Efficacy and safety of myocardial gene transfer of adenovirus, adeno-associated virus and lentivirus vectors in the mouse heart

Monitoring and modulating cardiac bioelectricity: from Einthoven to end-user

In 2024, we celebrate the 100th anniversary of Willem Einthoven receiving the Nobel Prize for his discovery of the mechanism of the electrocardiogram (ECG). Building on Einthoven's legacy, electrocardiography allows the monitoring of cardiac bioelectricity through solutions to the so-called forward and inverse problems. These solutions link local cardiac electrical signals with the morphology of the ECG, offering a reversible connection between the heart's electrical activity and its representation on the body surface. Inspired by Einthoven's work, researchers have explored the transition from monitoring to modulation of bioelectrical activity in the heart for the development of new anti-arrhythmic strategies, e.g. via optogenetics. In this review, we demonstrate the lasting influence that Einthoven has on our understanding of cardiac electrophysiology in general, and the diagnosis and treatment of cardiac arrhythmias in particular.

Optoelectronic control of cardiac rhythm: Toward shock-free ambulatory cardioversion of atrial fibrillation

Atrial fibrillation (AF) is the most prevalent cardiac arrhythmia, progressive in nature, and known to have a negative impact on mortality, morbidity, and quality of life. Patients requiring acute termination of AF to restore sinus rhythm are subjected to electrical cardioversion, which requires sedation and therefore hospitalization due to pain resulting from the electrical shocks. However, considering the progressive nature of AF and its detrimental effects, there is a clear need for acute out-of-hospital (i.e., ambulatory) cardioversion of AF. In the search for shock-free cardioversion methods to realize such ambulatory therapy, a method referred to as optogenetics has been put forward. Optogenetics enables optical control over the electrical activity of cardiomyocytes by targeted expression of light-activated ion channels or pumps and may therefore serve as a means for cardioversion. First proof-of-principle for such light-induced cardioversion came from in vitro studies, proving optogenetic AF termination to be very effective. Later, these results were confirmed in various rodent models of AF using different transgenes, illumination methods, and protocols, whereas computational studies in the human heart provided additional translational insight. Based on these results and fueled by recent advances in molecular biology, gene therapy, and optoelectronic engineering, a basis is now being formed to explore clinical translations of optoelectronic control of cardiac rhythm. In this review, we discuss the current literature regarding optogenetic cardioversion of AF to restore normal rhythm in a shock-free manner. Moreover, key translational steps will be discussed, both from a biological and technological point of view, to outline a path toward realizing acute shock-free ambulatory termination of AF.

Caridac vein retroinjections provide an efficient approach for global left ventricular gene transfer with adenovirus and adeno-associated virus

Heart failure (HF) is a major burden worldwide, and new therapies are urgently needed. Gene therapy is a promising new approach to treat myocardial diseases. However, current cardiac gene delivery methods for producing global myocardial effects have been inefficient. The aim of this study was to develop an endovascular, reproducible, and clinically applicable gene transfer method for global left ventricular (LV) transduction. Domestic pigs (n = 52) were used for the experiments. Global LV myocardium coverage was achieved by three retrograde injections into the three main LV vein branches. The distribution outcome was significantly improved by simultaneous transient occlusions of the corresponding coronary arteries and the main anastomotic veins of the retroinjected veins. The achieved cardiac distribution was visualized first by administering Indian Ink solution. Secondly, AdLacZ (2 × 1012vp) and AAV2-GFP (2 × 1013vg) gene transfers were performed to study gene transduction efficacy of the method. By retrograde injections with simultaneous coronary arterial occlusions, both adenovirus (Ad) and adeno-associated virus (AAV) vectors were shown to deliver an efficient transduction of the LV. We conclude that retrograde injections into the three main LV veins is a potential new approach for a global LV gene transfer.

p38γ/δ activation alters cardiac electrical activity and predisposes to ventricular arrhythmia

Ventricular fibrillation (VF) is a leading immediate cause of sudden cardiac death. There is a strong association between aging and VF, although the mechanisms are unclear, limiting the availability of targeted therapeutic interventions. Here we found that the stress kinases p38γ and p38δ are activated in the ventricles of old mice and mice with genetic or drug-induced arrhythmogenic conditions. We discovered that, upon activation, p38γ and p38δ cooperatively increase the susceptibility to stress-induced VF. Mechanistically, our data indicate that activated p38γ and p38δ phosphorylate ryanodine receptor 2 (RyR2) disrupt Kv4.3 channel localization, promoting sarcoplasmic reticulum calcium leak, Ito current reduction and action potential duration prolongation. In turn, this led to aberrant intracellular calcium handling, premature ventricular complexes and enhanced susceptibility to VF. Blocking this pathway protected genetically modified animals from VF development and reduced the VF duration in aged animals. These results indicate that p38γ and p38δ are a potential therapeutic target for sustained VF prevention.

CREB-binding protein and HIF-1α/β-catenin to upregulate miR-322 and alleviate myocardial ischemia-reperfusion injury

Myocardial ischemia/reperfusion injury (MIRI) is a prevalent condition associated with numerous critical clinical conditions. miR-322 has been implicated in MIRI through poorly understood mechanisms. Our preliminary analysis indicated potential interaction of CREB-binding protein (CBP), a transcriptional coactivator and acetyltransferase, with HIF-1α/β-catenin, which might regulate miR-322 expression. We, therefore, hypothesized that CBP/HIF-1α/β-catenin/miR-322 axis might play a role in MIRI. Rat cardiomyocytes subjected to oxygen-glucose deprivation /reperfusion (OGD/R) and Langendorff perfused heart model were used to model MIRI in vitro and in vivo, respectively. We used various techniques such as CCK-8 assay, transferase dUTP nick end labeling staining, western blotting, RT-qPCR, chromatin immunoprecipitation (ChIP), dual-luciferase assay, co-immunoprecipitation (Co-IP), hematoxylin and eosin staining, and TTC staining to assess cell viability, apoptosis, and the levels of CBP, HIF-1α, β-catenin, miR-322, and acetylation. Our results indicate that OGD/R in cardiomyocytes decreased CBP/HIF-1α/β-catenin/miR-322 expression, increased cell apoptosis and cytokines, and reduced cell viability. However, overexpression of CBP or miR-322 suppressed OGD/R-induced cell injury, while knockdown of HIF-1α/β-catenin further exacerbated the damage. HIF-1α/β-catenin bound to miR-322 promoter to promote its expression, while CBP acetylated HIF-1α/β-catenin for stabilization. Overexpression of CBP attenuated MIRI in rats by acetylating HIF-1α/β-catenin to stabilize their expression, resulting in stronger binding of HIF-1α/β-catenin with the miR-322 promoter and subsequent increased miR-322 levels. Therefore, activating CBP/HIF-1α/β-catenin/miR-322 signaling may be a potential approach to treat MIRI.

