Sex-related differences in intrinsic myocardial properties influence cardiac function in middle-aged rats during infarction-induced left ventricular remodeling

Advances, challenges, and future directions in the clinical translation of ECM biomaterials for regenerative medicine applications

Extracellular Matrix (ECM) scaffolds and biomaterials have been widely used for decades across a variety of diverse clinical applications and have been implanted in millions of patients worldwide. ECM-based biomaterials have been especially successful in soft tissue repair applications but their utility in other clinical applications such as for regeneration of bone or neural tissue is less well understood. The beneficial healing outcome with the use of ECM biomaterials is the result of their biocompatibility, their biophysical properties and their ability to modify cell behavior after injury. As a consequence of successful clinical outcomes, there has been motivation for the development of next-generation formulations of ECM materials ranging from hydrogels, bioinks, powders, to whole organ or tissue scaffolds. The continued development of novel ECM formulations as well as active research interest in these materials ensures a wealth of possibilities for future clinical translation and innovation in regenerative medicine. The clinical translation of next generation formulations ECM scaffolds faces predictable challenges such as manufacturing, manageable regulatory pathways, surgical implantation, and the cost required to address these challenges. The current status of ECM-based biomaterials, including clinical translation, novel formulations and therapies currently under development, and the challenges that limit clinical translation of ECM biomaterials are reviewed herein.

Local decorin delivery via hyaluronic acid microrods improves cardiac performance, ventricular remodeling after myocardial infarction

Heart failure (HF) remains a global public health burden and often results following myocardial infarction (MI). Following injury, cardiac fibrosis forms in the myocardium which greatly hinders cellular function, survival, and recruitment, thus severely limits tissue regeneration. Here, we leverage biophysical microstructural cues made of hyaluronic acid (HA) loaded with the anti-fibrotic proteoglycan decorin to more robustly attenuate cardiac fibrosis after acute myocardial injury. Microrods showed decorin incorporation throughout the entirety of the hydrogel structures and exhibited first-order release kinetics in vitro. Intramyocardial injections of saline (n = 5), microrods (n = 7), decorin microrods (n = 10), and free decorin (n = 4) were performed in male rat models of ischemia-reperfusion MI to evaluate therapeutic effects on cardiac remodeling and function. Echocardiographic analysis demonstrated that rats treated with decorin microrods (5.21% ± 4.29%) exhibited significantly increased change in ejection fraction (EF) at 8 weeks post-MI compared to rats treated with saline (-4.18% ± 2.78%, p < 0.001) and free decorin (-3.42% ± 1.86%, p < 0.01). Trends in reduced end diastolic volume were also identified in decorin microrod-treated groups compared to those treated with saline, microrods, and free decorin, indicating favorable ventricular remodeling. Quantitative analysis of histology and immunofluorescence staining showed that treatment with decorin microrods reduced cardiac fibrosis (p < 0.05) and cardiomyocyte hypertrophy (p < 0.05) at 8 weeks post-MI compared to saline control. Together, this work aims to contribute important knowledge to guide rationally designed biomaterial development that may be used to successfully treat cardiovascular diseases.

Sex Influences the Safety and Therapeutic Efficacy of Cardiac Nanomedicine Technologies

Nanomedicine technologies are being developed for the prevention, diagnosis, and treatment of cardiovascular disease (CVD), which is the leading cause of death worldwide. Before delving into the nuances of cardiac nanomedicine, it is essential to comprehend the fundamental sex-specific differences in cardiovascular health. Traditionally, CVDs have been more prevalent in males, but it is increasingly evident that females also face significant risks, albeit with distinct characteristics. Females tend to develop CVDs at a later age, exhibit different clinical symptoms, and often experience worse outcomes compared to males. These differences indicate the need for sex-specific approaches in cardiac nanomedicine. This Perspective discusses the importance of considering sex in the safety and therapeutic efficacy of nanomedicine approaches for the prevention, diagnosis, and treatment of CVD.

Sex matters: the frequently overlooked importance of considering sex in computational models

Personalised medicine and the development of a virtual human or a digital twin comprises visions of the future of medicine. To realise these innovations, an understanding of the biology and physiology of all people are required if we wish to apply these technologies at a population level. Sex differences in health and biology is one aspect that has frequently been overlooked, with young white males being seen as the "average" human being. This has not been helped by the lack of inclusion of female cells and animals in biomedical research and preclinical studies or the historic exclusion, and still low in proportion, of women in clinical trials. However, there are many known differences in health between the sexes across all scales of biology which can manifest in differences in susceptibility to diseases, symptoms in a given disease, and outcomes to a given treatment. Neglecting these important differences in the development of any health technologies could lead to adverse outcomes for both males and females. Here we highlight just some of the sex differences in the cardio-respiratory systems with the goal of raising awareness that these differences exist. We discuss modelling studies that have considered sex differences and touch on how and when to create sex-specific models. Scientific studies should ensure sex differences are included right from the study planning phase and results reported using sex as a biological variable. Computational models must have sex-specific versions to ensure a movement towards personalised medicine is realised.

Local delivery of decorin via hyaluronic acid microrods improves cardiac performance and ventricular remodeling after myocardial infarction

Heart failure (HF) is a global public health burden and associated with significant morbidity and mortality. HF can result as a complication following myocardial infarction (MI), with cardiac fibrosis forming in the myocardium as a response to injury. The dense, avascular scar tissue that develops in the myocardium after injury following MI creates an inhospitable microenvironment that hinders cellular function, survival, and recruitment, thus severely limiting tissue regeneration. We have previously demonstrated the ability of hyaluronic acid (HA) polymer microrods to modulate fibroblast phenotype using discrete biophysical cues and to improve cardiac outcomes after implantation in rodent models of ischemia-reperfusion MI injury. Here, we developed a dual-pronged biochemical and biophysical therapeutic strategy leveraging bioactive microrods to more robustly attenuate cardiac fibrosis after acute myocardial injury. Incorporation of the anti-fibrotic proteoglycan decorin within microrods led to sustained release of decorin over one month in vitro and after implantation, resulted in marked improvement in cardiac function and ventricular remodeling, along with decreased fibrosis and cardiomyocyte hypertrophy. Together, this body of work aims to contribute important knowledge to help develop rationally designed engineered biomaterials that may be used to successfully treat cardiovascular diseases.

