Plasma Small Extracellular Vesicle Cardiac miRNA Expression in Patients with Ischemic Heart Failure, Randomized to Percutaneous Intramyocardial Treatment of Adipose Derived Stem Cells or Placebo: Subanalysis of the SCIENCE Study.

Small extracellular vesicles (EVs) and their cargo are an important component of cell-to-cell communication in cardiac disease. Allogeneic adipose derived stem cells (ADSCs) are thought to be a potential approach for cardiac regenerative therapy in ischemic heart disease. The SCIENCE study investigated the effect of ADSCs administered via intramyocardial injection on cardiac function in patients with ischemic heart disease. The aim of this substudy, based on samples from 15 patients, was to explore small EV miRNA dynamics after treatment with ADSCs compared to a placebo. Small EVs were isolated at several timepoints after the percutaneous intramyocardial application of ADSCs. No significant effect of ADSC treatment on small EV concentration was detected. After 12 months, the expression of miR-126 decreased significantly in ADSC patients, but not in the placebo-treated group. However, all cardiac miRNAs correlated with plasma cardiac biomarkers. In line with the overall negative results of the SCIENCE study, with the exception of one miR, we did not detect any significant regulation of small EV miRNAs in this patient collective.

Identification of Gene Expression Signatures for Phenotype-Specific Drug Targeting of Cardiac Fibrosis.

We have designed translational animal models to investigate cardiac profibrotic gene signatures. Domestic pigs were treated with cardiotoxic drugs (doxorubicin, DOX, n = 5 or Myocet®, MYO, n = 5) to induce replacement fibrosis via cardiotoxicity. Reactive interstitial fibrosis was triggered by LV pressure overload by artificial isthmus stenosis with stepwise developing myocardial hypertrophy and final fibrosis (Hyper, n = 3) or by LV volume overload in the adverse remodeled LV after myocardial infarction (RemoLV, n = 3). Sham interventions served as controls and healthy animals (Control, n = 3) served as a reference in sequencing study. Myocardial samples from the LV of each group were subjected to RNA sequencing. RNA-seq analysis revealed a clear distinction between the transcriptomes of myocardial fibrosis (MF) models. Cardiotoxic drugs activated the TNF-alpha and adrenergic signaling pathways. Pressure or volume overload led to the activation of FoxO pathway. Significant upregulation of pathway components enabled the identification of potential drug candidates used for the treatment of heart failure, such as ACE inhibitors, ARB, ß-blockers, statins and diuretics specific to the distinct MF models. We identified candidate drugs in the groups of channel blockers, thiostrepton that targets the FOXM1-regulated ACE conversion to ACE2, tyrosine kinases or peroxisome proliferator-activated receptor inhibitors. Our study identified different gene targets involved in the development of distinct preclinical MF protocols enabling tailoring expression signature-based approach for the treatment of MF.

CDR132L improves systolic and diastolic function in a large animal model of chronic heart failure.

AIMS: Cardiac miR-132 activation leads to adverse remodelling and pathological hypertrophy. CDR132L is a synthetic lead-optimized oligonucleotide inhibitor with proven preclinical efficacy and safety in heart failure (HF) early after myocardial infarction (MI), and recently completed clinical evaluation in a Phase 1b study (NCT04045405). The aim of the current study was to assess safety and efficacy of CDR132L in a clinically relevant large animal (pig) model of chronic heart failure following MI. METHODS AND RESULTS: In a chronic model of post-MI HF, slow-growing pigs underwent 90 min left anterior descending artery occlusion followed by reperfusion. Animals were randomized and treatment started 1-month post-MI. Monthly intravenous (IV) treatments of CDR132L over 3 or 5 months (3× or 5×) were applied in a blinded randomized placebo-controlled fashion. Efficacy was evaluated based on serial magnetic resonance imaging, haemodynamic, and biomarker analyses. The treatment regime provided sufficient tissue exposure and CDR132L was well tolerated. Overall, CDR132L treatment significantly improved cardiac function and reversed cardiac remodelling. In addition to the systolic recovery, diastolic function was also ameliorated in this chronic model of HF. CONCLUSION: Monthly repeated dosing of CDR132L is safe and adequate to provide clinically relevant exposure and therapeutic efficacy in a model of chronic post-MI HF. CDR132L thus should be explored as treatment for the broad area of chronic heart failure.

