Myocardial aging as a T-cell-mediated phenomenon

Lipid nanoparticle (LNP) mediated mRNA delivery in cardiovascular diseases: Advances in genome editing and CAR T cell therapy

Cardiovascular diseases (CVDs) are the leading cause of global mortality among non-communicable diseases. Current cardiac regeneration treatments have limitations and may lead to adverse reactions. Hence, innovative technologies are needed to address these shortcomings. Messenger RNA (mRNA) emerges as a promising therapeutic agent due to its versatility in encoding therapeutic proteins and targeting "undruggable" conditions. It offers low toxicity, high transfection efficiency, and controlled protein production without genome insertion or mutagenesis risk. However, mRNA faces challenges such as immunogenicity, instability, and difficulty in cellular entry and endosomal escape, hindering its clinical application. To overcome these hurdles, lipid nanoparticles (LNPs), notably used in COVID-19 vaccines, have a great potential to deliver mRNA therapeutics for CVDs. This review highlights recent progress in mRNA-LNP therapies for CVDs, including Myocardial Infarction (MI), Heart Failure (HF), and hypercholesterolemia. In addition, LNP-mediated mRNA delivery for CAR T-cell therapy and CRISPR/Cas genome editing in CVDs and the related clinical trials are explored. To enhance the efficiency, safety, and clinical translation of mRNA-LNPs, advanced technologies like artificial intelligence (AGILE platform) in RNA structure design, and optimization of LNP formulation could be integrated. We conclude that the strategies to facilitate the extra-hepatic delivery and targeted organ tropism of mRNA-LNPs (SORT, ASSET, SMRT, and barcoded LNPs) hold great prospects to accelerate the development and translation of mRNA-LNPs in CVD treatment.

Rejuvenation of the Aging Heart: Molecular Determinants and Applications

In Canada and worldwide, the elderly population (ie, individuals > 65 years of age) is increasing disproportionately relative to the total population. This is expected to have a substantial impact on the health care system, as increased aged is associated with a greater incidence of chronic noncommunicable diseases. Within the elderly population, cardiovascular disease is a leading cause of death, therefore developing therapies that can prevent or slow disease progression in this group is highly desirable. Historically, aging research has focused on the development of anti-aging therapies that are implemented early in life and slow the age-dependent decline in cell and organ function. However, accumulating evidence supports that late-in-life therapies can also benefit the aged cardiovascular system by limiting age-dependent functional decline. Moreover, recent studies have demonstrated that rejuvenation (ie, reverting cellular function to that of a younger phenotype) of the already aged cardiovascular system is possible, opening new avenues to develop therapies for older individuals. In this review, we first provide an overview of the functional changes that occur in the cardiomyocyte with aging and how this contributes to the age-dependent decline in heart function. We then discuss the various anti-aging and rejuvenation strategies that have been pursued to improve the function of the aged cardiomyocyte, with a focus on therapies implemented late in life. These strategies include 1) established systemic approaches (caloric restriction, exercise), 2) pharmacologic approaches (mTOR, AMPK, SIRT1, and autophagy-targeting molecules), and 3) emerging rejuvenation approaches (partial reprogramming, parabiosis/modulation of circulating factors, targeting endogenous stem cell populations, and senotherapeutics). Collectively, these studies demonstrate the exciting potential and limitations of current rejuvenation strategies and highlight future areas of investigation that will contribute to the development of rejuvenation therapies for the aged heart.

Effects and mechanisms of the myocardial microenvironment on cardiomyocyte proliferation and regeneration

The adult mammalian cardiomyocyte has a limited capacity for self-renewal, which leads to the irreversible heart dysfunction and poses a significant threat to myocardial infarction patients. In the past decades, research efforts have been predominantly concentrated on the cardiomyocyte proliferation and heart regeneration. However, the heart is a complex organ that comprises not only cardiomyocytes but also numerous noncardiomyocyte cells, all playing integral roles in maintaining cardiac function. In addition, cardiomyocytes are exposed to a dynamically changing physical environment that includes oxygen saturation and mechanical forces. Recently, a growing number of studies on myocardial microenvironment in cardiomyocyte proliferation and heart regeneration is ongoing. In this review, we provide an overview of recent advances in myocardial microenvironment, which plays an important role in cardiomyocyte proliferation and heart regeneration.

Intersection of Immunology and Metabolism in Myocardial Disease

Immunometabolism is an emerging field at the intersection of immunology and metabolism. Immune cell activation plays a critical role in the pathogenesis of cardiovascular diseases and is integral for regeneration during cardiac injury. We currently possess a limited understanding of the processes governing metabolic interactions between immune cells and cardiomyocytes. The impact of this intercellular crosstalk can manifest as alterations to the steady state flux of metabolites and impact cardiac contractile function. Although much of our knowledge is derived from acute inflammatory response, recent work emphasizes heterogeneity and flexibility in metabolism between cardiomyocytes and immune cells during pathological states, including ischemic, cardiometabolic, and cancer-associated disease. Metabolic adaptation is crucial because it influences immune cell activation, cytokine release, and potential therapeutic vulnerabilities. This review describes current concepts about immunometabolic regulation in the heart, focusing on intercellular crosstalk and intrinsic factors driving cellular regulation. We discuss experimental approaches to measure the cardio-immunologic crosstalk, which are necessary to uncover unknown mechanisms underlying the immune and cardiac interface. Deeper insight into these axes holds promise for therapeutic strategies that optimize cardioimmunology crosstalk for cardiac health.

Autoimmune Myocarditis, Old Dogs and New Tricks

Autoimmunity significantly contributes to the pathogenesis of myocarditis, underscored by its increased frequency in autoimmune diseases such as systemic lupus erythematosus and polymyositis. Even in cases of myocarditis caused by viral infections, dysregulated immune responses contribute to pathogenesis. However, whether triggered by existing autoimmune conditions or viral infections, the precise antigens and immunologic pathways driving myocarditis remain incompletely understood. The emergence of myocarditis associated with immune checkpoint inhibitor therapy, commonly used for treating cancer, has afforded an opportunity to understand autoimmune mechanisms in myocarditis, with autoreactive T cells specific for cardiac myosin playing a pivotal role. Despite their self-antigen recognition, cardiac myosin-specific T cells can be present in healthy individuals due to bypassing the thymic selection stage. In recent studies, novel modalities in suppressing the activity of pathogenic T cells including cardiac myosin-specific T cells have proven effective in treating autoimmune myocarditis. This review offers an overview of the current understanding of heart antigens, autoantibodies, and immune cells as the autoimmune mechanisms underlying various forms of myocarditis, along with the latest updates on clinical management and prospects for future research.

Mineralocorticoid receptor promotes cardiac macrophage inflammaging

Inflammaging, a pro-inflammatory status that characterizes aging and primarily involving macrophages, is a master driver of age-related diseases. Mineralocorticoid receptor (MR) activation in macrophages critically regulates inflammatory and fibrotic processes. However, macrophage-specific mechanisms and the role of the macrophage MR for the regulation of inflammation and fibrotic remodeling in the aging heart have not yet been elucidated. Transcriptome profiling of cardiac macrophages from male/female young (4 months-old), middle (12 months-old) and old (18 and 24 months-old) mice revealed that myeloid cell-restricted MR deficiency prevents macrophage differentiation toward a pro-inflammatory phenotype. Pathway enrichment analysis showed that several biological processes related to inflammation and cell metabolism were modulated by the MR in aged macrophages. Further, transcriptome analysis of aged cardiac fibroblasts revealed that macrophage MR deficiency reduced the activation of pathways related to inflammation and upregulation of ZBTB16, a transcription factor involved in fibrosis. Phenotypic characterization of macrophages showed a progressive replacement of the TIMD4+MHC-IIneg/low macrophage population by TIMD4+MHC-IIint/high and TIMD4-MHC-IIint/high macrophages in the aging heart. By integrating cell sorting and transwell experiments with TIMD4+/TIMD4-macrophages and fibroblasts from old MRflox/MRLysMCre hearts, we showed that the inflammatory crosstalk between TIMD4- macrophages and fibroblasts may imply the macrophage MR and the release of mitochondrial superoxide anions. Macrophage MR deficiency reduced the expansion of the TIMD4- macrophage population and the emergence of fibrotic niches in the aging heart, thereby protecting against cardiac inflammation, fibrosis, and dysfunction. This study highlights the MR as an important mediator of cardiac macrophage inflammaging and age-related fibrotic remodeling.

