Transition of Macrophages to Fibroblast-Like Cells in Healing Myocardial Infarction

Single-cell sequencing reveals LRRc17-mediated modulation of cardiac fibroblast ferroptosis in regulating myocardial fibrosis after myocardial infarction

PURPOSE

Myocardial fibrosis after myocardial infarction (MI) is one of the main causes of death in patients, but there is no effective treatment for myocardial fibrosis at present. Hence, it is important to elucidate the pathogenesis of fibrosis after MI and find therapeutic targets for regulating ventricular remodeling after MI.

METHODS

Differentially expressed gene analysis, weighted Gene co-expression network analysis (WGCNA) and differential gene analysis in cardiac fibroblasts (CFs) were performed on the MI-related data (GSE153485 and GSE210159) from the GEO database to screen the hub genes related to ferroptosis in MI. After the establishment of MI model in vivo and in vitro, the myocardial CFs were observed by Masson staining, hematoxylin-eosin staining, CCK-8, and Transwell, and the changes of LRRc17 and ferroptosis-related proteins were detected by qRT-PCR and Western blotting. The expression of ROS was detected by fluorescence dye method.

RESULTS

Three DEGs were identified in MI related to ferroptosis, among which LRRc17 was selected for subsequent study. In both in vitro and in vivo models of MI, we found a sustained downregulation of LRRc17 expression and the expression of ferroptosis-related proteins GPX-4 and xCT, but increased ROS expression and enhanced migration and viability of CFs. After oe-LRRc17 treatment, the expression levels of GPX-4 and xCT were restored, while ROS levels were inhibited, and the migration and viability of CFs were inhibited. After treatment with ferroptosis inducer Erastin, there were down-regulated expressions of GPX-4 and xCT, increased expression of ROS, and enhanced migration and viability of CFs.

CONCLUSION

LRRc17 affects ventricular remodeling by mediating ferroptosis in CFs to regulate the degree of fibrosis after MI.

Comprehensive macro and micro views on immune cells in ischemic heart disease

Ischemic heart disease (IHD) is a prevalent cardiovascular condition that remains the primary cause of death due to its adverse ventricular remodelling and pathological changes in end-stage heart failure. As a complex pathologic condition, it involves intricate regulatory processes at the cellular and molecular levels. The immune system and cardiovascular system are closely interconnected, with immune cells playing a crucial role in maintaining cardiac health and influencing disease progression. Consequently, alterations in the cardiac microenvironment are influenced and controlled by various immune cells, such as macrophages, neutrophils, dendritic cells, eosinophils, and T-lymphocytes, along with the cytokines they produce. Furthermore, studies have revealed that Gata6+ pericardial cavity macrophages play a key role in regulating immune cell migration and subsequent myocardial tissue repair post IHD onset. This review outlines the role of immune cells in orchestrating inflammatory responses and facilitating myocardial repair following IHD, considering both macro and micro views. It also discusses innovative immune cell-based therapeutic strategies, offering new insights for further research on the pathophysiology of ischemic heart disease and immune cell-targeted therapy for IHD.

Macrophages in the infarcted heart acquire a fibrogenic phenotype, expressing matricellular proteins, but do not undergo fibroblast conversion

Although some studies have suggested that macrophages may secrete structural collagens, and convert to fibroblast-like cells, macrophage to fibroblast transdifferentiation in infarcted and remodeling hearts remains controversial. Our study uses linage tracing approaches and single cell transcriptomics to examine whether macrophages undergo fibroblast conversion, and to characterize the extracellular matrix expression profile of myeloid cells in myocardial infarction. To examine whether infarct macrophages undergo fibroblast conversion, we identified macrophage-derived progeny using the inducible CX3CR1CreER mice crossed with the PDGFRαEGFP reporter line for reliable fibroblast identification. The abundant fibroblasts that infiltrated the infarcted myocardium after 7 and 28 days of coronary occlusion were not derived from CX3CR1+ macrophages. Infarct macrophages retained myeloid cell characteristics and did not undergo conversion to myofibroblasts, endothelial or vascular mural cells. Single cell RNA-seq of CSF1R+ myeloid cells harvested from control and infarcted hearts showed no significant expression of fibroblast identity genes by myeloid cell clusters. Moreover, infarct macrophages did not express significant levels of genes encoding structural collagens. However, infarct macrophage and monocyte clusters were the predominant source of the fibrogenic growth factors Tgfb1 and Pdgfb, and of the matricellular proteins Spp1/Osteopontin, Thbs1/Thrombospondin-1, Emilin2, and Fn1/fibronectin, while expressing significant amounts of several other matrix genes, including Vcan/versican, Ecm1 and Sparc. ScRNA-seq data suggested similar patterns of matrix gene expression in human myocardial infarction. In conclusion, infarct macrophages do not undergo fibroblast or myofibroblast conversion and do not exhibit upregulation of structural collagens but may contribute to fibrotic remodeling by producing several fibrogenic matricellular proteins.

Macrophage heterogeneity in myocardial infarction: Evolution and implications for diverse therapeutic approaches

Given the extensive participation of myeloid cells (especially monocytes and macrophages) in both inflammation and resolution phases post-myocardial infarction (MI) owing to their biphasic role, these cells are considered as crucial players in the disease pathogenesis. Multiple studies have agreed on the significant contribution of macrophage polarization theory (M2 vs. M1) while determining the underlying reasons behind the observed biphasic effects; nevertheless, this simplistic classification attracts severe drawbacks. The advent of multiple advanced technologies based on OMICS platforms facilitated a successful path to explore comprehensive cellular signatures that could expedite our understanding of macrophage heterogeneity and plasticity. While providing an overall basis behind the MI disease pathogenesis, this review delves into the literature to discuss the current knowledge on multiple macrophage clusters, including the future directions in this research arena. In the end, our focus will be on outlining the possible therapeutic implications based on the emerging observations.

