Gender-related differences in proliferative responses of vascular smooth muscle cells to endothelin-1

Let's Talk About Sex-Biological Sex Is Underreported in Biomaterial Studies

Precision medicine aims to better individualize healthcare. It requires that biomaterials be designed for the physiological characteristics of a specific patient. To make this a reality, biomaterials research and development must address differences of biological sex. More specifically, biomaterials should be designed with properties optimized and appropriate for male and female patients. In analyzing research articles from seven prominent biomaterials journals, sex as a biological variable is missing from an overwhelming majority of in vitro biomaterial studies. From the survey, the reporting of the sex of primary cell cultures happened only 10.3% of the time. Contributing to this trend is that commercial vendors bias cell lines toward one sex or another by not disclosing information of cell line sex at the time of purchase; researchers do not communicate this pertinent information in published studies; and many journal policies have little to no requirements for reporting cell line characteristics. Omitting this valuable information leads to a gap in the understanding of sex-specific cell-biomaterial interactions and it creates a bias in research findings towards one sex or another. To curb this concerning trend and make precision biomaterials a reality will require the biomaterials field to "talk about sex" by reporting cell sex more broadly.

Reporting of sex as a variable in cardiovascular studies using cultured cells: A systematic review

Reporting the sex of biological material is critical for transparency and reproducibility in science. This study examined the reporting of the sex of cells used in cardiovascular studies. Articles from 16 cardiovascular journals that publish peer-reviewed studies in cardiovascular physiology and pharmacology in the year 2018 were systematically reviewed using terms "cultured" and "cells." Data were collected on the sex of cells, the species from which the cells were isolated, and the type of cells, and summarized as a systematic review. Sex was reported in 88 (38.6%) of the 228 studies meeting inclusion criteria. Reporting rates varied with Circulation, Cardiovascular Research and American Journal of Physiology: Heart and Circulatory Physiology having the highest rates of sex reporting (>50%). A majority of the studies used cells from male (54.5%) or both male and female animals (32.9%). Humans (31.8%), rats (20.4%), and mice (43.8%) were the most common sources for cells. Cardiac myocytes were the most commonly used cell type (37.0%). Overall reporting of sex of experimental material remains below 50% and is inconsistent among journals. Sex chromosomes in cells have the potential to affect protein expression and molecular signaling pathways and should be consistently reported.

Role of the endothelin system in sexual dimorphism in cardiovascular and renal diseases

Epidemiological studies of blood pressure in men and women and in experimental animal models point to substantial sex differences in the occurrence of arterial hypertension as well as in the various manifestations of arterial hypertension, including myocardial infarction, stroke, retinopathy, chronic kidney failure, as well as hypertension-associated diseases (e.g. diabetes mellitus). Increasing evidence demonstrates that the endothelin (ET) system is a major player in the genesis of sex differences in cardiovascular and renal physiology and diseases. Sex differences in the ET system have been described in the vasculature, heart and kidney of humans and experimental animals. In the current review, we briefly describe the role of the ET system in the cardiovascular and renal systems. We also update information on sex differences at different levels of the ET system including synthesis, circulating and tissue levels, receptors, signaling pathways, ET actions, and responses to antagonists in different organs that contribute to blood pressure regulation. Knowledge of the mechanisms underlying sex differences in arterial hypertension can impact therapeutic strategies. Sex-targeted and/or sex-tailored approaches may improve treatment of cardiovascular and renal diseases.

Effects of biological sex on the pathophysiology of the heart

Cardiovascular diseases are the leading causes of death in men and women in industrialized countries. While the effects of biological sex on cardiovascular pathophysiology have long been known, the sex-specific mechanisms mediating these processes have been further elucidated over recent years. This review aims at analysing the sex-based differences in cardiac structure and function in adult mammals, and the sex-based differences in the main molecular mechanisms involved in the response of the heart to pathological situations. It emerged from this review that the sex-based difference is a variable that should be dealt with, not only in basic science or clinical research, but also with regards to therapeutic approaches.

Why are sex and gender important to basic physiology and translational and individualized medicine?

Sex refers to biological differences between men and women. Although sex is a fundamental aspect of human physiology that splits the population in two approximately equal halves, this essential biological variable is rarely considered in the design of basic physiological studies, in translating findings from basic science to clinical research, or in developing personalized medical strategies. Contrary to sex, gender refers to social and cultural factors related to being a man or a woman in a particular historical and cultural context. Unfortunately, gender is often used incorrectly by scientists and clinical investigators as synonymous with sex. This article clarifies the definition of sex and gender and reviews evidence showing how sex and gender interact with each other to influence etiology, presentation of disease, and treatment outcomes. In addition, strategies to improve the inclusion of female and male human beings in preclinical and clinical studies will be presented, and the importance of embedding concepts of sex and gender into postgraduate and medical curricula will be discussed. Also, provided is a list of resources for educators. In the history of medical concepts, physiologists have provided pivotal contributions to understanding health and disease processes. In the future, physiologists should provide the evidence for advancing personalized medicine and for reducing sex and gender disparities in health care.