Cardiac fibrogenesis: an immuno-metabolic perspective

Cardiac fibrosis is a major and complex pathophysiological process that ultimately culminates in cardiac dysfunction and heart failure. This phenomenon includes not only the replacement of the damaged tissue by a fibrotic scar produced by activated fibroblasts/myofibroblasts but also a spatiotemporal alteration of the structural, biochemical, and biomechanical parameters in the ventricular wall, eliciting a reactive remodeling process. Though mechanical stress, post-infarct homeostatic imbalances, and neurohormonal activation are classically attributed to cardiac fibrosis, emerging evidence that supports the roles of immune system modulation, inflammation, and metabolic dysregulation in the initiation and progression of cardiac fibrogenesis has been reported. Adaptive changes, immune cell phenoconversions, and metabolic shifts in the cardiac nonmyocyte population provide initial protection, but persistent altered metabolic demand eventually contributes to adverse remodeling of the heart. Altered energy metabolism, mitochondrial dysfunction, various immune cells, immune mediators, and cross-talks between the immune cells and cardiomyocytes play crucial roles in orchestrating the transdifferentiation of fibroblasts and ensuing fibrotic remodeling of the heart. Manipulation of the metabolic plasticity, fibroblast-myofibroblast transition, and modulation of the immune response may hold promise for favorably modulating the fibrotic response following different cardiovascular pathological processes. Although the immunologic and metabolic perspectives of fibrosis in the heart are being reported in the literature, they lack a comprehensive sketch bridging these two arenas and illustrating the synchrony between them. This review aims to provide a comprehensive overview of the intricate relationship between different cardiac immune cells and metabolic pathways as well as summarizes the current understanding of the involvement of immune-metabolic pathways in cardiac fibrosis and attempts to identify some of the previously unaddressed questions that require further investigation. Moreover, the potential therapeutic strategies and emerging pharmacological interventions, including immune and metabolic modulators, that show promise in preventing or attenuating cardiac fibrosis and restoring cardiac function will be discussed.

RelA-mediated signaling connects adaptation to chronic cardiomyocyte stress with myocardial and systemic inflammation in the ADCY8 model of accelerated aging

Mice with cardiac-specific overexpression of adenylyl cyclase (AC) type 8 (TGAC8) are under a constant state of severe myocardial stress. They have a remarkable ability to adapt to this stress, but they eventually develop accelerated cardiac aging and experience reduced longevity. We have previously demonstrated through bioinformatics that constitutive adenylyl cyclase activation in TGAC8 mice is associated with the activation of inflammation-related signaling pathways. However, the immune response associated with chronic myocardial stress in the TGAC8 mouse remains unexplored. Here we demonstrate that chronic activation of adenylyl cyclase in cardiomyocytes of TGAC8 mice results in activation of cell-autonomous RelA-mediated NF-κB signaling. This is associated with non-cell-autonomous activation of proinflammatory and age-associated signaling in myocardial endothelial cells and myocardial smooth muscle cells, expansion of myocardial immune cells, increase in serum levels of inflammatory cytokines, and changes in the size or composition of lymphoid organs. All these changes precede the appearance of cardiac fibrosis. We provide evidence indicating that RelA activation in cardiomyocytes with chronic activation of adenylyl cyclase is mediated by calcium-protein Kinase A (PKA) signaling. Using a model of chronic cardiomyocyte stress and accelerated aging, we highlight a novel, calcium/PKA/RelA-dependent connection between cardiomyocyte stress, myocardial inflammation, and systemic inflammation. These findings suggest that RelA-mediated signaling in cardiomyocytes might be an adaptive response to stress that, when chronically activated, ultimately contributes to both cardiac and systemic aging.

The efferocytosis process in aging: Supporting evidence, mechanisms, and therapeutic prospects for age-related diseases

BACKGROUND

Aging is characterized by an ongoing struggle between the buildup of damage caused by a combination of external and internal factors. Aging has different effects on phagocytes, including impaired efferocytosis. A deficiency in efferocytosis can cause chronic inflammation, aging, and several other clinical disorders.

AIM OF REVIEW

Our review underscores the possible feasibility and extensive scope of employing dual targets in various age-related diseases to reduce the occurrence and progression of age-related diseases, ultimately fostering healthy aging and increasing lifespan. Key scientific concepts of review Hence, the concurrent implementation of strategies aimed at augmenting efferocytic mechanisms and anti-aging treatments has the potential to serve as a potent intervention for extending the duration of a healthy lifespan. In this review, we comprehensively discuss the concept and physiological effects of efferocytosis. Subsequently, we investigated the association between efferocytosis and the hallmarks of aging. Finally, we discuss growing evidence regarding therapeutic interventions for age-related disorders, focusing on the physiological processes of aging and efferocytosis.

CAR-T cell therapeutic avenue for fighting cardiac fibrosis: Roadblocks and perspectives

Heart diseases remain the primary cause of human mortality in the world. Although conventional therapeutic opportunities fail to halt or recover cardiac fibrosis, the promising clinical results and therapeutic efficacy of engineered chimeric antigen receptor (CAR) T cell therapy show several advancements. However, the current models of CAR-T cells need further improvement since the T cells are associated with the triggering of excessive inflammatory cytokines that directly affect cardiac functions. Thus, the current study highlights the critical function of heart immune cells in tissue fibrosis and repair. The study also confirms CAR-T cell as an emerging therapeutic for treating cardiac fibrosis, explores the current roadblocks to CAR-T cell therapy, and considers future outlooks for research development.

Immune checkpoint inhibitors break whose heart? Perspectives from cardio-immuno-oncology

Immune checkpoint inhibitors (ICIs) are monoclonal antibody antagonists, which can block cytotoxic T lymphocyte antigen-4 (CTLA-4), programmed death-1/ligand-1 (PD-1/PD-L1) pathways, and other molecules exploited by tumor cells to evade T cell-mediated immune response. ICIs have transformed the treatment landscape for various cancers due to their amazing efficacy. Many anti-tumor therapies, including targeted therapy, radiotherapy, and chemotherapy, combine ICIs to make the treatment more effective. However, the off-target immune activation caused by ICIs may lead to a broad spectrum of immune-related adverse events (irAEs) affecting multiple organ systems. Among irAEs, cardiotoxicity induced by ICIs, uncommon but fatal, has greatly offset survival benefits from ICIs, which is heartbreaking for both patients and clinicians. Consequently, such cardiotoxicity requires special vigilance, and it has become a common challenge both for patients and clinicians. This article reviewed the clinical manifestations and influence of cardiotoxicity from the view of patients and clinicians, elaborated on the underlying mechanisms in conjunction with animal studies, and then attempted to propose management strategies from a cardio-immuno-oncology multidisciplinary perspective.

