Pregnancy mitigates cardiac pathology in a mouse model of left ventricular pressure overload

Pregnancy-induced metabolic reprogramming and regenerative responses to pro-aging stresses

Pregnancy is associated with physiological adaptations that affect virtually all organs, enabling the mother to support the growing fetus and placenta while withstanding the demands of pregnancy. As a result, mammalian pregnancy is a unique state that exerts paradoxical effects on maternal health. On one hand, the metabolic stress induced by pregnancy can accelerate aging and functional decline in organs. On the other hand, pregnancy activates metabolic programming and tissue regenerative responses that can reverse age-related impairments. In this sense, the oocyte-to-blastocyst transition is not the only physiological reprogramming event in the mammalian body, as pregnancy-induced regeneration could constitute a second physiological reprogramming event. Here, we review findings on how pregnancy dualistically leads to aging and rejuvenation in the maternal body.

Insights from the use of erythropoietin in experimental Chagas disease

In addition to the long-established role in erythropoiesis, erythropoietin (Epo) has protective functions in a variety of tissues, including the heart. This is the most affected organ in chronic Chagas disease, caused by the protozoan Trypanosoma cruzi. Despite seven million people being infected with T. cruzi worldwide, there is no effective treatment preventing the disease progression to the chronic phase when the pathological involvement of the heart is often observed. Chronic chagasic cardiomyopathy has a wide variety of manifestations, like left ventricular systolic dysfunction, dilated cardiomyopathy, and heart failure. Since Epo may help maintain cardiac function by reducing myocardial necrosis, inflammation, and fibrosis, this study aimed to evaluate whether the Epo has positive effects on experimental Chagas disease. For that, we assessed the earlier (acute phase) and also the later (chronic phase) use of Epo in infected C57BL/6 mice. Blood cell count, biochemical parameters, parasitic load, and echocardiography data were evaluated. In addition, histopathological analysis was carried out. Our data showed that Epo had no trypanocide effect nor did it modify the production of anti-T. cruzi antibodies. Epo-treated groups exhibited parasitic burden much lower in the heart compared to blood. No pattern of hematological changes was observed combining infection with treatment with Epo. Chronic Epo administration reduced CK-MB serum activity from d0 to d180, irrespectively of T. cruzi infection. Likewise, echocardiography and histological results indicate that Epo treatment is more effective in the chronic phase of experimental Chagas disease. Since treatment is one of the greatest challenges of Chagas disease, alternative therapies should be investigated, including Epo combined with benznidazole.

Multiscale model of heart growth during pregnancy: integrating mechanical and hormonal signaling

Pregnancy stands at the interface of mechanics and biology. The growing fetus continuously loads the maternal organs as circulating hormone levels surge, leading to significant changes in mechanical and hormonal cues during pregnancy. In response, maternal soft tissues undergo remarkable growth and remodeling to support the mother and baby for a healthy pregnancy. We focus on the maternal left ventricle, which increases its cardiac output and mass during pregnancy. This study develops a multiscale cardiac growth model for pregnancy to understand how mechanical and hormonal cues interact to drive this growth process. We coupled a cell signaling network model that predicts cell-level hypertrophy in response to hormones and stretch to a compartmental model of the rat heart and circulation that predicts organ-level growth in response to hemodynamic changes. We calibrated this multiscale model to data from experimental volume overload and hormonal infusions of angiotensin 2 (AngII), estrogen (E2), and progesterone (P4). We then validated the model's ability to capture interactions between inputs by comparing model predictions against published observations for the combinations of VO + E2 and AngII + E2. Finally, we simulated pregnancy-induced changes in hormones and hemodynamics to predict heart growth during pregnancy. Our model produced growth consistent with experimental data. Overall, our analysis suggests that the rise in P4 during the first half of gestation is an important contributor to heart growth during pregnancy. We conclude with suggestions for future experimental studies that will provide a better understanding of how hormonal and mechanical cues interact to drive pregnancy-induced heart growth.

