Cardioprotection of Canagliflozin, Dapagliflozin, and Empagliflozin: Lessons from preclinical studies

Clinical and preclinical studies have elucidated the favorable effects of Inhibitors of Sodium-Glucose Cotransporter-2 (iSGLT2) in patients and animal models with type 2 diabetes. Notably, these inhibitors have shown significant benefits in reducing hospitalizations and mortality among patients with heart failure. However, despite their incorporation into clinical practice for indications beyond diabetes, the decision-making process regarding their use often lacks a systematic approach. The selection of iSGLT2 remains arbitrary, with only a limited number of studies simultaneously exploring the different classes of them. Currently, no unique guideline establishes their application in both clinical and basic research. This review delves into the prevalent use of iSGLT2 in animal models previously subjected to induced cardiac stress. We have compiled key findings related to cardioprotection across various animal models, encompassing diverse dosages and routes of administration. Beyond their established role in diabetes management, iSGLT2 has demonstrated utility as agents for safeguarding heart health and cardioprotection can be class-dependent among the iSGLT2. These findings may serve as valuable references for other researchers. Preclinical studies play a pivotal role in ensuring the safety of novel compounds or treatments for potential human use. By assessing side effects, toxicity, and optimal dosages, these studies offer a robust foundation for informed decisions, identifying interventions with the highest likelihood of success and minimal risk to patients. The insights gleaned from preclinical studies, which play a crucial role in highlighting areas of knowledge deficiency, can guide the exploration of novel mechanisms and strategies involving iSGLT2.

Preventive and treatment efficiency of dendrosomal nano-curcumin against ISO-induced cardiac fibrosis in mouse model

Cardiac fibrosis (c-fibrosis) is a critical factor in cardiovascular diseases, leading to impaired cardiac function and heart failure. This study aims to optimize the isoproterenol (ISO)-induced c-fibrosis model and evaluate the therapeutic efficacy of dendrosomal nano-curcumin (DNC) in both in-vitro and in-vivo conditions. Also, we were looking for the differentially expressed genes following the c-fibrosis induction. At the in-vitro condition, primary cardiac fibroblasts were exclusively cultured on collagen-coated or polystyrene plates and, were treated with ISO for fibrosis induction and post-treated or co-treated with DNC. RT-qPCR and flow cytometry analysis indicated that DNC treatment attenuated the fibrotic effect of ISO treatment in these cells. At the in-vivo condition, our findings demonstrated that ISO treatment effectively induces cardiac (and pulmonary) fibrosis, characterized by pro-fibrotic and pro-inflammatory gene expression and IHC (α-SMA, COL1A1, and TGFβ). Interestingly, fibrosis symptoms were reduced following the pretreatment, co-treatment, or post-treatment of DNC with ISO. Additionally, the intensive RNAseq analysis suggested the COMP gene is differentially expressed following the c-fibrosis and our RT-qPCR analysis suggested it as a novel potential marker. Overall, our results promise the application of DNC as a potential preventive or therapy agent before and after heart challenges that lead to c-fibrosis.

Comparison of mouse models of heart failure with reduced ejection fraction

AIMS

Heart failure with reduced ejection fraction (HFrEF) is a leading cause of death worldwide; thus, therapeutic improvements are needed. In vivo preclinical models are essential to identify molecular drug targets for future therapies. Transverse aortic constriction (TAC) is a well-established model of HFrEF; however, highly experienced personnel are needed for the surgery, and several weeks of follow-up are necessary to develop HFrEF. To this end, we aimed (i) to develop an easy-to-perform mouse model of HFrEF by treating Balb/c mice with angiotensin-II (Ang-II) for 2 weeks by minipump and (ii) to compare its cardiac phenotype and transcriptome to the well-established TAC model of HFrEF in C57BL/6J mice.

METHODS

Mortality and gross pathological data, cardiac structural and functional characteristics assessed by echocardiography and immunohistochemistry and differential gene expression obtained by RNA-sequencing and gene-ontology analyses were used to characterize and compare the two models. To achieve statistical comparability between the two models, changes in treatment groups related to the corresponding control were compared (ΔTAC vs. ΔAng-II).

RESULTS

Compared with the well-established TAC model, chronic Ang-II treatment of Balb/c mice shares similarities in cardiac systolic functional decline (left ventricular ejection fraction: -57.25 ± 7.17% vs. -43.68 ± 5.31% in ΔTAC vs. ΔAng-II; P = 0.1794) but shows a lesser degree of left ventricular dilation (left ventricular end-systolic volume: 190.81 ± 44.13 vs. 57.37 ± 10.18 mL in ΔTAC vs. ΔAng-II; P = 0.0252) and hypertrophy (cell surface area: 58.44 ± 6.1 vs. 10.24 ± 2.87 μm2 in ΔTAC vs. ΔAng-II; P < 0.001); nevertheless, transcriptomic changes in the two HFrEF models show strong correlation (Spearman's r = 0.727; P < 0.001). In return, Ang-II treatment in Balb/c mice needs significantly less procedural time [38 min, interquartile range (IQR): 31-46 min in TAC vs. 6 min, IQR: 6-7 min in Ang-II; P < 0.001] and surgical expertise, is less of an object for peri-procedural mortality (15.8% in TAC vs. 0% in Ang-II; P = 0.105) and needs significantly shorter follow-up for developing HFrEF.

CONCLUSIONS

Here, we demonstrate for the first time that chronic Ang-II treatment of Balb/c mice is also a relevant, reliable but significantly easier-to-perform preclinical model to identify novel pathomechanisms and targets in future HFrEF research.

From Beats to Metabolism: the Heart at the Core of Interorgan Metabolic Cross Talk

The heart, once considered a mere blood pump, is now recognized as a multifunctional metabolic and endocrine organ. Its function is tightly regulated by various metabolic processes, at the same time it serves as an endocrine organ, secreting bioactive molecules that impact systemic metabolism. In recent years, research has shed light on the intricate interplay between the heart and other metabolic organs, such as adipose tissue, liver, and skeletal muscle. The metabolic flexibility of the heart and its ability to switch between different energy substrates play a crucial role in maintaining cardiac function and overall metabolic homeostasis. Gaining a comprehensive understanding of how metabolic disorders disrupt cardiac metabolism is crucial, as it plays a pivotal role in the development and progression of cardiac diseases. The emerging understanding of the heart as a metabolic and endocrine organ highlights its essential contribution to whole body metabolic regulation and offers new insights into the pathogenesis of metabolic diseases, such as obesity, diabetes, and cardiovascular disorders. In this review, we provide an in-depth exploration of the heart's metabolic and endocrine functions, emphasizing its role in systemic metabolism and the interplay between the heart and other metabolic organs. Furthermore, emerging evidence suggests a correlation between heart disease and other conditions such as aging and cancer, indicating that the metabolic dysfunction observed in these conditions may share common underlying mechanisms. By unraveling the complex mechanisms underlying cardiac metabolism, we aim to contribute to the development of novel therapeutic strategies for metabolic diseases and improve overall cardiovascular health.

Control of cardiac contractions using Cre-lox and degron strategies in zebrafish

Cardiac contractions and hemodynamic forces are essential for organ development and homeostasis. Control over cardiac contractions can be achieved pharmacologically or optogenetically. However, these approaches lack specificity or require direct access to the heart. Here, we compare two genetic approaches to control cardiac contractions by modulating the levels of the essential sarcomeric protein Tnnt2a in zebrafish. We first recombine a newly generated tnnt2a floxed allele using multiple lines expressing Cre under the control of cardiomyocyte-specific promoters, and show that it does not recapitulate the tnnt2a/silent heart mutant phenotype in embryos. We show that this lack of early cardiac contraction defects is due, at least in part, to the long half-life of tnnt2a mRNA, which masks the gene deletion effects until the early larval stages. We then generate an endogenous Tnnt2a-eGFP fusion line that we use together with the zGRAD system to efficiently degrade Tnnt2a in all cardiomyocytes. Using single-cell transcriptomics, we find that Tnnt2a depletion leads to cardiac phenotypes similar to those observed in tnnt2a mutants, with a loss of blood and pericardial flow-dependent cell types. Furthermore, we achieve conditional degradation of Tnnt2a-eGFP by splitting the zGRAD protein into two fragments that, when combined with the cpFRB2-FKBP system, can be reassembled upon rapamycin treatment. Thus, this Tnnt2a degradation line enables non-invasive control of cardiac contractions with high spatial and temporal specificity and will help further understand how they shape organ development and homeostasis.