Cardiac Development at a Single-Cell Resolution

Mammalian cardiac development is a complex, multistage process. Though traditional lineage tracing studies have characterized the broad trajectories of cardiac progenitors, the advent and rapid optimization of single-cell RNA sequencing methods have yielded an ever-expanding toolkit for characterizing heterogeneous cell populations in the developing heart. Importantly, they have allowed for a robust profiling of the spatiotemporal transcriptomic landscape of the human and mouse heart, revealing the diversity of cardiac cells-myocyte and non-myocyte-over the course of development. These studies have yielded insights into novel cardiac progenitor populations, chamber-specific developmental signatures, the gene regulatory networks governing cardiac development, and, thus, the etiologies of congenital heart diseases. Furthermore, single-cell RNA sequencing has allowed for the exquisite characterization of distinct cardiac populations such as the hard-to-capture cardiac conduction system and the intracardiac immune population. Therefore, single-cell profiling has also resulted in new insights into the regulation of cardiac regeneration and injury repair. Single-cell multiomics approaches combining transcriptomics, genomics, and epigenomics may uncover an even more comprehensive atlas of human cardiac biology. Single-cell analyses of the developing and adult mammalian heart offer an unprecedented look into the fundamental mechanisms of cardiac development and the complex diseases that may arise from it.

The role of cardiac resident macrophage in cardiac aging

Advancements in longevity research have provided insights into the impact of cardiac aging on the structural and functional aspects of the heart. Notable changes include the gradual remodeling of the myocardium, the occurrence of left ventricular hypertrophy, and the decline in both systolic and diastolic functions. Macrophages, a type of immune cell, play a pivotal role in innate immunity by serving as vigilant agents against pathogens, facilitating wound healing, and orchestrating the development of targeted acquired immune responses. Distinct subsets of macrophages are present within the cardiac tissue and demonstrate varied functions in response to myocardial injury. The differentiation of cardiac macrophages according to their developmental origin has proven to be a valuable strategy in identifying reparative macrophage populations, which originate from embryonic cells and reside within the tissue, as well as inflammatory macrophages, which are derived from monocytes and recruited to the heart. These subsets of macrophages possess unique characteristics and perform distinct functions. This review aims to summarize the current understanding of the roles and phenotypes of cardiac macrophages in various conditions, including the steady state, aging, and other pathological conditions. Additionally, it will highlight areas that require further investigation to expand our knowledge in this field.

An interferon gamma response signature links myocardial aging and immunosenescence

AIMS

Aging entails profound immunological transformations that can impact myocardial homeostasis and predispose to heart failure. However, preclinical research in the immune-cardiology field is mostly conducted in young healthy animals, which potentially weakens its translational relevance. Herein, we sought to investigate how the aging T-cell compartment associates with changes in myocardial cell biology in aged mice.

METHODS AND RESULTS

We phenotyped the antigen-experienced effector/memory T cells purified from heart-draining lymph nodes of 2-, 6-, 12-, and 18-month-old C57BL/6J mice using single-cell RNA/T cell receptor sequencing. Simultaneously, we profiled all non-cardiomyocyte cell subsets purified from 2- to 18-month-old hearts and integrated our data with publicly available cardiomyocyte single-cell sequencing datasets. Some of these findings were confirmed at the protein level by flow cytometry. With aging, the heart-draining lymph node and myocardial T cells underwent clonal expansion and exhibited an up-regulated pro-inflammatory transcription signature, marked by an increased interferon-γ (IFN-γ) production. In parallel, all major myocardial cell populations showed increased IFN-γ responsive signature with aging. In the aged cardiomyocytes, a stronger IFN-γ response signature was paralleled by the dampening of expression levels of transcripts related to most metabolic pathways, especially oxidative phosphorylation. Likewise, induced pluripotent stem cells-derived cardiomyocytes exposed to chronic, low grade IFN-γ treatment showed a similar inhibition of metabolic activity.

CONCLUSIONS

By investigating the paired age-related alterations in the T cells found in the heart and its draining lymph nodes, we provide evidence for increased myocardial IFN-γ signaling with age, which is associated with inflammatory and metabolic shifts typically seen in heart failure.

Hallmarks of cardiovascular ageing

Normal circulatory function is a key determinant of disease-free life expectancy (healthspan). Indeed, pathologies affecting the cardiovascular system, which are growing in prevalence, are the leading cause of global morbidity, disability and mortality, whereas the maintenance of cardiovascular health is necessary to promote both organismal healthspan and lifespan. Therefore, cardiovascular ageing might precede or even underlie body-wide, age-related health deterioration. In this Review, we posit that eight molecular hallmarks are common denominators in cardiovascular ageing, namely disabled macroautophagy, loss of proteostasis, genomic instability (in particular, clonal haematopoiesis of indeterminate potential), epigenetic alterations, mitochondrial dysfunction, cell senescence, dysregulated neurohormonal signalling and inflammation. We also propose a hierarchical order that distinguishes primary (upstream) from antagonistic and integrative (downstream) hallmarks of cardiovascular ageing. Finally, we discuss how targeting each of the eight hallmarks might be therapeutically exploited to attenuate residual cardiovascular risk in older individuals.

Fractalkine/CX3CR1 in Dilated Cardiomyopathy: A Potential Future Target for Immunomodulatory Therapy?

Dilated cardiomyopathy (DCM) is a cardiac condition with structural and functional impairment, where either the left ventricle or both ventricular chambers are enlarged, coinciding with reduced systolic pump function (reduced ejection fraction, rEF). The prevalence of DCM is more than 1:250 individuals, and mortality largely due to heart failure in two-third of cases, and sudden cardiac death in one-third of patients. Damage to the myocardium, whether from a genetic or environmental cause such as viruses, triggers inflammation and recruits immune cells to the heart to repair the myocardium. Examination of myocardial biopsy tissue often reveals an inflammatory cell infiltrate, T lymphocyte (T cell) infiltration, or other activated immune cells. Despite medical therapy, adverse outcomes for DCM remain. The evidence base and existing literature suggest that upregulation of CX3CR1, migration of immune cells, together with cytomegalovirus (CMV) seropositivity is associated with worse outcomes in patients with dilated cardiomyopathy. We hypothesise that this potentially occurs through cardiac inflammation and fibrosis, resulting in adverse remodelling. Immune modulators to target this pathway may potentially improve outcomes above and beyond current guideline-recommended therapy.

Bibliometric analysis of trends in cardiac aging research over the past 20 years

BACKGROUND

In recent years, many studies have addressed cardiac aging and related diseases. This study aims to understand the research trend of cardiac aging and find new hot issues.

METHODS

We searched the web of science core collection database for articles published between 2003 and 2022 on the topic of "cardiac aging." Complete information including keywords, publication year, journal title, country, organization, and author were extracted for analysis. The VOS viewer software was used to generate network maps of keywords, countries, institutions, and author relationships for visual network analysis.

RESULTS

A total of 1002 papers were analyzed in the study. Overall, the number of annual publications on cardiac aging has increased since 2009, and new hot topics are emerging. The top 3 countries with the most publications were the United States (471 articles), China (209 articles) and Italy (101 articles). The University of Washington published the most papers (35 articles). The cluster analysis with author as the keyword found that the connections among different scholars are scattered and clustered in a small range. Network analysis based on keyword co-occurrence and year of publication identified relevant features and trends in cardiac aging research. According to the results of cluster analysis, all the articles are divided into 4 topics: "mechanisms of cardiac aging", "prevention and treatment of cardiac aging", "characteristics of cardiac aging", and "others." In recent years, the mechanism and treatment of cardiac aging have attracted the most attention. In both studies, animal models are used more often than in human populations. Mitochondrial dysfunction, autophagy and mitochondrial autophagy are hotspots in current research.

CONCLUSION

In this study, bibliometric analysis was used to analyze the research trend of cardiac aging in the past 20 years. The mechanism and treatment of cardiac aging are the most concerned contents. Mitochondrial dysfunction, autophagy and mitophagy are the focus of future research on cardiac aging.