Metabolic Coordination of Physiological and Pathological Cardiac Remodeling

Metabolic pathways integrate to support tissue homeostasis and to prompt changes in cell phenotype. In particular, the heart consumes relatively large amounts of substrate not only to regenerate ATP for contraction but also to sustain biosynthetic reactions for replacement of cellular building blocks. Metabolic pathways also control intracellular redox state, and metabolic intermediates and end products provide signals that prompt changes in enzymatic activity and gene expression. Mounting evidence suggests that the changes in cardiac metabolism that occur during development, exercise, and pregnancy as well as with pathological stress (eg, myocardial infarction, pressure overload) are causative in cardiac remodeling. Metabolism-mediated changes in gene expression, metabolite signaling, and the channeling of glucose-derived carbon toward anabolic pathways seem critical for physiological growth of the heart, and metabolic inefficiency and loss of coordinated anabolic activity are emerging as proximal causes of pathological remodeling. This review integrates knowledge of different forms of cardiac remodeling to develop general models of how relationships between catabolic and anabolic glucose metabolism may fortify cardiac health or promote (mal)adaptive myocardial remodeling. Adoption of conceptual frameworks based in relational biology may enable further understanding of how metabolism regulates cardiac structure and function.

Guidelines for measuring cardiac physiology in mice

Cardiovascular disease is a leading cause of death, and translational research is needed to understand better mechanisms whereby the left ventricle responds to injury. Mouse models of heart disease have provided valuable insights into mechanisms that occur during cardiac aging and in response to a variety of pathologies. The assessment of cardiovascular physiological responses to injury or insult is an important and necessary component of this research. With increasing consideration for rigor and reproducibility, the goal of this guidelines review is to provide best-practice information regarding how to measure accurately cardiac physiology in animal models. In this article, we define guidelines for the measurement of cardiac physiology in mice, as the most commonly used animal model in cardiovascular research.

Listen to this article’s corresponding podcast at http://ajpheart.podbean.com/e/guidelines-for-measuring-cardiac-physiology-in-mice/.

Mechanisms contributing to cardiac remodelling

Cardiac remodelling is classified as physiological (in response to growth, exercise and pregnancy) or pathological (in response to inflammation, ischaemia, ischaemia/reperfusion (I/R) injury, biomechanical stress, excess neurohormonal activation and excess afterload). Physiological remodelling of the heart is characterized by a fine-tuned and orchestrated process of beneficial adaptations. Pathological cardiac remodelling is the process of structural and functional changes in the left ventricle (LV) in response to internal or external cardiovascular damage or influence by pathogenic risk factors, and is a precursor of clinical heart failure (HF). Pathological remodelling is associated with fibrosis, inflammation and cellular dysfunction (e.g. abnormal cardiomyocyte/non-cardiomyocyte interactions, oxidative stress, endoplasmic reticulum (ER) stress, autophagy alterations, impairment of metabolism and signalling pathways), leading to HF. This review describes the key molecular and cellular responses involved in pathological cardiac remodelling.

Thinking Outside the Box

A broad definition of preconditioning is "the preparation for a subsequent action." Mounting evidence demonstrates that novel remote preconditioning paradigms, in which protective stimuli experienced locally can capacitate systemic tolerance and enhanced cell viability upon exposure to ensuing cellular insults, have been largely successful in the field of cardiovascular ischemia/reperfusion injury. To ensure successful protective preconditioning, some models (including the uterus) have been demonstrated to activate the unfolded protein response (UPR), which is a cellular stress response controlled at the level of the endoplasmic reticulum. However, in the context of remote preconditioning, activation of these intracellular molecular pathways must result in the extracellular transmission of adaptive signals to remote targets. In our recently published manuscript, we have described the activation of the UPR in the pregnant uterine myocyte to be associated with increased uterine myocyte quiescence and normal gestational length. We hypothesize that ubiquitous uterine gestational stresses experienced in every pregnancy, which have been demonstrated in other systems to activate the UPR, may induce a robust paracrine dissemination of a uterine secretome, for example, glucose-regulated protein 78, with preconditioning-like properties. Furthermore, we speculate that the gestational stress-induced uterine secretome acts to promote both local and systemic tolerance to the ensuing gestational insults, allowing for the maintenance of uterine quiescence. In this context, preterm labor may be the result of a pregnant uterus experiencing a stress it cannot accommodate or when it is unable to host an appropriate UPR resulting in insufficient preconditioning and a diminished local and systemic capacity to tolerate pregnancy-dependent increases in normal gestational stress. This is highly attractive from a clinical viewpoint as we ultimately aim to identify local and systemic adaptations that may serve as preconditioning stimuli for use as a strategy to restore appropriate preconditioning profiles to prolong uterine quiescence in pregnancy.