Takotsubo syndrome is a coronary microvascular disease: experimental evidence

BACKGROUND AND AIMS

Takotsubo syndrome (TTS) is a conundrum without consensus about the cause. In a murine model of coronary microvascular dysfunction (CMD), abnormalities in myocardial perfusion played a key role in the development of TTS.

METHODS AND RESULTS

Vascular Kv1.5 channels connect coronary blood flow to myocardial metabolism and their deletion mimics the phenotype of CMD. To determine if TTS is related to CMD, wild-type (WT), Kv1.5-/-, and TgKv1.5-/- (Kv1.5-/- with smooth muscle-specific expression Kv1.5 channels) mice were studied following transaortic constriction (TAC). Measurements of left ventricular (LV) fractional shortening (FS) in base and apex, and myocardial blood flow (MBF) were completed with standard and contrast echocardiography. Ribonucleic Acid deep sequencing was performed on LV apex and base from WT and Kv1.5-/- (control and TAC). Changes in gene expression were confirmed by real-time-polymerase chain reaction. MBF was increased with chromonar or by smooth muscle expression of Kv1.5 channels in the TgKv1.5-/-. TAC-induced systolic apical ballooning in Kv1.5-/-, shown as negative FS (P < 0.05 vs. base), which was not observed in WT, Kv1.5-/- with chromonar, or TgKv1.5-/-. Following TAC in Kv1.5-/-, MBF was lower in LV apex than in base. Increasing MBF with either chromonar or in TgKv1.5-/- normalized perfusion and function between LV apex and base (P = NS). Some genetic changes during TTS were reversed by chromonar, suggesting these were independent of TAC and more related to TTS.

CONCLUSION

Abnormalities in flow regulation between the LV apex and base cause TTS. When perfusion is normalized between the two regions, normal ventricular function is restored.

Understanding the Pathogenesis of Cardiac Complications in Patients with Propionic Acidemia and Exploring Therapeutic Alternatives for Those Who Are Not Eligible or Are Waiting for Liver Transplantation

The guidelines for the management of patients affected by propionic acidemia (PA) recommend standard cardiac therapy in the presence of cardiac complications. A recent revision questioned the impact of high doses of coenzyme Q10 on cardiac function in patients with cardiomyopathy (CM). Liver transplantation is a therapeutic option for several patients since it may stabilize or reverse CM. Both the patients waiting for liver transplantation and, even more, the ones not eligible for transplant programs urgently need therapies to improve cardiac function. To this aim, the identification of the pathogenetic mechanisms represents a key point. Aims: This review summarizes: (1) the current knowledge of the pathogenetic mechanisms underlying cardiac complications in PA and (2) the available and potential pharmacological options for the prevention or the treatment of cardiac complications in PA. To select articles, we searched the electronic database PubMed using the Mesh terms "propionic acidemia" OR "propionate" AND "cardiomyopathy" OR "Long QT syndrome". We selected 77 studies, enlightening 12 potential disease-specific or non-disease-specific pathogenetic mechanisms, namely: impaired substrate delivery to TCA cycle and TCA dysfunction, secondary mitochondrial electron transport chain dysfunction and oxidative stress, coenzyme Q10 deficiency, metabolic reprogramming, carnitine deficiency, cardiac excitation-contraction coupling alteration, genetics, epigenetics, microRNAs, micronutrients deficiencies, renin-angiotensin-aldosterone system activation, and increased sympathetic activation. We provide a critical discussion of the related therapeutic options. Current literature supports the involvement of multiple cellular pathways in cardiac complications of PA, indicating the growing complexity of their pathophysiology. Elucidating the mechanisms responsible for such abnormalities is essential to identify therapeutic strategies going beyond the correction of the enzymatic defect rather than engaging the dysregulated mechanisms. Although these approaches are not expected to be resolutive, they may improve the quality of life and slow the disease progression. Available pharmacological options are limited and tested in small cohorts. Indeed, a multicenter approach is mandatory to strengthen the efficacy of therapeutic options.

Qiangxin recipe improves doxorubicin-induced chronic heart failure by enhancing KLF5-mediated glucose metabolism

BACKGROUND

Qiangxin recipe (QXF) is a well-known Chinese herbal medicine commonly used in Asia for thousands of years to treat cardiovascular diseases, but its underlying mechanism remains unclear.

PURPOSE

This study aimed to illustrate whether Qiangxin Recipe (QXF) induce glucose metabolism and inhibit cardiomyocyte apoptosis by promoting the activation of the transcription factor Krüppel like factor 5 (KLF5).

MATERIAL AND METHODS

In vitro experiments, we constructed an H9C2 cardiomyocyte injury model using doxorubicin and used RNA-seq data analysis to detect the mechanism of QXF. In in vivo experiments, C57 BL/6 mice injected with doxorubicin (4 mg/kg every 6 days, for 30 days) to construct a CHF mouse model and randomly divided into to the normal control group, Dox group and Dox+QXF group (2.12 g/kg/day, 4.24 g/kg/day, for 30 days). Using Echocardiography, serum biochemical indices BNP, cTnl; and histopathological tests involving HE staining, Tunel staining and Immuno-dual fluorescence colocalization to analyze the therapeutic mechanism of QXF.

RESULTS

We verified that the Qiangxin recipe could reverse cardiomyocyte dying through enhancing glucose metabolism and reducing apoptosis to improve CHF. Mechanistically, we discovered that the Qiangxin recipe promoted the activation of transcription factor Krüppel-like factor 5 (KLF5) to induce glucose metabolism and inhibit apoptosis in cardiomyocytes. Further, we identified that KLF5 increased the promoter activity of hexokinase 2 (HK2) and B-cell CLL/lymphoma 2 (BCL2) genes, which further enhanced glucose metabolism and inhibited apoptosis of cardiomyocytes.

CONCLUSIONS

We highlighted the importance of KLF5-mediated signaling pathways in the treatment of CHF as shown by their participation in glucose metabolism and apoptosis in a doxorubicin-induced model of cardiomyocyte injury, as well as show that Qiangxin recipe can be used as a novel targeted therapy for the treatment of CHF. Compared with previous studies, we provide new ideas for the treatment of Doxorubicin-induced CHF from the perspective of energy metabolism.

A review on experimental surgical models and anesthetic protocols of heart failure in rats

Heart failure (HF) is a serious health and economic burden worldwide, and its prevalence is continuously increasing. Current medications effectively moderate the progression of symptoms, and there is a need for novel preventative and reparative treatments. The development of novel HF treatments requires the testing of potential therapeutic procedures in appropriate animal models of HF. During the past decades, murine models have been extensively used in fundamental and translational research studies to better understand the pathophysiological mechanisms of HF and develop more effective methods to prevent and control congestive HF. Proper surgical approaches and anesthetic protocols are the first steps in creating these models, and each successful approach requires a proper anesthetic protocol that maintains good recovery and high survival rates after surgery. However, each protocol may have shortcomings that limit the study's outcomes. In addition, the ethical regulations of animal welfare in certain countries prohibit the use of specific anesthetic agents, which are widely used to establish animal models. This review summarizes the most common and recent surgical models of HF and the anesthetic protocols used in rat models. We will highlight the surgical approach of each model, the use of anesthesia, and the limitations of the model in the study of the pathophysiology and therapeutic basis of common cardiovascular diseases.

Ultrathin and Flexible Bioelectronic Arrays for Functional Measurement of iPSC-Cardiomyocytes under Cardiotropic Drug Administration and Controlled Microenvironments

Emerging heart-on-a-chip technology is a promising tool to establish in vitro cardiac models for therapeutic testing and disease modeling. However, due to the technical complexity of integrating cell culture chambers, biosensors, and bioreactors into a single entity, a microphysiological system capable of reproducing controlled microenvironmental cues to regulate cell phenotypes, promote iPS-cardiomyocyte maturity, and simultaneously measure the dynamic changes of cardiomyocyte function in situ is not available. This paper reports an ultrathin and flexible bioelectronic array platform in 24-well format for higher-throughput contractility measurement under candidate drug administration or defined microenvironmental conditions. In the array, carbon black (CB)-PDMS flexible strain sensors were embedded for detecting iPSC-CM contractility signals. Carbon fiber electrodes and pneumatic air channels were integrated to provide electrical and mechanical stimulation to improve iPSC-CM maturation. Performed experiments validate that the bioelectronic array accurately reveals the effects of cardiotropic drugs and identifies mechanical/electrical stimulation strategies for promoting iPSC-CM maturation.

