Mitigation of myocardial fibrosis by molecular cardiac surgery-mediated gene overexpression

Unraveling the Cardiac Matrix: From Diabetes to Heart Failure, Exploring Pathways and Potential Medications

Myocardial infarction (MI) often leads to heart failure (HF) through acute or chronic maladaptive remodeling processes. This establishes coronary artery disease (CAD) and HF as significant contributors to cardiovascular illness and death. Therefore, treatment strategies for patients with CAD primarily focus on preventing MI and lessening the impact of HF after an MI event. Myocardial fibrosis, characterized by abnormal extracellular matrix (ECM) deposition, is central to cardiac remodeling. Understanding these processes is key to identifying new treatment targets. Recent studies highlight SGLT2 inhibitors (SGLT2i) and GLP-1 receptor agonists (GLP1-RAs) as favorable options in managing type 2 diabetes due to their low hypoglycemic risk and cardiovascular benefits. This review explores inflammation's role in cardiac fibrosis and evaluates emerging anti-diabetic medications' effectiveness, such as SGLT2i, GLP1-RAs, and dipeptidyl peptidase-4 inhibitors (DPP4i), in preventing fibrosis in patients with diabetes post-acute MI. Recent studies were analyzed to identify effective medications in reducing fibrosis risk in these patients. By addressing these areas, we can advance our understanding of the potential benefits of anti-diabetic medications in reducing cardiac fibrosis post-MI and improve patient outcomes in individuals with diabetes at risk of HF.

Sarco/endoplasmic reticulum Ca2+ ATPase (SERCA)-mediated ER stress crosstalk with autophagy is involved in tris(2-chloroethyl) phosphate stress-induced cardiac fibrosis

Excessive organophosphate flame retardant (OPFR) use in consumer products has been reported to increase human disease susceptibility. However, the adverse effects of tris(2-chloroethyl) phosphate (TCEP) (a chlorinated alkyl OPFR) on the heart remain unknown. In this study, we tested whether cardiac fibrosis occurred in animal models of TCEP (10 mg/kg b.w./day) administered continuously by gavage for 30 days and evaluated the specific role of sarco/endoplasmic reticulum Ca²⁺ ATPase (SERCA). First, we confirmed that TCEP could trigger cardiac fibrosis by histopathological observation and cardiac fibrosis markers. We further verified that cardiac fibrosis occurred in animal models of TCEP exposure accompanied by SERCA2a, SERCA2b and SERCA2c downregulation. Notably, inductively coupled plasma-mass spectrometry (ICP-MS) analysis revealed that the cardiac concentrations of Ca²⁺ increased by 45.3% after TCEP exposure. Using 4-Isopropoxy-N-(2-methylquinolin-8-yl)benzamide (CDN1163, a small molecule SERCA activator), we observed that Ca²⁺ overload and subsequent cardiac fibrosis caused by TCEP were both alleviated. Simultaneously, the protein levels of endoplasmic reticulum (ER) markers (protein kinase R-like endoplasmic reticulum kinase (PERK), inositol requiring protein 1α (IRE1α), eukaryotic initiation factor 2 α (eIF2α)) were upregulated by TCEP, which could be abrogated by CDN1163 pretreatment. Furthermore, we observed that CDN1163 supplementation prevented overactive autophagy induced by TCEP in the heart. Mechanistically, TCEP could lead to Ca²⁺ overload by inhibiting the expression of SERCA, thereby triggering ER stress and overactive autophagy, eventually resulting in cardiac fibrosis. Together, our results suggest that the Ca²⁺ overload/ER stress/autophagy axis can act as a driver of cardiotoxicity induced by TCEP.