Harnessing cell reprogramming for cardiac biological pacing

Electrical impulses from cardiac pacemaker cardiomyocytes initiate cardiac contraction and blood pumping and maintain life. Abnormal electrical impulses bring patients with low heart rates to cardiac arrest. The current therapy is to implant electronic devices to generate backup electricity. However, complications inherent to electronic devices remain unbearable suffering. Therefore, cardiac biological pacing has been developed as a hardware-free alternative. The approaches to generating biological pacing have evolved recently using cell reprogramming technology to generate pacemaker cardiomyocytes in-vivo or in-vitro. Different from conventional methods by electrical re-engineering, reprogramming-based biological pacing recapitulates various phenotypes of de novo pacemaker cardiomyocytes and is more physiological, efficient, and easy for clinical implementation. This article reviews the present state of the art in reprogramming-based biological pacing. We begin with the rationale for this new approach and review its advances in creating a biological pacemaker to treat bradyarrhythmia.

Targeting and delivery of microRNA-targeting antisense oligonucleotides in cardiovascular diseases

Discovered three decades ago, microRNAs (miRNAs) are now recognized as key players in the pathophysiology of multiple human diseases, including those affecting the cardiovascular system. As such, miRNAs have emerged as promising therapeutic targets for preventing the onset and/or progression of several cardiovascular diseases. Anti-miRNA antisense oligonucleotides or "antagomirs" precisely block the activity of specific miRNAs and are therefore a promising therapeutic strategy to repress pathological miRNAs. In this review, we describe advancements in antisense oligonucleotide chemistry that have significantly improved efficacy and safety. Moreover, we summarize recent approaches for the targeted delivery of antagomirs to cardiovascular tissues, highlighting major advantages as well as limitations of viral (i.e., adenovirus, adeno-associated virus, and lentivirus) and non-viral (i.e., liposomes, extracellular vesicles, and polymer nanoparticles) delivery systems. We discuss recent preclinical studies that use targeted antagomir delivery systems to treat three major cardiovascular diseases (atherosclerosis, myocardial infarction, and cardiac hypertrophy, including hypertrophy caused by hypertension), highlighting therapeutic results and discussing challenges that limit clinical applicability.

OSMR deficiency aggravates pressure overload-induced cardiac hypertrophy by modulating macrophages and OSM/LIFR/STAT3 signalling

BACKGROUND

Oncostatin M (OSM) is a secreted cytokine of the interleukin (IL)-6 family that induces biological effects by activating functional receptor complexes of the common signal transducing component glycoprotein 130 (gp130) and OSM receptor β (OSMR) or leukaemia inhibitory factor receptor (LIFR), which are mainly involved in chronic inflammatory and cardiovascular diseases. The effect and underlying mechanism of OSM/OSMR/LIFR on the development of cardiac hypertrophy remains unclear.

METHODS AND RESULTS

OSMR-knockout (OSMR-KO) mice were subjected to aortic banding (AB) surgery to establish a model of pressure overload-induced cardiac hypertrophy. Echocardiographic, histological, biochemical and immunological analyses of the myocardium and the adoptive transfer of bone marrow-derived macrophages (BMDMs) were conducted for in vivo studies. BMDMs were isolated and stimulated with lipopolysaccharide (LPS) for the in vitro study. OSMR deficiency aggravated cardiac hypertrophy, fibrotic remodelling and cardiac dysfunction after AB surgery in mice. Mechanistically, the loss of OSMR activated OSM/LIFR/STAT3 signalling and promoted a proresolving macrophage phenotype that exacerbated inflammation and impaired cardiac repair during remodelling. In addition, adoptive transfer of OSMR-KO BMDMs to WT mice after AB surgery resulted in a consistent hypertrophic phenotype. Moreover, knockdown of LIFR in myocardial tissue with Ad-shLIFR ameliorated the effects of OSMR deletion on the phenotype and STAT3 activation.

CONCLUSIONS

OSMR deficiency aggravated pressure overload-induced cardiac hypertrophy by modulating macrophages and OSM/LIFR/STAT3 signalling, which provided evidence that OSMR might be an attractive target for treating pathological cardiac hypertrophy and heart failure.

AAV2-VEGF-B gene therapy failed to induce angiogenesis in ischemic porcine myocardium due to inflammatory responses

Therapeutic angiogenesis induced by gene therapy is a promising approach to treat patients suffering from severe coronary artery disease. In small experimental animals, adeno-associated viruses (AAVs) have shown good transduction efficacy and long-term transgene expression in heart muscle and other tissues. However, it has been difficult to achieve cardiac-specific angiogenic effects with AAV vectors. We tested the hypothesis whether AAV2 gene transfer (1 × 1013 vg) of vascular endothelial growth factor B (VEGF-B186) together with immunosuppressive corticosteroid treatment can induce long-term cardiac-specific therapeutic effects in the porcine ischemic heart. Gene transfers were delivered percutaneously using direct intramyocardial injections, improving targeting and avoiding direct contact with blood, thus reducing the likelihood of immediate immune reactions. After 1- and 6-month time points, the capillary area was analyzed, myocardial perfusion reserve (MPR) was measured with radiowater positron emission tomography ([15O]H2O-PET), and fluorodeoxyglucose ([18F]FDG) uptake was used to evaluate myocardial viability. Clinical chemistry and immune responses were analyzed using standard methods. After 1- and 6-month follow-up, AAV2-VEGF-B186 gene transfer failed to induce angiogenesis and improve myocardial perfusion and viability. Here, we show that inflammatory responses attenuated the therapeutic effect of AAV2 gene transfer by significantly reducing successful transduction and long-term gene expression despite the efforts to reduce the likelihood of immune reactions and the use of targeted local gene transfer methods.