Role of macrophage polarization in heart failure and traditional Chinese medicine treatment

Heart failure (HF) has a severe impact on public health development due to high morbidity and mortality and is associated with imbalances in cardiac immunoregulation. Macrophages, a major cell population involved in cardiac immune response and inflammation, are highly heterogeneous and polarized into M1 and M2 types depending on the microenvironment. M1 macrophage releases inflammatory factors and chemokines to activate the immune response and remove harmful substances, while M2 macrophage releases anti-inflammatory factors to inhibit the overactive immune response and promote tissue repair. M1 and M2 restrict each other to maintain cardiac homeostasis. The dynamic balance of M1 and M2 is closely related to the Traditional Chinese Medicine (TCM) yin-yang theory, and the imbalance of yin and yang will result in a pathological state of the organism. Studies have confirmed that TCM produces positive effects on HF by regulating macrophage polarization. This review describes the critical role of macrophage polarization in inflammation, fibrosis, angiogenesis and electrophysiology in the course of HF, as well as the potential mechanism of TCM regulation of macrophage polarization in preventing and treating HF, thereby providing new ideas for clinical treatment and scientific research design of HF.

Macrophage-mediated heart repair and remodeling: A promising therapeutic target for post-myocardial infarction heart failure

Heart failure (HF) remains prevalent in patients who survived myocardial infarction (MI). Despite the accessibility of the primary percutaneous coronary intervention and medications that alleviate ventricular remodeling with functional improvement, there is an urgent need for clinicians and basic scientists to further reveal the mechanisms behind post-MI HF as well as investigate earlier and more efficient treatment after MI. Growing numbers of studies have highlighted the crucial role of macrophages in cardiac repair and remodeling following MI, and timely intervention targeting the immune response via macrophages may represent a promising therapeutic avenue. Recently, technology such as single-cell sequencing has provided us with an updated and in-depth understanding of the role of macrophages in MI. Meanwhile, the development of biomaterials has made it possible for macrophage-targeted therapy. Thus, an overall and thorough understanding of the role of macrophages in post-MI HF and the current development status of macrophage-based therapy will assist in the further study and development of macrophage-targeted treatment for post-infarction cardiac remodeling. This review synthesizes the spatiotemporal dynamics, function, mechanism and signaling of macrophages in the process of HF after MI, as well as discusses the emerging bio-materials and possible therapeutic agents targeting macrophages for post-MI HF.

Interrelation of adipose tissue macrophages and fibrosis in obesity

Obesity is characterized by adipose tissue expansion, extracellular matrix remodelling and unresolved inflammation that contribute to insulin resistance and fibrosis. Adipose tissue macrophages represent the most abundant class of immune cells in adipose tissue inflammation and could be key mediators of adipocyte dysfunction and fibrosis in obesity. Although macrophage activation states are classically defined by the M1/M2 polarization nomenclature, novel studies have revealed a more complex range of macrophage phenotypes in response to external condition or the surrounding microenvironment. Here, we discuss the plasticity of adipose tissue macrophages (ATMs) in response to their microenvironment in obesity, with special focus on macrophage infiltration and polarization, and their contribution to adipose tissue fibrosis. A better understanding of the role of ATMs as regulators of adipose tissue remodelling may provide novel therapeutic strategies against obesity and associated metabolic diseases.

The Multifaceted Nature of Macrophages in Cardiovascular Disease

As the leading cause of mortality worldwide, cardiovascular disease (CVD) represents a variety of heart diseases and vascular disorders, including atherosclerosis, aneurysm, ischemic injury in the heart and brain, arrythmias, and heart failure. Macrophages, a diverse population of immune cells that can promote or suppress inflammation, have been increasingly recognized as a key regulator in various processes in both healthy and disease states. In healthy conditions, these cells promote the proper clearance of cellular debris, dead and dying cells, and provide a strong innate immune barrier to foreign pathogens. However, macrophages can play a detrimental role in the progression of disease as well, particularly those inflammatory in nature. This review will focus on the current knowledge regarding the role of macrophages in cardiovascular diseases.

Repair of the Infarcted Heart: Cellular Effectors, Molecular Mechanisms and Therapeutic Opportunities

The adult mammalian heart has limited endogenous regenerative capacity and heals through the activation of inflammatory and fibrogenic cascades that ultimately result in the formation of a scar. After infarction, massive cardiomyocyte death releases a broad range of damage-associated molecular patterns that initiate both myocardial and systemic inflammatory responses. TLRs (toll-like receptors) and NLRs (NOD-like receptors) recognize damage-associated molecular patterns (DAMPs) and transduce downstream proinflammatory signals, leading to upregulation of cytokines (such as interleukin-1, TNF-α [tumor necrosis factor-α], and interleukin-6) and chemokines (such as CCL2 [CC chemokine ligand 2]) and recruitment of neutrophils, monocytes, and lymphocytes. Expansion and diversification of cardiac macrophages in the infarcted heart play a major role in the clearance of the infarct from dead cells and the subsequent stimulation of reparative pathways. Efferocytosis triggers the induction and release of anti-inflammatory mediators that restrain the inflammatory reaction and set the stage for the activation of reparative fibroblasts and vascular cells. Growth factor-mediated pathways, neurohumoral cascades, and matricellular proteins deposited in the provisional matrix stimulate fibroblast activation and proliferation and myofibroblast conversion. Deposition of a well-organized collagen-based extracellular matrix network protects the heart from catastrophic rupture and attenuates ventricular dilation. Scar maturation requires stimulation of endogenous signals that inhibit fibroblast activity and prevent excessive fibrosis. Moreover, in the mature scar, infarct neovessels acquire a mural cell coat that contributes to the stabilization of the microvascular network. Excessive, prolonged, or dysregulated inflammatory or fibrogenic cascades accentuate adverse remodeling and dysfunction. Moreover, inflammatory leukocytes and fibroblasts can contribute to arrhythmogenesis. Inflammatory and fibrogenic pathways may be promising therapeutic targets to attenuate heart failure progression and inhibit arrhythmia generation in patients surviving myocardial infarction.