The use of semi-compliant versus non-compliant balloon systems for predilatation during the implantation of self-expandable transcatheter aortic valves: Data from the VIenna CardioThOracic Aortic Valve RegistrY (VICTORY).

BACKGROUND: This study aimed to evaluate the differences in outcome arising from the use of semi-compliant (SCB) versus non-compliant balloon (NCB) systems for predilatation during self-expanding transcatheter aortic valve replacement (TAVR). METHODS: 251 TAVR procedures with the implantation of self-expanding valves after predilatation were analyzed. SCB systems were used in 166 and NCB systems in 85 patients. The primary endpoint was defined as device success, a composite endpoint comprising the absence of procedural mortality, correct valve positioning, adequate valve performance and the absence of more than a mild paravalvular leak. The secondary endpoints were chosen in accordance with the valve academic research consortium (VARC-2) endpoint definitions. RESULTS: No significant differences were observed with regard to procedural device success between the SCB- and NCB cohort (SCB: 142 [85.5%%] vs. NCB: 77 [90.6%]; P = .257). There was a notable difference between the rates of conversion to open surgery and the postdilatation rate, both of which were higher for the NCB group (SCB: 1 [0.6%] vs. NCB: 4 [5.1%]; P = .042; SCB: 30 [18.1%] vs. NCB: 34 [40%]; P < .001). In a multivariate logistic regression analysis, the use of semi-compliant balloon systems for predilatation was associated with a lower risk for postdilatation (OR: 0.296; 95% CI: 0.149-0.588) and conversion to open surgery (OR: 0.205; 95% CI: 0.085-0.493; P = .001) but not for device success. CONCLUSION: While the balloon compliance did not affect the procedural mortality, device success or the rate of paravalvular leakage, the use of semi-compliant balloons for predilatation during TAVR should be investigated in larger randomized trials in the light of the lower rates of postdilatation and conversion to open surgery compared to their non-compliant counterparts.

Non-Coding RNAs in Stem Cell Regulation and Cardiac Regeneration: Current Problems and Future Perspectives.

Although advances in rapid revascularization strategies following acute myocardial infarction (AMI) have led to improved short and long-term outcomes, the associated loss of cardiomyocytes and the subsequent remodeling result in an impaired ventricular function that can lead to heart failure or death. The poor regenerative capacity of the myocardium and the current lack of effective regenerative therapies have driven stem cell research in search of a possible solution. One approach involves the delivery of stem cells to the site of injury in order to stimulate repair response. Although animal studies initially delivered promising results, the application of similar techniques in humans has been hampered by poor target site retention and oncogenic considerations. In response, several alternative strategies, including the use of non-coding RNAs (ncRNAs), have been introduced with the aim of activating and regulating stem cells or inducing stem cell status in resident cells. Circular RNAs (circRNAs) and microRNAs (miRNAs) are ncRNAs with pivotal functions in cell proliferation and differentiation, whose role in stem cell regulation and potential significance for the field of cardiac regeneration is the primary focus of this review. We also address the general advantages of ncRNAs as promising drivers of cardiac regeneration and potent stem cell regulators.

Novel Identified Circular Transcript of RCAN2, circ-RCAN2, Shows Deviated Expression Pattern in Pig Reperfused Infarcted Myocardium and Hypoxic Porcine Cardiac Progenitor Cells In Vitro.

