal insulin signaling pathway, as a common pathogenic mechanism in T2DM and HF, could lead to pathological features such as insulin resistance (IR), myocardial energy metabolism disorders, and vascular endothelial disorders. The therapy based on the insulin signaling pathway may become a specific therapeutic target for T2DM patients with HF. Here, we reviewed the mechanisms and potential drugs of insulin signaling pathway in the treatment of T2DM complicated with HF, with a view to opening up a new perspective for the treatment of T2DM patients with HF and the research and development of new drugs.

Endothelial Retargeting of AAV9 In Vivo

Adeno-associated viruses (AAVs) are frequently used for gene transfer and gene editing in vivo, except for endothelial cells, which are remarkably resistant to unmodified AAV-transduction. AAVs are retargeted here toward endothelial cells by coating with second-generation polyamidoamine dendrimers (G2) linked to endothelial-affine peptides (CNN). G2CNN AAV9-Cre (encoding Cre recombinase) are injected into mTmG-mice or mTmG-pigs, cell-specifically converting red to green fluorescence upon Cre-activity. Three endothelial-specific functions are assessed: in vivo quantification of adherent leukocytes after systemic injection of - G2CNN AAV9 encoding 1) an artificial adhesion molecule (S1FG) in wildtype mice (day 10) or 2) anti-inflammatory Annexin A1 (Anxa1) in ApoE-/- mice (day 28). Moreover, 3) in Cas9-transgenic mice, blood pressure is monitored till day 56 after systemic application of G2CNN AAV9-gRNAs, targeting exons 6-10 of endothelial nitric oxide synthase (eNOS), a vasodilatory enzyme. G2CNN AAV9-Cre transduces microvascular endothelial cells in mTmG-mice or mTmG-pigs. Functionally, G2CNN AAV9-S1FG mediates S1FG-leukocyte adhesion, whereas G2CNN AAV9-Anxa1-application reduces long-term leukocyte recruitment. Moreover, blood pressure increases in Cas9-expressing mice subjected to G2CNN AAV9-gRNAeNOS . Therefore, G2CNN AAV9 may enable gene transfer in vascular and atherosclerosis models.

Calcium dysregulation in heart diseases: Targeting calcium channels to achieve a correct calcium homeostasis

Intracellular calcium signaling is a universal language source shared by the most part of biological entities inside cells that, all together, give rise to physiological and functional anatomical units, the organ. Although preferentially recognized as signaling between cell life and death processes, in the heart it assumes additional relevance considered the importance of calcium cycling coupled to ATP consumption in excitation-contraction coupling. The concerted action of a plethora of exchangers, channels and pumps inward and outward calcium fluxes where needed, to convert energy and electric impulses in muscle contraction. All this without realizing it, thousands of times, every day. An improper function of those proteins (i.e., variation in expression, mutations onset, dysregulated channeling, differential protein-protein interactions) being part of this signaling network triggers a short circuit with severe acute and chronic pathological consequences reported as arrhythmias, cardiac remodeling, heart failure, reperfusion injury and cardiomyopathies. By acting with chemical, peptide-based and pharmacological modulators of these players, a correction of calcium homeostasis can be achieved accompanied by an amelioration of clinical symptoms. This review will focus on all those defects in calcium homeostasis which occur in the most common cardiac diseases, including myocardial infarction, arrhythmia, hypertrophy, heart failure and cardiomyopathies. This part will be introduced by the state of the art on the proteins involved in calcium homeostasis in cardiomyocytes and followed by the therapeutic treatments that to date, are able to target them and to revert the pathological phenotype.

Potential Applications for Targeted Gene Therapy to Protect Against Anthracycline Cardiotoxicity: JACC: CardioOncology Primer

Anthracyclines are associated with risk of significant dose-dependent cardiotoxicity. Conventional heart failure therapies have neither ameliorated declining cardiac function nor addressed the underlying cause. Gene therapy may confer long-term cardioprotection by rendering the heart resistant to anthracyclines after 1 treatment, although the optimal therapeutic target remains to be elucidated. Recombinant adeno-associated virus is now clinically approved for the treatment of lipoprotein lipase deficiency, spinal muscular atrophy, and hereditary transthyretin amyloidosis. High-throughput methods allow selection of recombinant adeno-associated virus capsids that facilitate efficient gene delivery to specific target cells. Vector safety is enhanced by incorporating cardiac-specific promoters into vector design and localizing delivery to reduce off-target risk. Any cardioprotective transgene may bear a degree of risk as they may play as yet unknown roles, which require careful assessment using clinically relevant models. The innovative technologies outlined here make gene therapy a promising proof of principle, with potential further application to nonanthracycline chemotherapeutics.

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Protection against anthracycline cardiotoxicity may be achieved by gene delivery to the heart.