Macrophages in cardiovascular diseases: molecular mechanisms and therapeutic targets

The immune response holds a pivotal role in cardiovascular disease development. As multifunctional cells of the innate immune system, macrophages play an essential role in initial inflammatory response that occurs following cardiovascular injury, thereby inducing subsequent damage while also facilitating recovery. Meanwhile, the diverse phenotypes and phenotypic alterations of macrophages strongly associate with distinct types and severity of cardiovascular diseases, including coronary heart disease, valvular disease, myocarditis, cardiomyopathy, heart failure, atherosclerosis and aneurysm, which underscores the importance of investigating macrophage regulatory mechanisms within the context of specific diseases. Besides, recent strides in single-cell sequencing technologies have revealed macrophage heterogeneity, cell-cell interactions, and downstream mechanisms of therapeutic targets at a higher resolution, which brings new perspectives into macrophage-mediated mechanisms and potential therapeutic targets in cardiovascular diseases. Remarkably, myocardial fibrosis, a prevalent characteristic in most cardiac diseases, remains a formidable clinical challenge, necessitating a profound investigation into the impact of macrophages on myocardial fibrosis within the context of cardiac diseases. In this review, we systematically summarize the diverse phenotypic and functional plasticity of macrophages in regulatory mechanisms of cardiovascular diseases and unprecedented insights introduced by single-cell sequencing technologies, with a focus on different causes and characteristics of diseases, especially the relationship between inflammation and fibrosis in cardiac diseases (myocardial infarction, pressure overload, myocarditis, dilated cardiomyopathy, diabetic cardiomyopathy and cardiac aging) and the relationship between inflammation and vascular injury in vascular diseases (atherosclerosis and aneurysm). Finally, we also highlight the preclinical/clinical macrophage targeting strategies and translational implications.

Cardiac and perivascular myofibroblasts, matrifibrocytes, and immune fibrocytes in hypertension; commonalities and differences with other cardiovascular diseases

Hypertension is a major cause of cardiovascular diseases such as myocardial infarction and stroke. Cardiovascular fibrosis occurs with hypertension and contributes to vascular resistance, aortic stiffness, and cardiac hypertrophy. However, the molecular mechanisms leading to fibroblast activation in hypertension remain largely unknown. There are two types of fibrosis: replacement fibrosis and reactive fibrosis. Replacement fibrosis occurs in response to the loss of viable tissue to form a scar. Reactive fibrosis occurs in response to an increase in mechanical and neurohormonal stress. Although both types of fibrosis are considered adaptive processes, they become maladaptive when the tissue loss is too large, or the stress persists. Myofibroblasts represent a subpopulation of activated fibroblasts that have gained contractile function to promote wound healing. Therefore, myofibroblasts are a critical cell type that promotes replacement fibrosis. Although myofibroblasts were recognized as the fibroblasts participating in reactive fibrosis, recent experimental evidence indicated there are distinct fibroblast populations in cardiovascular reactive fibrosis. Accordingly, we will discuss the updated definition of fibroblast subpopulations, the regulatory mechanisms, and their potential roles in cardiovascular pathophysiology utilizing new knowledge from various lineage tracing and single-cell RNA sequencing studies. Among the fibroblast subpopulations, we will highlight the novel roles of matrifibrocytes and immune fibrocytes in cardiovascular fibrosis including experimental models of hypertension, pressure overload, myocardial infarction, atherosclerosis, aortic aneurysm, and nephrosclerosis. Exploration into the molecular mechanisms involved in the differentiation and activation of those fibroblast subpopulations may lead to novel treatments for end-organ damage associated with hypertension and other cardiovascular diseases.

Dynamic molecular signatures of acute myocardial infarction based on transcriptomics and metabolomics

Acute myocardial infarction (AMI) commonly precedes ventricular remodeling, heart failure. Few dynamic molecular signatures have gained widespread acceptance in mainstream clinical testing despite the discovery of many potential candidates. These unmet needs with respect to biomarker and drug discovery of AMI necessitate a prioritization. We enrolled patients with AMI aged between 30 and 70. RNA-seq analysis was performed on the peripheral blood mononuclear cells collected from the patients at three time points: 1 day, 7 days, and 3 months after AMI. PLC/LC-MS analysis was conducted on the peripheral blood plasma collected from these patients at the same three time points. Differential genes and metabolites between groups were screened by bio-informatics methods to understand the dynamic changes of AMI in different periods. We obtained 15 transcriptional and 95 metabolite expression profiles at three time points after AMI through high-throughput sequencing. AMI-1d: enrichment analysis revealed the biological features of 1 day after AMI primarily included acute inflammatory response, elevated glycerophospholipid metabolism, and decreased protein synthesis capacity. Phosphatidylcholine (PC) and phosphatidylethanolamine (PE) might stand promising biomarkers to differentiate post-AMI stage. Anti-inflammatory therapy during the acute phase is an important direction for preventing related pathology. AMI-7d: the biological features of this stage primarily involved the initiation of cardiac fibrosis response and activation of platelet adhesion pathways. Accompanied by upregulated TGF-beta signaling pathway and ECM receptor interaction, GP5 help assess platelet activation, a potential therapeutic target to improve haemostasis. AMI-3m: the biological features of 3 months after AMI primarily showed a vascular regeneration response with VEGF signaling pathway, NOS3 and SHC2 widely activated, which holds promise for providing new therapeutic approaches for AMI. Our analysis highlights transcriptional and metabolomics signatures at different time points after MI, which deepens our understanding of the dynamic biological responses and associated molecular mechanisms that occur during cardiac repair.