A framework for developing sex-specific engineered heart models

The convergence of tissue engineering and patient-specific stem cell biology has enabled the engineering of in vitro tissue models that allow the study of patient-tailored treatment modalities. However, sex-related disparities in health and disease, from systemic hormonal influences to cellular-level differences, are often overlooked in stem cell biology, tissue engineering and preclinical screening. The cardiovascular system, in particular, shows considerable sex-related differences, which need to be considered in cardiac tissue engineering. In this Review, we analyse sex-related properties of the heart muscle in the context of health and disease, and discuss a framework for including sex-based differences in human cardiac tissue engineering. We highlight how sex-based features can be implemented at the cellular and tissue levels, and how sex-specific cardiac models could advance the study of cardiovascular diseases. Finally, we define design criteria for sex-specific cardiac tissue engineering and provide an outlook to future research possibilities beyond the cardiovascular system.

Effects of Estrogen on Cardiac mRNA and LncRNA Expression Profiles in Hypertensive Mice

Estrogen is a vascular protection factor and plays a protective role in the pathogenesis of gender differences in cardiovascular diseases. This study was to address the possible mechanisms that may explain the relationship between estradiol configuration-17β-estradiol (E2) and ventricular remodeling. Here, we show that a total of 1499 LncRNAs and 680 mRNAs significantly differently expressed were identified. This result indicates that estradiol has a global role in regulating heart gene expression profiles in female mice. Go and Pathway functional cluster analysis showed that the antagonism of E2 on cardiac remodeling and AngII-induced pathological changes in female mice may be related to physiological processes such as circadian rhythm disorder and ion channel dysfunction. Graphical Abstract.

Preservation of Functional Microvascular Bed Is Vital for Long-Term Survival of Cardiac Myocytes Within Large Transmural Post-Myocardial Infarction Scar

This study was aimed to understand the mechanism of persistent cardiac myocyte (CM) survival in myocardial infarction (MI) scars. A transmural MI was induced in 12-month-old Sprague-Dawley rats by permanent coronary artery ligation. The hearts were collected 3 days, 1, 2, 4, 8, and 12 weeks after MI and evaluated with histology, immunohistochemistry, and quantitative morphometry. Vasculature patency was assessed in 4-, 8-, and 12-week-old scars by infusion of 15-micron microspheres into the left ventricle before euthanasia. The infarcted/scarred area has a small continually retained population of surviving CMs in subendocardial and subepicardial regions. Surprisingly, whereas the transverse area of subepicardial CMs remained relatively preserved or even enlarged over 12 post-MI weeks, subendocardial CMs underwent progressive atrophy. Nevertheless, the fractional volume of viable CMs remained comparable in mature scars 4, 8, and 12 weeks after MI (3.6 ± 0.4%, 3.4 ± 0.5%, and 2.5 ± 0.3%, respectively). Despite the opposite dynamics of changes in size, CMs of both regions displayed sarcomeres and gap junctions. Most importantly, surviving CMs were always accompanied by patent microvessels linked to a venous network composed of Thebesian veins, intramural sinusoids, and subepicardial veins. Our findings reveal that long-term survival of CMs in transmural post-MI scars is sustained by a local microcirculatory bed.

Sex-related differences in intrinsic myocardial properties influence cardiac function in middle-aged rats during infarction-induced left ventricular remodeling

We previously determined that residual left ventricular (LV) myocardium of middle-aged rats had sex-related differences in regional tissue properties 4 weeks after a large myocardial infarction (MI). However, the impact of such differences on cardiac performance remained unclear. Therefore, our current study aimed to elucidate whether sex-related changes in MI-induced myocardial remodeling can influence cardiac function. A similar-sized MI was induced in 12-month-old male (M-MI) and female (F-MI) Sprague-Dawley rats by ligation of the left coronary artery. The cardiac function was monitored for 2 months after MI and then various LV parameters were compared between sexes. We found that although two sex groups had a similar pattern of MI-induced decline in LV function, F-MI rats had greater cardiac performance compared to M-MI rats, considering the higher values of EF (39.9 ± 3.4% vs. 26.7 ± 7.7%, P < 0.05), SW index (40.4 ± 2.1 mmHg • mL/kg vs. 20.2 ± 3.3 mmHg • mL/kg, P < 0.001), and CI (139.2 ± 7.9 mL/min/kg vs. 74.9 ± 14.7 mL/min/kg, P < 0.01). The poorer pumping capacity in M-MI hearts was associated with markedly reduced LV compliance and prolonged relaxation. On the tissue level, F-MI rats revealed a higher, than in M-MI rats, density of cardiac myocytes in the LV free wall (2383.8 ± 242.6 cells/mm(2) vs. 1785.7 ± 55.9 cells/mm(2), P < 0.05). The latter finding correlated with a lower density of apoptotic cardiac myocytes in residual LV myocardium of F-MI rats (0.18 ± 0.08 cells/mm(2) vs. 0.91 ± 0.30 cells/mm(2) in males, P < 0.01). Thus, our data suggested that F-MI rats had markedly attenuated decline in cardiac performance compared to males due to ability of female rats to better retain functionally favorable intrinsic myocardial properties.