Substitution of SERCA2 Cys674 aggravates cardiac fibrosis by promoting the transformation of cardiac fibroblasts to cardiac myofibroblasts

Sarcoplasmic/endoplasmic reticulum Ca²⁺ ATPase 2 (SERCA2) is vital to maintain intracellular calcium homeostasis, and its redox Cys⁶⁷⁴ (C674) is the key to regulating activity. Our goal was to investigate whether the redox state of SERCA2 C674 is critical for cardiac fibrosis and the mechanisms involved. Heterozygous SERCA2 C674S knock-in (SKI) mice, in which half of C674 was substituted by serine, were used to mimic the partial loss of the reactive C674 thiol in pathological conditions. In cardiac fibroblasts, the substitution of C674 thiol increased Ca²⁺ levels in cytoplasm and mitochondria, and intracellular ROS levels, and activated calcineurin/nuclear factor of activated T-lymphocytes (NFAT) pathway, increased the protein expression of profibrotic factors TGF beta 1 (TGF-β1), alpha smooth muscle actin, collagen I and collagen III, and promoted the transformation of cardiac fibroblasts to cardiac myofibroblasts, which could be reversed by calcineurin/NFAT inhibitor, SERCA2 agonist, or ROS scavenger. Activation of SERCA2 or scavenging ROS is beneficial to alleviate cardiac fibrosis caused by the substitution of C674. In conclusion, the partial loss of the reactive C674 thiol in the SERCA2 exacerbates cardiac fibrosis by activating the calcineurin/NFAT/TGF-β1 pathway to promote the transformation of cardiac fibroblasts to cardiac myofibroblasts, which highlights the importance of C674 redox state in maintaining the homeostasis of cardiac fibroblasts. SERCA2 is a potential therapeutic target for the treatment of cardiac fibrosis.

Impact of oxidative posttranslational modifications of SERCA2 on heart failure exacerbation in young patients with non-ischemic cardiomyopathy: A pilot study

BACKGROUND

Oxidative posttranslational modifications (OPTM) impair the function of Sarcoplasmic/endoplasmic reticulum (SR) calcium (Ca2+) ATPase (SERCA) 2 and trigger cytosolic Ca2+ dysregulation. We investigated the extent of OPTM of SERCA2 in patients with non-ischemic cardiomyopathy (NICM).

METHODS AND RESULTS

Endomyocardial biopsy (EMB) was obtained in 40 consecutive patients with NICM. Total expression and OPTM of SERCA2, including sulfonylation at cysteine-674 (S-SERCA2) and nitration at tyrosine-294/295 (N-SERCA2), were examined by immunohistochemical analysis. S-SERCA2 increased in the presence of late gadolinium enhancement on cardiac magnetic resonance imaging. S-SERCA2/SERCA2 and N-SERCA2/SERCA2 correlated with cardiac fibrosis evaluated by Masson's trichrome staining of EMB. SERCA2 expression modestly increased in parallel with an upward trend in OPTM of SERCA2 with aging. This tendency became prominent only in patients aged >65 years. OPTM of SERCA2 positively correlated with brain natriuretic peptide (BNP) values only in patients aged ≤65 years. Composite major adverse cardiac events (MACE) increased more in the high OPTM group of younger patients; however, MACE-free survival was similar irrespective of the extent of OPTM in older patients.

CONCLUSIONS

OPTM of SERCA2 correlate with myocardial fibrosis in NICM. In younger patients, OPTM of SERCA2 correlate with elevated BNP and increased composite MACE.

Effects of genetic transfection on calcium cycling pathways mediated by double-stranded adeno-associated virus in postinfarction remodeling

OBJECTIVE

Restoring calcium sensor protein (S100A1) activity in failing hearts poses a promising therapeutic strategy. We hypothesize that cardiac overexpression of the S100A1 gene mediated by a double-stranded adeno-associated virus (scAAV) results in better functional and molecular improvements compared with the single-stranded virus (ssAAV).

METHODS

Heart failure was induced by coronary artery ligation. Then, intramyocardial injections of saline, AAV9 empty capsid, scAAV9.S100A1, and ssAAV9.S100A1 were performed. Ten weeks postinfarction, all rats received cardiac evaluation; serum and tissue were collected for genetic analysis, cytokine profiling, and assessments of mitochondrial function and structure.