Experimental heart failure models in small animals

Heart failure (HF) is one of the most critical health and economic burdens worldwide, and its prevalence is continuously increasing. HF is a disease that occurs due to a pathological change arising from the function or structure of the heart tissue and usually progresses. Numerous experimental HF models have been created to elucidate the pathophysiological mechanisms that cause HF. An understanding of the pathophysiology of HF is essential for the development of novel efficient therapies. During the past few decades, animal models have provided new insights into the complex pathogenesis of HF. Success in the pathophysiology and treatment of HF has been achieved by using animal models of HF. The development of new in vivo models is critical for evaluating treatments such as gene therapy, mechanical devices, and new surgical approaches. However, each animal model has advantages and limitations, and none of these models is suitable for studying all aspects of HF. Therefore, the researchers have to choose an appropriate experimental model that will fully reflect HF. Despite some limitations, these animal models provided a significant advance in the etiology and pathogenesis of HF. Also, experimental HF models have led to the development of new treatments. In this review, we discussed widely used experimental HF models that continue to provide critical information for HF patients and facilitate the development of new treatment strategies.

Contraction pressure analysis using optical imaging in normal and MYBPC3-mutated hiPSC-derived cardiomyocytes grown on matrices with tunable stiffness

Current in vivo disease models and analysis methods for cardiac drug development have been insufficient in providing accurate and reliable predictions of drug efficacy and safety. Here, we propose a custom optical flow-based analysis method to quantitatively measure recordings of contracting cardiomyocytes on polydimethylsiloxane (PDMS), compatible with medium-throughput systems. Movement of the PDMS was examined by covalently bound fluorescent beads on the PDMS surface, differences caused by increased substrate stiffness were compared, and cells were stimulated with β-agonist. We further validated the system using cardiomyocytes treated with endothelin-1 and compared their contractions against control and cells incubated with receptor antagonist bosentan. After validation we examined two MYBPC3-mutant patient-derived cell lines. Recordings showed that higher substrate stiffness resulted in higher contractile pressure, while beating frequency remained similar to control. β-agonist stimulation resulted in both higher beating frequency as well as higher pressure values during contraction and relaxation. Cells treated with endothelin-1 showed an increased beating frequency, but a lower contraction pressure. Cells treated with both endothelin-1 and bosentan remained at control level of beating frequency and pressure. Lastly, both MYBPC3-mutant lines showed a higher beating frequency and lower contraction pressure. Our validated method is capable of automatically quantifying contraction of hiPSC-derived cardiomyocytes on a PDMS substrate of known shear modulus, returning an absolute value. Our method could have major benefits in a medium-throughput setting.

Daidzein alleviates doxorubicin-induced heart failure via the SIRT3/FOXO3a signaling pathway

Heart failure (HF) is a clinical syndrome characterized by typical symptoms that usually occur at the end stage of various heart diseases and lead to death. Daidzein (DAI), an isoflavone found in soy foods, is widely used to treat menopausal syndrome, prostate cancer, breast cancer, heart disease, cardiovascular disease, and osteoporosis, and has anti-oxidant and anti-inflammatory properties. However, the effects of DAI in HF remain unknown. In this study, doxorubicin (DOX) was used to establish HF models of C57BL/6J mice and H9c2 cells with DAI treatment. Our results showed that DAI markedly improved the DOX-induced decline in cardiac function, and decreased the left ventricular ejection fraction, cardiac inflammation, oxidative stress, apoptosis, and fibrosis. Mechanistically, DAI affects cardiac energy metabolism by regulating SIRT3, and meets the ATP demand of the heart by improving glucose, lipid, and ketone body metabolism as well as restoring mitochondrial dysfunction in vivo and in vitro. Additionally, DAI can exert an antioxidant function and alleviate HF through the SIRT3/FOXO3a pathway. In conclusion, we demonstrate that DAI alleviates DOX-induced cardiotoxicity by regulating cardiac energy metabolism as well as reducing inflammation, oxidative stress, apoptosis and fibrosis, indicating its potential application for HF treatment.

A Carbon-Based Biosensing Platform for Simultaneously Measuring the Contraction and Electrophysiology of iPSC-Cardiomyocyte Monolayers

Heart beating is triggered by the generation and propagation of action potentials through the myocardium, resulting in the synchronous contraction of cardiomyocytes. This process highlights the importance of electrical and mechanical coordination in organ function. Investigating the pathogenesis of heart diseases and potential therapeutic actions in vitro requires biosensing technologies which allow for long-term and simultaneous measurement of the contractility and electrophysiology of cardiomyocytes. However, the adoption of current biosensing approaches for functional measurement of in vitro cardiac models is hampered by low sensitivity, difficulties in achieving multifunctional detection, and costly manufacturing processes. Leveraging carbon-based nanomaterials, we developed a biosensing platform that is capable of performing on-chip and simultaneous measurement of contractility and electrophysiology of human induced pluripotent stem-cell-derived cardiomyocyte (iPSC-CM) monolayers. This platform integrates with a flexible thin-film cantilever embedded with a carbon black (CB)-PDMS strain sensor for high-sensitivity contraction measurement and four pure carbon nanotube (CNT) electrodes for the detection of extracellular field potentials with low electrode impedance. Cardiac functional properties including contractile stress, beating rate, beating rhythm, and extracellular field potential were evaluated to quantify iPSC-CM responses to common cardiotropic agents. In addition, an in vitro model of drug-induced cardiac arrhythmia was established to further validate the platform for disease modeling and drug testing.

Change of Heart: the Epitranscriptome of Small Non-coding RNAs in Heart Failure

Purpose of Review

Small non-coding RNAs regulate gene expression and are highly implicated in heart failure. Recently, an additional level of post-transcriptional regulation has been identified, referred to as the epitranscriptome, which encompasses the body of post-transcriptional modifications that are placed on RNA molecules. In this review, we summarize the current knowledge on the small non-coding RNA epitranscriptome in heart failure.

Recent Findings

With the rise of new methods to study RNA modifications, epitranscriptome research has begun to take flight. Over the past 3 years, the number of publications on the epitranscriptome in heart failure has significantly increased, and we expect many more highly relevant publications to come out over the next few years.

Summary

Currently, at least six modifications on small non-coding RNAs have been investigated in heart failure-relevant studies, namely N6-adenosine, N5-cytosine and N7-guanosine methylation, 2’-O-ribose-methylation, adenosine-to-inosine editing, and isomiRs. Their potential role in heart failure is discussed.

Microengineered platforms for characterizing the contractile function of in vitro cardiac models

Emerging heart-on-a-chip platforms are promising approaches to establish cardiac cell/tissue models in vitro for research on cardiac physiology, disease modeling and drug cardiotoxicity as well as for therapeutic discovery. Challenges still exist in obtaining the complete capability of in situ sensing to fully evaluate the complex functional properties of cardiac cell/tissue models. Changes to contractile strength (contractility) and beating regularity (rhythm) are particularly important to generate accurate, predictive models. Developing new platforms and technologies to assess the contractile functions of in vitro cardiac models is essential to provide information on cell/tissue physiologies, drug-induced inotropic responses, and the mechanisms of cardiac diseases. In this review, we discuss recent advances in biosensing platforms for the measurement of contractile functions of in vitro cardiac models, including single cardiomyocytes, 2D monolayers of cardiomyocytes, and 3D cardiac tissues. The characteristics and performance of current platforms are reviewed in terms of sensing principles, measured parameters, performance, cell sources, cell/tissue model configurations, advantages, and limitations. In addition, we highlight applications of these platforms and relevant discoveries in fundamental investigations, drug testing, and disease modeling. Furthermore, challenges and future outlooks of heart-on-a-chip platforms for in vitro measurement of cardiac functional properties are discussed.

Evaluation of β-adrenergic ligands for development of pharmacological heart failure and transparency models in zebrafish

Cardiovascular toxicity represents one of the most common reasons for clinical trial failure. Consequently, early identification of novel cardioprotective strategies could prevent the later-stage drug-induced cardiac side effects. The use of zebrafish (Danio rerio) in preclinical studies has greatly increased. High-throughput and low-cost of assays make zebrafish model ideal for initial drug discovery. A common strategy to induce heart failure is a chronic β-adrenergic (βAR) stimulation. Herein, we set out to test a panel of βAR agonists to develop a pharmacological heart failure model in zebrafish. We assessed βAR agonists with respect to the elicited mortality, changes in heart rate, and morphological alterations in zebrafish larvae according to Fish Embryo Acute Toxicity Test. Among the tested βAR agonists, epinephrine elicited the most potent onset of heart stimulation (EC₅₀ = 0.05 mM), which corresponds with its physiological role as catecholamine. However, when used at ten-fold higher dose (0.5 mM), the same compound caused severe heart rate inhibition (-28.70 beats/min), which can be attributed to its cardiotoxicity. Further studies revealed that isoetharine abolished body pigmentation at the sublethal dose of 7.50 mM. Additionally, as a proof of concept that zebrafish can mimic human cardiac physiology, we tested βAR antagonists (propranolol, carvedilol, metoprolol, and labetalol) and verified that they inhibited fish heart rate in a similar fashion as in humans. In conclusion, we proposed two novel pharmacological models in zebrafish; i.e., epinephrine-dependent heart failure and isoetharine-dependent transparent zebrafish. We provided strong evidence that the zebrafish model constitutes a valuable tool for cardiovascular research.