Cardiac Fibroblast Growth Factor 23 Excess Does Not Induce Left Ventricular Hypertrophy in Healthy Mice

Fibroblast growth factor (FGF) 23 is elevated in chronic kidney disease (CKD) to maintain phosphate homeostasis. FGF23 is associated with left ventricular hypertrophy (LVH) in CKD and induces LVH via klotho-independent FGFR4-mediated activation of calcineurin/nuclear factor of activated T cells (NFAT) signaling in animal models, displaying systemic alterations possibly contributing to heart injury. Whether elevated FGF23 per se causes LVH in healthy animals is unknown. By generating a mouse model with high intra-cardiac Fgf23 synthesis using an adeno-associated virus (AAV) expressing murine Fgf23 (AAV-Fgf23) under the control of the cardiac troponin T promoter, we investigated how cardiac Fgf23 affects cardiac remodeling and function in C57BL/6 wild-type mice. We report that AAV-Fgf23 mice showed increased cardiac-specific Fgf23 mRNA expression and synthesis of full-length intact Fgf23 (iFgf23) protein. Circulating total and iFgf23 levels were significantly elevated in AAV-Fgf23 mice compared to controls with no difference in bone Fgf23 expression, suggesting a cardiac origin. Serum of AAV-Fgf23 mice stimulated hypertrophic growth of neonatal rat ventricular myocytes (NRVM) and induced pro-hypertrophic NFAT target genes in klotho-free culture conditions in vitro. Further analysis revealed that renal Fgfr1/klotho/extracellular signal-regulated kinases 1/2 signaling was activated in AAV-Fgf23 mice, resulting in downregulation of sodium-phosphate cotransporter NaPi2a and NaPi2c and suppression of Cyp27b1, further supporting the bioactivity of cardiac-derived iFgf23. Of interest, no LVH, LV fibrosis, or impaired cardiac function was observed in klotho sufficient AAV-Fgf23 mice. Verified in NRVM, we show that co-stimulation with soluble klotho prevented Fgf23-induced cellular hypertrophy, supporting the hypothesis that high cardiac Fgf23 does not act cardiotoxic in the presence of its physiological cofactor klotho. In conclusion, chronic exposure to elevated cardiac iFgf23 does not induce LVH in healthy mice, suggesting that Fgf23 excess per se does not tackle the heart.

Targeting cardiomyocyte proliferation as a key approach of promoting heart repair after injury

Cardiovascular diseases such as myocardial infarction (MI) is a major contributor to human mortality and morbidity. The mammalian adult heart almost loses its plasticity to appreciably regenerate new cardiomyocytes after injuries, such as MI and heart failure. The neonatal heart exhibits robust proliferative capacity when exposed to varying forms of myocardial damage. The ability of the neonatal heart to repair the injury and prevent pathological left ventricular remodeling leads to preserved or improved cardiac function. Therefore, promoting cardiomyocyte proliferation after injuries to reinitiate the process of cardiomyocyte regeneration, and suppress heart failure and other serious cardiovascular problems have become the primary goal of many researchers. Here, we review recent studies in this field and summarize the factors that act upon the proliferation of cardiomyocytes and cardiac repair after injury and discuss the new possibilities for potential clinical treatment strategies for cardiovascular diseases.

Applications and developments of gene therapy drug delivery systems for genetic diseases

Genetic diseases seriously threaten human health and have always been one of the refractory conditions facing humanity. Currently, gene therapy drugs such as siRNA, shRNA, antisense oligonucleotide, CRISPR/Cas9 system, plasmid DNA and miRNA have shown great potential in biomedical applications. To avoid the degradation of gene therapy drugs in the body and effectively deliver them to target tissues, cells and organelles, the development of excellent drug delivery vehicles is of utmost importance. Viral vectors are the most widely used delivery vehicles for gene therapy in vivo and in vitro due to their high transfection efficiency and stable transgene expression. With the development of nanotechnology, novel nanocarriers are gradually replacing viral vectors, emerging superior performance. This review mainly illuminates the current widely used gene therapy drugs, summarizes the viral vectors and non-viral vectors that deliver gene therapy drugs, and sums up the application of gene therapy to treat genetic diseases. Additionally, the challenges and opportunities of the field are discussed from the perspective of developing an effective nano-delivery system.

Dihydrolycorine Attenuates Cardiac Fibrosis and Dysfunction by Downregulating Runx1 following Myocardial Infarction

In spite of early interventions to treat acute myocardial infarction (MI), the occurrence of adverse cardiac remodeling following heart failure due to acute MI remains a clinical challenge. Thus, there is an increasing demand for the development of novel therapeutic agents capable of inhibiting the development of pathological ventricular remodeling. RNA-seq data analysis of acute MI rat models from GEO revealed that Runx1 was the most differentially expressed MI-related gene. In this study, we demonstrated that increased Runx1 expression under pathological conditions results in decreased cardiac contractile function. We identified dihydrolycorine, an alkaloid lycorine, as a promising inhibitor of Runx1. Our results showed that treatment with this drug could prevent adverse cardiac remodeling, as indicated by the downregulation of fibrotic genes using western blotting (collagen I, TGFβ, and p-smad3), downregulation of the apoptosis gene Bax, upregulation of the apoptosis gene Bcl-2, and improved cardiac functions, such as LVEF, LVSF, LVESD, and LVEDD. Additionally, dihydrolycorine treatment could rescue cardiomyocyte hypertrophy as demonstrated by wheat germ agglutinin staining, increased expression levels of the punctuate gap junction protein connexin 43, and decreased α-SMA expression, resulting in cardiomyocyte fibrosis in immunofluorescence staining. Molecular docking, binding modeling, and pull-down assays were used to identify potential dihydrolycorine-binding sites in Runx1. When Ad-sh-Runx1 was transfected into hypoxia-cardiomyocytes or injected into the hearts of MI rats, the cardioprotective effects of dihydrolycorine were abolished, and the normal electrophysiological activity of cardiomyocytes was disrupted. Taken together, the results of the present study indicate that dihydrolycorine may inhibit adverse cardiac remodeling after MI through the reduction of Runx1, suggesting that dihydrolycorine-mediated-Runx1 regulation might represent a novel therapeutic approach for adverse cardiac remodeling after MI.