Cardiomyocyte-specific adenylyl cyclase type-8 overexpression induces cell-autonomous activation of RelA and non-cell-autonomous myocardial and systemic inflammation

Mice with cardiac-specific overexpression of adenylyl cyclase (AC) type 8 (TG AC8 ) are under a constant state of severe myocardial stress and have been shown to have a remarkable ability to adapt to this stress. However, they eventually develop accelerated cardiac aging and cardiac fibrosis, and experience reduced longevity. Here we show that young (3-month-old) TG AC8 animals are characterized by a broad and extensive inflammatory state, that precedes the development of cardiac fibrosis. We demonstrate that activation of ACVIII in the cardiomyocytes results in cell-autonomous RelA-mediated NF-κB signaling. This is associated with non-cell-autonomous activation of proinflammatory and age-associated signaling in myocardial endothelial cells, increases in serum levels of inflammatory cytokines, changes in myocardial immune cells, and changes in the size or composition of lymphoid organs. Finally, we provide evidence suggesting that ACVIII-driven RelA activation in cardiomyocytes might be mediated by calcium-Protein Kinase A (PKA) signaling. Our findings highlight a novel mechanistic connection between cardiomyocyte stress, myocardial para-inflammation, systemic inflammation, and aging, and therefore point to novel potential therapeutic targets to reduce age-associated myocardial deterioration.

Fibroblast and Immune Cell Cross-Talk in Cardiac Fibrosis

PURPOSE OF REVIEW

The intricate interplay between inflammatory and reparative responses in the context of heart injury is central to the pathogenesis of heart failure. Recent clinical studies have shown the therapeutic benefits of anti-inflammatory strategies in the treatment of cardiovascular diseases. This review provides a comprehensive overview of the cross-talk between immune cells and fibroblasts in the diseased heart.

RECENT FINDINGS

The role of inflammatory cells in fibroblast activation after cardiac injury is well-documented, but recent single-cell transcriptomics studies have identified putative pro-inflammatory fibroblasts in the infarcted heart, suggesting that fibroblasts, in turn, can modify inflammatory cell behavior. Furthermore, anti-inflammatory immune cells and fibroblasts have been described. The use of spatial and temporal-omics analyses may provide additional insights toward a better understanding of disease-specific microenvironments, where activated fibroblasts and inflammatory cells are in proximity. Recent studies focused on the interplay between fibroblasts and immune cells have brought us closer to the identification of cell type-specific targets for intervention. Further exploration of these intercellular communications will provide deeper insights toward the development of novel therapeutics.

Senescent Cells: A Therapeutic Target in Cardiovascular Diseases

Senescent cell accumulation has been observed in age-associated diseases including cardiovascular diseases. Senescent cells lack proliferative capacity and secrete senescence-associated secretory phenotype (SASP) factors that may cause or worsen many cardiovascular diseases. Therapies targeting senescent cells, especially senolytic drugs that selectively induce senescent cell removal, have been shown to delay, prevent, alleviate, or treat multiple age-associated diseases in preclinical models. Some senolytic clinical trials have already been completed or are underway for a number of diseases and geriatric syndromes. Understanding how cellular senescence affects the various cell types in the cardiovascular system, such as endothelial cells, vascular smooth muscle cells, fibroblasts, immune cells, progenitor cells, and cardiomyocytes, is important to facilitate translation of senotherapeutics into clinical interventions. This review highlights: (1) the characteristics of senescent cells and their involvement in cardiovascular diseases, focusing on the aforementioned cardiovascular cell types, (2) evidence about senolytic drugs and other senotherapeutics, and (3) the future path and clinical potential of senotherapeutics for cardiovascular diseases.

Impact of Non-Muscle Cells on Excitation-Contraction Coupling in the Heart and the Importance of In Vitro Models

Excitation-coupling (ECC) is paramount for coordinated contraction to maintain sufficient cardiac output. The study of ECC regulation has primarily been limited to cardiomyocytes (CMs), which conduct voltage waves via calcium fluxes from one cell to another, eliciting contraction of the atria followed by the ventricles. CMs rapidly transmit ionic flux via gap junction proteins, predominantly connexin 43. While the expression of connexin isoforms has been identified in each of the individual cell populations comprising the heart, the formation of gap junctions with nonmuscle cells (i.e., macrophages and Schwann cells) has gained new attention. Evaluating nonmuscle contributions to ECC in vivo or in situ remains difficult and necessitates the development of simple, yet biomimetic in vitro models to better understand and prevent physiological dysfunction. Standard 2D cell culture often consists of homogenous cell populations and lacks the dynamic mechanical environment of native tissue, confounding the phenotypic and proteomic makeup of these highly mechanosensitive cell populations in prolonged culture conditions. This review will highlight the recent developments and the importance of new microphysiological systems to better understand the complex regulation of ECC in cardiac tissue.

Myocardial Immune Cells: The Basis of Cardiac Immunology

The mammalian heart is characterized by the presence of striated myocytes, which allow continuous rhythmic contraction from early embryonic development until the last moments of life. However, the myocardium contains a significant contingent of leukocytes from every major class. This leukocyte pool includes both resident and nonresident immune cells. Over recent decades, it has become increasingly apparent that the heart is intimately sensitive to immune signaling and that myocardial leukocytes exhibit an array of critical functions, both in homeostasis and in the context of cardiac adaptation to injury. Here, we systematically review current knowledge of all major leukocyte classes in the heart, discussing their functions in health and disease. We also highlight the connection between the myocardium, immune cells, lymphoid organs, and both local and systemic immune responses.

Hydroxytyrosol Interference with Inflammaging via Modulation of Inflammation and Autophagy

Inflammaging refers to a chronic, systemic, low-grade inflammation, driven by immune (mainly macrophages) and non-immune cells stimulated by endogenous/self, misplaced or altered molecules, belonging to physiological aging. This age-related inflammatory status is characterized by increased inflammation and decreased macroautophagy/autophagy (a degradation process that removes unnecessary or dysfunctional cell components). Inflammaging predisposes to age-related diseases, including obesity, type-2 diabetes, cancer, cardiovascular and neurodegenerative disorders, as well as vulnerability to infectious diseases and vaccine failure, representing thus a major target for anti-aging strategies. Phenolic compounds-found in extra-virgin olive oil (EVOO)-are well known for their beneficial effect on longevity. Among them, hydroxytyrosol (HTyr) appears to greatly contribute to healthy aging by its documented potent antioxidant activity. In addition, HTyr can modulate inflammation and autophagy, thus possibly counteracting and reducing inflammaging. In this review, we reference the literature on pure HTyr as a modulatory agent of inflammation and autophagy, in order to highlight its possible interference with inflammaging. This HTyr-mediated activity might contribute to healthy aging and delay the development or progression of diseases related to aging.

Immune mechanisms of cardiac aging

Advances in healthcare and improvements in living conditions have led to rising life expectancy worldwide. Aging is associated with excessive oxidative stress, a chronic inflammatory state, and limited tissue healing, all of which result in an increased risk of heart failure. In fact, the prevalence of heart failure approaches 40% in the ninth decade of life, with the majority of these cases suffering from heart failure with preserved ejection fraction (HFpEF). In cardiomyocytes (CMs), age-related mitochondrial dysfunction results in disrupted calcium signaling and covalent protein-linked aggregates, which cause cardiomyocyte functional disturbances, resulting in increased stiffness and diastolic dysfunction. Importantly, aging is also associated with chronic low-grade, sterile inflammation, which alters the function of interstitial cardiac cells and leads to cardiac fibrosis. Taken together, cardiac aging is associated with cellular, structural, and functional changes in the heart that contribute to the rising prevalence of heart failure in older people.

Myocardial Milieu Favors Local Differentiation of Regulatory T Cells

BACKGROUND

In the past years, several studies investigated how distinct immune cell subsets affects post-myocardial infarction repair. However, whether and how the tissue environment controls these local immune responses has remained poorly understood. We sought to investigate how antigen-specific T-helper cells differentiate under myocardial milieu's influence.

METHODS

We used a transgenic T cell receptor (TCR-M) model and major histocompatibility complex-II tetramers, both myosin-specific, combined with single-cell transcriptomics (single-cell RNA sequencing [scRNA-seq]) and functional phenotyping to elucidate how the antigen-specific CD4⁺ T cells differentiate in the murine infarcted myocardium and influence tissue repair. Additionally, we transferred proinflammatory versus regulatory predifferentiated TCR-M-cells to dissect how they specially contribute to post-myocardial infarction inflammation.