Models of cardiovascular surgery biobanking to facilitate translational research and precision medicine

Biobanking in health care has evolved over the last few decades from simple biological sample repositories to complex and dynamic units with multi‐organizational infrastructure networks and has become an essential tool for modern medical research. Cardiovascular tissue biobanking provides a unique opportunity to utilize cardiac and vascular samples for translational research into heart failure and other related pathologies. Current techniques for diagnosis, classification, and treatment monitoring of cardiac disease relies primarily on interpretation of clinical signs, imaging, and blood biomarkers. Further research at the disease source (i.e. myocardium and blood vessels) has been limited by a relative lack of access to quality human cardiac tissue and the inherent shortcomings of most animal models of heart disease. In this review, we describe a model for cardiovascular tissue biobanking and databasing, and its potential to facilitate basic and translational research. We share techniques to procure endocardial samples from patients with hypertrophic cardiomyopathy, heart failure with reduced ejection fraction, and heart failure with preserved ejection fraction, in addition to aortic disease samples. We discuss some of the issues with respect to data collection, privacy, biobank consent, and the governance of tissue biobanking. The development of tissue biobanks as described here has significant scope to improve and facilitate translational research in multi‐omic fields such as genomics, transcriptomics, proteomics, and metabolomics. This research heralds an era of precision medicine, in which patients with cardiovascular pathology can be provided with optimized and personalized medical care for the treatment of their individual phenotype.

Compound Danshen Dripping Pill inhibits doxorubicin or isoproterenol-induced cardiotoxicity

Heart failure (HF) is the advanced heart disease with high morbidity and mortality. Compound DanShen Dripping Pill (CDDP) is a widely used Traditional Chinese Medicine for cardiovascular disease treatment. Herein, we investigated if CDDP can protect mice against doxorubicin (DOX) or isoprenaline (ISO)-induced HF. After 3 days feeding of normal chow containing CDDP, mice were started DOX or ISO treatment for 4 weeks or 18 days. At the end of treatment, mice were conducted electrocardiogram and echocardiographic test. Blood and heart samples were determined biochemical parameters, myocardial structure and expression of the related molecules. CDDP normalized DOX/ISO-induced heart weight changes, HF parameters and fibrogenesis. The DOX/ISO-impaired left ventricular ejection fraction and fractional shortening were restored by CDDP. Mechanistically, CDDP blocked DOX/ISO-inhibited expression of antioxidant enzymes and DOX/ISO-induced expression of pro-fibrotic molecules, inflammation and cell apoptosis. Additional DOX/ISO-impaired targets in cardiac function but protected by CDDP were identified by RNAseq, qRT-PCR and Western blot. In addition, CDDP protected cardiomyocytes against oxygen-glucose deprivation-induced injuries. Taken together, our study shows that CDDP can protect against myocardial injuries in different models, suggesting its potential application for HF treatment.

Stress-driven cardiac calcium mishandling via a kinase-to-kinase crosstalk

Calcium homeostasis in the cardiomyocyte is critical to the regulation of normal cardiac function. Abnormal calcium dynamics such as altered uptake by the sarcoplasmic reticulum (SR) Ca²⁺-ATPase and increased diastolic SR calcium leak are involved in the development of maladaptive cardiac remodeling under pathological conditions. Ca²⁺/calmodulin-dependent protein kinase II-δ (CaMKIIδ) is a well-recognized key molecule in calcium dysregulation in cardiomyocytes. Elevated cellular stress is known as a common feature during pathological remodeling, and c-jun N-terminal kinase (JNK) is an important stress kinase that is activated in response to intrinsic and extrinsic stress stimuli. Our lab recently identified specific actions of JNK isoform 2 (JNK2) in CaMKIIδ expression, activation, and CaMKIIδ-dependent SR Ca²⁺ mishandling in the stressed heart. This review focuses on the current understanding of cardiac SR calcium handling under physiological and pathological conditions as well as the newly identified contribution of the stress kinase JNK2 in CaMKIIδ-dependent SR Ca²⁺ abnormal mishandling. The new findings identifying dual roles of JNK2 in CaMKIIδ expression and activation are also discussed in this review.

Cardiomyocytes Derived from Induced Pluripotent Stem Cells as a Disease Model for Propionic Acidemia

Propionic acidemia (PA), one of the most frequent life-threatening organic acidemias, is caused by mutations in either the PCCA or PCCB genes encoding both subunits of the mitochondrial propionyl-CoA carboxylase (PCC) enzyme. Cardiac alterations (hypertrophy, dilated cardiomyopathy, long QT) are one of the major causes of mortality in patients surviving the neonatal period. To overcome limitations of current cellular models of PA, we generated induced pluripotent stem cells (iPSCs) from a PA patient with defects in the PCCA gene, and successfully differentiated them into cardiomyocytes. PCCA iPSC-derived cardiomyocytes exhibited reduced oxygen consumption, an accumulation of residual bodies and lipid droplets, and increased ribosomal biogenesis. Furthermore, we found increased protein levels of HERP, GRP78, GRP75, SIG-1R and MFN2, suggesting endoplasmic reticulum stress and calcium perturbations in these cells. We also analyzed a series of heart-enriched miRNAs previously found deregulated in the heart tissue of a PA murine model and confirmed their altered expression. Our novel results show that PA iPSC-cardiomyocytes represent a promising model for investigating the pathological mechanisms underlying PA cardiomyopathies, also serving as an ex vivo platform for therapeutic evaluation.

Preparation and Identification of Cardiac Myofibrils from Whole Heart Samples

Mouse models are extensively studied and well-used to study cardiomyopathies due to the genetic relevance of this model organism and increasing need to identify therapeutic targets. Cardiac myofibril preparation for whole hearts has proved to be an invaluable in vitro method for determining the fundamental molecular mechanisms in heart failure. The technique described below consistently yields intact cardiac myofibrils, which can be used in subsequent techniques such as western blotting, immunofluorescence, and mass spectrometry. Here, we describe a method to optimize the separation and yield of cardiac myofibrils from murine whole tissue samples and preparation for subsequent mass spectrometry. This method allows for quick visual identification of multiple cardiac myofibril proteins.

Genomic characterization reveals novel mechanisms underlying the valosin-containing protein-mediated cardiac protection against heart failure

Chronic hypertension is a key risk factor for heart failure. However, the underlying molecular mechanisms are not fully understood. Our previous studies found that the valosin-containing protein (VCP), an ATPase-associated protein, was significantly decreased in the hypertensive heart tissues. In this study, we tested the hypothesis that restoration of VCP protected the heart against pressure overload-induced heart failure. With a cardiac-specific transgenic (TG) mouse model, we showed that a moderate increase of VCP was able to attenuate chronic pressure overload-induced maladaptive cardiac hypertrophy and dysfunction. RNA sequencing and a comprehensive bioinformatic analysis further demonstrated that overexpression of VCP in the heart normalized the pressure overload-stimulated hypertrophic signals and repressed the stress-induced inflammatory response. In addition, VCP overexpression promoted cell survival by enhancing the mitochondria resistance to the oxidative stress via activating the Rictor-mediated-gene networks. VCP was also found to be involved in the regulation of the alternative splicing and differential isoform expression for some genes that are related to ATP production and protein synthesis by interacting with long no-coding RNAs and histone deacetylases, indicating a novel epigenetic regulation of VCP in integrating coding and noncoding genomic network in the stressed heart. In summary, our study demonstrated that the rescuing of a deficient VCP in the heart could prevent pressure overload-induced heart failure by rectifying cardiac hypertrophic and inflammatory signaling and enhancing the cardiac resistance to oxidative stress, which brought in novel insights into the understanding of the mechanism of VCP in protecting patients from hypertensive heart failure.