Circular RNAs (circRNAs) are crucial in gene regulatory networks and disease development, yet circRNA expression in myocardial infarction (MI) is poorly understood. Here, we harvested myocardium samples from domestic pigs 3 days after closed-chest reperfused MI or sham surgery. Cardiac circRNAs were identified by RNA-sequencing of rRNA-depleted RNA from infarcted and healthy myocardium tissue samples. Bioinformatics analysis was performed using the CIRIfull and KNIFE algorithms, and circRNAs identified with both algorithms were subjected to differential expression (DE) analysis and validation by qPCR. Circ-RCAN2 and circ-C12orf29 expressions were significantly downregulated in infarcted tissue compared to healthy pig heart. Sanger sequencing was performed to identify the backsplice junctions of circular transcripts. Finally, we compared the expressions of circ-C12orf29 and circ-RCAN2 between porcine cardiac progenitor cells (pCPCs) that were incubated in a hypoxia chamber for different time periods versus normoxic pCPCs. Circ-C12orf29 did not show significant DE in vitro, whereas circ-RCAN2 exhibited significant ischemia-time-dependent upregulation in hypoxic pCPCs. Overall, our results revealed novel cardiac circRNAs with DE patterns in pCPCs, and in infarcted and healthy myocardium. Circ-RCAN2 exhibited differential regulation by myocardial infarction in vivo and by hypoxia in vitro. These results will improve our understanding of circRNA regulation during acute MI.

Impact of Circulating Anti-Spike Protein Antibody Levels on Multi-Organ Long COVID Symptoms.

Patients with long COVID syndrome present with various symptoms affecting multiple organs. Vaccination before or after SARS-CoV-2 infection appears to reduce the incidence of long COVID or at least limit symptom deterioration. However, the impact of vaccination on the severity and extent of multi-organ long COVID symptoms and the relationship between the circulating anti-spike protein antibody levels and the severity and extent of multi-organ symptoms are unclear. This prospective cohort study included 198 patients with previous PCR-verified SARS-CoV-2 infection who met the criteria for long COVID syndrome. Patients were divided into vaccinated (n = 138, 69.7%) or unvaccinated (n = 60, 30.3%) groups. Anti-spike protein antibody levels were determined at initial clinical presentation and compared between the groups. Long COVID symptoms were quantified on the basis of the number of affected organs: Class I (mild) with symptoms in three organs, Class II (moderate) with symptoms in four to five organs, and Class III (severe) with symptoms in six or more organ systems. Associations between time to infection and vaccination with anti-spike protein antibody levels were assessed. The anti-spike protein antibody levels were 1925 ± 938 vs. 481 ± 768 BAU/mL (p < 0.001) in the vaccinated vs. unvaccinated patients. The circulating anti-spike antibody cutoff of 665.5 BAU/mL allowed us to differentiate the vaccinated from the unvaccinated patients. Vaccinated patients had fewer class II and class III multi-organ symptoms (Class II 39.9% vs. 45.0%; Class III 10.1% vs. 23.3%, p-value 0.014). Anti-spike antibody level correlated negatively with multi-organ symptom classes (p = 0.016; 95% CI -1.229 to -0.126). Anti-spike antibody levels in unvaccinated patients declined markedly with time, in contrast to the persistence of high anti-spike antibody levels in the vaccinated patients. Multi-organ symptoms were lower in vaccinated long-COVID patients, especially in those with higher anti-spike antibody levels (≥665.5 BAU/mL). Classifying the symptoms on the basis of the number of affected organs enables a more objective symptom quantification.

A CircRNA-miRNA-mRNA Network for Exploring Doxorubicin- and Myocet-Induced Cardiotoxicity in a Translational Porcine Model.

Despite the widespread use of doxorubicin (DOX) as a chemotherapeutic agent, its severe cumulative cardiotoxicity represents a significant limitation. While the liposomal encapsulation of doxorubicin (Myocet, MYO) reduces cardiotoxicity, it is crucial to understand the molecular background of doxorubicin-induced cardiotoxicity. Here, we examined circular RNA expression in a translational model of pigs treated with either DOX or MYO and its potential impact on the global gene expression pattern in the myocardium. This study furthers our knowledge about the regulatory network of circRNA/miRNA/mRNA and its interaction with chemotherapeutics. Domestic pigs were treated with three cycles of anthracycline drugs (DOX, n = 5; MYO, n = 5) to induce cardiotoxicity. Untreated animals served as controls (control, n = 3). We applied a bulk mRNA-seq approach and the CIRIquant algorithm to identify circRNAs. The most differentially regulated circRNAs were validated under cell culture conditions, following forecasting of the circRNA-miRNA-mRNA network. We identified eight novel significantly regulated circRNAs from exonic and mitochondrial regions in the porcine myocardium. The forecasted circRNA-miRNA-mRNA network suggested candidate circRNAs that sponge miR-17, miR-15b, miR-130b, the let-7 family, and miR125, together with their mRNA targets. The identified circRNA-miRNA-mRNA network provides an updated, coherent view of the mechanisms involved in anthracycline-induced cardiotoxicity.