Recent Advances in the Development of Exogenous dsRNA for the Induction of RNA Interference in Cancer Therapy

Selective regulation of gene expression by means of RNA interference has revolutionized molecular biology. This approach is not only used in fundamental studies on the roles of particular genes in the functioning of various organisms, but also possesses practical applications. A variety of methods are being developed based on gene silencing using dsRNA-for protecting agricultural plants from various pathogens, controlling insect reproduction, and therapeutic techniques related to the oncological disease treatment. One of the main problems in this research area is the successful delivery of exogenous dsRNA into cells, as this can be greatly affected by the localization or origin of tumor. This overview is dedicated to describing the latest advances in the development of various transport agents for the delivery of dsRNA fragments for gene silencing, with an emphasis on cancer treatment.

High Levels of Frataxin Overexpression Lead to Mitochondrial and Cardiac Toxicity in Mouse Models

Friedreich ataxia (FA) is currently an incurable inherited mitochondrial disease caused by reduced levels of frataxin (FXN). Cardiac dysfunction is the main cause of premature death in FA. Adeno-associated virus (AAV)-mediated gene therapy constitutes a promising approach for FA, as demonstrated in cardiac and neurological mouse models. While the minimal therapeutic level of FXN protein to be restored and biodistribution have recently been defined for the heart, it is unclear if FXN overexpression could be harmful. Indeed, depending on the vector delivery route and dose administered, the resulting FXN protein level could reach very high levels in the heart, cerebellum, or off-target organs such as the liver. The present study demonstrates safety of FXN cardiac overexpression up to 9-fold the normal endogenous level but significant toxicity to the mitochondria and heart above 20-fold. We show gradual severity with increasing FXN overexpression, ranging from subclinical cardiotoxicity to left ventricle dysfunction. This appears to be driven by impairment of the mitochondria respiratory chain and ultrastructure, which leads to cardiomyocyte subcellular disorganization, cell death, and fibrosis. Overall, this study underlines the need, during the development of gene therapy approaches, to consider appropriate vector expression level, long-term safety, and biomarkers to monitor such events.

Efficient in Utero Gene Transfer to the Mammalian Inner Ears by the Synthetic Adeno-Associated Viral Vector Anc80L65

Sensorineural hearing loss is one of the most common sensory disorders worldwide. Recent advances in vector design have paved the way for investigations into the use of adeno-associated vectors (AAVs) for hearing disorder gene therapy. Numerous AAV serotypes have been discovered to be applicable to inner ears, constituting a key advance for gene therapy for sensorineural hearing loss, where transduction efficiency of AAV in inner ear cells is critical for success. One such viral vector, AAV2/Anc80L65, has been shown to yield high expression in the inner ears of mice treated as neonates or adults. Here, to evaluate the feasibility of prenatal gene therapy for deafness, we assessed the transduction efficiency of AAV2/Anc80L65-eGFP (enhanced green fluorescent protein) after microinjection into otocysts in utero. This embryonic delivery method achieved high transduction efficiency in both inner and outer hair cells of the cochlea. Additionally, the transduction efficiency was high in the hair cells of the vestibules and semicircular canals and in spiral ganglion neurons. Our results support the potential of Anc80L65 as a gene therapy vehicle for prenatal inner ear disorders.

Biology of Tissue Inhibitor of Metalloproteinase 3 (TIMP3), and Its Therapeutic Implications in Cardiovascular Pathology

Tissue inhibitor of metalloproteinase 3 (TIMP3) is unique among the four TIMPs due to its extracellular matrix (ECM)-binding property and broad range of inhibitory substrates that includes matrix metalloproteinases (MMPs), a disintegrin and metalloproteinases (ADAMs), and ADAM with thrombospondin motifs (ADAMTSs). In addition to its metalloproteinase-inhibitory function, TIMP3 can interact with proteins in the extracellular space resulting in its multifarious functions. TIMP3 mRNA has a long 3' untranslated region (UTR) which is a target for numerous microRNAs. TIMP3 levels are reduced in various cardiovascular diseases, and studies have shown that TIMP3 replenishment ameliorates the disease, suggesting a therapeutic potential for TIMP3 in cardiovascular diseases. While significant efforts have been made in identifying the effector targets of TIMP3, the regulatory mechanism for the expression of this multi-functional TIMP has been less explored. Here, we provide an overview of TIMP3 gene structure, transcriptional and post-transcriptional regulators (transcription factors and microRNAs), protein structure and partners, its role in cardiovascular pathology and its application as therapy, while also drawing reference from TIMP3 function in other diseases.

Molecular Mechanism of HSF1-Upregulated ALDH2 by PKC in Ameliorating Pressure Overload-Induced Heart Failure in Mice

Evidences abound that HSF1 and ALDH2 are of cardioprotective effect, yet there is still no report on whether HSF1 can regulate ALDH2 to delay the occurrence of heart failure. We first established the pressure overload-induced heart failure model of mice by transverse aortic constriction (TAC) and discovered that, in the forming period of heart failure, changes of HSF1 and ALDH2 expression recorded the consistent trend. When HSF1 was upregulated/downregulated to delay/promote the occurrence of heart failure, PKC and ALDH2 also showed increased/decreased expression. And when ALDH2 was upregulated/downregulated, the role of HSF1 in delaying the occurrence of heart failure strengthened/weakened. Next, we used mechanical stretch to establish a pressure-stimulated myocardial hypertrophy model and discovered an increased expression of both HSF1 and ALDH2. When HSF1 was upregulated/downregulated to increase/decrease the expression of myocardial hypertrophy gene beta-MHC, PKC and ALDH2 recorded an increased/decreased expression. When an inhibitor was used to downregulate the expression of PKC in cardiomyocytes, we found that the role of HSF1 in upregulating ALDH2 beta-MHC weakened. These findings suggest that HSF1 can upregulate the expression of ALDH2 via PKC to promote pressure-stimulated myocardial compensatory hypertrophy, which is an important molecular pathway for HSF1 to ameliorate heart failure.