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Deficiency of VCP contributes to the pathogenesis of hypertensive heart failure.

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Rescue of VCP prevents stress-induced cardiac remodeling and cell death.

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VCP attenuates stress-induced inflammatory and hypertrophic signaling.

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VCP promotes cardiac resistance to oxidative stress.

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VCP mediates a novel epigenetic integrating regulation in the stressed heart.

Multiparametric Mechanistic Profiling of Inotropic Drugs in Adult Human Primary Cardiomyocytes

Effects of non-cardiac drugs on cardiac contractility can lead to serious adverse events. Furthermore, programs aimed at treating heart failure have had limited success and this therapeutic area remains a major unmet medical need. The challenges in assessing drug effect on cardiac contractility point to the fundamental translational value of the current preclinical models. Therefore, we sought to develop an adult human primary cardiomyocyte contractility model that has the potential to provide a predictive preclinical approach for simultaneously predicting drug-induced inotropic effect (sarcomere shortening) and generating multi-parameter data to profile different mechanisms of action based on cluster analysis of a set of 12 contractility parameters. We report that 17 positive and 9 negative inotropes covering diverse mechanisms of action exerted concentration-dependent increases and decreases in sarcomere shortening, respectively. Interestingly, the multiparametric readout allowed for the differentiation of inotropes operating via distinct mechanisms. Hierarchical clustering of contractility transient parameters, coupled with principal component analysis, enabled the classification of subsets of both positive as well as negative inotropes, in a mechanism-related mode. Thus, human cardiomyocyte contractility model could accurately facilitate informed mechanistic-based decision making, risk management and discovery of molecules with the most desirable pharmacological profile for the correction of heart failure.

CRISPLD1: a novel conserved target in the transition to human heart failure

Heart failure is a major health problem worldwide with a significant morbidity and mortality rate. Although studied extensively in animal models, data from patients at the compensated disease stage are lacking. We sampled myocardium biopsies from aortic stenosis patients with compensated hypertrophy and moderate heart failure and used transcriptomics to study the transition to failure. Sequencing and comparative analysis of analogous samples of mice with transverse aortic constriction identified 25 candidate genes with similar regulation in response to pressure overload, reflecting highly conserved molecular processes. The gene cysteine-rich secretory protein LCCL domain containing 1 (CRISPLD1) is upregulated in the transition to failure in human and mouse and its function is unknown. Homology to ion channel regulatory toxins suggests a role in Ca²⁺ cycling. CRISPR/Cas9-mediated loss-of-function leads to dysregulated Ca²⁺ handling in human-induced pluripotent stem cell-derived cardiomyocytes. The downregulation of prohypertrophic, proapoptotic and Ca²⁺-signaling pathways upon CRISPLD1-KO and its upregulation in the transition to failure implicates a contribution to adverse remodeling. These findings provide new pathophysiological data on Ca²⁺ regulation in the transition to failure and novel candidate genes with promising potential for therapeutic interventions.

IRX1 hypermethylation promotes heart failure by inhibiting CXCL14 expression

To identify the mechanism and functions of IRX1 in heart failure (HF) and provide evidence for new therapies. Bioinformatic analysis was performed to select target genes in HF cells compared to normal groups. Experimental rats were treated in a controllable manner to explore how IRX1 methylation accounted for this disease in vivo. Cardiac ultrasonic and morphologic examinations were conducted to test the mouse heart and evaluate the degree of cardiac impairment at in the level of organization. GSEA analysis revealed the relative enrichment of functions. Immunofluorescent assays, western blotting and qRT-PCR were used to determine the DNA methylation and expression levels. IRX1 was hypermethylated in heart failure and identified as a target gene by bioinformatic analysis. Transverse aortic constriction (TAC) induced heart failure in rats, while 5-aza-2'-deoxycytidine (5-Aza) alleviated heart failure in rats according to medical cardiac indexes. Western blotting and qRT-PCR revealed that a conspicuous difference in the expression of IRX1 and CXCL14 between HF and normal cardiac cells. As a result of gene methylation, left ventricular hypertrophy and cardiac fibrosis is usually accompanied by heart failure. Moreover, is the results implied that the demethylation of IRX1 improves heart failure in vivo and in vitro. IRX1 methylation induced damaged cardiac function and even heart failure, which has important implications for HF treatment and diagnosis.

Implantation of an Isoproterenol Mini-Pump to Induce Heart Failure in Mice

Isoproterenol (ISO), is a non-selective beta-adrenergic agonist, that is used widely to induce cardiac injury in mice. While the acute model mimics stress-induced cardiomyopathy, the chronic model, administered through an osmotic pump, mimics advanced heart failure in humans. The purpose of the described protocol is to create the chronic ISO-induced heart failure model in mice using an implanted mini-pump. This protocol has been used to induce heart failure in 100+ strains of inbred mice. Techniques on surgical pump implantation are described in detail and may be relevant to anyone interested in creating a heart failure model in mice. In addition, the weekly cardiac remodeling changes based on echocardiographic parameters for each strain and expected time to model development are presented. In summary, the method is simple and reproducible. Continuous ISO administered via the implanted mini-pump over 3 to 4 weeks is sufficient to induce cardiac remodeling. Finally, the success for ISO model creation may be assessed in vivo by serial echocardiography demonstrating hypertrophy, ventricular dilation, and dysfunction.

"TRPV1 is a component of the atrial natriuretic signaling complex, and using orally delivered antagonists, presents a valid therapeutic target in the longitudinal reversal and treatment of cardiac hypertrophy and heart failure"

Activation of the atrial natriuretic signaling pathway is intrinsic to the pathological responses associated with a range of cardiovascular diseases that stress the heart, especially those involved in sustained cardiac pressure overload which induces hypertrophy and the pathological remodeling that frequently leads to heart failure. We identify transient receptor potential cation channel, subfamily V, member 1, as a regulated molecular component, and therapeutic target of this signaling system. Data show that TRPV1 is a physical component of the natriuretic peptide A, cGMP, PKG signaling complex, interacting with the Natriuretic Peptide Receptor 1 (NPR1), and upon binding its ligand, Natriuretic Peptide A (NPPA, ANP) TRPV1 activation is subsequently suppressed through production of cGMP and PKG mediated phosphorylation of the TRPV1 channel. Further, inhibition of TRPV1, with orally delivered drugs, suppresses chamber and myocyte hypertrophy, and can longitudinally improve in vivo heart function in mice exposed to chronic pressure overload induced by transverse aortic constriction, reversing pre-established hypertrophy induced by pressure load while restoring chamber function. TRPV1 is a physical and regulated component of the natriuretic peptide signaling system, and TRPV1 inhibition may provide a new treatment strategy for treating, and reversing the loss of function associated with cardiac hypertrophy and heart failure.

Cardioprotective Potential of an SGLT2 Inhibitor Against Doxorubicin-Induced Heart Failure

BACKGROUND AND OBJECTIVES

Recent studies have shown that sodium-glucose co-transporter 2 (SGLT2) inhibitors reduce the risk of heart failure (HF)-associated hospitalization and mortality in patients with diabetes. However, it is not clear whether SGLT2 inhibitors have a cardiovascular benefit in patients without diabetes. We aimed to determine whether empagliflozin (EMPA), an SGLT2 inhibitor, has a protective role in HF without diabetes.

METHODS

Cardiomyopathy was induced in C57BL/6J mice using intraperitoneal injection of doxorubicin (Dox). Mice with HF were fed a normal chow diet (NCD) or an NCD containing 0.03% EMPA. Then we analyzed their phenotypes and performed in vitro experiments to reveal underlying mechanisms of the EMPA's effects.

RESULTS

Mice fed NCD with EMPA showed improved heart function and reduced fibrosis. In vitro studies showed similar results. Phloridzin, a non-specific SGLT inhibitor, did not show any protective effect against Dox toxicity in H9C2 cells. SGLT2 inhibitor can cause increase in blood ketone levels. Beta hydroxybutyrate (βOHB), which is well known ketone body associated with SGLT2 inhibitor, showed a protective effect against Dox in H9C2 cells and in Dox-treated mice. These results suggest elevating βOHB might be a convincing mechanism for the protective effects of SGLT2 inhibitor.

CONCLUSIONS

SGLT2 inhibitors have a protective effect in Dox-induced HF in mice. This implied that SGLT2 inhibitor therapy could be a good treatment strategy even in HF patients without diabetes.