Improvement of Symptoms and Cardiac Magnetic Resonance Abnormalities in Patients with Post-Acute Sequelae of SARS-CoV-2 Cardiovascular Syndrome (PASC-CVS) after Guideline-Oriented Therapy.

Cardiac magnetic resonance (CMR) studies reported CMR abnormalities in patients with mild-moderate SARS-CoV-2 infection, suggesting ongoing myocardial inflammation. Patients (n = 278, 43 ± 13 years, 70.5% female) with post-acute sequelae of SARS-CoV-2 cardiovascular syndrome (PASC-CVS) were included prospectively into the Vienna POSTCOV Registry between March 2021 and March 2023 (clinicaltrials.gov NCT05398952). Clinical, laboratory, and CMR findings were recorded. Patients with abnormal CMR results were classified into isolated chronic pericardial (with/without pleural) effusion, isolated cardiac function impairment, or both (myopericarditis) groups. Medical treatment included a nonsteroidal anti-inflammatory agent (NSAID) for pericardial effusion and a condition-adapted maximal dose of heart failure (HF) treatment. Three months after medical therapy, clinical assessment and CMR were repeated in 82 patients. Laboratory analyses revealed normal hematological, inflammatory, coagulation, and cardiac biomarkers. CMR abnormalities were found in 155 patients (55.8%). Condition-adapted HF treatment led to a significant increase in the left ventricular ejection fraction (LVEF) in patients with initially reduced LVEF (from 49 ± 5% to 56 ± 4%, p = 0.009, n = 25). Low-moderate doses of NSAIDs for 3 months significantly reduced pericardial effusion (from 4/3;5.75/mm to 2/0;3/mm, median/interquartile ranges/p < 0.001, n = 51). Clinical symptoms improved markedly with a decrease in CMR abnormalities, which might be attributed to the maintenance of NSAID and HF medical treatment for PASC-CVS.

A multi-omics based anti-inflammatory immune signature characterizes long COVID-19 syndrome.

To investigate long COVID-19 syndrome (LCS) pathophysiology, we performed an exploratory study with blood plasma derived from three groups: 1) healthy vaccinated individuals without SARS-CoV-2 exposure; 2) asymptomatic recovered patients at least three months after SARS-CoV-2 infection and; 3) symptomatic patients at least 3 months after SARS-CoV-2 infection with chronic fatigue syndrome or similar symptoms, here designated as patients with long COVID-19 syndrome (LCS). Multiplex cytokine profiling indicated slightly elevated pro-inflammatory cytokine levels in recovered individuals in contrast to patients with LCS. Plasma proteomics demonstrated low levels of acute phase proteins and macrophage-derived secreted proteins in LCS. High levels of anti-inflammatory oxylipins including omega-3 fatty acids in LCS were detected by eicosadomics, whereas targeted metabolic profiling indicated high levels of anti-inflammatory osmolytes taurine and hypaphorine, but low amino acid and triglyceride levels and deregulated acylcarnitines. A model considering alternatively polarized macrophages as a major contributor to these molecular alterations is presented.

Effect of monovalent COVID-19 vaccines on viral interference between SARS-CoV-2 and several DNA viruses in patients with long-COVID syndrome.

Epstein-Barr virus (EBV) reactivation may be involved in long-COVID symptoms, but reactivation of other viruses as a factor has received less attention. Here we evaluated the reactivation of parvovirus-B19 and several members of the Herpesviridae family (DNA viruses) in patients with long-COVID syndrome. We hypothesized that monovalent COVID-19 vaccines inhibit viral interference between SARS-CoV-2 and several DNA viruses in patients with long-COVID syndrome, thereby reducing clinical symptoms. Clinical and laboratory data for 252 consecutive patients with PCR-verified past SARS-CoV-2 infection and long-COVID syndrome (155 vaccinated and 97 non-vaccinated) were recorded during April 2021-May 2022 (median 243 days post-COVID-19 infection). DNA virus-related IgG and IgM titers were compared between vaccinated and non-vaccinated long-COVID patients and with age- and sex-matched non-infected, unvaccinated (pan-negative for spike-antibody) controls. Vaccination with monovalent COVID-19 vaccines was associated with significantly less frequent fatigue and multiorgan symptoms (p < 0.001), significantly less cumulative DNA virus-related IgM positivity, significantly lower levels of plasma IgG subfractions 2 and 4, and significantly lower quantitative cytomegalovirus IgG and IgM and EBV IgM titers. These results indicate that anti-SARS-CoV-2 vaccination may interrupt viral cross-talk in patients with long-COVID syndrome (ClinicalTrials.gov Identifier: NCT05398952).

