Sex similarities and differences in the reverse and anti-remodeling effect of pressure unloading therapy in a rat model of aortic banding and debanding

Gene expression profiles, potential targets and treatments of cardiac remodeling

Hypertensive and ischemic heart diseases have high morbidity all over the world, and they primarily contribute to heart failure associated with high mortality. Cardiac remodeling, as a basic pathological process in heart diseases, is mainly comprised of cardiac hypertrophy and fibrosis, as well as cell death which occurs especially in the ischemic cardiomyopathy. Myocardial remodeling has been widely investigated by a variety of animal models, including pressure overload, angiotensin II stimulation, and myocardial infarction. Pressure overload can cause compensatory cardiac hypertrophy at the early stage, followed by decompensatory hypertrophy and heart failure at the end. Recently, RNA sequencing and differentially expressed gene (DEG) analyses have been extensively employed to elucidate the molecular mechanisms of cardiac remodeling and related heart failure, which also provide potential targets for high-throughput drug screenings. In this review, we summarize recent advancements in gene expression profiling, related gene functions, and signaling pathways pertinent to myocardial remodeling induced by pressure overload at distinct stages, ischemia-reperfusion, myocardial infarction, and diabetes. We also discuss the effects of sex differences and inflammation on DEGs and their transcriptional regulatory mechanisms in cardiac remodeling. Additionally, we summarize emerging therapeutic agents and strategies aimed at modulating gene expression profiles during myocardial remodeling.

Guidelines for assessing ventricular pressure-volume relationships in rodents

Ventricular catheterization with a pressure-volume (PV) catheter is the gold-standard method for assessing in vivo cardiac function in animal studies, providing valuable "load-independent" indices of systolic and diastolic heart performance. PV studies are commonly performed to elucidate mechanistic insights into cardiovascular disease using surgical and genetically engineered rat and mouse models, but there is considerable heterogeneity in how these studies are performed. Wide variation in protocol design, volume calibration, anesthesia, manipulation of cardiac loading conditions, how load-independent indices of cardiac function are derived, as well as in data analysis and reporting is constraining reliability and reproducibility in the field. The purpose of this manuscript is to combine our collective expertise in performing open- and closed-chest left and right ventricle PV studies in rodents to provide consensus guidelines on how to perform, analyze, and interpret these studies using either conductance or admittance PV catheters. We first review recent methodological reporting in rodent PV studies in this journal and discuss important details required to improve reproducibility within and across PV studies. We then recommend steps to obtain high-quality PV data, from volume calibration to choice of anesthetic agent and acquiring load-independent indices of both systolic and diastolic function. We also consider between- and within-animal variation and recommend how to perform data analysis and visualization. We hope that this consensus paper guides those performing PV studies in rodents and helps align the field with best practices in surgical/analytical methodologies and reporting, facilitating better reliability and reproducibility in the PV field.

Sex as a biological variable for cardiovascular physiology

There have been ongoing efforts by federal agencies and scientific communities since the early 1990s to incorporate sex and/or gender in all aspects of cardiovascular research. Scientific journals provide a critical function as change agents to influence transformation by encouraging submissions for topic areas, and by setting standards and expectations for articles submitted to the journal. As part of ongoing efforts to advance sex and gender in cardiovascular physiology research, the American Journal of Physiology-Heart and Circulatory Physiology recently launched a call for papers on Considering Sex as a Biological Variable. This call was an overwhelming success, resulting in 78 articles published in this collection. This review summarizes the major themes of the collection, including Sex as a Biological Variable Within: Endothelial Cell and Vascular Physiology, Cardiovascular Immunity and Inflammation, Metabolism and Mitochondrial Energy, Extracellular Matrix Turnover and Fibrosis, Neurohormonal Signaling, and Cardiovascular Clinical and Epidemiology Assessments. Several articles also focused on establishing rigor and reproducibility of key physiological measurements involved in cardiovascular health and disease, as well as recommendations and considerations for study design. Combined, these articles summarize our current understanding of sex and gender influences on cardiovascular physiology and pathophysiology and provide insight into future directions needed to further expand our knowledge.