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The optimal cardioprotective target gene remains to be identified.

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Targeted gene expression in human myocytes can now be achieved with advances in AAV vectorology.

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It is critical to minimize risk of off-target effects which may impede anthracycline oncotherapy.

Design and Production of Heart Chamber-Specific AAV9 Vectors

Adeno-associated virus serotype 9 (AAV9) is often used in heart research involving gene delivery due to its cardiotropism, high transduction efficiency, and little to no pathogenicity, making it highly applicable for gene manipulation, in vivo. However, current AAV9 technology is limited by the lack of strains that can selectively express and elucidate gene function in an atrial- and ventricular-specific manner. In fact, study of gene function in cardiac atria has been limited due to the lack of an appropriate tool to study atrial gene expression in vivo, hindering progress in the study of atrial-specific diseases such as atrial fibrillation, the most common cardiac arrhythmia in the USA.This chapter describes the method for the design and production of such chamber-specific AAV9 vectors, with the use of Nppa and Myl2 promoters to enhance atrial- and ventricular-specific expression. While several gene promoter candidates were considered and tested, Nppa and Myl2 were selected for use here because of their clearly defined regulatory elements that confer cardiac chamber-specific expression. Accordingly, Nppa (-425/+25) and Myl2 (-226/+36) promoter fragments are inserted into AAV9 vectors. The atrial- and ventricular-specific expression conferred by these new recombinant AAV9 was confirmed in a double-fluorescent Cre-dependent reporter mouse model. At only 450 and 262 base pairs of Nppa and Myl2 promoters, respectively, these AAV9 that drive chamber-specific AAV9 transgene expression address two major limitations of AAV9 technology, i.e., achieving chamber-specificity while maximizing space in the AAV genome for insertion of larger transgenes.

Medical Management of Patients With Heart Failure and Reduced Ejection Fraction

The options for treating heart failure with reduced ejection fraction (HFrEF) have expanded considerably over the past decade. While neurohormonal modulation using angiotensin converting enzyme inhibitors and angiotensin receptor blockers, beta blockers and mineralocorticoid receptor antagonists remain the cornerstone of therapy, additional novel approaches including angiotensin receptor neprilysin inhibitors, sodium glucose cotransporter 2 inhibitors, ivrabradine, vericiguat and omecamtiv mecarbil have been shown to improve outcomes in patients with HFrEF. This reviews summarizes currently available approaches as well as promising additional strategies that may be used in the future.

Treatment options for patients with heart failure (HF) with reduced ejection fraction (HFrEF) have expanded considerably over the past few decades. Whereas neurohormonal modulation remains central to the management of patients with HFrEF, other pathways have been targeted with drugs that have novel mechanisms of action. The angiotensin receptor-neprilysin inhibitors (ARNIs) which enhance levels of compensatory molecules such as the natriuretic peptides while simultaneously providing angiotensin receptor blockade have emerged as the preferred strategy for inhibiting the renin angiotensin system. Sodium glucose cotransporter 2 (SGLT2) inhibitors which were developed as hypoglycemic agents have been shown to improve outcomes in patients with HF regardless of their diabetic status. These agents along with beta blockers and mineralocorticoid receptor antagonists are the core medical therapies for patients with HFrEF. Additional approaches using ivabradine to slow heart rate in patients with sinus rhythm, the hydralazine/isosorbide dinitrate combination to unload the heart, digoxin to provide inotropic support and vericiguat to augment cyclic guanosine monophosphate production have been shown in well-designed trials to have beneficial effects in the HFrEF population and are used as adjuncts to the core therapies in selected patients. This review provides an overview of the medical management of patients with HFrEF with focus on the major developments that have taken place in the field. It offers prospective of how these drugs should be employed in clinical practice and also a glimpse into some strategies that may prove to be useful in the future.

Current and future therapeutic perspective in chronic heart failure

The incidence of heart failure is primarily flat or declining for a presumably reflecting better management of cardiovascular diseases, but that of heart failure with preserved ejection fraction (HFpEF) is probably increasing for the lack of an established effective treatment. Moreover, there is no specific pharmacological treatment for patients with heart failure with mildly reduced ejection fraction (HFmrEF) since no substantial prospective randomized clinical trial has been performed exclusively in such population. According to the recent 2021 European Society of Cardiology (ESC) guidelines, the triad composed of an Angiotensin Converting Enzyme inhibitor or Angiotensin Receptor-Neprilysin Inhibitor (ARNI), a beta-blocker, and a Mineralcorticoid Receptor Antagonist is the cornerstone therapy for all patients with heart failure with reduced ejection fraction (HFrEF) but a substantial gap exists for patients with HFpEF/HFmrEF. Despite the important role of the Renin-Angiotensin-Aldosterone System (RAAS) in heart failure pathophysiology, RAAS blockers were found ineffective for HFpEF patients. Indeed, even the new drug class of ARNI was found effective only in HFrEF patients. In this regard, a therapeutic alternative may be represented by drug stimulating the non-classic RAAS (ACE2 and A1-7) as well as other emerging drug classes (such as SGLT2 inhibitors). Reflecting on this global health burden and the gap in treatments among heart failure phenotypes, we summarize the leading players of heart failure pathophysiology, the available pharmacological treatments for each heart failure phenotype, and that in future development.