RESULTS

Flow cytometry and scRNA-/TCR-seq analyses revealed that transferred TCR-M cells acquired an induced regulatory phenotype (induced regulatory T cell) in the infarcted myocardium and blunted local inflammation. Myocardial TCR-M cells differentiated into 2 main lineages enriched with either cell activation and profibrotic transcripts (eg, Tgfb1) or suppressor immune checkpoints (eg, Pdcd1), which we also found in human myocardial tissue. These cells produced high levels of LAP (latency-associated peptide) and inhibited IL-17 (interleukin-17) responses. Endogenous myosin-specific T-helper cells, identified using genetically barcoded tetramers, also accumulated in infarcted hearts and exhibited a regulatory phenotype. Notably, TCR-M cells that were predifferentiated toward a regulatory phenotype in vitro maintained stable in vivo FOXP3 (Forkhead box P3) expression and anti-inflammatory activity whereas T_H17 partially converted toward a regulatory phenotype in the injured myocardium. Overall, the myosin-specific Tregs dampened post-myocardial infarction inflammation, suppressed neighboring T cells, and were associated with improved cardiac function.

CONCLUSIONS

These findings provide novel evidence that the heart and its draining lymph nodes actively shape local immune responses by promoting the differentiation of antigen-specific Tregs poised with suppressive function.

Progranulin (PGRN) as a regulator of inflammation and a critical factor in the immunopathogenesis of cardiovascular diseases

Immune dysregulation has been identified as a critical cause of the most common types of cardiovascular diseases (CVDs). Notably, the innate and adaptive immune responses under physiological conditions are typically regulated with high sensitivity to avoid the exacerbation of inflammation, but any dysregulation can probably be associated with CVDs. In this respect, progranulin (PGRN) serves as one of the main components of the regulation of inflammatory processes, which significantly contributes to the immunopathogenesis of such disorders. PGRN has been introduced among the secreted growth factors as one related to wound healing, inflammation, and human embryonic development, as well as a wide variety of autoimmune diseases. The relationship between the serum PGRN and TNF-α ratio with the spontaneous bacterial peritonitis constitute one of the independent predictors of these conditions. The full-length PGRN can thus effectively reduce the calcification of valve interstitial cells, and the granulin precursor (GRN), among the degradation products of PGRN, can be beneficial. Moreover, it was observed that, PGRN protects the heart against ischemia-reperfusion injury. Above all, PGRN also provides protection in the initial phase following myocardial ischemia-reperfusion injury. The protective impact of PGRN on this may be associated with the early activation of the PI3K/Akt signaling pathway. PGRN also acts as a protective factor in hyperhomocysteinemia, probably by down-regulating the wingless-related integration site Wnt/β-catenin signaling pathway. Many studies have further demonstrated that SARS-CoV-2 (COVID-19) has dramatically increased the risks of CVDs due to inflammation, so PGRN has drawn much more attention among scholars. Lysosomes play a pivotal role in the inflammation process, and PGRN is one of the key regulators in their functioning, which contributes to the immunomodulatory mechanism in the pathogenesis of CVDs. Therefore, investigation of PGRN actions can help find new prospects in the treatment of CVDs. This review aims to summarize the role of PGRN in the immunopathogenesis of CVD, with an emphasis on its treatment.

Macrophages in cardiac remodelling after myocardial infarction

Myocardial infarction (MI), as a result of thrombosis or vascular occlusion, is the most prevalent cause of morbidity and mortality among all cardiovascular diseases. The devastating consequences of MI are compounded by the complexities of cellular functions involved in the initiation and resolution of early-onset inflammation and the longer-term effects related to scar formation. The resultant tissue damage can occur as early as 1 h after MI and activates inflammatory signalling pathways to elicit an immune response. Macrophages are one of the most active cell types during all stages after MI, including the cardioprotective, inflammatory and tissue repair phases. In this Review, we describe the phenotypes of cardiac macrophage involved in MI and their cardioprotective functions. A specific subset of macrophages called resident cardiac macrophages (RCMs) are derived from yolk sac progenitor cells and are maintained as a self-renewing population, although their numbers decrease with age. We explore sophisticated sequencing techniques that demonstrate the cardioprotective properties of this cardiac macrophage phenotype. Furthermore, we discuss the interactions between cardiac macrophages and other important cell types involved in the pathology and resolution of inflammation after MI. We summarize new and promising therapeutic approaches that target macrophage-mediated inflammation and the cardioprotective properties of RCMs after MI. Finally, we discuss future directions for the study of RCMs in MI and cardiovascular health in general.

Interaction of Cardiovascular Nonmodifiable Risk Factors, Comorbidities and Comedications With Ischemia/Reperfusion Injury and Cardioprotection by Pharmacological Treatments and Ischemic Conditioning

Preconditioning, postconditioning, and remote conditioning of the myocardium enhance the ability of the heart to withstand a prolonged ischemia/reperfusion insult and the potential to provide novel therapeutic paradigms for cardioprotection. While many signaling pathways leading to endogenous cardioprotection have been elucidated in experimental studies over the past 30 years, no cardioprotective drug is on the market yet for that indication. One likely major reason for this failure to translate cardioprotection into patient benefit is the lack of rigorous and systematic preclinical evaluation of promising cardioprotective therapies prior to their clinical evaluation, since ischemic heart disease in humans is a complex disorder caused by or associated with cardiovascular risk factors and comorbidities. These risk factors and comorbidities induce fundamental alterations in cellular signaling cascades that affect the development of ischemia/reperfusion injury and responses to cardioprotective interventions. Moreover, some of the medications used to treat these comorbidities may impact on cardioprotection by again modifying cellular signaling pathways. The aim of this article is to review the recent evidence that cardiovascular risk factors as well as comorbidities and their medications may modify the response to cardioprotective interventions. We emphasize the critical need for taking into account the presence of cardiovascular risk factors as well as comorbidities and their concomitant medications when designing preclinical studies for the identification and validation of cardioprotective drug targets and clinical studies. This will hopefully maximize the success rate of developing rational approaches to effective cardioprotective therapies for the majority of patients with multiple comorbidities. SIGNIFICANCE STATEMENT: Ischemic heart disease is a major cause of mortality; however, there are still no cardioprotective drugs on the market. Most studies on cardioprotection have been undertaken in animal models of ischemia/reperfusion in the absence of comorbidities; however, ischemic heart disease develops with other systemic disorders (e.g., hypertension, hyperlipidemia, diabetes, atherosclerosis). Here we focus on the preclinical and clinical evidence showing how these comorbidities and their routine medications affect ischemia/reperfusion injury and interfere with cardioprotective strategies.

Imaging Targets to Visualize the Cardiac Immune Landscape in Heart Failure

Heart failure involves a complex interplay between diverse populations of immune cells that dynamically shift across the natural history of disease. Within this context, the character of the immune response is a key determinant of clinical outcomes. Recent technological advances in single-cell transcriptomic, spatial, and proteomic technologies have fueled an explosion of new and clinically relevant insights into distinct immune cell populations that reside within the diseased heart including potential targets for molecular imaging and therapy. In this review, we will discuss the immune cell types and their respective functions with respect to myocardial infarction remodeling, dilated cardiomyopathy, and heart failure with preserved ejection fraction. In addition, we give a brief overview regarding myocarditis and cardiac sarcoidosis as inflammatory heart failure etiologies. We will highlight markers and cell populations as targets for molecular imaging to visualize inflammation and tissue healing and discuss clinical implications including the development and implementation of precision medicine approaches.