Deviations From the Ideal Plasma Volume and Isolated Tricuspid Valve Surgery-Paving the Way for New Risk Stratification Parameters.

Background: Congestion and plasma volume expansion are important features of heart failure, whose prognostic significance has been investigated in a range of surgical and non-surgical settings. The aim of this study was to evaluate the value of the estimated plasma volume status (ePVS) in patients undergoing isolated tricuspid valve surgery. Methods: This study included patients who underwent isolated tricuspid valve surgery at the Vienna General Hospital (Austria) between July 2008 and November 2018. The PVS cut-off was calculated using ROC analysis and Youden's Index. Results: Eighty eight patients (median age: 58 [IQR: 35-70] years; 44.3% male; 75.6% NYHA III/IV; median EuroSCORE II 2.65 [IQR: 1.70-5.10]; 33.0% endocarditis-related regurgitation; 60.2% isolated repair; 39.8% isolated replacement) were included in this study. Patients who died within 1 year following surgery had significantly higher baseline ePVS values than survivors (median ePVS 5.29 [IQR: -1.55-13.55] vs. -3.68 [IQR: -10.92-4.22]; p = 0.005). During a median actuarial follow-up of 3.02 (IQR: 0.36-6.80) years, patients with a preoperative ePVS ≥ -4.17 had a significantly increased mortality (log-rank p = 0.006). Conclusions: ePVS is an easily obtainable risk parameter for patients undergoing isolated tricuspid valve surgery capable of predicting mid- and long-term outcomes after isolated tricuspid valve surgery.

Alternative Splicing in Cardiovascular Disease-A Survey of Recent Findings.

Alternative splicing, a driver of posttranscriptional variance, differs from canonical splicing by arranging the introns and exons of an immature pre-mRNA transcript in a multitude of different ways. Although alternative splicing was discovered almost half a century ago, estimates of the proportion of genes that undergo alternative splicing have risen drastically over the last two decades. Deep sequencing methods and novel bioinformatic algorithms have led to new insights into the prevalence of spliced variants, tissue-specific splicing patterns and the significance of alternative splicing in development and disease. Thus far, the role of alternative splicing has been uncovered in areas ranging from heart development, the response to myocardial infarction to cardiac structural disease. Circular RNAs, a product of alternative back-splicing, were initially discovered in 1976, but landmark publications have only recently identified their regulatory role, tissue-specific expression, and transcriptomic abundance, spurring a renewed interest in the topic. The aim of this review is to provide a brief insight into some of the available findings on the role of alternative splicing in cardiovascular disease, with a focus on atherosclerosis, myocardial infarction, heart failure, dilated cardiomyopathy and circular RNAs in myocardial infarction.

Identifying Patients without a Survival Benefit following Transfemoral and Transapical Transcatheter Aortic Valve Replacement.

Transcatheter aortic valve replacement (TAVR) offers a novel treatment option for patients with severe symptomatic aortic valve stenosis, particularly for patients who are unsuitable candidates for surgical intervention. However, high therapeutical costs, socio-economic considerations, and numerous comorbidities make it necessary to target and allocate available resources efficiently. In the present study, we aimed to identify risk factors associated with futile treatment following transfemoral (TF) and transapical (TA) TAVR. Five hundred and thirty-two consecutive patients (82 ± 9 years, female 63%) who underwent TAVR between June 2009 and December 2016 at the Vienna Heart Center Hietzing were retrospectively analyzed to identify predictors of futility, defined as all-cause mortality at one year following the procedure for the overall patient cohort, as well as the TF and TA cohort. Out of 532 patients, 91 (17%) did not survive the first year after TAVR. A multivariate logistic model identified cerebrovascular disease, home oxygen dependency, wheelchair dependency, periinterventional myocardial infarction, and postinterventional renal replacement therapy as the factors independently associated with an increased one-year mortality. Our findings underscore the significance of a precise preinterventional evaluation, as well as illustrating the subtle differences in baseline characteristics in the TF and TA cohort and their impact on one-year mortality.