Fibroblasts under pressure: cardiac fibroblast responses to hypertension and antihypertensive therapies

Approximately 50% of Americans have hypertension, which significantly increases the risk of heart failure. In response to increased peripheral resistance in hypertension, intensified mechanical stretch in the myocardium induces cardiomyocyte hypertrophy and fibroblast activation to withstand increased pressure overload. This changes the structure and function of the heart, leading to pathological cardiac remodeling and eventual progression to heart failure. In the presence of hypertensive stimuli, cardiac fibroblasts activate and differentiate to myofibroblast phenotype capable of enhanced extracellular matrix secretion in coordination with other cell types, mainly cardiomyocytes. Both systemic and local renin-angiotensin-aldosterone system activation lead to increased angiotensin II stimulation of fibroblasts. Angiotensin II directly activates fibrotic signaling such as transforming growth factor β/SMAD and mitogen-activated protein kinase (MAPK) signaling to produce extracellular matrix comprised of collagens and matricellular proteins. With the advent of single-cell RNA sequencing techniques, heterogeneity in fibroblast populations has been identified in the left ventricle in models of hypertension and pressure overload. The various clusters of fibroblasts reveal a range of phenotypes and activation states. Select antihypertensive therapies have been shown to be effective in limiting fibrosis, with some having direct actions on cardiac fibroblasts. The present review focuses on the fibroblast-specific changes that occur in response to hypertension and pressure overload, the knowledge gained from single-cell analyses, and the effect of antihypertensive therapies. Understanding the dynamics of hypertensive fibroblast populations and their similarities and differences by sex is crucial for the advent of new targets and personalized medicine.

Guidelines on the use of sex and gender in cardiovascular research

In cardiovascular research, sex and gender have not typically been considered in research design and reporting until recently. This has resulted in clinical research findings from which not only all women, but also gender-diverse individuals have been excluded. The resulting dearth of data has led to a lack of sex- and gender-specific clinical guidelines and raises serious questions about evidence-based care. Basic research has also excluded considerations of sex. Including sex and/or gender as research variables not only has the potential to improve the health of society overall now, but it also provides a foundation of knowledge on which to build future advances. The goal of this guidelines article is to provide advice on best practices to include sex and gender considerations in study design, as well as data collection, analysis, and interpretation to optimally establish rigor and reproducibility needed to inform clinical decision-making and improve outcomes. In cardiovascular physiology, incorporating sex and gender is a necessary component when optimally designing and executing research plans. The guidelines serve as the first guidance on how to include sex and gender in cardiovascular research. We provide here a beginning path toward achieving this goal and improve the ability of the research community to interpret results through a sex and gender lens to enable comparison across studies and laboratories, resulting in better health for all.

Regression of cardiac hypertrophy in health and disease: mechanisms and therapeutic potential

Left ventricular hypertrophy is a leading risk factor for cardiovascular morbidity and mortality. Although reverse ventricular remodelling was long thought to be irreversible, evidence from the past three decades indicates that this process is possible with many existing heart disease therapies. The regression of pathological hypertrophy is associated with improved cardiac function, quality of life and long-term health outcomes. However, less than 50% of patients respond favourably to most therapies, and the reversibility of remodelling is influenced by many factors, including age, sex, BMI and disease aetiology. Cardiac hypertrophy also occurs in physiological settings, including pregnancy and exercise, although in these cases, hypertrophy is associated with normal or improved ventricular function and is completely reversible postpartum or with cessation of training. Studies over the past decade have identified the molecular features of hypertrophy regression in health and disease settings, which include modulation of protein synthesis, microRNAs, metabolism and protein degradation pathways. In this Review, we summarize the evidence for hypertrophy regression in patients with current first-line pharmacological and surgical interventions. We further discuss the molecular features of reverse remodelling identified in cell and animal models, highlighting remaining knowledge gaps and the essential questions for future investigation towards the goal of designing specific therapies to promote regression of pathological hypertrophy.

Rodent Models of Dilated Cardiomyopathy and Heart Failure for Translational Investigations and Therapeutic Discovery

Even with modern therapy, patients with heart failure only have a 50% five-year survival rate. To improve the development of new therapeutic strategies, preclinical models of disease are needed to properly emulate the human condition. Determining the most appropriate model represents the first key step for reliable and translatable experimental research. Rodent models of heart failure provide a strategic compromise between human in vivo similarity and the ability to perform a larger number of experiments and explore many therapeutic candidates. We herein review the currently available rodent models of heart failure, summarizing their physiopathological basis, the timeline of the development of ventricular failure, and their specific clinical features. In order to facilitate the future planning of investigations in the field of heart failure, a detailed overview of the advantages and possible drawbacks of each model is provided.