RESULTS

Overexpression of AAV9.S100A1 improved systolic and diastolic function. Compared with control, ejection fraction was greater in treated groups (54.8% vs 32.3%, P < .05). Similarly, end-diastolic volume index was significantly less in the treated group than in control (1.14 vs 1.59 mL/cm²), whereas fractional shortening was greater in treated groups than control (26% vs 38%, P < .05). Interestingly, cardiac mechanics were significantly better when treated with double-stranded virus compared with single-stranded. Quantitative polymerase chain reaction demonstrated robust transfection of myocardium with the S100A1 gene, with more infection in the self-complimentary group compared with the single-stranded group (5.68 ± 0.44 vs 4.09 ± 0.25 log₁₀ genome copies per 100 ng of DNA; P < .0001). Concentrations of the inflammatory cytokines were elevated in the ssAAV9/S100A1 group compared with the scAAV9/S100A1. Assessment of mitochondrial respiration and morphology demonstrated that injection of self-complementary vector saved both mitochondrial structure and function.

CONCLUSIONS

Gene therapy of S100A1 can prevent pathologic postmyocardial infarction remodeling and decrease inflammatory response in ischemic heart failure.

Human Cardiac Gene Therapy

In the past 10 years, there has been tremendous progress made in the field of gene therapy. Effective treatments of Leber congenital amaurosis, hemophilia, and spinal muscular atrophy have been largely based on the efficiency and safety of adeno-associated vectors. Myocardial gene therapy has been tested in patients with heart failure using adeno-associated vectors with no safety concerns but lacking clinical improvements. Cardiac gene therapy is adapting to the new developments in vectors, delivery systems, targets, and clinical end points and is poised for success in the near future.

Analysis of recombinant adeno-associated viral vector shedding in sheep following intracoronary delivery

Differences between mouse and human hearts pose a significant limitation to the value of small animal models when predicting vector behavior following recombinant adeno-associated viral (rAAV) vector-mediated cardiac gene therapy. Hence, sheep have been adopted as a preclinical animal, as they better model the anatomy and cardiac physiological processes of humans. There is, however, no comprehensive data on the shedding profile of rAAV in sheep following intracoronary delivery, so as to understand biosafety risks in future preclinical and clinical applications. In this study, sheep received intracoronary delivery of rAAV serotypes 2/6 (2 × 10¹² vg), 2/8, and 2/9 (1 × 10¹³ vg) at doses previously administered in preclinical and clinical trials. This was followed by assessment over 96 h to examine vector shedding in urine, feces, nasal mucus, and saliva samples. Vector genomes were detected via real-time quantitative PCR in urine and feces up to 48 and 72 h post vector delivery, respectively. Of these results, functional vector particles were only detected via a highly sensitive infectious replication assay in feces samples up to 48 h following vector delivery. We conclude that rAAV-mediated gene transfer into sheep hearts results in low-grade shedding of non-functional vector particles for all excreta samples, except in the case of feces, where functional vector particles are present up to 48 h following vector delivery. These results may be used to inform containment and decontamination guidelines for large animal dealings, and to understand the biosafety risks associated with future preclinical and clinical uses of rAAV.

Primary Effect of SERCA 2a Gene Transfer on Conduction Reserve in Chronic Myocardial Infarction