IGF1-PI3K-induced physiological cardiac hypertrophy: Implications for new heart failure therapies, biomarkers, and predicting cardiotoxicity

Heart failure represents the end point of a variety of cardiovascular diseases. It is a growing health burden and a leading cause of death worldwide. To date, limited treatment options exist for the treatment of heart failure, but exercise has been well-established as one of the few safe and effective interventions, leading to improved outcomes in patients. However, a lack of patient adherence remains a significant barrier in the implementation of exercise-based therapy for the treatment of heart failure. The insulin-like growth factor 1 (IGF1)-phosphoinositide 3-kinase (PI3K) pathway has been recognized as perhaps the most critical pathway for mediating exercised-induced heart growth and protection. Here, we discuss how modulating activity of the IGF1-PI3K pathway may be a valuable approach for the development of therapies that mimic the protective effects of exercise on the heart. We outline some of the promising approaches being investigated that utilize PI3K-based therapy for the treatment of heart failure. We discuss the implications for cardiac pathology and cardiotoxicity that arise in a setting of reduced PI3K activity. Finally, we discuss the use of animal models of cardiac health and disease, and genetic mice with increased or decreased cardiac PI3K activity for the discovery of novel drug targets and biomarkers of cardiovascular disease.

Sarco/endoplasmic reticulum Ca2+ -ATPase 2b mediates oxidation-induced endoplasmic reticulum stress to regulate neuropathic pain

BACKGROUND AND PURPOSE

Neuropathic pain is a widespread health problem with limited curative treatment. Decreased sarco/endoplasmic reticulum Ca²⁺ -ATPase (SERCA) expression has been reported in dorsal root ganglion (DRG) of animals suffering from neuropathic pain. We aimed to establish the relationship between SERCA expression and the pain responses and to elucidate the underlying molecular mechanism.

EXPERIMENTAL APPROACH

Neuropathic pain was modeled using rat chronic constriction injury (CCI). Ca²⁺ imaging and current clamp patch-clamp were used to determine cytosolic Ca²⁺ levels and action potential firing, respectively. Western blots, immunofluorescence staining and RT-PCR were used to quantitatively assess protein and mRNA expression, respectively. H&E staining and coupled enzyme assay were used to evaluate the nerve injury and SERCA2b activity, respectively.

KEY RESULTS

SERCA2b is the predominant SERCA isoform in rat DRG and its expression is decreased after CCI at mRNA, protein and activity levels. Whereas inhibiting SERCA with thapsigargin causes neuronal hyperexcitation, nerve injury, ER stress, satellite glial cell activation and mechanical allodynia, activating SERCA by CDN1163 or overexpressing SERCA2b in DRG after CCI produces long-term relief of mechanical and thermal allodynia with accompanied morphological and functional restoration through alleviation of ER stress. Furthermore, the downregulation of DRG SERCA2b in CCI rats is caused by increased production of reactive oxygen species (ROS) through Sp1-dependent transcriptional inhibition.

CONCLUSION AND IMPLICATIONS

Our findings reveal a novel pathway centering around SERCA2b as the key molecule underlying the mechanism of development and maintenance of neuropathic pain, and SERCA2b activators have the potential for therapeutic treatment of neuropathic pain.

Non-pharmaceutical Interventions for Hypertrophic Cardiomyopathy: A Mini Review

Hypertrophic cardiomyopathy is an inherited cardiovascular disease, and 70% of patients have left ventricular outflow tract obstruction. Ventricular septal myectomy has been the gold standard treatment for most patients with refractory symptoms. Due to higher mortality associated with medical facilities with less experience, alcohol septal ablation has been accepted as an alternative to conventional surgical myectomy. It offers lower all-cause in-hospital complications and mortality, which could be potentially more preferable for patients with serious comorbidities. In recent years, radiofrequency ablation, providing another option with reproducibility and a low risk of permanent atrioventricular block, has become an effective invasive treatment to relieve left ventricular outflow tract obstruction. Moreover, substantial progress has been made in gene therapy for hypertrophic cardiomyopathy. The principal objective of this review is to present recent advances in non-pharmaceutical interventions in hypertrophic cardiomyopathy.