Macrophages promote the transition from myocardial ischemia reperfusion injury to cardiac fibrosis in mice through GMCSF/CCL2/CCR2 and phenotype switching

Following acute myocardial ischemia reperfusion (MIR), macrophages infiltrate damaged cardiac tissue and alter their polarization phenotype to respond to acute inflammation and chronic fibrotic remodeling. In this study we investigated the role of macrophages in post-ischemic myocardial fibrosis and explored therapeutic targets for myocardial fibrosis. Male mice were subjected to ligation of the left coronary artery for 30 min. We first detected the levels of chemokines in heart tissue that recruited immune cells infiltrating into the heart, and found that granulocyte-macrophage colony-stimulating factor (GMCSF) released by mouse cardiac microvascular endothelial cells (MCMECs) peaked at 6 h after reperfusion, and c-c motif chemokine ligand 2 (CCL2) released by GMCSF-induced macrophages peaked at 24 h after reperfusion. In co-culture of BMDMs with MCMECs, we demonstrated that GMCSF derived from MCMECs stimulated the release of CCL2 by BMDMs and effectively promoted the migration of BMDMs. We also confirmed that GMCSF promoted M1 polarization of macrophages in vitro, while GMCSF neutralizing antibodies (NTABs) blocked CCL2/CCR2 signaling. In MIR mouse heart, we showed that GMCSF activated CCL2/CCR2 signaling to promote NLRP3/caspase-1/IL-1β-mediated and amplified inflammatory damage. Knockdown of CC chemokine receptor 2 gene (CCR2-/-), or administration of specific CCR2 inhibitor RS102895 (5 mg/kg per 12 h, i.p., one day before MIR and continuously until the end of the experiment) effectively reduced the area of myocardial infarction, and down-regulated inflammatory mediators and NLRP3/Caspase-1/IL-1β signaling. Mass cytometry confirmed that M2 macrophages played an important role during fibrosis, while macrophage-depleted mice exhibited significantly reduced transforming growth factor-β (Tgf-β) levels in heart tissue after MIR. In co-culture of macrophages with fibroblasts, treatment with recombinant mouse CCL2 stimulated macrophages to release a large amount of Tgf-β, and promoted the release of Col1α1 by fibroblasts. This effect was diminished in BMDMs from CCR2-/- mice. After knocking out or inhibiting CCR2-gene, the levels of Tgf-β were significantly reduced, as was the level of myocardial fibrosis, and cardiac function was protected. This study confirms that the acute injury to chronic fibrosis transition after MIR in mice is mediated by GMCSF/CCL2/CCR2 signaling in macrophages through NLRP3 inflammatory cascade and the phenotype switching.

Prophylactic Supplementation with Lactobacillus Reuteri or Its Metabolite GABA Protects Against Acute Ischemic Cardiac Injury

The gut microbiome has emerged as a potential target for the treatment of cardiovascular disease. Ischemia/reperfusion (I/R) after myocardial infarction is a serious complication and whether certain gut bacteria can serve as a treatment option remains unclear. Lactobacillus reuteri (L. reuteri) is a well-studied probiotic that can colonize mammals including humans with known cholesterol-lowering properties and anti-inflammatory effects. Here, the prophylactic cardioprotective effects of L. reuteri or its metabolite γ-aminobutyric acid (GABA) against acute ischemic cardiac injury caused by I/R surgery are demonstrated. The prophylactic gavage of L. reuteri or GABA confers cardioprotection mainly by suppressing cardiac inflammation upon I/R. Mechanistically, GABA gavage results in a decreased number of proinflammatory macrophages in I/R hearts and GABA gavage no longer confers any cardioprotection in I/R hearts upon the clearance of macrophages. In vitro studies with LPS-stimulated bone marrow-derived macrophages (BMDM) further reveal that GABA inhibits the polarization of macrophages toward the proinflammatory M1 phenotype by inhibiting lysosomal leakage and NLRP3 inflammasome activation. Together, this study demonstrates that the prophylactic oral administration of L. reuteri or its metabolite GABA attenuates macrophage-mediated cardiac inflammation and therefore alleviates cardiac dysfunction after I/R, thus providing a new prophylactic strategy to mitigate acute ischemic cardiac injury.

Targeting Interactions between Fibroblasts and Macrophages to Treat Cardiac Fibrosis

Excessive extracellular matrix (ECM) deposition is a defining feature of cardiac fibrosis. Most notably, it is characterized by a significant change in the concentration and volume fraction of collagen I, a disproportionate deposition of collagen subtypes, and a disturbed ECM network arrangement, which directly affect the systolic and diastolic functions of the heart. Immune cells that reside within or infiltrate the myocardium, including macrophages, play important roles in fibroblast activation and consequent ECM remodeling. Through both direct and indirect connections to fibroblasts, monocyte-derived macrophages and resident cardiac macrophages play complex, bidirectional, regulatory roles in cardiac fibrosis. In this review, we discuss emerging interactions between fibroblasts and macrophages in physiology and pathologic conditions, providing insights for future research aimed at targeting macrophages to combat cardiac fibrosis.

Cardiac resident macrophages: Spatiotemporal distribution, development, physiological functions, and their translational potential on cardiac diseases

Cardiac resident macrophages (CRMs) are the main population of cardiac immune cells. The role of these cells in regeneration, functional remodeling, and repair after cardiac injury is always the focus of research. However, in recent years, their dynamic changes and contributions in physiological states have a significant attention. CRMs have specific phenotypes and functions in different cardiac chambers or locations of the heart and at different stages. They further show specific differentiation and development processes. The present review will summarize the new progress about the spatiotemporal distribution, potential developmental regulation, and their roles in cardiac development and aging as well as the translational potential of CRMs on cardiac diseases. Of course, the research tools for CRMs, their respective advantages and disadvantages, and key issues on CRMs will further be discussed.

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.

The mechanisms and therapeutic potential of clopidogrel in mitigating diabetic cardiomyopathy in db/db mice

Clopidogrel has been shown to play a protective role against diabetic nephropathy. However, whether clopidogrel exerts a protective effect against diabetic cardiomyopathy (DCM) is unknown. Three-month-old male db/db mice were administered clopidogrel daily at doses of 5, 10, and 20 mg/kg by gavage for 5 months. Here, we showed that clopidogrel effectively attenuated diabetes-induced cardiac hypertrophy and cardiac dysfunction by inhibiting cardiac fibrosis, inflammatory responses, and oxidative stress damage in db/db mice. Diabetes-induced cardiac fibrosis was inhibited by clopidogrel treatment via blockade of the TGF-β1/Smad3/P2RY12 pathway and inhibition of macrophage infiltration in db/db mice. The protective effects of clopidogrel against oxidative damage were mediated by the induction of the Nrf2 signaling pathway. Taken together, our findings provide strong evidence that clopidogrel is a promising effective agent for the treatment of DCM by alleviating diabetes-induced cardiac hypertrophy and dysfunction. P2RY12 might be an effective target for the treatment of DCM.