Neurotrophin gene therapy to promote survival of spiral ganglion neurons after deafness

Hearing impairment is a major health and economic concern worldwide. Currently, the cochlear implant (CI) is the standard of care for remediation of severe to profound hearing loss, and in general, contemporary CIs are highly successful. But there is great variability in outcomes among individuals, especially in children, with many CI users deriving much less or even marginal benefit. Much of this variability is related to differences in auditory nerve survival, and there has been substantial interest in recent years in exploring potential therapies to improve survival of the cochlear spiral ganglion neurons (SGN) after deafness. Preclinical studies using osmotic pumps and other approaches in deafened animal models to deliver neurotrophic factors (NTs) directly to the cochlea have shown promising results, especially with Brain-Derived Neurotrophic Factor (BDNF). More recent studies have focused on the use of NT gene therapy to force expression of NTs by target cells within the cochlea. This could provide the means for a one-time treatment to promote long-term NT expression and improve neural survival after deafness. This review summarizes the evidence for the efficacy of exogenous NTs in preventing SGN degeneration after hearing loss and reviews the animal research to date suggesting that NT gene therapy can elicit long-term NT expression in the cochlea, resulting in significantly improved SGN and radial nerve fiber survival after deafness. In addition, we discuss NT gene therapy in other non-auditory applications and consider some of the remaining issues with regard to selecting optimal vectors, timing of treatment, and place/method of delivery, etc. that must be resolved prior to considering clinical application.

Saraf-dependent activation of mTORC1 regulates cardiac growth

Pathological cardiac hypertrophy is an independent risk for heart failure (HF) and sudden death. Deciphering signaling pathways regulating intracellular Ca²⁺ homeostasis that control adaptive and pathological cardiac growth may enable identification of novel therapeutic targets. The objective of the present study is to determine the role of the store-operated calcium entry-associated regulatory factor (Saraf), encoded by the Tmem66 gene, on cardiac growth control in vitro and in vivo. Saraf is a single-pass membrane protein located at the sarco/endoplasmic reticulum and regulates intracellular calcium homeostasis. We found that Saraf expression was upregulated in the hypertrophied myocardium and was sufficient for cell growth in response to neurohumoral stimulation. Increased Saraf expression caused cell growth, which was associated with dysregulation of calcium-dependent signaling and sarcoplasmic reticulum calcium content. In vivo, Saraf augmented cardiac myocyte growth in response to angiotensin II and resulted in increased cardiac remodeling together with worsened cardiac function. Mechanistically, Saraf activated mTORC1 (mechanistic target of rapamycin complex 1) and increased protein synthesis, while mTORC1 inhibition blunted Saraf-dependent cell growth. In contrast, the hearts of Saraf knockout mice and Saraf-deficient myocytes did not show any morphological or functional alterations after neurohumoral stimulation, but Saraf depletion resulted in worsened cardiac function after acute pressure overload. SARAF knockout blunted transverse aortic constriction cardiac myocyte hypertrophy and impaired cardiac function, demonstrating a role for SARAF in compensatory myocyte growth. Collectively, these results reveal a novel link between sarcoplasmic reticulum calcium homeostasis and mTORC1 activation that is regulated by Saraf.

Transcription Factor TBX18 Reprograms Vascular Smooth Muscle Cells of Ascending Aorta to Pacemaker-Like Cells

Vascular smooth muscle cells (VSMCs) of ascending aorta and TBX18⁺ sinus node both originated from the second heart field. The study explored whether ascending aortic smooth muscle cells in vitro could be reprogrammed into pacemaker-like cells with human TBX18. In the study, VSMCs were infected with TBX18, and then cocultured with neonatal rat ventricular cardiomyocytes (NRVMs) in vitro. By overexpressing TBX18, the transfected VSMCs expressed high levels of hyperpolarization-activated cyclic nucleotide-gated channel 4 (HCN4), insulin gene enhancer binding protein 1, and human dwarf homeobox gene SHOX2, cardiac troponin I, and low level of connexin 43. In addition, funny current (I_f) was recorded by patch clamp appeared the time and voltage dependence in TBX18 group, which the amplitude of I_f density was from -5.164 ± 0.662 pA/pF to -0.765 ± 0.358 pA/pF (n = 14). Furthermore, TBX18-transfected VSMCs coupled with NRVMs showed typical action potential of pacemaker-like cells and the beating rate was faster (178.00 ± 7.55 bpm, p < 0.05) compared with other groups. In conclusion, our study indicated that transcription factor TBX18 could reprogram VSMCs into pacemaker-like cells in vitro.

Allele-Specific Silencing Ameliorates Restrictive Cardiomyopathy Attributable to a Human Myosin Regulatory Light Chain Mutation

BACKGROUND

Restrictive cardiomyopathy is a rare heart disease associated with mutations in sarcomeric genes and with phenotypic overlap with hypertrophic cardiomyopathy. There is no approved therapy directed at the underlying cause. Here, we explore the potential of an interfering RNA (RNAi) therapeutic for a human sarcomeric mutation in MYL2 causative of restrictive cardiomyopathy in a mouse model.

METHODS

A short hairpin RNA (M7.8L) was selected from a pool for specificity and efficacy. Two groups of myosin regulatory light chain N47K transgenic mice were injected with M7.8L packaged in adeno-associated virus 9 at 3 days of age and 60 days of age. Mice were subjected to treadmill exercise and echocardiography after treatment to determine maximal oxygen uptake and left ventricular mass. At the end of treatment, heart, lung, liver, and kidney tissue was harvested to determine viral tropism and for transcriptomic and proteomic analysis. Cardiomyocytes were isolated for single-cell studies.