Toward a New Paradigm for Targeted Natriuretic Peptide Enhancement in Heart Failure

The natriuretic peptide system (NPS) plays a fundamental role in maintaining cardiorenal homeostasis, and its potent filling pressure-regulated diuretic and vasodilatory effects constitute a beneficial compensatory mechanism in heart failure (HF). Leveraging the NPS for therapeutic benefit in HF has been the subject of intense investigation during the last three decades and has ultimately reached widespread clinical use in the form of angiotensin receptor-neprilysin inhibition (ARNi). NPS enhancement via ARNi confers beneficial effects on mortality and hospitalization in HF, but inhibition of neprilysin leads to the accumulation of a number of other vasoactive peptides in the circulation, often resulting in hypotension and raising potential concerns over long-term adverse effects. Moreover, ARNi is less effective in the large group of HF patients with preserved ejection fraction. Alternative approaches for therapeutic augmentation of the NPS with increased specificity and efficacy are therefore warranted, and are now becoming feasible particularly with recent development of RNA therapeutics. In this review, the current state-of-the-art in terms of experimental and clinical strategies for NPS augmentation and their implementation will be reviewed and discussed.

Value of SERCA2a as a Biomarker for the Identification of Patients with Heart Failure Requiring Circulatory Support

Background: Heart failure (HF) alters the nucleo-cytoplasmic transport of cardiomyocytes and reduces SERCA2a levels, essential for intracellular calcium homeostasis. We consider in this study whether the molecules involved in these processes can differentiate those patients with advanced HF and the need for mechanical circulatory support (MCS) as a bridge to recovery or urgent heart transplantation from those who are clinically stable and who are transplanted in an elective code. Material and method: Blood samples from 29 patients with advanced HF were analysed by ELISA, and the plasma levels of Importin5, Nucleoporin153 kDa, RanGTPase-Activating Protein 1 and sarcoplasmic reticulum Ca²⁺ ATPase were compared between patients requiring MCS and those patients without a MCS need prior to heart transplantation. Results: SERCA2a showed significantly lower levels in patients who had MCS compared to those who did not require it (0.501 ± 0.530 ng/mL vs. 1.123 ± 0.661 ng/mL; p = 0.01). A SERCA2a cut-off point of 0.84 ng/mL (AUC 0.812 ± 0.085, 95% CI: 0.646–0.979; p = 0.004) provided a 92% sensitivity, 62% specificity, 91% negative predictive value and 67% positive predictive value. Conclusions: In this cohort, patients with advanced HF and a need for MCS have shown significantly lower levels of SERCA2a as compared to stable patients without a need for MCS prior to heart transplantation. This is a small study with preliminary findings, and larger-powered dedicated studies are required to confirm and validate these results.

Bone Morphogenetic Protein 7 Gene Delivery Improves Cardiac Structure and Function in a Murine Model of Diabetic Cardiomyopathy

Diabetes is a major contributor to the increasing burden of heart failure prevalence globally, at least in part due to a disease process termed diabetic cardiomyopathy. Diabetic cardiomyopathy is characterised by cardiac structural changes that are caused by chronic exposure to the diabetic milieu. These structural changes are a major cause of left ventricular (LV) wall stiffness and the development of LV dysfunction. In the current study, we investigated the therapeutic potential of a cardiac-targeted bone morphogenetic protein 7 (BMP7) gene therapy, administered once diastolic dysfunction was present, mimicking the timeframe in which clinical management of the cardiomyopathy would likely be desired. Following 18 weeks of untreated diabetes, mice were administered with a single tail-vein injection of recombinant adeno-associated viral vector (AAV), containing the BMP7 gene, or null vector. Our data demonstrated, after 8 weeks of treatment, that rAAV6-BMP7 treatment exerted beneficial effects on LV functional and structural changes. Importantly, diabetes-induced LV dysfunction was significantly attenuated by a single administration of rAAV6-BMP7. This was associated with a reduction in cardiac fibrosis, cardiomyocyte hypertrophy and cardiomyocyte apoptosis. In conclusion, BMP7 gene therapy limited pathological remodelling in the diabetic heart, conferring an improvement in cardiac function. These findings provide insight for the potential development of treatment strategies urgently needed to delay or reverse LV pathological remodelling in the diabetic heart.