Pharmacogenomics, pharmacokinetics and pharmacodynamics: interaction with biological differences between men and women

Pharmacological response depends on multiple factors and one of them is sex-gender. Data on the specific effects of sex-gender on pharmacokinetics, as well as the safety and efficacy of numerous medications, are beginning to emerge. Nevertheless, the recruitment of women for clinical research is inadequate, especially during the first phases. In general, pharmacokinetic differences between males and females are more numerous and consistent than disparities in pharmacodynamics. However, sex-gender pharmacodynamic differences are now increasingly being identified at the molecular level. It is now even becoming apparent that sex-gender influences pharmacogenomics and pharmacogenetics. Sex-related differences have been reported for several parameters, and it is consistently shown that women have a worse safety profile, with drug adverse reactions being more frequent and severe in women than in men. Overall, the pharmacological status of women is less well studied than that of men and deserves much more attention. The design of clinical and preclinical studies should have a sex-gender-based approach with the aim of tailoring therapies to an individual's needs and concerns.

Considerations of sex and gender differences in preclinical and clinical trials

Women continue to be underrepresented in clinical trials, particularly in Phases I and II of experimental drug studies in spite of legislative guidelines in the USA, Canada, the European Union, Australia, and Japan requiring the inclusion of women in clinical trials. As such, women remain a vulnerable population subject to the adverse effects of pharmacological therapies. Thus, women experience higher rates of adverse drug reactions than do men and for women of reproductive age or who may be pregnant, therapeutic options may be limited. This chapter provides a brief history of inclusion of sex and gender as variables in clinical trials, summarizes governmental legislation for consideration of sex and gender in clinical trials and provides specific examples of drugs which have been withdrawn from the market because of side effects in women. Additional information related to sex and gender in preclinical testing, trial design, challenges to recruitment of women for clinical trials and statistical methods for analysis of data also is considered.

Strategies and methods to study sex differences in cardiovascular structure and function: a guide for basic scientists

Background

Cardiovascular disease remains the primary cause of death worldwide. In the US, deaths due to cardiovascular disease for women exceed those of men. While cultural and psychosocial factors such as education, economic status, marital status and access to healthcare contribute to sex differences in adverse outcomes, physiological and molecular bases of differences between women and men that contribute to development of cardiovascular disease and response to therapy remain underexplored.

Methods

This article describes concepts, methods and procedures to assist in the design of animal and tissue/cell based studies of sex differences in cardiovascular structure, function and models of disease.

Results

To address knowledge gaps, study designs must incorporate appropriate experimental material including species/strain characteristics, sex and hormonal status. Determining whether a sex difference exists in a trait must take into account the reproductive status and history of the animal including those used for tissue (cell) harvest, such as the presence of gonadal steroids at the time of testing, during development or number of pregnancies. When selecting the type of experimental animal, additional consideration should be given to diet requirements (soy or plant based influencing consumption of phytoestrogen), lifespan, frequency of estrous cycle in females, and ability to investigate developmental or environmental components of disease modulation. Stress imposed by disruption of sleep/wake cycles, patterns of social interaction (or degree of social isolation), or handling may influence adrenal hormones that interact with pathways activated by the sex steroid hormones. Care must be given to selection of hormonal treatment and route of administration.

Conclusions

Accounting for sex in the design and interpretation of studies including pharmacological effects of drugs is essential to increase the foundation of basic knowledge upon which to build translational approaches to prevent, diagnose and treat cardiovascular diseases in humans.

Atherosclerosis and sex hormones: current concepts

CVD (cardiovascular disease) is the leading cause of death for women. Considerable progress has been made in both our understanding of the complexities governing menopausal hormone therapy and our understanding of the cellular and molecular mechanisms underlying hormone and hormone receptor function. Understanding the interplay of atherosclerosis and sex steroid hormones and their cognate receptors at the level of the vessel wall has important ramifications for clinical practice. In the present review, we discuss the epidemiology of CVD in men and women, the clinical impact of sex hormones on CVD, and summarize our current understanding of the pathogenesis of atherosclerosis with a focus on gender differences in CVD, its clinical presentation and course, and pathobiology. The critical animal and human data that pertain to the role of oestrogens, androgens and progestins on the vessel wall is also reviewed, with particular attention to the actions of sex hormones on each of the three key cell types involved in atherogenesis: the endothelium, smooth muscle cells and macrophages. Where relevant, the systemic (metabolic) effects of sex hormones that influence atherogenesis, such as those involving vascular reactivity, inflammation and lipoprotein metabolism, are discussed. In addition, four key current concepts in the field are explored: (i) total hormone exposure time and coronary heart disease risk; (ii) the importance of tissue specificity of sex steroid hormones, critical timing and the stage of atherosclerosis in hormone action; (iii) biomarkers for atherosclerosis with regard to hormone therapy; and (iv) the complex role of sex steroids in inflammation. Future studies in this field will contribute to guiding clinical treatment recommendations for women and help define research priorities.