Background SERCA 2a gene transfer ( GT ) improves mechano-electrical function in animal models of nonischemic heart failure Whether SERCA 2a GT reverses pre-established remodeling at an advanced stage of ischemic heart failure is unclear. We sought to uncover the electrophysiological effects of adeno-associated virus serotype 1. SERCA 2a GT following myocardial infarction ( MI ). Methods and Results Pigs developed mechanical dysfunction 1 month after anterior MI , at which point they received intracoronary adeno-associated virus serotype 1. SERCA 2a ( MI + SERCA 2a) or saline ( MI ) and were maintained for 2 months. Age-matched naive pigs served as controls (Control). In vivo ECG -and-hemodynamic properties were assessed before and after dobutamine stress. The electrophysiological substrate was measured using optical action potential ( AP ) mapping in controls, MI , and MI + SERCA 2a preparations. In vivo ECG measurements revealed comparable QT durations between groups. In contrast, prolonged QRS duration and increased frequency of R' waves were present in MI but not MI + SERCA 2a pigs relative to controls. SERCA 2a GT reduced in in vivo arrhythmias in response to dobutamine. Ex vivo preparations from MI but not MI + SERCA 2a or control pigs were prone to pacing-induced ventricular tachycardia and fibrillation. Underlying these arrhythmias was pronounced conduction velocity slowing in MI versus MI + SERCA 2a at elevated rates leading to ventricular tachycardia and fibrillation. Reduced susceptibility to ventricular tachycardia and fibrillation in MI + SERCA 2a pigs was not related to hemodynamic function, contractile reserve, fibrosis, or the expression of Cx43 and Nav1.5. Rather, SERCA 2a GT decreased phosphoactive CAMKII -delta levels by >50%, leading to improved excitability at fast rates. Conclusions SERCA 2a GT increases conduction velocity reserve, likely by preventing CAMKII overactivation. Our findings suggest a primary effect of SERCA 2a GT on myocardial excitability, independent of altered mechanical function.

Technique of Complete Heart Isolation with Continuous Cardiac Perfusion During Cardiopulmonary Bypass: New Opportunities for Gene Therapy

Cardiopulmonary bypass (CPB) featuring complete heart isolation and continuous cardiac perfusion is a very promising approach for solving the problem of efficient gene delivery. In the technique presented here, separate pumps are used for the systemic and cardiac circuits. This system permits continuous isolated arrested heart perfusion through optimizing a number of delivery parameters including temperature, flow rate, driving pressure, ionic composition, and exposure time to the cardiac vessels. During complete cardiac isolation, the blood vector concentration trended from 11.51 ± 1.73 log genome copies (GCs)/cm³ to 9.84 ± 1.65 log GC/cm³ (p > .05). Despite restructuring a very high concentration to the heart, GCs were detectable in the systemic circuit. These values over time were near negligible by comparison but detectable 1.66 ± .26 during 20 minutes of recirculation and did not change (p > .05). After the completion of the recirculation interval and subsequent washing procedure, the initial systemic blood vector GC concentration slightly increased to 2.08 ± .38 log GCs/cm³ (p > .05). During the recirculation period, we supported flow via the cardiac circuit around 300 mL/min. In this technique of heart isolation with continuous cardiac perfusion, >99% of the vector remains in coronary circulation during recirculation period. The animal's non recirculation blood, or that in the system, was routinely tested during and after recirculation to contain much less than 1% of the original dose obtained via logging concentration of therapeutic over time. All of the sheep in this group recovered from anesthesia and received critical postoperative care, including all organ function, in the first 24-36 hours. Twenty-one sheep (84%) survived to euthanasia at 12 weeks. Average CPB time was 107 ± 19.0 minutes and cross-clamp time was 49 ± 7.9 minutes. This technology readily provides multiple pass recirculation of genes through the heart with minimal side effects of collateral expression of other organs.

Adeno-Associated Virus Gene Therapy: Translational Progress and Future Prospects in the Treatment of Heart Failure

Despite advances in treatment over the past decade, heart failure remains a significant public health burden and a leading cause of death in the developed world. Gene therapy provides a promising approach for preventing and reversing cardiac abnormalities, however, clinical application has shown limited success to date. A substantial effort is being invested into the development of recombinant adeno-associated viruses (AAVs) for cardiac gene therapy as AAV gene therapy offers a high safety profile and provides sustained and efficient transgene expression following a once-off administration. Due to the physiological, anatomical and genetic similarities between large animals and humans, preclinical studies using large animal models for AAV gene therapy are crucial stepping stones between the laboratory and the clinic. Many molecular targets selected to treat heart failure using AAV gene therapy have been chosen because of their potential to regulate and restore cardiac contractility. Other genes targeted with AAV are involved with regulating angiogenesis, beta-adrenergic sensitivity, inflammation, physiological signalling and metabolism. While significant progress continues to be made in the field of AAV cardiac gene therapy, challenges remain in overcoming host neutralising antibodies, improving AAV vector cardiac-transduction efficiency and selectivity, and optimising the dose, route and method of delivery.