Hypertrophic Cardiomyopathy: From Phenotype and Pathogenesis to Treatment

Hypertrophic cardiomyopathy (HCM) is a very common inherited cardiovascular disease (CAD) and the incidence is about 1/500 of the common population. It is caused by more than 1,400 mutations in 11 or more genes encoding the proteins of the cardiac sarcomere. HCM presents a heterogeneous clinical profile and complex pathophysiology and HCM is the most important cause of sudden cardiac death (SCD) in young people. HCM also contributes to functional disability from heart failure and stroke (caused by atrial fibrillation). Current treatments for HCM (medication, myectomy, and alcohol septal ablation) are geared toward slowing down the disease progression and symptom relief and implanted cardiac defibrillator (ICD) to prevent SCD. HCM is, however, entering a period of tight translational research that holds promise for the major advances in disease-specific therapy. Main insights into the genetic landscape of HCM have improved our understanding of molecular pathogenesis and pointed the potential targets for the development of therapeutic agents. We reviewed the critical discoveries about the treatments, mechanism of HCM, and their implications for future research.

Understanding the Genetic and Molecular Basis of Familial Hypertrophic Cardiomyopathy and the Current Trends in Gene Therapy for Its Management

Hypertrophic cardiomyopathy (HCM) is a genetically acquired disease of cardiac myocytes. Studies show that 70% of this disease is a result of different mutations in various sarcomere genes. This review aims to discuss several genetic mutations, epigenetic factors, and signal transduction pathways leading to the development of HCM. In addition, this article elaborates on recent advances in gene therapies and their implications for managing this condition. We start by discussing the founding mutations in HCM and their effect on power stroke generation. The less explored field of epigenetics including methylation, acetylation, and the role of different micro RNAs in the development of cardiac muscle hypertrophy has been highlighted in this article. The signal transduction pathways that lead to gene transcription, which in turn lead to increased protein synthesis of cardiac muscle fibers are elaborated. Finally, the microscopic events leading to the pathophysiologic macro events of cardiac failure, and the current experimental trials of gene therapy models, and the clustered regularly interspaced short palindromic repeats (CRISPR) type 2 system proteins, are discussed. We have concluded our discussion by emphasizing the need for more studies on epigenomics and experimental designs for gene therapy in HCM patients. This review focuses on the process of HCM from initial mutation to the development of phenotypic expression and various points of intervention in cardiac myocardial hypertrophy development.

Cardiac sarcomere mechanics in health and disease

The sarcomere is the fundamental structural and functional unit of striated muscle and is directly responsible for most of its mechanical properties. The sarcomere generates active or contractile forces and determines the passive or elastic properties of striated muscle. In the heart, mutations in sarcomeric proteins are responsible for the majority of genetically inherited cardiomyopathies. Here, we review the major determinants of cardiac sarcomere mechanics including the key structural components that contribute to active and passive tension. We dissect the molecular and structural basis of active force generation, including sarcomere composition, structure, activation, and relaxation. We then explore the giant sarcomere-resident protein titin, the major contributor to cardiac passive tension. We discuss sarcomere dynamics exemplified by the regulation of titin-based stiffness and the titin life cycle. Finally, we provide an overview of therapeutic strategies that target the sarcomere to improve cardiac contraction and filling.

Non-Viral Gene Delivery Systems for Treatment of Myocardial Infarction: Targeting Strategies and Cardiac Cell Modulation

Cardiovascular diseases (CVD) are the leading cause of morbidity and mortality worldwide. Conventional therapies involving surgery or pharmacological strategies have shown limited therapeutic effects due to a lack of cardiac tissue repair. Gene therapy has opened an avenue for the treatment of cardiac diseases through manipulating the underlying gene mechanics. Several gene therapies for cardiac diseases have been assessed in clinical trials, while the clinical translation greatly depends on the delivery technologies. Non-viral vectors are attracting much attention due to their safety and facile production compared to viral vectors. In this review, we discuss the recent progress of non-viral gene therapies for the treatment of cardiovascular diseases, with a particular focus on myocardial infarction (MI). Through a summary of delivery strategies with which to target cardiac tissue and different cardiac cells for MI treatment, this review aims to inspire new insights into the design/exploitation of non-viral delivery systems for gene cargos to promote cardiac repair/regeneration.

An mRNA assay system demonstrates proteasomal-specific degradation contributes to cardiomyopathic phospholamban null mutation

Background

The human L39X phospholamban (PLN) cardiomyopathic mutant has previously been reported as a null mutation but the detailed molecular pathways that lead to the complete lack of detectable protein remain to be clarified. Previous studies have shown the implication between an impaired cellular degradation homeostasis and cardiomyopathy development. Therefore, uncovering the underlying mechanism responsible for the lack of PLN protein has important implications in understanding the patient pathology, chronic human calcium dysregulation and aid the development of potential therapeutics.

Methods

A panel of mutant and wild-type reporter tagged PLN modified mRNA (modRNA) constructs were transfected in human embryonic stem cell-derived cardiomyocytes. Lysosomal and proteasomal chemical inhibitors were used together with cell imaging and protein analysis tools in order to dissect degradation pathways associated with expressed PLN constructs. Transcriptional profiling of the cardiomyocytes transfected by wild-type or L39X mutant PLN modRNA was analysed with bulk RNA sequencing.