RESULTS

A one-time injection of AAV9-M7.8L RNAi in 3-day-old humanized regulatory light chain mutant transgenic mice silenced the mutated allele (RLC-47K) with minimal effects on the normal allele (RLC-47N) assayed at 16 weeks postinjection. AAV9-M7.8L RNAi suppressed the expression of hypertrophic biomarkers, reduced heart weight, and attenuated a pathological increase in left ventricular mass. Single adult cardiac myocytes from mice treated with AAV9-M7.8L showed partial restoration of contraction, relaxation, and calcium kinetics. In addition, cardiac stress protein biomarkers, such as calmodulin-dependent protein kinase II and the transcription activator Brg1 were reduced, suggesting recovery toward a healthy myocardium. Transcriptome analyses further revealed no significant changes of argonaute (AGO1, AGO2) and endoribonuclease dicer (DICER1) transcripts, and endogenous microRNAs were preserved, suggesting that the RNAi pathway was not saturated.

CONCLUSIONS

Our results show the feasibility, efficacy, and safety of RNAi therapeutics directed towards human restrictive cardiomyopathy. This is a promising step toward targeted therapy for a prevalent human disease.

AAV cis-regulatory sequences are correlated with ocular toxicity

Adeno-associated viral (AAV) gene therapy is becoming an important therapeutic modality, especially for ocular diseases, due to its efficiency of gene delivery and relative lack of pathogenicity. However, AAV sometimes can cause inflammation and toxicity. We explored such effects using injections into the mouse eye. We found a strong correlation of toxicity and inflammation with the use of promoters that were broadly active, or specifically active in the retinal pigment epithelium. AAVs with photoreceptor-specific promoters were found to be nontoxic at all doses tested. These studies reveal that safer vectors can be designed if assays for relevant and specific cell types are developed and tested with a range of vectors with different genomic elements.

Adeno-associated viral vectors (AAVs) have become popular for gene therapy, given their many advantages, including their reduced inflammatory profile compared with that of other viruses. However, even in areas of immune privilege such as the eye, AAV vectors are capable of eliciting host-cell responses. To investigate the effects of such responses on several ocular cell types, we tested multiple AAV genome structures and capsid types using subretinal injections in mice. Assays of morphology, inflammation, and physiology were performed. Pathological effects on photoreceptors and the retinal pigment epithelium (RPE) were observed. Müller glia and microglia were activated, and the proinflammatory cytokines TNF-α and IL-1β were up-regulated. There was a strong correlation between cis-regulatory sequences and toxicity. AAVs with any one of three broadly active promoters, or an RPE-specific promoter, were toxic, while AAVs with four different photoreceptor-specific promoters were not toxic at the highest doses tested. There was little correlation between toxicity and transgene, capsid type, preparation method, or cellular contaminants within a preparation. The toxic effect was dose-dependent, with the RPE being more sensitive than photoreceptors. Our results suggest that ocular AAV toxicity is associated with certain AAV cis-regulatory sequences and/or their activity and that retinal damage occurs due to responses by the RPE and/or microglia. By applying multiple, sensitive assays of toxicity, AAV vectors can be designed so that they can be used safely at high dose, potentially providing greater therapeutic efficacy.

Comparison of Periodontal Ligament Cell Lines with Adenovirus- and Lentivirus-Mediated Human Telomerase Reverse Transcription Expression

The aims of this study were to generate periodontal ligament (PDL) cells that have adenovirus- or lentivirus-mediated overexpression of human telomerase reverse transcriptase (hTERT) and to compare the osteogenic and proliferative abilities of the two cell lines to establish an efficient and stable cell model that will be more suitable for studies of PDL regeneration. After construction of the recombinant adenovirus plasmid pAd-pshuttle-cmv-hTERT, human PDL cells were infected by packaged adenovirus and lentivirus particles to establish two PDL cell lines. The expression levels of hTERT and mRNA for alkaline phosphatase, osteopontin, osteocalcin, bone sialoprotein, core-binding factor (runt-related transcription factor 2), and type I collagen were assessed for each cell line. After culture in osteoinductive culture medium for 14 days, the PDL cells were stained with alizarin red to observe formation of mineralized nodules, and proliferation activity was measured with a CCK-8 kit. A quantitative polymerase chain reaction assay indicated that the two transduced cell lines expressed hTERT levels that were significantly higher than that seen for normal PDL cells. Expression of all osteogenic genes tested, with the exception of osteopontin, was higher for both the adenovirus- and lentivirus-transduced cells relative to normal PDL cells. The expression of bone sialoprotein, osteocalcin, and runt-related transcription factor 2 in adenovirus-transduced cells was significantly higher than that for lentivirus-transduced cells. Alizarin red staining showed that the adenovirus-transduced cell line produced more mineralized nodules than the lentivirus-transduced cell line, whereas a CCK-8 test showed that the adenovirus-transduced cell line had higher proliferation activity than lentivirus-transduced cells. In conclusion, a PDL cell line established by adenovirus transduction had superior osteogenic differentiation and proliferative activity compared to the cell line produced by lentivirus transduction. The results indicate that PDL cells having adenovirus-mediated expression of hTERT would be a more suitable model for studies of PDL regeneration.

Molecular discoveries and treatment strategies by direct reprogramming in cardiac regeneration

Cardiac tissue has minimal endogenous regenerative capacity in response to injury. Treatment options are limited following tissue damage after events such as myocardial infarction. Current strategies are aimed primarily at injury prevention, but attention has been increasingly targeted toward the development of regenerative therapies. This review focuses on recent developments in the field of cardiac fibroblast reprogramming into induced cardiomyocytes. Early efforts to produce cardiac regeneration centered around induced pluripotent stem cells, but clinical translation has proved elusive. Currently, techniques are being developed to directly transdifferentiate cardiac fibroblasts into induced cardiomyocytes. Viral vector-driven expression of a combination of transcription factors including Gata4, Mef2c, and Tbx5 induced cardiomyocyte development in mice. Subsequent combinational modifications have extended these results to human cell lines and increased efficacy. The miRNAs including combinations of miR-1, miR-133, miR-208, and miR-499 can improve or independently drive regeneration of cardiomyocytes. Similar results could be obtained by combinations of small molecules with or without transcription factor or miRNA expression. The local tissue environment greatly impacts favorability for reprogramming. Modulation of signaling pathways, especially those mediated by VEGF and TGF-β, enhance differentiation to cardiomyocytes. Current reprogramming strategies are not ready for clinical application, but recent breakthroughs promise regenerative cardiac therapies in the near future.