A Sneak-Peek into the Physician's Brain: A Retrospective Machine Learning-Driven Investigation of Decision-Making in TAVR versus SAVR for Young High-Risk Patients with Severe Symptomatic Aortic Stenosis.

Transcatheter aortic valve replacement (TAVR) has rapidly become a viable alternative to the conventional isolated surgical aortic valve replacement (iSAVR) for treating severe symptomatic aortic stenosis. However, data on younger patients is scarce and a gap exists between data-based recommendations and the clinical use of TAVR. In our study, we utilized a machine learning (ML) driven approach to model the complex decision-making process of Heart Teams when treating young patients with severe symptomatic aortic stenosis with either TAVR or iSAVR and to identify the relevant considerations. Out of the considered factors, the variables most prominently featured in our ML model were congestive heart failure, established risk assessment scores, previous cardiac surgeries, a reduced left ventricular ejection fraction and peripheral vascular disease. Our study demonstrates a viable application of ML-based approaches for studying and understanding complex clinical decision-making processes.

Transcatheter versus Isolated Surgical Aortic Valve Replacement in Young High-Risk Patients: A Propensity Score-Matched Analysis.

BACKGROUND: Younger patients with severe symptomatic aortic stenosis are a particularly challenging collective with regard to the choice of intervention. High-risk patients younger than 75 years of age are often eligible for both the transcatheter aortic valve replacement (TAVR) and the isolated surgical aortic valve replacement (iSAVR). Data on the outcomes of both interventions in this set of patients are scarce. METHODS: One hundred and forty-four propensity score-matched patients aged 75 years or less who underwent TAVR or iSAVR at the Hietzing Heart Center in Vienna, Austria, were included in the study. The mean age was 68.9 years (TAVR 68.7 vs. SAVR 67.6 years; p = 0.190) and the average EuroSCORE II was 5.4% (TAVR 4.3 [3.2%] vs. iSAVR 6.4 (4.3%); p = 0.194). RESULTS: Postprocedural adverse event data showed higher rates of newly acquired atrial fibrillation (6.9% vs. 19.4%; p = 0.049), prolonged ventilation (2.8% vs. 25.0%; p < 0.001) and multi-organ failure (0% vs. 6.9%) in the surgical cohort. The in-hospital and 30-day mortality was significantly higher for iSAVR (1.4% vs. 13.9%; p = 0.012; 12.5% vs. 2.8%; p = 0.009, respectively). The long-term survival (median follow-up 5.0 years (2.2-14.1 years)) of patients treated with the surgical approach was superior to that of patients undergoing TAVR (p < 0.001). CONCLUSION: Although the survival analysis revealed a higher in-hospital and 30-day survival rate for high-risk patients aged ≤75 years who underwent TAVR, iSAVR was associated with a significantly higher long-term survival rate.

New Insights and Current Approaches in Cardiac Hypertrophy Cell Culture, Tissue Engineering Models, and Novel Pathways Involving Non-Coding RNA.

Cardiac hypertrophy is an ongoing clinical challenge, as risk factors such as obesity, smoking and increasing age become more widespread, which lead to an increasing prevalence of developing hypertrophy. Pathological hypertrophy is a maladaptive response to stress conditions, such as pressure overload, and involve a number of changes in cellular mechanisms, gene expression and pathway regulations. Although several important pathways involved in the remodeling and hypertrophy process have been identified, further research is needed to achieve a better understanding and explore new and better treatment options. More recently discovered pathways showed the involvement of several non-coding RNAs, including micro RNAs (miRNAs), long non-coding RNAs (lncRNAs), and circular RNAs (circRNAs), which either promote or inhibit the remodeling process and pose a possible target for novel therapy approaches. In vitro modeling serves as a vital tool for this further pathway analysis and treatment testing and has vastly improved over the recent years, providing a less costly and labor-intensive alternative to in vivo animal models.