Results

Our modRNA assay system revealed that transfected L39X mRNA was stable and actively translated in vitro but with only trace amount of protein detectable. Proteasomal inhibition of cardiomyocytes transfected with L39X mutant PLN modRNA showed a fourfold increase in protein expression levels. Additionally, RNA sequencing analysis of protein degradational pathways showed a significant distinct transcriptomic signature between wild-type and L39X mutant PLN modRNA transfected cardiomyocytes.

Conclusion

Our results demonstrate that the cardiomyopathic PLN null mutant L39X is rapidly, actively and specifically degraded by proteasomal pathways. Herein, and to the best of our knowledge, we report for the first time the usage of modified mRNAs to screen for and illuminate alternative molecular pathways found in genes associated with inherited cardiomyopathies.

Supplementary Information

The online version contains supplementary material available at 10.1186/s10020-021-00362-8.

Gene Therapy: Targeting Cardiomyocyte Proliferation to Repopulate the Ischemic Heart

ABSTRACT

Adult mammalian cardiomyocytes show scarce division ability, which makes the heart ineffective in replacing lost contractile cells after ischemic cardiomyopathy. In the past decades, there have been increasing efforts in the search for novel strategies to regenerate the injured myocardium. Among them, gene therapy is one of the most promising ones, based on recent and emerging studies that support the fact that functional cardiomyocyte regeneration can be accomplished by the stimulation and enhancement of the endogenous ability of these cells to achieve cell division. This capacity can be targeted by stimulating several molecules, such as cell cycle regulators, noncoding RNAs, transcription, and metabolic factors. Therefore, the proposed target, together with the selection of the vector used, administration route, and the experimental animal model used in the development of the therapy would determine the success in the clinical field.

Focus on the Lymphatic Route to Optimize Drug Delivery in Cardiovascular Medicine

While oral agents have been the gold standard for cardiovascular disease therapy, the new generation of treatments is switching to other administration options that offer reduced dosing frequency and more efficacy. The lymphatic network is a unidirectional and low-pressure vascular system that is responsible for the absorption of interstitial fluids, molecules, and cells from the peripheral tissue, including the skin and the intestines. Targeting the lymphatic route for drug delivery employing traditional or new technologies and drug formulations is exponentially gaining attention in the quest to avoid the hepatic first-pass effect. The present review will give an overview of the current knowledge on the involvement of the lymphatic vessels in drug delivery in the context of cardiovascular disease.

Calcium and Heart Failure: How Did We Get Here and Where Are We Going?

The occurrence and prevalence of heart failure remain high in the United States as well as globally. One person dies every 30 s from heart disease. Recognizing the importance of heart failure, clinicians and scientists have sought better therapeutic strategies and even cures for end-stage heart failure. This exploration has resulted in many failed clinical trials testing novel classes of pharmaceutical drugs and even gene therapy. As a result, along the way, there have been paradigm shifts toward and away from differing therapeutic approaches. The continued prevalence of death from heart failure, however, clearly demonstrates that the heart is not simply a pump and instead forces us to consider the complexity of simplicity in the pathophysiology of heart failure and reinforces the need to discover new therapeutic approaches.

Ca2+ mishandling in heart failure: Potential targets

Ca²⁺ mishandling is a common feature in several cardiovascular diseases such as heart failure (HF). In many cases, impairment of key players in intracellular Ca²⁺ homeostasis has been identified as the underlying mechanism of cardiac dysfunction and cardiac arrhythmias associated with HF. In this review, we summarize primary novel findings related to Ca²⁺ mishandling in HF progression. HF research has increasingly focused on the identification of new targets and the contribution of their role in Ca²⁺ handling to the progression of the disease. Recent research studies have identified potential targets in three major emerging areas implicated in regulation of Ca²⁺ handling: the innate immune system, bone metabolism factors and post-translational modification of key proteins involved in regulation of Ca²⁺ handling. Here, we describe their possible contributions to the progression of HF.