Comprehensive bioinformatics analysis reveals the role of cuproptosis-related gene Ube2d3 in myocardial infarction

Background

Myocardial infarction (MI) caused by severe coronary artery disease has high incidence and mortality rates, making its prevention and treatment a central and challenging aspect of clinical work for cardiovascular practitioners. Recently, researchers have turned their attention to a novel mechanism of cell death caused by Cu2+, cuproptosis.

Methods

This study integrated data from three MI-related bulk datasets downloaded from the Gene Expression Omnibus (GEO) database, and identified 16 differentially expressed genes (DEGs) related to cuproptosis by taking intersection of the 6378 DEGs obtained by differential analysis with 49 cuproptosis-related genes. Four hub genes, Dbt, Dlat, Ube2d1 and Ube2d3, were screened out through random forest analysis and Lasso analysis. In the disease group, Dbt, Dlat, and Ube2d1 showed low expression, while Ube2d3 exhibited high expression.

Results

Focusing on Ube2d3 for subsequent functional studies, we confirmed its high expression in the MI group through qRT-PCR and Western Blot detection after successful construction of a MI mouse model by left anterior descending (LAD) coronary artery ligation, and further clarified the correlation of cuproptosis with MI development by detecting the levels of cuproptosis-related proteins. Moreover, through in vitro experiments, Ube2d3 was confirmed to be highly expressed in oxygen-glucose deprivation (OGD)-treated cardiomyocytes AC16. In order to further clarify the role of Ube2d3, we knocked down Ube2d3 expression in OGD-treated AC16 cells, and confirmed Ube2d3's promoting role in the hypoxia damage of AC16 cells by inducing cuproptosis, as evidenced by the detection of MTT, TUNEL, LDH release and cuproptosis-related proteins.

Conclusion

In summary, our findings indicate that Ube2d3 regulates cuproptosis to affect the progression of MI.

Special Issue "Role of Apoptosis and Cellular Senescence in Cancer and Aging"

The intention of this Special Issue is to elucidate the role of apoptosis and cellular senescence in different pathological processes, such as cancer and aging [...].

Collagenase-based wound debridement agent induces extracellular matrix supporting phenotype in macrophages

Macrophages assume diverse phenotypes and functions in response to cues from the microenvironment. Earlier we reported an anti-inflammatory effect of Collagenase Santyl® Ointment (CSO) and the active constituent of CSO (CS-API) on wound macrophages in resolving wound inflammation indicating roles beyond debridement in wound healing. Building upon our prior finding, this study aimed to understand the phenotypes and subsets of macrophages following treatment with CS-API. scRNA-sequencing was performed on human blood monocyte-derived macrophages (MDM) following treatment with CS-API for 24 h. Unbiased data analysis resulted in the identification of discrete macrophage subsets based on their gene expression profiles. Following CS-API treatment, clusters 3 and 4 displayed enrichment of macrophages with high expression of genes supporting extracellular matrix (ECM) function. IPA analysis identified the TGFβ-1 pathway as a key hub for the CS-API-mediated ECM-supportive phenotype of macrophages. Earlier we reported the physiological conversion of wound-site macrophages to fibroblasts in granulation tissue and impairment of such response in diabetic wounds, leading to compromised ECM and tensile strength. The findings that CSO can augment the physiological conversion of macrophages to fibroblast-like cells carry significant clinical implications. This existing clinical intervention, already employed for wound care, can be readily repurposed to improve the ECM response in chronic wounds.

A Rare Cause of Recurrent Pericarditis

Recurrent pericarditis poses a significant challenge to clinicians, particularly when patients are unresponsive or intolerant to conventional treatments. Accurate diagnosis of recurrent pericarditis, potentially facilitated by collaboration with other medical specialties, is crucial for ensuring timely and appropriate treatment of symptoms and prevention of further episodes. We present a case of a 52-year-old male patient with a history of multiple episodes of pericarditis, who was admitted to the Cardiology Department due to another recurrence. The first episode of pericarditis was diagnosed nearly a year before his current hospitalization. Initially, the patient received high doses of Ibuprofen and colchicine, but there was no favorable response to this treatment regimen. At that point, intravenous prednisolone was initiated, which led to clinical and laboratory improvement. Since then, the patient had experienced two more recurrences while tapering off prednisolone. Immunological tests, Mantoux tuberculin skin test, and chest and abdominal computed tomography (CT) had revealed no evidence of an underlying cause. On admission the patient was febrile and the electrocardiogram showed diffuse ST elevation and PR depression in leads I, II, aVF, V2-V6. Bedside echocardiogram revealed a small pericardial effusion and since the chest X-ray was normal and no other potential infection sites were identified, the diagnosis of recurrent pericarditis was established. During his current hospitalization, intravenous prednisolone was initiated, colchicine was continued and a more detailed history was taken, raising the suspicion upon the presence of an auto-inflammatory disease. Genetic investigation identified an uncommon heterozygous mutation in the familial Mediterranean fever gene (MEFV) and after consideration of patient's history, familial Mediterranean fever was diagnosed. Anakinra was initiated on top of colchicine and gradual tapering of corticosteroids and the patient showed significant improvement, with no other recurrence during the two-year follow-up.

The Current State of Extracellular Matrix Therapy for Ischemic Heart Disease

The extracellular matrix (ECM) is a three-dimensional, acellular network of diverse structural and nonstructural proteins embedded within a gel-like ground substance composed of glycosaminoglycans and proteoglycans. The ECM serves numerous roles that vary according to the tissue in which it is situated. In the myocardium, the ECM acts as a collagen-based scaffold that mediates the transmission of contractile signals, provides means for paracrine signaling, and maintains nutritional and immunologic homeostasis. Given this spectrum, it is unsurprising that both the composition and role of the ECM has been found to be modulated in the context of cardiac pathology. Myocardial infarction (MI) provides a familiar example of this; the ECM changes in a way that is characteristic of the progressive phases of post-infarction healing. In recent years, this involvement in infarct pathophysiology has prompted a search for therapeutic targets: if ECM components facilitate healing, then their manipulation may accelerate recovery, or even reverse pre-existing damage. This possibility has been the subject of numerous efforts involving the integration of ECM-based therapies, either derived directly from biologic sources or bioengineered sources, into models of myocardial disease. In this paper, we provide a thorough review of the published literature on the use of the ECM as a novel therapy for ischemic heart disease, with a focus on biologically derived models, of both the whole ECM and the components thereof.