Use of Adeno-Associated Virus Vector for Cardiac Gene Delivery in Large-Animal Surgical Models of Heart Failure

The advancement of gene therapy-based approaches to treat heart disease represents a need for clinically relevant animal models with characteristics equivalent to human pathologies. Rodent models of cardiac disease do not precisely reproduce heart failure phenotype and molecular defects. This has motivated researchers to use large animals whose heart size and physiological processes more similar and comparable to those of humans. Today, adeno-associated viruses (AAV)-based vectors are undoubtedly among the most promising DNA delivery vehicles. Here, AAV biology and technology are reviewed and discussed in the context of their use and efficacy for cardiac gene delivery in large-animal models of heart failure, using different surgical approaches. The remaining challenges and opportunities for the use of AAV-based vector delivery for gene therapy applications in the clinic are also highlighted.

Cardiac gene therapy with adeno-associated virus-based vectors

PURPOSE OF REVIEW

Cardiac gene therapy with adeno-associated virus (AAV)-based vectors is emerging as an entirely new platform to treat, or even cure, so far intractable cardiac disorders. This review describes our current knowledge of cardiac AAV gene therapy with a particular focus on the biggest obstacle for the successful translation of cardiac AAV gene therapy into the clinic, namely the efficient delivery of the therapeutic gene to the myocardium.

RECENT FINDINGS

We summarize the significant recent progress that has been made in treating heart failure in preclinically relevant animal models with AAV gene therapy and the recent results of clinical trials with cardiac AAV gene therapy for the treatment of heart failure. We also discuss the benefits and shortcomings of the currently available delivery methods of AAV to the heart. Finally, we describe the current state of identifying novel AAV variants that have enhanced tropism for human cardiomyocytes and that show increased resistance to preexisting neutralizing antibodies.

SUMMARY

Here, we describe the successes and challenges in cardiac AAV gene therapy, a treatment modality that has the potential to transform current treatment approaches for cardiac diseases.

Sex Differences in Metabolic Cardiomyopathy

In contrast to ischemic cardiomyopathies which are more common in men, women are over-represented in diabetic cardiomyopathies. Diabetes is a risk factor for cardiovascular disease; however, there is a sexual dimorphism in this risk factor: heart disease is five times more common in diabetic women but only two-times more common in diabetic men. Heart failure with preserved ejection fraction, which is associated with metabolic syndrome, is also more prevalent in women. This review will examine potential mechanisms for the sex differences in metabolic cardiomyopathies. Sex differences in metabolism, calcium handling, nitric oxide, and structural proteins will be evaluated. Nitric oxide synthase and PPARα exhibit sex differences and have also been proposed to mediate the development of hypertrophy and heart failure. We focused on a role for these signalling pathways in regulating sex differences in metabolic cardiomyopathies.

Gene Therapy in Heart Failure

Heart failure is a significant burden to the global healthcare system and represents an underserved market for new pharmacologic strategies, especially therapies which can address root cause myocyte dysfunction. Modern drugs, surgeries, and state-of-the-art interventions are costly and do not improve survival outcome measures. Gene therapy is an attractive strategy, whereby selected gene targets and their associated regulatory mechanisms can be permanently managed therapeutically in a single treatment. This in theory could be sustainable for the patient's life. Despite the promise, however, gene therapy has numerous challenges that must be addressed together as a treatment plan comprising these key elements: myocyte physiologic target validation, gene target manipulation strategy, vector selection for the correct level of manipulation, and carefully utilizing an efficient delivery route that can be implemented in the clinic to efficiently transfer the therapy within safety limits. This chapter summarizes the key developments in cardiac gene therapy from the perspective of understanding each of these components of the treatment plan. The latest pharmacologic gene targets, gene therapy vectors, delivery routes, and strategies are reviewed.