Sex-Based Differences in Cardiac Gene Expression and Function in BDNF Val66Met Mice

Brain-derived neurotrophic factor (BDNF) is a pleiotropic neuronal growth and survival factor that is indispensable in the brain, as well as in multiple other tissues and organs, including the cardiovascular system. In approximately 30% of the general population, BDNF harbors a nonsynonymous single nucleotide polymorphism that may be associated with cardiometabolic disorders, coronary artery disease, and Duchenne muscular dystrophy cardiomyopathy. We recently showed that transgenic mice with the human BDNF rs6265 polymorphism (Val66Met) exhibit altered cardiac function, and that cardiomyocytes isolated from these mice are also less contractile. To identify the underlying mechanisms involved, we compared cardiac function by echocardiography and performed deep sequencing of RNA extracted from whole hearts of all three genotypes (Val/Val, Val/Met, and Met/Met) of both male and female Val66Met mice. We found female-specific cardiac alterations in both heterozygous and homozygous carriers, including increased systolic (26.8%, p = 0.047) and diastolic diameters (14.9%, p = 0.022), increased systolic (57.9%, p = 0.039) and diastolic volumes (32.7%, p = 0.026), and increased stroke volume (25.9%, p = 0.033), with preserved ejection fraction and fractional shortening. Both males and females exhibited lower heart rates, but this change was more pronounced in female mice than in males. Consistent with phenotypic observations, the gene encoding SERCA2 (Atp2a2) was reduced in homozygous Met/Met mice but more profoundly in females compared to males. Enriched functions in females with the Met allele included cardiac hypertrophy in response to stress, with down-regulation of the gene encoding titin (Tcap) and upregulation of BNP (Nppb), in line with altered cardiac functional parameters. Homozygous male mice on the other hand exhibited an inflammatory profile characterized by interferon-γ (IFN-γ)-mediated Th1 immune responses. These results provide evidence for sex-based differences in how the BDNF polymorphism modifies cardiac physiology, including female-specific alterations of cardiac-specific transcripts and male-specific activation of inflammatory targets.

Adeno-associated viral (AAV) vector-mediated therapeutics for diabetic cardiomyopathy - current and future perspectives

Diabetes increases the prevalence of heart failure by 6-8-fold, independent of other comorbidities such as hypertension and coronary artery disease, a phenomenon termed diabetic cardiomyopathy. Several key signalling pathways have been identified that drive the pathological changes associated with diabetes-induced heart failure. This has led to the development of multiple pharmacological agents that are currently available for clinical use. While fairly effective at delaying disease progression, these treatments do not reverse the cardiac damage associated with diabetes. One potential alternative avenue for targeting diabetes-induced heart failure is the use of adeno-associated viral vector (AAV) gene therapy, which has shown great versatility in a multitude of disease settings. AAV gene therapy has the potential to target specific cells or tissues, has a low host immune response and has the possibility to represent a lifelong cure, not possible with current conventional pharmacotherapies. In this review, we will assess the therapeutic potential of AAV gene therapy as a treatment for diabetic cardiomyopathy.

Increasing SERCA function promotes initiation of calcium sparks and breakup of calcium waves

KEY POINTS

Increasing sarcoplasmic/endoplasmic reticulum calcium ATPase (SERCA) pump activity enhances sarcoplasmic reticulum calcium (Ca) load, which increases both ryanodine receptor opening and driving force of Ca release flux. Both of these effects promote Ca spark formation and wave propagation. However, increasing SERCA activity also accelerates local cytosolic Ca decay as the wave front travels to the next cluster, which limits wave propagation. As a result, increasing SERCA pump activity has a biphasic effect on the propensity of arrhythmogenic Ca waves, but a monotonic effect to increase Ca spark frequency and amplitude.

ABSTRACT

Waves of sarcoplasmic reticulum (SR) calcium (Ca) release can cause arrhythmogenic afterdepolarizations in cardiac myocytes. Ca waves propagate when Ca sparks at one Ca release unit (CRU) recruit new Ca sparks in neighbouring CRUs. Under normal conditions, Ca sparks are too small to recruit neighbouring Ca sparks where Ca sensitivity is also low. However, under pathological conditions such as a Ca overload or ryanodine receptor (RyR) sensitization, Ca sparks can be larger and propagate more readily as macro-sparks or full Ca waves. Increasing SERCA pump activity promotes SR Ca load, which promotes RyR opening and increases driving force of the Ca release flux from SR to cytosol, promoting Ca waves. However, high sarcoplasmic/endoplasmic reticulum calcium ATPase (SERCA) activity can also decrease local cytosolic [Ca] as it approaches the next CRU, thereby reducing wave appearance and propagation. In this study, we use a physiologically detailed model of subcellular Ca cycling and experiments in phospholamban-knockout mice, to show how Ca waves are initiated and propagate and how different conditions contribute to the generation and propagation of Ca waves. We show that reducing diffusive coupling between Ca sparks by increasing SERCA activity prevents Ca waves by reducing [Ca] at the next CRU, as do Ca buffers, low intra-SR Ca diffusion and distance between CRUs. Increasing SR Ca uptake rate has a biphasic effect on Ca wave propagation; initially it enhances Ca spark probability and amplitude and CRU coupling, thereby promoting arrhythmogenic Ca wave propagation, but at higher levels SR Ca uptake can abort those arrhythmogenic Ca waves.