Single-cell RNA sequencing reveals S100a9hi macrophages promote the transition from acute inflammation to fibrotic remodeling after myocardial ischemia‒reperfusion

Rationale: The transition from acute inflammation to fibrosis following myocardial ischemia‒reperfusion (MIR) significantly affects prognosis. Macrophages play a pivotal role in inflammatory damage and repair after MIR. However, the heterogeneity and transformation mechanisms of macrophages during this transition are not well understood. Methods: In this study, we used single-cell RNA sequencing (scRNA-seq) and mass cytometry to examine murine monocyte-derived macrophages after MIR to investigate macrophage subtypes and their roles in the MIR process. S100a9-/- mice were used to establish MIR model to clarify the mechanism of alleviating inflammation and fibrosis after MIR. Reinfusion of bone marrow-derived macrophages (BMDMs) after macrophage depletion (MD) in mice subjected to MIR were performed to further examine the role of S100a9hi macrophages in MIR. Results: We identified a unique subtype of S100a9hi macrophages that originate from monocytes and are involved in acute inflammation and fibrosis. These S100a9hi macrophages infiltrate the heart as early as 2 h post-reperfusion and activate the Myd88/NFκB/NLRP3 signaling pathway, amplifying inflammatory responses. As the tissue environment shifts from proinflammatory to reparative, S100a9 activates transforming growth factor-β (Tgf-β)/p-smad3 signaling. This activation not only induces the transformation of myocardial fibroblasts to myofibroblasts but also promotes fibrosis via the macrophage-to-myofibroblast transition (MMT). Targeting S100a9 with a specific inhibitor could effectively mitigate acute inflammatory damage and halt the progression of fibrosis, including MMT. Conclusion: S100a9hi macrophages are a promising therapeutic target for managing the transition from inflammation to fibrosis after MIR.

FADD- and RIPK3-Mediated Cell Death Ensures Clearance of Ly6Chigh Wound Macrophages from Damaged Tissue

Cells of the monocyte/macrophage lineage are an integral component of the body's innate ability to restore tissue function after injury. In parallel to mounting an inflammatory response, clearance of monocytes/macrophages from the wound site is critical to re-establish tissue functionality and integrity during the course of healing. The role of regulated cell death in macrophage clearance from damaged tissue and its implications for the outcome of the healing response is little understood. In this study, we explored the role of macrophage-specific FADD-mediated cell death on Ripk3-/- background in a mechanical skin injury model in mice. We found that combined inhibition of RIPK3-mediated necroptosis and FADD-caspase-8-mediated apoptosis in macrophages profoundly delayed wound healing. Importantly, RIPK3 deficiency alone did not considerably alter the wound healing process and macrophage population dynamics, arguing that inhibition of FADD-caspase-8-dependent death of macrophages is primarily responsible for delayed wound closure. Notably, TNF blockade reversed the accumulation of Ly6Chigh macrophages induced by combined deficiency of FADD and RIPK3, indicating a critical dual role of TNF-mediated prosurvival and cell death signaling, particularly in this highly proinflammatory macrophage subset. Our findings reveal a previously uncharacterized cross-talk of inflammatory and cell death signaling in macrophages in regulating repair processes in the skin.

Fibroblast activation protein: Pivoting cancer/chemotherapeutic insight towards heart failure

An important mechanism for cancer progression is degradation of the extracellular matrix (ECM) which is accompanied by the emergence and proliferation of an activated fibroblast, termed the cancer associated fibroblast (CAF). More specifically, an enzyme pathway identified to be amplified with local cancer progression and proliferation of the CAF, is fibroblast activation protein (FAP). The development and progression of heart failure (HF) irrespective of the etiology is associated with left ventricular (LV) remodeling and changes in ECM structure and function. As with cancer, HF progression is associated with a change in LV myocardial fibroblast growth and function, and expresses a protein signature not dissimilar to the CAF. The overall goal of this review is to put forward the postulate that scientific discoveries regarding FAP in cancer as well as the development of specific chemotherapeutics could be pivoted to target the emergence of FAP in the activated fibroblast subtype and thus hold translationally relevant diagnostic and therapeutic targets in HF.

Microenvironment of pancreatic inflammation: calling for nanotechnology for diagnosis and treatment

Acute pancreatitis (AP) is a common and life-threatening digestive disorder. However, its diagnosis and treatment are still impeded by our limited understanding of its etiology, pathogenesis, and clinical manifestations, as well as by the available detection methods. Fortunately, the progress of microenvironment-targeted nanoplatforms has shown their remarkable potential to change the status quo. The pancreatic inflammatory microenvironment is typically characterized by low pH, abundant reactive oxygen species (ROS) and enzymes, overproduction of inflammatory cells, and hypoxia, which exacerbate the pathological development of AP but also provide potential targeting sites for nanoagents to achieve early diagnosis and treatment. This review elaborates the various potential targets of the inflammatory microenvironment of AP and summarizes in detail the prospects for the development and application of functional nanomaterials for specific targets. Additionally, it presents the challenges and future trends to develop multifunctional targeted nanomaterials for the early diagnosis and effective treatment of AP, providing a valuable reference for future research.