Endothelin, sex and hypertension

The ETs (endothelins) comprise a family of three 21-amino-acid peptides (ET-1, ET-2 and ET-3) and 31-amino-acid ETs (ET-1(1-31), ET-2(1-31) and ET-3(1-31)). ET-1 is synthesized from a biologically inactive precursor, big ET-1, by ECEs (ET-converting enzymes). The actions of ET-1 are mediated through activation of the G-protein-coupled ET(A) and ET(B) receptors, which are found in a variety of cells in the cardiovascular and renal systems. ET-1 has potent vasoconstrictor, mitogenic, pro-inflammatory and antinatriuretic properties, which have been implicated in the pathophysiology of a number of cardiovascular diseases. Overexpression of ET-1 has been consistently described in salt-sensitive models of hypertension and in models of renal failure, and has been associated with disease progression. Sex differences are observed in many aspects of mammalian cardiovascular function and pathology. Hypertension, as well as other cardiovascular diseases, is more common in men than in women of similar age. In experimental models of hypertension, males develop an earlier and more severe form of hypertension than do females. Although the reasons for these differences are not well established, the effects of gonadal hormones on arterial, neural and renal mechanisms that control blood pressure are considered contributing factors. Sex differences in the ET-1 pathway, with males displaying higher ET-1 levels, greater ET-1-mediated vasoconstrictor and enhanced pressor responses in comparison with females, are addressed in the present review. Sex-associated differences in the number and function of ET(B) receptors appear to be particularly important in the specific characteristics of hypertension between females and males. Although the gonadal hormones modulate some of the differences in the ET pathway in the cardiovascular system, a better understanding of the exact mechanisms involved in sex-related differences in this peptidergic system is needed. With further insights into these differences, we may learn that men and women could require different antihypertensive regimens.

Gender differences in biomechanical properties of intramural coronary resistance arteries of rats, an in vitro microarteriographic study

The prevalence of ischemic heart disease is lower in premenopausal females than in males of corresponding age. This should be related to gender differences in coronary functions. We tested whether biomechanical differences exist between intramural coronary resistance arteries of male and female rats. Intramural branches of the left anterior descending coronary artery (uniformly approximately 200microm in diameter) were isolated, cannulated and studied by microarteriography. Intraluminal pressure was increased from 2 to 90mmHg in steps and steady-state diameters were measured. Measurements were repeated in the presence of vasoconstrictor U46619 (10(-6)M) and the endothelial coronary vasodilator bradykinin (BK) (10(-6)M). Finally, passive diameters were recorded in calcium-free saline. A similar inner radius and a higher wall thickness (41.5+/-2.9microm vs. 31.4+/-2.7microm at 50mmHg in the passive condition, p<0.05) resulted in lower tangential wall stresses in male rats (18.9+/-1.9kPa vs. 24.9+/-2.5kPa at 50mmHg, p<0.05). Isobaric elastic modulus of vessels from male animals was significantly smaller at higher pressures. Vasoconstrictor response was significantly stronger in male than in female animals. Endothelial relaxations induced by BK were not different. This is the first demonstration that biomechanical characteristics of intramural coronary resistance arteries of a mammalian species are different in the male and female sexes. Higher wall thickness and higher vascular contractility in males are associated with similar endothelial function and larger high-pressure elasticity compared to females. These gender differences in biomechanics of coronary resistance arteries of rats may contribute to our better understanding the characteristic physiological and pathological differences in humans.

Sex-specific effects of dual ET-1/ANG II receptor (Dear) variants in Dahl salt-sensitive/resistant hypertension rat model

Essential (polygenic) hypertension is a complex genetic disorder that remains a major risk factor for cardiovascular disease despite clinical advances, reiterating the need to elucidate molecular genetic mechanisms. Elucidation of susceptibility genes remains a challenge, however. Blood pressure (BP) regulatory pathways through angiotensin II (ANG II) and endothelin-1 (ET-1) receptor systems comprise a priori candidate susceptibility pathways. Here we report that the dual ET-1/ANG II receptor gene ( Dear) is structurally and functionally distinct between Dahl salt-sensitive, hypertensive (S) and salt-resistant, normotensive (R) rats. The Dahl S S44/M74 variant is identical to the previously reported Dear cDNA with equivalent affinities for both ET-1 and ANG II, in contrast to Dahl R S44P/M74T variant, which exhibits absent ANG II binding but effective ET-1 binding. The S44P substitution localizes to the ANG II-binding domain predicted by the molecular recognition theory, providing compelling support of this theory. The Dear gene maps to rat chromosome 2 and cosegregates with BP in female F2(R×S) intercross rats with highly significant linkage (LOD 3.61) accounting for 14% of BP variance, but not in male F2(R×S) intercross rats. Altogether, the data suggest the hypothesis that modification of the critical balance between ANG II and ET-1 systems through variant Dear contributes to hypertension susceptibility in female F2(R×S) intercross rats. Further investigations are necessary to corroborate genetic linkage through congenic rat studies, to investigate putative gene interactions, and to show causality by transgenesis and/or intervention. More importantly, the data reiterate the importance of sex-specific factors in hypertension susceptibility.