Bioengineering Technologies for Cardiac Regenerative Medicine

Cardiac regenerative medicine faces big challenges such as a lack of adult cardiac stem cells, low turnover of mature cardiomyocytes, and difficulty in therapeutic delivery to the injured heart. The interaction of bioengineering and cardiac regenerative medicine offers innovative solutions to this field. For example, cell reprogramming technology has been applied by both direct and indirect routes to generate patient-specific cardiomyocytes. Various viral and non-viral vectors have been utilized for gene editing to intervene gene expression patterns during the cardiac remodeling process. Cell-derived protein factors, exosomes, and miRNAs have been isolated and delivered through engineered particles to overcome many innate limitations of live cell therapy. Protein decoration, antibody modification, and platelet membranes have been used for targeting and precision medicine. Cardiac patches have been used for transferring therapeutics with better retention and integration. Other technologies such as 3D printing and 3D culture have been used to create replaceable cardiac tissue. In this review, we discuss recent advancements in bioengineering and biotechnologies for cardiac regenerative medicine.

Attenuation of the upregulation of NF‑κB and AP‑1 DNA‑binding activities induced by tunicamycin or hypoxia/reoxygenation in neonatal rat cardiomyocytes by SERCA2a overexpression

The present study aimed to investigate the effects of the overexpression of sarco/endoplasmic reticulum Ca2+‑ATPase (SERCA2a) on endoplasmic reticulum (ER) stress (ERS)‑associated inflammation in neonatal rat cardiomyocytes (NRCMs) induced by tunicamycin (TM) or hypoxia/reoxygenation (H/R). The optimal multiplicity of infection (MOI) was 2 pfu/cell. Neonatal Sprague‑Dawley rat cardiomyocytes cultured in vitro were infected with adenoviral vectors carrying SERCA2a or enhanced green fluorescent protein genes, the latter used as a control. At 48 h following gene transfer, the NRCMs were treated with TM (10 µg/ml) or subjected to H/R to induce ERS. The results of electrophoretic mobility shift assay (EMSA) revealed that overexpression of SERCA2a attenuated the upregulation of nuclear factor (NF)‑κB and activator protein‑1 (AP‑1) DNA‑binding activities induced by TM or H/R. Western blot analysis and semi‑quantitative RT‑PCR revealed that the overexpression of SERCA2a attenuated the activation of the inositol‑requiring 1α (IRE1α) signaling pathway and ERS‑associated apoptosis induced by TM. The overexpression of SERCA2a also decreased the level of phospho‑p65 (Ser536) in the nucleus, as assessed by western blot analysis. However, the overexpression of SERCA2a induced the further nuclear translocation of NF‑κB p65 and higher levels of tumor necrosis factor (TNF)‑α transcripts in the NRCMs, indicating the occurrence of the ER overload response (EOR). Therefore, the overexpression of SERCA2a has a 'double‑edged sword' effect on ERS‑associated inflammation. On the one hand, it attenuates ERS and the activation of the IRE1α signaling pathway induced by TM, resulting in the attenuation of the upregulation of NF‑κB and AP‑1 DNA‑binding activities in the nucleus, and on the other hand, it induces EOR, leading to the further nuclear translocation of NF‑κB and the transcription of TNF‑α. The preceding EOR may precondition the NRCMs against subsequent ERS induced by TM. Further studies using adult rat cardiomyocytes are required to prevent the interference of EOR. The findings of the present study may enhance the current understanding of the role of SERCA2a in cardiomyocytes.

A review of the underlying genetics and emerging therapies for canine cardiomyopathies

Cardiomyopathies such as dilated cardiomyopathy and arrhythmogenic right ventricular cardiomyopathy are common in large breed dogs and carry an overall poor prognosis. Research shows that these diseases have strong breed predilections, and selective breeding has historically been recommended to reduce the disease prevalence in affected breeds. Treatment of these diseases is typically palliative and aimed at slowing disease progression and managing clinical signs of heart failure as they develop. The discovery of specific genetic mutations underlying cardiomyopathies, such as the striatin mutation in Boxer arrhythmogenic right ventricular cardiomyopathy and the pyruvate dehydrogenase kinase 4 and titin mutations in Doberman Pinschers, has strengthened our ability to screen and selectively breed individuals in an attempt to produce unaffected offspring. The discovery of these disease-linked mutations has also opened avenues for the development of gene therapies, including gene transfer and genome-editing approaches. This review article discusses the known genetics of cardiomyopathies in dogs, reviews existing gene therapy strategies and the status of their development in canines, and discusses ongoing challenges in the clinical translation of these technologies for treating heart disease. While challenges remain in using these emerging technologies, the exponential growth of the gene therapy field holds great promise for future clinical applications.