Macrophage-driven cardiac inflammation and healing: insights from homeostasis and myocardial infarction

Early and prompt reperfusion therapy has markedly improved the survival rates among patients enduring myocardial infarction (MI). Nonetheless, the resulting adverse remodeling and the subsequent onset of heart failure remain formidable clinical management challenges and represent a primary cause of disability in MI patients worldwide. Macrophages play a crucial role in immune system regulation and wield a profound influence over the inflammatory repair process following MI, thereby dictating the degree of myocardial injury and the subsequent pathological remodeling. Despite numerous previous biological studies that established the classical polarization model for macrophages, classifying them as either M1 pro-inflammatory or M2 pro-reparative macrophages, this simplistic categorization falls short of meeting the precision medicine standards, hindering the translational advancement of clinical research. Recently, advances in single-cell sequencing technology have facilitated a more profound exploration of macrophage heterogeneity and plasticity, opening avenues for the development of targeted interventions to address macrophage-related factors in the aftermath of MI. In this review, we provide a summary of macrophage origins, tissue distribution, classification, and surface markers. Furthermore, we delve into the multifaceted roles of macrophages in maintaining cardiac homeostasis and regulating inflammation during the post-MI period.

Excretory/secretory products from Trichinella spiralis adult worms ameliorate myocardial infarction by inducing M2 macrophage polarization in a mouse model

BACKGROUND

Ischemia-induced inflammatory response is the main pathological mechanism of myocardial infarction (MI)-caused heart tissue injury. It has been known that helminths and worm-derived proteins are capable of modulating host immune response to suppress excessive inflammation as a survival strategy. Excretory/secretory products from Trichinella spiralis adult worms (Ts-AES) have been shown to ameliorate inflammation-related diseases. In this study, Ts-AES were used to treat mice with MI to determine its therapeutic effect on reducing MI-induced heart inflammation and the immunological mechanism involved in the treatment.

METHODS

The MI model was established by the ligation of the left anterior descending coronary artery, followed by the treatment of Ts-AES by intraperitoneal injection. The therapeutic effect of Ts-AES on MI was evaluated by measuring the heart/body weight ratio, cardiac systolic and diastolic functions, histopathological change in affected heart tissue and observing the 28-day survival rate. The effect of Ts-AES on mouse macrophage polarization was determined by stimulating mouse bone marrow macrophages in vitro with Ts-AES, and the macrophage phenotype was determined by flow cytometry. The protective effect of Ts-AES-regulated macrophage polarization on hypoxic cardiomyocytes was determined by in vitro co-culturing Ts-AES-induced mouse bone marrow macrophages with hypoxic cardiomyocytes and cardiomyocyte apoptosis determined by flow cytometry.

RESULTS

We observed that treatment with Ts-AES significantly improved cardiac function and ventricular remodeling, reduced pathological damage and mortality in mice with MI, associated with decreased pro-inflammatory cytokine levels, increased regulatory cytokine expression and promoted macrophage polarization from M1 to M2 type in MI mice. Ts-AES-induced M2 macrophage polarization also reduced apoptosis of hypoxic cardiomyocytes in vitro.

CONCLUSIONS

Our results demonstrate that Ts-AES ameliorates MI in mice by promoting the polarization of macrophages toward the M2 type. Ts-AES is a potential pharmaceutical agent for the treatment of MI and other inflammation-related diseases.

Cardiac Pericytes Acquire a Fibrogenic Phenotype and Contribute to Vascular Maturation After Myocardial Infarction

BACKGROUND

Pericytes have been implicated in tissue repair, remodeling, and fibrosis. Although the mammalian heart contains abundant pericytes, their fate and involvement in myocardial disease remains unknown.

METHODS

We used NG2Dsred;PDGFRαEGFP pericyte:fibroblast dual reporter mice and inducible NG2CreER mice to study the fate and phenotypic modulation of pericytes in myocardial infarction. The transcriptomic profile of pericyte-derived cells was studied using polymerase chain reaction arrays and single-cell RNA sequencing. The role of transforming growth factor-β (TGF-β) signaling in regulation of pericyte phenotype was investigated in vivo using pericyte-specific TGF-β receptor 2 knockout mice and in vitro using cultured human placental pericytes.

RESULTS

In normal hearts, neuron/glial antigen 2 (NG2) and platelet-derived growth factor receptor α (PDGFRα) identified distinct nonoverlapping populations of pericytes and fibroblasts, respectively. After infarction, a population of cells expressing both pericyte and fibroblast markers emerged. Lineage tracing demonstrated that in the infarcted region, a subpopulation of pericytes exhibited transient expression of fibroblast markers. Pericyte-derived cells accounted for ~4% of PDGFRα+ infarct fibroblasts during the proliferative phase of repair. Pericyte-derived fibroblasts were overactive, expressing higher levels of extracellular matrix genes, integrins, matricellular proteins, and growth factors, when compared with fibroblasts from other cellular sources. Another subset of pericytes contributed to infarct angiogenesis by forming a mural cell coat, stabilizing infarct neovessels. Single-cell RNA sequencing showed that NG2 lineage cells diversify after infarction and exhibit increased expression of matrix genes, and a cluster with high expression of fibroblast identity markers emerges. Trajectory analysis suggested that diversification of infarct pericytes may be driven by proliferating cells. In vitro and in vivo studies identified TGF-β as a potentially causative mediator in fibrogenic activation of infarct pericytes. However, pericyte-specific TGF-β receptor 2 disruption had no significant effects on infarct myofibroblast infiltration and collagen deposition. Pericyte-specific TGF-β signaling was involved in vascular maturation, mediating formation of a mural cell coat investing infarct neovessels and protecting from dilative remodeling.

CONCLUSIONS

In the healing infarct, cardiac pericytes upregulate expression of fibrosis-associated genes, exhibiting matrix-synthetic and matrix-remodeling profiles. A fraction of infarct pericytes exhibits expression of fibroblast identity markers. Pericyte-specific TGF-β signaling plays a central role in maturation of the infarct vasculature and protects from adverse dilative remodeling, but it does not modulate fibrotic remodeling.