Future directions for therapeutic strategies in post-ischaemic vascularization: a position paper from European Society of Cardiology Working Group on Atherosclerosis and Vascular Biology

Modulation of vessel growth holds great promise for treatment of cardiovascular disease. Strategies to promote vascularization can potentially restore function in ischaemic tissues. On the other hand, plaque neovascularization has been shown to associate with vulnerable plaque phenotypes and adverse events. The current lack of clinical success in regulating vascularization illustrates the complexity of the vascularization process, which involves a delicate balance between pro- and anti-angiogenic regulators and effectors. This is compounded by limitations in the models used to study vascularization that do not reflect the eventual clinical target population. Nevertheless, there is a large body of evidence that validate the importance of angiogenesis as a therapeutic concept. The overall aim of this Position Paper of the ESC Working Group of Atherosclerosis and Vascular biology is to provide guidance for the next steps to be taken from pre-clinical studies on vascularization towards clinical application. To this end, the current state of knowledge in terms of therapeutic strategies for targeting vascularization in post-ischaemic disease is reviewed and discussed. A consensus statement is provided on how to optimize vascularization studies for the identification of suitable targets, the use of animal models of disease, and the analysis of novel delivery methods.

Dual targeting delivery of miR-328 by functionalized mesoporous silica nanoparticles for colorectal cancer therapy

Aim: We aim to explore the regulatory mechanism of miR-328 and further develop miR-328-loaded mesoporous silica nanoparticles (MSNs) and surface-decorated with polymerized dopamine, epithelial cell adhesion molecule aptamer and bevacizumab for the dual-targeting treatment of colorectal cancer (CRC). Materials & methods: The relationship between miR-328 and CPTP and the mechanism and antitumor effect of MSNs-miR-328@PDA-PEG-Apt-Bev were evaluated. Results: We found CPTP is a direct target of miR-328. Compared with other groups, MSNs-miR-328@PDA-PEG-Apt-Bev can significantly increase the level of miR-328 and inhibit the expression of CPTP in SW480 cells. The results exhibit this multifunctional bioconjugates can achieve an increased binding ability and much higher cytotoxicity to CRC both in vitro and in vivo. Conclusion: This multifunctional nanoplatform is a promising miRNA replacement therapy for CRC.

Correcting Calcium Dysregulation in Chronic Heart Failure Using SERCA2a Gene Therapy

Chronic heart failure (CHF) is a major contributor to cardiovascular disease and is the leading cause of hospitalization for those over the age of 65, which is estimated to account for close to seventy billion dollars in healthcare costs by 2030 in the US alone. The successful therapies for preventing and reversing CHF progression are urgently required. One strategy under active investigation is to restore dysregulated myocardial calcium (Ca²⁺), a hallmark of CHF. It is well established that intracellular Ca²⁺ concentrations are tightly regulated to control efficient myocardial systolic contraction and diastolic relaxation. Among the many cell surface proteins and intracellular organelles that act as the warp and woof of the regulatory network controlling intracellular Ca²⁺ signals in cardiomyocytes, sarco/endoplasmic reticulum Ca²⁺ ATPase type 2a (SERCA2a) undoubtedly plays a central role. SERCA2a is responsible for sequestrating cytosolic Ca²⁺ back into the sarcoplasmic reticulum during diastole, allowing for efficient uncoupling of actin-myosin and subsequent ventricular relaxation. Accumulating evidence has demonstrated that the expression of SERCA2a is downregulated in CHF, which subsequently contributes to severe systolic and diastolic dysfunction. Therefore, restoring SERCA2a expression and improving cardiomyocyte Ca²⁺ handling provides an excellent alternative to currently used transplantation and mechanical assist devices in the treatment of CHF. Indeed, advancements in safe and effective gene delivery techniques have led to the emergence of SERCA2a gene therapy as a potential therapeutic choice for CHF patients. This mini-review will succinctly detail the progression of SERCA2a gene therapy from its inception in plasmid and animal models, to its clinical trials in CHF patients, highlighting potential avenues for future work along the way.

Therapeutic Benefit and Gene Network Regulation by Combined Gene Transfer of Apelin, FGF2, and SERCA2a into Ischemic Heart

Despite considerable advances in cardiovascular disease treatment, heart failure remains a public health challenge. In this context, gene therapy appears as an attractive approach, but clinical trials using single therapeutic molecules result in moderate benefit. With the objective of improving ischemic heart failure therapy, we designed a combined treatment, aimed to simultaneously stimulate angiogenesis, prevent cardiac remodeling, and restore contractile function. We have previously validated IRES-based vectors as powerful tools to co-express genes of interest. Mono- and multicistronic lentivectors expressing fibroblast growth factor 2 (angiogenesis), apelin (cardioprotection), and/or SERCA2a (contractile function) were produced and administrated by intramyocardial injection into a mouse model of myocardial infarction. Data reveal that combined treatment simultaneously improves vessel number, heart function parameters, and fibrosis prevention, due to FGF2, SERCA2a, and apelin, respectively. Furthermore, addition of SERCA2a in the combination decreases cardiomyocyte hypertrophy. Large-scale transcriptome analysis reveals that the triple treatment is the most efficient in restoring angiogenic balance as well as expression of genes involved in cardiac function and remodeling. Our study validates the concept of combined treatment of ischemic heart disease with apelin, FGF2, and SERCA2a and shows that such therapeutic benefit is mediated by a more effective recovery of gene network regulation.