Effects of RAGE Deletion on the Cardiac Transcriptome during Aging

Cardiac aging is characterized by increased cardiomyocyte hypertrophy, myocardial stiffness, and fibrosis, which enhance cardiovascular risk. The receptor for advanced glycation end-products (RAGE) is involved in several age-related diseases. RAGE knockout (Rage−/−) mice show an acceleration of cardiac dimension changes and interstitial fibrosis with aging. This study identifies the age-associated cardiac gene expression signature induced by RAGE deletion. We analyzed the left ventricle transcriptome of 2.5-(Young), 12-(Middle age, MA), and 21-(Old) months-old female Rage−/− and C57BL/6N (WT) mice. By comparing Young, MA, and Old Rage−/− versus age-matched WT mice, we identified 122, 192, and 12 differently expressed genes, respectively. Functional inference analysis showed that RAGE deletion is associated with: (i) down-regulation of genes involved in antigen processing and presentation of exogenous antigen, adaptive immune response, and cellular responses to interferon beta and gamma in Young animals; (ii) up-regulation of genes related to fatty acid oxidation, cardiac structure remodeling and cellular response to hypoxia in MA mice; (iii) up-regulation of few genes belonging to complement activation and triglyceride biosynthetic process in Old animals. Our findings show that the age-dependent cardiac phenotype of Rage−/− mice is associated with alterations of genes related to adaptive immunity and cardiac stress pathways.

Association of immune cell subsets with incident heart failure in two population-based cohorts

AIMS

Circulating inflammatory markers are associated with incident heart failure (HF), but prospective data on associations of immune cell subsets with incident HF are lacking. We determined the associations of immune cell subsets with incident HF as well as HF subtypes [with reduced ejection fraction (HFrEF) and preserved ejection fraction (HFpEF)].

METHODS AND RESULTS

Peripheral blood immune cell subsets were measured in adults from the Multi-Ethnic Study of Atherosclerosis (MESA) and Cardiovascular Health Study (CHS). Cox proportional hazard models adjusted for demographics, HF risk factors, and cytomegalovirus serostatus were used to evaluate the association of the immune cell subsets with incident HF. The average age of the MESA cohort at the time of immune cell measurements was 63.0 ± 10.4 years with 51% women, and in the CHS cohort, it was 79.6 ± 4.4 years with 62% women. In the meta-analysis of CHS and MESA, a higher proportion of CD4+ T helper (Th) 1 cells (per one standard deviation) was associated with a lower risk of incident HF [hazard ratio (HR) 0.91, (95% CI 0.83-0.99), P = 0.03]. Specifically, higher proportion of CD4+ Th1 cells was significantly associated with a lower risk of HFrEF [HR 0.73, (95% CI 0.62-0.85), <0.001] after correction for multiple testing. No association was observed with HFpEF. No other cell subsets were associated with incident HF.

CONCLUSIONS

We observed that higher proportions of CD4+ Th1 cells were associated with a lower risk of incident HFrEF in two distinct population-based cohorts, with similar effect sizes in both cohorts demonstrating replicability. Although unexpected, the consistency of this finding across cohorts merits further investigation.

Pericardial effusion in a dog due to T‐cell lymphoma of granular lymphocyte type

Pericardial effusions in dogs are most often diagnosed as haemorrhagic and idiopathic. Pericardial effusions secondary to an underlying neoplastic process are infrequently diagnosed, as neoplastic cells are rarely observed in a sample of the effusion. In the present report, we describe a 9‐year‐old dog with pericardial effusion due to T‐cell lymphoma of granular lymphocyte type. Immunophenotyping and molecular clonality PCR were performed to confirm the cytologic diagnosis. To our knowledge, this is the first report of pericardial effusion in a dog due to T‐cell lymphoma of granular lymphocyte type.

CD4+ T-lymphocytes exhibit biphasic kinetics post-myocardial infarction

CD4⁺ T-cells facilitate wound healing post-myocardial infarction (MI) but promote left-ventricular (LV) remodeling during ischemic heart failure (HF; 8 weeks post-MI). Therefore, it is critical to understand if sustained CD4⁺ T-cell activation leads to this pathological response, or if phenotypically different T-cells are activated during MI vs. HF. Using flow cytometry, we found that cardiac CD4⁺ T-cells exhibit two distinct patterns of transmigration. First pattern consisted of a rapid CD4⁺ T-cell response with maximal levels seen at 3 days post-MI which return to baseline by 14 days. However, during HF we observed a 2nd phase of activation and CD4⁺ T-cells were ∼20-fold higher in HF as compared to sham-operated mice. Importantly, these biphasic kinetics were observed with all major T-cell subsets such as Th1, Th2, Th17, and regulatory T-cells suggesting a global change. To determine the role of this 2nd peak of T-cell activation, CD4-iDTR mice were generated and treated with DT every 10 from 28 days post-MI to deplete CD4⁺ T-cells during chronic HF. While littermate control mice showed increased end-systolic and end-diastolic volumes (ESV and EDV) and decreased ejection fraction (EF) from 4 to 8 weeks post-MI, depletion of CD4⁺ T-cells in Cre + mice significantly blunted LV remodeling and inhibited progressive increases in the EDV and ESV, and reduction in EF. This suggests that CD4⁺ T-cell responses occurring during HF are different than those occurring during MI and promote LV remodeling and progressive cardiac dysfunction. Temporal immunomodulation of CD4⁺ T-cells could be a translatable modality for ischemic HF.

Advancing Engineered Heart Muscle Tissue Complexity with Hydrogel Composites

A heart attack results in the permanent loss of heart muscle and can lead to heart disease, which kills more than 7 million people worldwide each year. To date, outside of heart transplantation, current clinical treatments cannot regenerate lost heart muscle or restore full function to the damaged heart. There is a critical need to create engineered heart tissues with structural complexity and functional capacity needed to replace damaged heart muscle. The inextricable link between structure and function suggests that hydrogel composites hold tremendous promise as a biomaterial-guided strategy to advance heart muscle tissue engineering. Such composites provide biophysical cues and functionality as a provisional extracellular matrix that hydrogels cannot on their own. This review describes the latest advances in the characterization of these biomaterial systems and using them for heart muscle tissue engineering. The review integrates results across the field to provide new insights on critical features within hydrogel composites and perspectives on the next steps to harnessing these promising biomaterials to faithfully reproduce the complex structure and function of native heart muscle.

Immunosenescence in atherosclerosis: A role for chronic viral infections

Immune system is a versatile and dynamic body organ which offers survival and endurance of human beings in their hostile living environment. However, similar to other cells, immune cells are hijacked by senescence. The ageing immune cells lose their beneficial functions but continue to produce inflammatory mediators which draw other immune and non-immune cells to the senescence loop. Immunosenescence has been shown to be associated with different pathological conditions and diseases, among which atherosclerosis has recently come to light. There are common drivers of both immunosenescence and atherosclerosis; e.g. inflammation, reactive oxygen species (ROS), chronic viral infections, genomic damage, oxidized-LDL, hypertension, cigarette smoke, hyperglycaemia, and mitochondrial failure. Chronic viral infections induce inflammaging, sustained cytokine signaling, ROS generation and DNA damage which are associated with atherogenesis. Accumulating evidence shows that several DNA and RNA viruses are stimulators of immunosenescence and atherosclerosis in an interrelated network. DNA viruses such as CMV, EBV and HBV upregulate p16, p21 and p53 senescence-associated molecules; induce inflammaging, metabolic reprogramming of infected cells, replicative senescence and telomere shortening. RNA viruses such as HCV and HIV induce ROS generation, DNA damage, induction of senescence-associated secretory phenotype (SASP), metabolic reprogramming of infected cells, G1 cell cycle arrest, telomere shortening, as well as epigenetic modifications of DNA and histones. The newly emerged SARS-CoV-2 virus is also a potent inducer of cytokine storm and SASP. The spike protein of SARS-CoV-2 promotes senescence phenotype in endothelial cells by augmenting p16, p21, senescence-associated β-galactosidase (SA-β-Gal) and adhesion molecules expression. The impact of SARS-CoV-2 mega-inflammation on atherogenesis, however, remains to be investigated. In this review we focus on the common processes in immunosenescence and atherogenesis caused by chronic viral infections and discuss the current knowledge on this topic.