Deletion of protein kinase B2 preserves cardiac function by blocking interleukin-6-mediated injury and restores blood pressure during angiotensin II/high-salt-diet-induced hypertension

OBJECTIVE

Protein kinase B2 (AKT2) is implicated in cardiomyocyte survival during various stress conditions. However, the role of AKT2 in heart function, cardiac hypertrophy and blood pressure (BP) control during hypertension is not fully understood. Therefore, we sought to determine whether the deletion of AKT2 protects cardiac function during angiotensin II/high-salt-diet (AngII/HSD) treatment and find out the signaling pathway.

METHODS

Male C57BL/6J (wild type), AKT2 knockout and interleukin (IL)-6 knockout mice were fed a 4% NaCl diet for 5 weeks. In the last week, mice were split in two groups and infused subcutaneously with either vehicle or AngII (1.5 μg/h per mouse) for 1 week. Then, BP and cardiac function were assessed. Immunohistology of IL-6 and monocyte chemoattractant protein 1 was performed to detect inflammation in the heart. Masson's trichrome staining was performed to evaluate cardiac fibrosis. Heart tissue homogenates and neonatal mice cardiomyocytes were collected to analyze oxidative stress.

RESULTS

Compared with wild-type mice, AKT2 knockout mice maintained BP and showed better left ventricle ejection fraction, lower level of fibrosis, reduced oxidative stress, reduced IL-6 expression and less macrophage infiltration, when treated with AngII/HSD. IL-6 knockout mice treated with AngII/HSD also showed alleviated left ventricular function, fibrosis, oxidative stress and macrophage infiltration compared with wild type.

CONCLUSION

AKT2 deficiency prevents the development of AngII/HSD-induced hypertension, cardiac dysfunction and myocardial injury including oxidative stress, fibrosis and inflammation by suppressing IL-6 expression. These data reveal an important role of the AKT2-IL-6 pathway in mediating AngII/HSD-induced hypertension and cardiomyopathy.

MR Angiography of the Head/Neck Vascular System in Mice on a Clinical MRI System

Background

Magnetic resonance angiography (MRA) represents a clinical reference standard for the in vivo assessment of the vasculature. In this study, the potential of non-contrast-enhanced and contrast-enhanced angiography of the head/neck vasculature in mice on a clinical MR imaging system was tested.

Methods

All in vivo magnetic resonance imaging was performed with a 3T clinical system (Siemens). Non-contrast-enhanced (time-of-flight, TOF) and contrast-enhanced angiography (gadofosveset-trisodium, GdT) were performed in C57BL/6J mouse strain. Lumen-to-muscle ratios (LMRs) and area measurements were assessed. Histology was performed as reference standard of all relevant vascular structures.

Results

A close correlation between TOF (R² = 0.79; p < 0.05) and contrast-enhanced (GdT) angiography (R² = 0.92; p < 0.05) with histological area measurements was found. LMRs were comparable between both sequences. Regarding interobserver reproducibility, contrast-enhanced (GdT) angiography yielded a smaller 95% confidence interval and a closer interreader correlation compared to non-contrast-enhanced (TOF) measurements (−0.73–0.89; R² = 0.81 vs. −0.55–0.56; R² = 0.94).

Conclusion

This study demonstrates that non-contrast-enhanced and contrast-enhanced angiographies of the head/neck vasculature of small animals can reliably performed on a clinical 3T MR scanner. Contrast-enhanced angiography enables the visualization of vascular structures with higher intravascular contrast and higher reproducibility.

MiR-1a-3p mitigates isoproterenol-induced heart failure by enhancing the expression of mitochondrial ND1 and COX1

MicroRNAs (miRNAs) have become potential targets for the treatment of heart failure (HF). It has been shown that miR-1 can reverse cardiac hypertrophy during the compensatory phase of HF development, but it is unknown whether miR-1 can still reverse cardiac dysfunction and improve cardiac remodeling after HF progresses to the decompensation stage. We established a mouse model of isoproterenol-induced HF and then injected miR-1a-3p agomir (agomir-1) into the tail vein. Echocardiography showed that the mice treated with agomir-1 had significantly increased ejection fraction and fractional shortening. These mice also showed a decrease in the N-terminal pro-B type natriuretic peptide (NT-proBNP) levels, but this remained higher than in controls. Cardiac hypertrophy, myocardial fibrosis, apoptosis, and glycogen deposition were reduced in mice treated with agomir-1. Furthermore, we found that supplementation of agomir-1 increased the expression of two mitochondrial DNA-encoded proteins, mitochondrially encoded NADH dehydrogenase 1 (ND1) and mitochondrially encoded cytochrome c oxidase I (COX1). In conclusion, our study found that miR-1a-3p alleviated the symptoms of ISO-induced HF in mice by enhancing mitochondrial ND1 and COX1. The results of this work may provide new therapeutic strategies for the treatment of HF patients.

A Mitochondrial Progesterone Receptor Increases Cardiac Beta-Oxidation and Remodeling

Progesterone is primarily a pregnancy-related hormone, produced in substantial quantities after ovulation and during gestation. Traditionally known to function via nuclear receptors for transcriptional regulation, there is also evidence of nonnuclear action. A previously identified mitochondrial progesterone receptor (PR-M) increases cellular respiration in cell models. In these studies, we demonstrated that expression of PR-M in rat H9c2 cardiomyocytes resulted in a ligand-dependent increase in oxidative cellular respiration and beta-oxidation. Cardiac expression in a TET-On transgenic mouse resulted in gene expression of myofibril proteins for remodeling and proteins involved in oxidative phosphorylation and fatty acid metabolism. In a model of increased afterload from constant transverse aortic constriction, mice expressing PR-M showed a ligand-dependent preservation of cardiac function. From these observations, we propose that PR-M is responsible for progesterone-induced increases in cellular energy production and cardiac remodeling to meet the physiological demands of pregnancy.

Temporal Frame of Immune Cell Infiltration during Heart Failure Establishment: Lessons from Animal Models

Heart failure (HF) is a cardiovascular syndrome characterized by maladaptive changes with an underlying inflammatory mediated pathogenesis. Nevertheless, current therapy is aimed at the heart workload and neurohormonal axis; thus, prognosis remains poor. To continue improving treatment, we rely on murine models for a better understanding of HF pathophysiology. Among them, pressure overload HF (PO-HF) animal models are a common strategy. Development of PO-HF is characterized by monocyte infiltration, which orchestrates a cascade of events leading to sustained inflammation and maladaptive changes. Here, we divide the PO-HF model progression into four phases and describe the inflammatory, structural, and gene expression profiles. This division is relevant due to its similarities with clinical hypertensive heart disease progression to HF. Evidence shows improvement in hemodynamic and other local parameters by altering the inflammatory response in a specific immune response at a specific point of time. Thus, it is relevant to focus on the time-dependent immune response interaction in order to provide more effective therapy. This review summarizes the pathogenesis of PO-HF murine models, highlighting the inflammatory events in a time frame view. By this approach, we expect to provide researchers with a better understanding of the intertwining time-dependent events that occur in PO-HF.

Bid maintains mitochondrial cristae structure and function and protects against cardiac disease in an integrative genomics study

Bcl-2 family proteins reorganize mitochondrial membranes during apoptosis, to form pores and rearrange cristae. In vitro and in vivo analysis integrated with human genetics reveals a novel homeostatic mitochondrial function for Bcl-2 family protein Bid. Loss of full-length Bid results in apoptosis-independent, irregular cristae with decreased respiration. Bid-/- mice display stress-induced myocardial dysfunction and damage. A gene-based approach applied to a biobank, validated in two independent GWAS studies, reveals that decreased genetically determined BID expression associates with myocardial infarction (MI) susceptibility. Patients in the bottom 5% of the expression distribution exhibit >4 fold increased MI risk. Carrier status with nonsynonymous variation in Bid’s membrane binding domain, Bid^M148T, associates with MI predisposition. Furthermore, Bid but not Bid^M148T associates with Mcl-1^Matrix, previously implicated in cristae stability; decreased MCL-1 expression associates with MI. Our results identify a role for Bid in homeostatic mitochondrial cristae reorganization, that we link to human cardiac disease.

Cells contain specialized structures called mitochondria, which help to convert fuel into energy. These tiny energy factories have a unique double membrane, with a smooth outer and a folded inner lining. The folds, called cristae, provide a scaffold for the molecular machinery that produces chemical energy that the cell can use. The cristae are dynamic, and can change shape, condensing to increase energy output.