Optogenetic targeting of cardiac myocytes and non-myocytes: Tools, challenges and utility

In optogenetics, light-activated proteins are used to monitor and modulate cellular behaviour with light. Combining genetic targeting of distinct cellular populations with defined patterns of optical stimulation enables one to study specific cell classes in complex biological tissues. In the current study we attempted to investigate the functional relevance of heterocellular electrotonic coupling in cardiac tissue in situ. In order to do that, we used a Cre-Lox approach to express the light-gated cation channel Channelrhodopsin-2 (ChR2) specifically in either cardiac myocytes or non-myocytes. Despite high specificity when using the same Cre driver lines in a previous study in combination with a different optogenetic probe, we found patchy off-target ChR2 expression in cryo-sections and extended z-stack imaging through the ventricular wall of hearts cleared using CLARITY. Based on immunohistochemical analysis, single-cell electrophysiological recordings and whole-genome sequencing, we reason that non-specificity is caused on the Cre recombination level. Our study highlights the importance of careful design and validation of the Cre recombination targets for reliable cell class specific expression of optogenetic tools.

Gene Transfer in Cardiomyocytes Derived from ES and iPS Cells

The advent of human induced pluripotent stem cell (hiPSC) technology has produced patient-specific hiPSC derived cardiomyocytes (hiPSC-CMs) that can be used as a platform to study cardiac diseases and to explore new therapies.The ability to genetically manipulate hiPSC-CMs not only is essential for identifying the structural and/or functional role of a protein but can also provide valuable information regarding therapeutic applications. In this chapter, we describe protocols for culture, maintenance, and cardiac differentiation of hiPSCs. Then, we provide a basic procedure to transduce hiPSC-CMs.

Intramyocardial Injection of siRNAs Can Efficiently Establish Myocardial Tissue-Specific Renalase Knockdown Mouse Model

Ischaemia/reperfusion (I/R) injury will cause additional death of cardiomyocytes in ischaemic heart disease. Recent studies revealed that renalase was involved in the I/R injury. So, the myocardial tissue-specific knockdown mouse models were needed for the investigations of renalase. To establish the mouse models, intramyocardial injection of siRNAs targeting renalase was performed in mice. The wild distribution and high transfection efficiency of the siRNAs were approved. And the renalase expression was efficiently suppressed in myocardial tissue. Compared with the high cost, time consumption, and genetic compensation risk of the Cre/loxP technology, RNA interference (RNAi) technology is much cheaper and less time-consuming. Among the RNAi technologies, injection of siRNAs is safer than virus. And considering the properties of the I/R injury mouse models, the efficiency and durability of injection with siRNAs are acceptable for the studies. Altogether, intramyocardial injection of siRNAs targeting renalase is an economical, safe, and efficient method to establish myocardial tissue-specific renalase knockdown mouse models.

Isoform-Specific Modulation of Inflammation Induced by Adenoviral Mediated Delivery of Platelet-Derived Growth Factors in the Adult Mouse Heart

Platelet-derived growth factors (PDGFs) are key regulators of mesenchymal cells in vertebrate development. To what extent PDGFs also exert beneficial homeostatic or reparative roles in adult organs, as opposed to adverse fibrogenic responses in pathology, are unclear. PDGF signaling plays critical roles during heart development, during which forced overexpression of PDGFs induces detrimental cardiac fibrosis; other studies have implicated PDGF signaling in post-infarct myocardial repair. Different PDGFs may exert different effects mediated through the two PDGF receptors (PDGFRα and PDGFRβ) in different cell types. Here, we assessed responses induced by five known PDGF isoforms in the adult mouse heart in the context of adenovirus vector-mediated inflammation. Our results show that different PDGFs have different, in some cases even opposing, effects. Strikingly, whereas the major PDGFRα agonists (PDGF-A and -C) decreased the amount of scar tissue and increased the numbers of PDGFRα-positive fibroblasts, PDGFRβ agonists either induced large scars with extensive inflammation (PDGF-B) or dampened the adenovirus-induced inflammation and produced a small and dense scar (PDGF-D). These results provide evidence for PDGF isoform-specific inflammation-modulating functions that may have therapeutic implications. They also illustrate a surprising complexity in the PDGF-mediated pathophysiological responses.

Cationic microRNA-delivering nanocarriers for efficient treatment of colon carcinoma in xenograft model

Manipulation of tumor microRNAs (miRNAs) may offer novel avenues for treatment of cancer. However, development of safe, robust, non-viral delivery methods remains a main challenge to obtain the promise of gene therapy. The miR-145 is dysregulated in many cancers, including colon carcer, and further in vitro investigation established antiproliferative and proapoptotic roles of miR-145. Herein, we study a PLGA/PEI (poly (d, l-lactide-co-glycolide)/polyethylenimine)-mediated miRNA vector delivery system; the validation of the method was carried out using a colon cancer xenograft model with miR-145 vector encoding for the expression of miR-145 (pDNA). First, high-molecular-weight PEI (25000 Da) was conjugated with cetyl to formulate reducible cetylated PEI (PEI-cet), and then PEI-cet was introduced to PLGA suspension. Next, PLGA/PEI-cet was crosslinked with hyaluronic acid (HA) to facilitate cellular uptake of miRNA plasmid vector via HA receptor-mediated endocytosis. After local administration of PLGA/PEI/HA complexes, intact miRNA plasmid vectors were delivered into HCT-116 colon cancer cells and xenograft tumor-bearing mice, and significant antitumor effects were achieved. The results show that the HA-based miR-145 nanocarrier could efficiently facilitate cellular uptake and significantly enhance miR-145 expression in HCT-116 cells. Consequently, the increased miR-145 induced G1 cell cycle arrest, reduced tumor proliferation and increased apoptosis, inhibited HCT-116 cell migration and suppressed c-MYC expressions, a regulatory target of miR-145. Of particular importance is the significant decrease in tumor growth in the mice model of colon cancer with the targeting miR-145 delivery system. The results in this work show that miR-145 has been effectively delivered to colon carcinomas through a PLGA/PEI/HA vehicle, indicating a promising miRNA replacement therapy strategy.