The Dynamic Role of Cardiac Macrophages in Aging and Disease

PURPOSE OF REVIEW

The cardiac immune landscape dynamically changes in response to aging, hemodynamic stress, and myocardial injury. Here, we highlight key cardiac immune cell types, their role in reshaping the cellular landscape and promoting tissue remodeling following cardiac insults, and how understanding of these processes uncovers novel disease mechanisms that contribute to cardiac pathology.

RECENT FINDINGS

Distinct subsets of cardiac macrophages reside within the heart and exhibit divergent functions in response to myocardial injury. Parsing cardiac macrophages based on developmental origin has served as a valuable approach to define functionally divergent populations of reparative (embryonic-derived, tissue resident) and inflammatory (monocyte-derived, recruited) cardiac macrophages. Single-cell transcriptomics and elucidation of the effector mechanisms that orchestrate macrophage functions has provided new and therapeutically tractable insights into the pathogenesis of numerous cardiac diseases. The immune landscape of the heart is dynamic and represents an important mediator of disease pathogenesis across an array of cardiac pathology. Elucidation of mechanisms that drive inflammatory monocyte/macrophage recruitment, activation, and effector responses may lead to the identification of new therapeutic targets.

Immune remodeling and atrial fibrillation

Atrial fibrillation (AF) is a highly prevalent arrhythmia that causes high morbidity and mortality. However, the underlying mechanism of AF has not been fully elucidated. Recent research has suggested that, during AF, the immune system changes considerably and interacts with the environment and cells involved in the initiation and maintenance of AF. This may provide a new direction for research and therapeutic strategies for AF. In this review, we elaborate the concept of immune remodeling based on available data in AF. Then, we highlight the complex relationships between immune remodeling and atrial electrical, structural and neural remodeling while also pointing out some research gaps in these field. Finally, we discuss several potential immunomodulatory treatments for AF. Although the heterogeneity of existing evidence makes it ambiguous to extrapolate immunomodulatory treatments for AF into the clinical practice, immune remodeling is still an evolving concept in AF pathophysiology and further studies within this field are likely to provide effective therapies for AF.

A cardioimmunologist's toolkit: genetic tools to dissect immune cells in cardiac disease

Cardioimmunology is a field that encompasses the immune cells and pathways that modulate cardiac function in homeostasis and regulate the temporal balance between tissue injury and repair in disease. Over the past two decades, genetic fate mapping and high-dimensional sequencing techniques have defined increasing functional heterogeneity of innate and adaptive immune cell populations in the heart and other organs, revealing a complexity not previously appreciated and challenging established frameworks for the immune system. Given these rapid advances, understanding how to use these tools has become crucial. However, cardiovascular biologists without immunological expertise might not be aware of the strengths and caveats of immune-related tools and how they can be applied to examine the pathogenesis of myocardial diseases. In this Review, we guide readers through case-based examples to demonstrate how tool selection can affect data quality and interpretation and we provide critical analysis of the experimental tools that are currently available, focusing on their use in models of ischaemic heart injury and heart failure. The goal is to increase the use of relevant immunological tools and strategies among cardiovascular researchers to improve the precision, translatability and consistency of future studies of immune cells in cardiac disease.

Genome-wide transcript and protein analysis highlights the role of protein homeostasis in the aging mouse heart

Investigation of the molecular mechanisms of aging in the human heart is challenging because of confounding factors, such as diet and medications, as well as limited access to tissues from healthy aging individuals. The laboratory mouse provides an ideal model to study aging in healthy individuals in a controlled environment. However, previous mouse studies have examined only a narrow range of the genetic variation that shapes individual differences during aging. Here, we analyze transcriptome and proteome data from 185 genetically diverse male and female mice at ages 6, 12, and 18 mo to characterize molecular changes that occur in the aging heart. Transcripts and proteins reveal activation of pathways related to exocytosis and cellular transport with age, whereas processes involved in protein folding decrease with age. Additional changes are apparent only in the protein data including reduced fatty acid oxidation and increased autophagy. For proteins that form complexes, we see a decline in correlation between their component subunits with age, suggesting age-related loss of stoichiometry. The most affected complexes are themselves involved in protein homeostasis, which potentially contributes to a cycle of progressive breakdown in protein quality control with age. Our findings highlight the important role of post-transcriptional regulation in aging. In addition, we identify genetic loci that modulate age-related changes in protein homeostasis, suggesting that genetic variation can alter the molecular aging process.

Early Protective Role of Inflammation in Cardiac Remodeling and Heart Failure: Focus on TNFα and Resident Macrophages

Cardiac hypertrophy, initiated by a variety of physiological or pathological stimuli (hemodynamic or hormonal stimulation or infarction), is a critical early adaptive compensatory response of the heart. The structural basis of the progression from compensated hypertrophy to pathological hypertrophy and heart failure is still largely unknown. In most cases, early activation of an inflammatory program reflects a reparative or protective response to other primary injurious processes. Later on, regardless of the underlying etiology, heart failure is always associated with both local and systemic activation of inflammatory signaling cascades. Cardiac macrophages are nodal regulators of inflammation. Resident macrophages mostly attenuate cardiac injury by secreting cytoprotective factors (cytokines, chemokines, and growth factors), scavenging damaged cells or mitochondrial debris, and regulating cardiac conduction, angiogenesis, lymphangiogenesis, and fibrosis. In contrast, excessive recruitment of monocyte-derived inflammatory macrophages largely contributes to the transition to heart failure. The current review examines the ambivalent role of inflammation (mainly TNFα-related) and cardiac macrophages (Mφ) in pathophysiologies from non-infarction origin, focusing on the protective signaling processes. Our objective is to illustrate how harnessing this knowledge could pave the way for innovative therapeutics in patients with heart failure.

Immunomodulatory Treatment Strategies Targeting B Cells for Heart Failure

Cardio-oncology, a nascent specialty, has evolved as a concerted strategy to address the cardiovascular complications of cancer therapies. On the other hand, emerging evidence has shown that some anti-tumor drugs, such as CD20-targeted rotuximab, also have markedly cardioprotective effects in addition to treating cancers. Rituximab is a CD20-targeted monoclonal antibody and kill tumor B-cells through antibody-mediated and antibody-independent pathways, indicating that B cells participate and promote the progression of cardiovascular diseases. In this review, we mainly present the evidence that B cells contribute to the development of hypertrophy, inflammation, and maladaptive tissue remodeling, with the aim of proposing novel immunomodulatory therapeutic strategies targeting B cells and their products for the treatment of heart failure.

Effects of acute ischemia and hypoxia in young and adult calsequestrin (CSQ2) knock-out and wild-type mice

Calsequestrin (CSQ2) is the main Ca²⁺-binding protein in the sarcoplasmic reticulum of the mammalian heart. In order to understand the function of calsequestrin better, we compared two age groups (young: 4-5 months of age versus adult: 18 months of age) of CSQ2 knock-out mice (CSQ2(-/-)) and littermate wild-type mice (CSQ2(+/+)). Using echocardiography, in adult mice, the basal left ventricular ejection fraction and the spontaneous beating rate were lower in CSQ2(-/-) compared to CSQ2(+/+). The increase in ejection fraction by β-adrenergic stimulation (intraperitoneal injection of isoproterenol) was lower in adult CSQ2(-/-) versus adult CSQ2(+/+). After hypoxia in vitro (isolated atrial preparations) by gassing the organ bath buffer with 95% N₂, force of contraction in electrically driven left atria increased to lower values in young CSQ2(-/-) than in young CSQ2(+/+). In addition, after global ischemia and reperfusion (buffer-perfused hearts according to Langendorff; 20-min ischemia and 15-min reperfusion), the rate of tension development was higher in young CSQ2(-/-) compared to young CSQ2(+/+). Finally, we evaluated signs of inflammation (immune cells, autoantibodies, and fibrosis). However, whereas no immunological alterations were found between all investigated groups, pronounced fibrosis was found in the ventricles of adult CSQ2(-/-) compared to all other groups. We suggest that in young mice, CSQ2 is important for cardiac performance especially in isolated cardiac preparations under conditions of impaired oxygen supply, but with differences between atrium and ventricle. Lack of CSQ2 leads age dependently to fibrosis and depressed cardiac performance in echocardiographic studies.