Mitochondria also play a role in cell death. In certain situations, cristae can widen and release the proteins held within their folds. This can trigger a program of self-destruction in the cell. A family of proteins called Bcl-2 control such a ‘programmed cell death’ through the release of mitochondrial proteins. Some family members, including a protein called Bid, can reorganize cristae to regulate this cell-death program. When cells die, Bid proteins that had been split move to the mitochondria. But, even when cells are healthy, Bid molecules that are intact are always there, suggesting that this form of the protein may have another purpose.

To investigate this further, Salisbury-Ruf, Bertram et al. used mice with Bid, and mice that lacked the protein. Without Bid, cells – including heart cells – struggled to work properly and used less oxygen than their normal counterparts. A closer look using electron microscopy revealed abnormalities in the cristae. However, adding ‘intact’ Bid proteins back in to the deficient cells restored them to normal.

Moreover, without Bid, the mice hearts were less able to respond to an increased demand for energy. This decreased their performance and caused the formation of scars in the heart muscle called fibrosis, similar to a pattern observed in human patients following a heart attack.

DNA data from an electronic health record database revealed a link between low levels of Bid genes and heart attack in humans, which was confirmed in further studies. In addition, a specific mutation in the Bid gene was found to affect its ability to regulate the formation of proper cristae.

Combining evidence from mice with human genetics revealed new information about heart diseases. Mitochondrial health may be affected by a combination of specific variations in genes and changes in the Bid protein, which could affect heart attack risk. Understanding more about this association could help to identify and potentially reduce certain risk factors for heart attack.

A dose-dependent perturbation in cardiac energy metabolism is linked to radiation-induced ischemic heart disease in Mayak nuclear workers

Epidemiological studies show a significant increase in ischemic heart disease (IHD) incidence associated with total external gamma-ray dose among Mayak plutonium enrichment plant workers. Our previous studies using mouse models suggest that persistent alteration of heart metabolism due to the inhibition of peroxisome proliferator-activated receptor (PPAR) alpha accompanies cardiac damage after high doses of ionising radiation. The aim of the present study was to elucidate the mechanism of radiation-induced IHD in humans. The cardiac proteome response to irradiation was analysed in Mayak workers who were exposed only to external doses of gamma rays. All participants were diagnosed during their lifetime with IHD that also was the cause of death. Label-free quantitative proteomics analysis was performed on tissue samples from the cardiac left ventricles of individuals stratified into four radiation dose groups (0 Gy, < 100 mGy, 100–500 mGy, and > 500 mGy). The groups could be separated using principal component analysis based on all proteomics features. Proteome profiling showed a dose-dependent increase in the number of downregulated mitochondrial and structural proteins. Both proteomics and immunoblotting showed decreased expression of several oxidative stress responsive proteins in the irradiated hearts. The phosphorylation of transcription factor PPAR alpha was increased in a dose-dependent manner, which is indicative of a reduction in transcriptional activity with increased radiation dose. These data suggest that chronic external radiation enhances the risk for IHD by inhibiting PPAR alpha and altering the expression of mitochondrial, structural, and antioxidant components of the heart.

Ischemia/reperfusion injury in male guinea pigs: An efficient model to investigate myocardial damage in cardiovascular complications

Myocardial ischemia/reperfusion (I/R) injury is the major problem that aggravates cardiac damage. Several established animal models fail to explain the similarity in disease mechanism and progression as seen in humans; whereas guinea pig shows high similarity in cardiovascular parameters. Hence, current study is aimed to develop an animal model using guinea pigs that may best correlate with disease mechanism of human myocardial I/R injury. Male guinea pigs were randomized into three groups: normal diet (ND), high fat diet (HFD) and sham; fed with respective diets for 90 days. Myocardial infarction (MI) was induced by ligating left anterior descending artery (LAD) for 30 min followed by 24 h and 7 days of reperfusion in ND and HFD groups. Electrocardiogram (ECG) showed the alterations in electrical conduction during myocardial I/R injury. Elevated levels of lactate dehydrogenase (LDH) and creatine kinase-MB ((CK-MB)) were higher in HFD compared to ND. Inflammatory markers such as tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) were up-regulated in I/R injury animals compared to sham. Fold change of these protein expression levels were higher in HFD compared to ND. Elevated lipid profile and increased aortic wall thickness in HFD animals depicts the risk of developing cardiovascular complications. ECG analysis strongly confirmed MI through changes in sinus rhythm that are reflected in infarcted tissue as verified through TTC staining. Thus the combination of HFD followed by I/R injury proved to be an efficient model to study pathophysiology of myocardial I/R injury with minimal tissue damage and surgical mortality.

Conventional Method of Transverse Aortic Constriction in Mice

Transverse aortic constriction is a widely used surgical model to reflect the progression from cardiac hypertrophy to heart failure states due to left ventricular pressure overload in mice. It produces afterload increase on the left ventricle in which compensated hypertrophy initially occurs in the first 2 weeks. This develops into maladaptive remodeling of the left ventricle and atrium, leading to heart failure. This model is useful for cardiac studies since transverse aortic constriction can be consistently replicated and has low surgical mortality. Additionally, the gradual progression to cardiac failure makes it a valuable method to evaluate the efficacy of potential therapeutic intervention. We introduce this chapter to offer practical approaches to facilitate a simple methodology for transverse aortic constriction.

Methods To Assess Shear-Thinning Hydrogels for Application As Injectable Biomaterials

Injectable hydrogels have gained popularity as a vehicle for the delivery of cells, growth factors, and other molecules to localize and improve their retention at the injection site, as well as for the mechanical bulking of tissues. However, there are many factors, such as viscosity, storage and loss moduli, and injection force, to consider when evaluating hydrogels for such applications. There are now numerous tools that can be used to quantitatively assess these factors, including for shear-thinning hydrogels because their properties change under mechanical load. Here, we describe relevant rheological tests and ways to measure injection force using a force sensor or a mechanical testing machine toward the evaluation of injectable hydrogels. Injectable, shear-thinning hydrogels can be used in a variety of clinical applications, and as an example we focus on methods for injection into the heart, where an understanding of injection properties and mechanical forces is imperative for consistent hydrogel delivery and retention. We discuss methods for delivery of hydrogels to mouse, rat, and pig hearts in models of myocardial infarction, and compare methods of tissue postprocessing for hydrogel preservation. Our intent is that the methods described herein can be helpful in the design and assessment of shear-thinning hydrogels for widespread biomedical applications.

Murine Models of Heart Failure with Preserved Ejection Fraction: a "Fishing Expedition"

Heart failure with preserved ejection fraction (HFpEF) is characterized by signs and symptoms of HF in the presence of a normal left ventricular (LV) ejection fraction (EF). Despite accounting for up to 50% of all clinical presentations of HF, the mechanisms implicated in HFpEF are poorly understood, thus precluding effective therapy. The pathophysiological heterogeneity in the HFpEF phenotype also contributes to this disease and likely to the absence of evidence-based therapies. Limited access to human samples and imperfect animal models that completely recapitulate the human HFpEF phenotype have impeded our understanding of the mechanistic underpinnings that exist in this disease. Aging and comorbidities such as atrial fibrillation, hypertension, diabetes and obesity, pulmonary hypertension and renal dysfunction are highly associated with HFpEF. Yet, the relationship and contribution between them remains ill-defined. This review discusses some of the distinctive clinical features of HFpEF in association with these comorbidities and highlights the advantages and disadvantage of commonly used murine models, used to study the HFpEF phenotype.

Myocardial fibrosis: biomedical research from bench to bedside

Myocardial fibrosis refers to a variety of quantitative and qualitative changes in the interstitial myocardial collagen network that occur in response to cardiac ischaemic insults, systemic diseases, drugs, or any other harmful stimulus affecting the circulatory system or the heart itself. Myocardial fibrosis alters the architecture of the myocardium, facilitating the development of cardiac dysfunction, also inducing arrhythmias, influencing the clinical course and outcome of heart failure patients. Focusing on myocardial fibrosis may potentially improve patient care through the targeted diagnosis and treatment of emerging fibrotic pathways. The European Commission funded the FIBROTARGETS consortium as a multinational academic and industrial consortium with the primary aim of performing a systematic and collaborative search of targets of myocardial fibrosis, and then translating these mechanisms into individualized diagnostic tools and specific therapeutic pharmacological options for heart failure. This review focuses on those methodological and technological aspects considered and developed by the consortium to facilitate the transfer of the new mechanistic knowledge on myocardial fibrosis into potential biomedical applications.