Large Animal Models of Cell-Free Cardiac Regeneration.

The adult mammalian heart lacks the ability to sufficiently regenerate itself, leading to the progressive deterioration of function and heart failure after ischemic injuries such as myocardial infarction. Thus far, cell-based therapies have delivered unsatisfactory results, prompting the search for cell-free alternatives that can induce the heart to repair itself through cardiomyocyte proliferation, angiogenesis, and advantageous remodeling. Large animal models are an invaluable step toward translating basic research into clinical applications. In this review, we give an overview of the state-of-the-art in cell-free cardiac regeneration therapies that have been tested in large animal models, mainly pigs. Cell-free cardiac regeneration therapies involve stem cell secretome- and extracellular vesicles (including exosomes)-induced cardiac repair, RNA-based therapies, mainly regarding microRNAs, but also modified mRNA (modRNA) as well as other molecules including growth factors and extracellular matrix components. Various methods for the delivery of regenerative substances are used, including adenoviral vectors (AAVs), microencapsulation, and microparticles. Physical stimulation methods and direct cardiac reprogramming approaches are also discussed.

Circular RNAs in Cardiac Regeneration: Cardiac Cell Proliferation, Differentiation, Survival, and Reprogramming.

Circular RNAs (circRNAs) are classified as long non-coding RNAs (lncRNAs) that are characterized by a covalent closed-loop structure. This closed-loop shape is the result of a backsplicing event in which the 3' and 5' splice sites are ligated. Through the lack of 3' poly(A) tails and 5' cap structures, circRNAs are more stable than linear RNAs because these adjustments make the circular loop less susceptible to exonucleases. The majority of identified circRNAs possess cell- and tissue-specific expression patterns. In addition, high-throughput RNA-sequencing combined with novel bioinformatics algorithms revealed that circRNA sequences are often conserved across different species suggesting a positive evolutionary pressure. Implicated as regulators of protein turnover, micro RNA (miRNA) sponges, or broad effectors in cell differentiation, proliferation, and senescence, research of circRNA has increased in recent years. Particularly in cardiovascular research, circRNA-related discoveries have opened the door for the development of potential diagnostic and therapeutic tools. Increasing evidence links deviating circRNA expression patterns to various cardiovascular diseases including ischemic heart failure. In this mini-review, we summarize the current state of knowledge on circRNAs in cardiac regeneration with a focus on cardiac cell proliferation, differentiation, cardiomyocyte survival, and cardiac reprogramming.

Association between Circular RNA CDR1as and Post-Infarction Cardiac Function in Pig Ischemic Heart Failure: Influence of the Anti-Fibrotic Natural Compounds Bufalin and Lycorine.

Anti-fibrotic therapies are of increasing interest to combat cardiac remodeling and heart failure progression. Recently, anti-fibrotic circular RNAs (circRNAs) have been identified in human and rodent cardiac tissue. In vivo (rodent) experiments proved cardiac anti-fibrotic effects of the natural compounds bufalin and lycorine by downregulating miRNA-671-5p, associated with a theoretic increase in the tissue level of circRNA CDR1as. Accordingly, we hypothesized that both anti-fibrotic drugs may inhibit focal myocardial fibrosis of the remodeled left ventricle (LV) also in a translational large animal model of heart failure (HF). Domestic pigs were repeatedly treated with subcutaneous injections of either bufalin, lycorine, or saline, (n = 5/group) between days 7-21 post acute myocardial infarction (AMI). At the 2-month follow-up, both bufalin and lycorine led to significantly reduced cardiac fibrosis. Bufalin treatment additionally led to smaller end-diastolic volumes, higher LV ejection fraction (EF), and increased expression of CDR1as of the AMI region. Elevated tissue levels of the circRNA CDR1as in the AMI region of the pig heart correlated significantly with LV and right ventricular EF, LV stroke volume, and negatively with infarct size. In conclusion, we successfully identified the circRNA CDR1as in pig hearts and show a significant association with improved LV and RV function by anti-fibrotic therapies in a translational animal model of HF.