Cardiovascular Inflammaging: Mechanisms and Translational Aspects

Aging is one of the major non-reversible risk factors for several chronic diseases, including cancer, type 2 diabetes, dementia, and cardiovascular diseases (CVD), and it is a key cause of multimorbidity, disability, and frailty (decreased physical activity, fatigue, and weight loss). The underlying cellular mechanisms are complex and consist of multifactorial processes, such as telomere shortening, chronic low-grade inflammation, oxidative stress, mitochondrial dysfunction, accumulation of senescent cells, and reduced autophagy. In this review, we focused on the molecular mechanisms and translational aspects of cardiovascular aging-related inflammation, i.e., inflammaging.

Immunometabolic Mechanisms of Heart Failure with Preserved Ejection Fraction

Heart failure with preserved ejection fraction (HFpEF) is increasing in prevalence worldwide, already accounting for at least half of all heart failure (HF). As most patients with HFpEF are obese with metabolic syndrome, metabolic stress has been implicated in syndrome pathogenesis. Recently, compelling evidence for bidirectional crosstalk between metabolic stress and chronic inflammation has emerged, and alterations in systemic and cardiac immune responses are held to participate in HFpEF pathophysiology. Indeed, based on both preclinical and clinical evidence, comorbidity-driven systemic inflammation, coupled with metabolic stress, have been implicated together in HFpEF pathogenesis. As metabolic alterations impact immune function(s) in HFpEF, major changes in immune cell metabolism are also recognized in HFpEF and in HFpEF-predisposing conditions. Both arms of immunity - innate and adaptive - are implicated in the cardiomyocyte response in HFpEF. Indeed, we submit that crosstalk among adipose tissue, the immune system, and the heart represents a critical component of HFpEF pathobiology. Here, we review recent evidence in support of immunometabolic mechanisms as drivers of HFpEF pathogenesis, discuss pivotal biological mechanisms underlying the syndrome, and highlight questions requiring additional inquiry.

Role of Distinct Macrophage Populations in the Development of Heart Failure in Macrophage Activation Syndrome

Macrophage activation syndrome (MAS) is one of the few entities in rheumatology with the potential to quickly cause multiple organ failure and loss of life, and as such, requires urgent clinical intervention. It has a broad symptomatology, depending on the organs it affects. One especially dangerous aspect of MAS’s course of illness is myocarditis leading to acute heart failure and possibly death. Research in recent years has proved that macrophages settled in different organs are not a homogenous group, with particular populations differing in both structure and function. Within the heart, we can determine two major groups, based on the presence of the C-C 2 chemokine receptor (CCR2): CCR2+ and CCR2−. There are a number of studies describing their function and the changes in the population makeup between normal conditions and different illnesses; however, to our knowledge, there has not been one touching on the matter of changes occurring in the populations of heart macrophages during MAS and their possible consequences. This review summarizes the most recent knowledge on heart macrophages, the influence of select cytokines (those particularly significant in the development of MAS) on their activity, and both the immediate and long-term consequences of changes in the makeup of specific macrophage populations—especially the loss of CCR2− cells that are responsible for regenerative processes, as well as the substitution of tissue macrophages by the highly proinflammatory CCR2+ macrophages originating from circulating monocytes. Understanding the significance of these processes may lead to new discoveries that could improve the therapeutic methods in the treatment of MAS.

The Yin and Yang of Immunity in Stem Cell Decision Guidance in Tissue Ecologies: An Infection Independent Perspective

The impact of immune system and inflammation on organ homeostasis and tissue stem cell niches in the absence of pathogen invasion has long remained a conundrum in the field of regenerative medicine. The paradoxical role of immune components in promoting tissue injury as well as resolving tissue damage has complicated therapeutic targeting of inflammation as a means to attain tissue homeostasis in degenerative disease contexts. This confound could be resolved by an integrated intricate assessment of cross-talk between inflammatory components and micro- and macro-environmental factors existing in tissues during health and disease. Prudent fate choice decisions of stem cells and their differentiated progeny are key to maintain tissue integrity and function. Stem cells have to exercise this fate choice in consultation with other tissue components. With this respect tissue immune components, danger/damage sensing molecules driving sterile inflammatory signaling cascades and barrier cells having immune-surveillance functions play pivotal roles in supervising stem cell decisions in their niches. Stem cells learn from their previous damage encounters, either endogenous or exogenous, or adapt to persistent micro-environmental changes to orchestrate their decisions. Thus understanding the communication networks between stem cells and immune system components is essential to comprehend stem cell decisions in endogenous tissue niches. Further the systemic interactions between tissue niches integrated through immune networks serve as patrolling systems to establish communication links and orchestrate micro-immune ecologies to better organismal response to injury and promote regeneration. Understanding these communication links is key to devise immune-centric regenerative therapies. Thus the present review is an integrated attempt to provide a unified purview of how inflammation and immune cells provide guidance to stem cells for tissue sculpting during development, organismal aging and tissue crisis based on the current knowledge in the field.

The heart under pressure: immune cells in fibrotic remodeling

The complex syndrome of heart failure (HF) is characterized by increased left ventricular pressures. Cardiomyocytes increase in size, cardiac fibroblasts transform and make extracellular matrix, and leukocytes infiltrate the cardiac tissue and alter cardiomyocyte and cardiac fibroblast function. Here we review recent advances in our understanding of the cellular composition of the heart during homeostasis and in response to cardiac pressure overload, with an emphasis on immune cell communication with cardiac fibroblasts and its consequences in cardiac remodeling.

Heart Failure in Chronic Infectious and Inflammatory Conditions: Mechanistic Insights from Clinical Heterogeneity

PURPOSE OF REVIEW

The balance between inflammation and its resolution plays an important and increasingly appreciated role in heart failure (HF) pathogenesis. In humans, different chronic inflammatory conditions and immune-inflammatory responses to infection can lead to diverse HF manifestations. Reviewing the phenotypic and mechanistic diversity of these HF presentations offers useful clinical and scientific insights.

RECENT FINDINGS

HF risk is increased in patients with chronic inflammatory and autoimmune disorders and relates to disease severity. Inflammatory condition-specific HF manifestations exist and underlying pathophysiologic causes may differ across conditions. Although inflammatory disease-specific presentations of HF differ, chronic excess in inflammation and auto-inflammation relative to resolution of this inflammation is a common underlying contributor to HF. Further studies are needed to phenotypically refine inflammatory condition-specific HF pathophysiologies and prognoses, as well as potential targets for intervention.

Organized Chaos: Deciphering Immune Cell Heterogeneity's Role in Inflammation in the Heart

During homeostasis, immune cells perform daily housekeeping functions to maintain heart health by acting as sentinels for tissue damage and foreign particles. Resident immune cells compose 5% of the cellular population in healthy human ventricular tissue. In response to injury, there is an increase in inflammation within the heart due to the influx of immune cells. Some of the most common immune cells recruited to the heart are macrophages, dendritic cells, neutrophils, and T-cells. In this review, we will discuss what is known about cardiac immune cell heterogeneity during homeostasis, how these cell populations change in response to a pathology such as myocardial infarction or pressure overload, and what stimuli are regulating these processes. In addition, we will summarize technologies used to evaluate cell heterogeneity in models of cardiovascular disease.