The Processes and Mechanisms of Cardiac and Pulmonary Fibrosis

Fibrosis is the formation of fibrous connective tissue in response to injury. It is characterized by the accumulation of extracellular matrix components, particularly collagen, at the site of injury. Fibrosis is an adaptive response that is a vital component of wound healing and tissue repair. However, its continued activation is highly detrimental and a common final pathway of numerous disease states including cardiovascular and respiratory disease. Worldwide, fibrotic diseases cause over 800,000 deaths per year, accounting for ~45% of total deaths. With an aging population, the incidence of fibrotic disease and subsequently the number of fibrosis-related deaths will rise further. Although, fibrosis is a well-recognized cause of morbidity and mortality in a range of disease states, there are currently no viable therapies to reverse the effects of chronic fibrosis. Numerous predisposing factors contribute to the development of fibrosis. Biological aging in particular, interferes with repair of damaged tissue, accelerating the transition to pathological remodeling, rather than a process of resolution and regeneration. When fibrosis progresses in an uncontrolled manner, it results in the irreversible stiffening of the affected tissue, which can lead to organ malfunction and death. Further investigation into the mechanisms of fibrosis is necessary to elucidate novel, much needed, therapeutic targets. Fibrosis of the heart and lung make up a significant proportion of fibrosis-related deaths. It has long been established that the heart and lung are functionally and geographically linked when it comes to health and disease, and thus exploring the processes and mechanisms that contribute to fibrosis of each organ, the focus of this review, may help to highlight potential avenues of therapeutic investigation.

Porcine model of progressive cardiac hypertrophy and fibrosis with secondary postcapillary pulmonary hypertension

BACKGROUND

Meaningful translational large animal models for cardiac diseases are indispensable for studying disease mechanisms, development of novel therapeutic strategies, and evaluation of potential drugs.

METHODS

For induction of heart failure, cardiac hypertrophy and fibrosis, a bare metal stent was implanted in the descending aorta of growing pigs (n = 7), inducing pressure stress on the left ventricle (group HYPI). The constant stent size in growing pigs resulted in antegrade partial obstruction of the aortic flow with a gradual increase in afterload. Five pigs with sham intervention served as control. Serial haemodynamic, pressure-volume loop measurements and transthoracic echocardiography (TTE) were performed to detect developing pressure overload of the LV and cardiac MRI with late enhancement for measuring LV and RV mass and ejection fraction.

RESULTS

At 5-month follow-up, CT and contrast aortography, and intraluminal echocardiography confirmed aortic isthmus stenosis with a mean trans-stenotic gradient of 64 ± 13.9 mmHg. Invasive haemodynamic measurements revealed a secondary increase in pulmonary artery pressure (44.6 ± 5.1 vs 25.9 ± 6.2 mmHg, HYPI vs control, p < 0.05). TTE and ex vivo analyses confirmed severe concentric LV hypertrophy (mean circumferential wall thickness, 19.4 ± 3.1, n = 7 vs 11.4 ± 1.0 mm, n = 5, HYPI vs controls, p < 0.05). The LV and RV mass increased significantly, paralleled by increased isovolumic relaxation constant (tau). Histological analyses confirmed substantial fibrosis and myocyte hypertrophy in both LV and RV. Expressions of ANP, BNP, and miRNA-29a were up-regulated, while SERCA2a and miRNA-1 were down-regulated. Plasma NGAL levels increased gradually, while the elevation of NT-proBNP was detected only at the 5-month FUP.

CONCLUSION

These data prove that percutaneous artificial aortic stenosis in pigs is useful for inducing clinically relevant progredient heart failure based on myocardial hypertrophy and fibrosis.

Treatment of the cardiac hypertrophic response and heart failure with ginseng, ginsenosides, and ginseng-related products

Heart failure is a major medical and economic burden throughout the world. Although various treatment options are available to treat heart failure, death rates in both men and women remain high. Potential adjunctive therapies may lie with use of herbal medications, many of which possess potent pharmacological properties. Among the most widely studied is ginseng, a member of the genus Panax that is grown in many parts of the world and that has been used as a medical treatment for a variety of conditions for thousands of years, particularly in Asian societies. There are a number of ginseng species, each possessing distinct pharmacological effects due primarily to differences in their bioactive components including saponin ginsenosides and polysaccharides. While experimental evidence for salutary effects of ginseng on heart failure is robust, clinical evidence is less so, primarily due to a paucity of large-scale well-controlled clinical trials. However, there is evidence from small trials that ginseng-containing Chinese medications such as Shenmai can offer benefit when administered as adjunctive therapy to heart failure patients. Substantial additional studies are required, particularly in the clinical arena, to provide evidence for a favourable effect of ginseng in heart failure patients.

Preclinical models in the study of sex differences

The biology of sex differences deals with the study of the disparities between females and males and the related biological mechanisms. Gender medicine focuses on the impact of gender and sex on human physiology, pathophysiology and clinical features of diseases that are common to women and men. The term gender refers to a complex interrelation and integration of sex-as a biological and functional determinant-and psychological and cultural behaviours (due to ethnical, social or religious background). The attention to the impact of gender differences on the pathophysiology and, therefore, on the clinical management of the most common diseases, such as cardiovascular diseases (CVD), neurodegenerative disorders, immune and autoimmune diseases as well as several tumours, is in fact often neglected. Hence, studies covering different fields of investigation and including sex differences in the pathogenesis, in diagnostic and prognostic criteria as well as in response to therapy appear mandatory. However, prerequisites for this development are preclinical studies, including in vitro and in vivo approaches. They represent the first step in the development of a drug or in the comprehension of the pathogenetic mechanisms of diseases, in turn a necessary step for the development of new or more appropriate therapeutic strategies. However, sex differences are still poorly considered and the great majority of preclinical studies do not take into account the relevance of such disparities. In this review, we describe the state of the art of these studies and provide some paradigmatic examples of key fields of investigation, such as oncology, neurology and CVD, where preclinical models should be improved.

Cognitive impairment in heart failure: A protective role for angiotensin-(1-7)

Patients with congestive heart failure (CHF) have increased hospital readmission rates and mortality if they are concomitantly diagnosed with cognitive decline and memory loss. Accordingly, we developed a preclinical model of CHF-induced cognitive impairment with the goal of developing novel protective therapies against CHF related cognitive decline. CHF was induced by ligation of the left coronary artery to instigate a myocardial infarction (MI). By 4- and 8-weeks post-MI, CHF mice had approximately a 50% and 70% decline in ejection fraction as measured by echocardiography. At both 4- and 8-weeks post-MI, spatial memory performance in CHF mice as tested using the Morris water task was significantly impaired as compared with sham. In addition, CHF mice had significantly worse performance on object recognition when compared with shams as measured by discrimination ratios during the novel object recognition NOR task. At 8-weeks post-MI, a subgroup of CHF mice were given Angiotensin (Ang)-(1-7) (50mcg/kg/hr) subcutaneously for 4 weeks. Following 3 weeks treatment with systemic Ang-(1-7), the CHF mice NOR discrimination ratios were similar to shams and significantly better than the performance of CHF mice treated with saline. Ang-(1-7) also improved spatial memory in CHF mice as compared with shams. Ang-(1-7) had no effect on cardiac function. Inflammatory biomarker studies from plasma revealed a pattern of neuroprotection that may underlie the observed improvements in cognition. These results demonstrate a preclinical mouse model of CHF that exhibits both spatial memory and object recognition dysfunction. Furthermore, this CHF-induced cognitive impairment is attenuated by treatment with systemic Ang-(1-7). (PsycINFO Database Record

A Model of Cardiac Remodeling Through Constriction of the Abdominal Aorta in Rats

Heart failure is one of the leading causes of death worldwide. It is a complex clinical syndromethat includes fatigue, dyspnea, exercise intolerance, and fluid retention. Changes in myocardial structure, electrical conduction, and energy metabolism develop with heart failure, leading to contractile dysfunction, increased risk of arrhythmias, and sudden death. Hypertensive heart disease is one of the key contributing factors of cardiac remodeling associated with heart failure. The most commonly-used animal model mimicking hypertensive heart disease is created via surgical interventions, such as by narrowing the aorta. Abdominal aortic constriction is a useful experimental technique to induce a pressure overload, which leads to heart failure. The surgery can be easily performed, without the need for chest opening or mechanical ventilation. Abdominal aortic constriction-induced cardiac pathology progresses gradually, making this model relevant to clinical hypertensive heart failure. Cardiac injury and remodeling can be observed 10 weeks after the surgery. The method described here provides a simple and effective approach to produce a hypertensive heart disease animal model that is suitable for studying disease mechanisms and for testing novel therapeutics.