Macrophage-Myofibroblast Transition Contributes to Myofibroblast Formation in Proliferative Vitreoretinal Disorders

Inflammation and fibrosis are key features of proliferative vitreoretinal disorders. We aimed to define the macrophage phenotype and investigate the role of macrophage-myofibroblast transition (MMT) in the contribution to myofibroblast populations present in epiretinal membranes. Vitreous samples from proliferative diabetic retinopathy (PDR), proliferative vitreoretinopathy (PVR) and nondiabetic control patients, epiretinal fibrovascular membranes from PDR patients and fibrocellular membranes from PVR patients, human retinal Müller glial cells and human retinal microvascular endothelial cells (HRMECs) were studied by ELISA, immunohistochemistry and flow cytometry analysis. Myofibroblasts expressing α-SMA, fibroblast activation protein-α (FAP-α) and fibroblast-specific protein-1 (FSP-1) were present in all membranes. The majority of CD68+ monocytes/macrophages co-expressed the M2 macrophage marker CD206. In epiretinal membranes, cells undergoing MMT were identified by co-expression of the macrophage marker CD68 and myofibroblast markers α-SMA and FSP-1. Further analysis revealed that CD206+ M2 macrophages co-expressed α-SMA, FSP-1, FAP-α and ß-catenin. Soluble (s) CD206 and sFAP-α levels were significantly higher in vitreous samples from PDR and PVR patients than in nondiabetic control patients. The proinflammatory cytokine TNF-α and the hypoxia mimetic agent cobalt chloride induced upregulation of sFAP-α in culture media of Müller cells but not of HRMECs. The NF-ĸß inhibitor BAY11-7085 significantly attenuated TNF-α-induced upregulation of sFAP-α in Müller cells. Our findings suggest that the process of MMT might contribute to myofibroblast formation in epiretinal membranes, and this transition involved macrophages with a predominant M2 phenotype. In addition, sFAP-α as a vitreous biomarker may be derived from M2 macrophages transitioned to myofibroblasts and from Müller cells.

Intragraft immune cells: accomplices or antagonists of recipient-derived macrophages in allograft fibrosis?

Organ fibrosis caused by chronic allograft rejection is a major concern in the field of transplantation. Macrophage-to-myofibroblast transition plays a critical role in chronic allograft fibrosis. Adaptive immune cells (such as B and CD4⁺ T cells) and innate immune cells (such as neutrophils and innate lymphoid cells) participate in the occurrence of recipient-derived macrophages transformed to myofibroblasts by secreting cytokines, which eventually leads to fibrosis of the transplanted organ. This review provides an update on the latest progress in understanding the plasticity of recipient-derived macrophages in chronic allograft rejection. We discuss here the immune mechanisms of allograft fibrosis and review the reaction of immune cells in allograft. The interactions between immune cells and the process of myofibroblast formulation are being considered for the potential therapeutic targets of chronic allograft fibrosis. Therefore, research on this topic seems to provide novel clues for developing strategies for preventing and treating allograft fibrosis.

Single-cell transcriptomics reveals cellular heterogeneity and macrophage-to-mesenchymal transition in bicuspid calcific aortic valve disease

BACKGROUND

Bicuspid aortic valve (BAV) is the most prevalent congenital valvular heart defect, and around 50% of severe isolated calcific aortic valve disease (CAVD) cases are associated with BAV. Although previous studies have demonstrated the cellular heterogeneity of aortic valves, the cellular composition of specific BAV at the single-cell level remains unclear.

METHODS

Four BAV specimens from aortic valve stenosis patients were collected to conduct single-cell RNA sequencing (scRNA-seq). In vitro experiments were performed to further validate some phenotypes.

RESULTS

The heterogeneity of stromal cells and immune cells were revealed based on comprehensive analysis. We identified twelve subclusters of VICs, four subclusters of ECs, six subclusters of lymphocytes, six subclusters of monocytic cells and one cluster of mast cells. Based on the detailed cell atlas, we constructed a cellular interaction network. Several novel cell types were identified, and we provided evidence for established mechanisms on valvular calcification. Furthermore, when exploring the monocytic lineage, a special population, macrophage derived stromal cells (MDSC), was revealed to be originated from MRC1+ (CD206) macrophages (Macrophage-to-Mesenchymal transition, MMT). FOXC1 and PI3K-AKT pathway were identified as potential regulators of MMT through scRNA analysis and in vitro experiments.

CONCLUSIONS

With an unbiased scRNA-seq approach, we identified a full spectrum of cell populations and a cellular interaction network in stenotic BAVs, which may provide insights for further research on CAVD. Notably, the exploration on mechanism of MMT might provide potential therapeutic targets for bicuspid CAVD.

Crosstalk between macrophages and cardiac cells after myocardial infarction

Cardiovascular diseases, such as myocardial infarction (MI), are a leading cause of death worldwide. Acute MI (AMI) inflicts massive injury to the coronary microcirculation, causing large-scale cardiomyocyte death due to ischemia and hypoxia. Inflammatory cells such as monocytes and macrophages migrate to the damaged area to clear away dead cells post-MI. Macrophages are pleiotropic cells of the innate immune system, which play an essential role in the initial inflammatory response that occurs following MI, inducing subsequent damage and facilitating recovery. Besides their recognized role within the immune response, macrophages participate in crosstalk with other cells (including cardiomyocytes, fibroblasts, immune cells, and vascular endothelial cells) to coordinate post-MI processes within cardiac tissue. Macrophage-secreted exosomes have recently attracted increasing attention, which has led to a more elaborate understanding of macrophage function. Currently, the functional roles of macrophages in the microenvironment of the infarcted heart, particularly with regard to their interaction with surrounding cells, remain unclear. Understanding the specific mechanisms that mediate this crosstalk is essential in treating MI. In this review, we discuss the origin of macrophages, changes in their distribution post-MI, phenotypic and functional plasticity, as well as the specific signaling pathways involved, with a focus on the crosstalk with other cells in the heart. Thus, we provide a new perspective on the treatment of MI. Further in-depth research is required to elucidate the mechanisms underlying crosstalk between macrophages and other cells within cardiac tissue for the identification of potential therapeutic targets. Video Abstract.

Fusobacterium nucleatum aggravates rheumatoid arthritis through FadA-containing outer membrane vesicles

Rheumatoid arthritis (RA) is an autoimmune disorder that has been associated with the gut microbiota. However, whether and how the gut microbiota plays a pathogenic role in RA remains unexplored. Here, we observed that Fusobacterium nucleatum is enriched in RA patients and positively associated with RA severity. F. nucleatum similarly aggravates arthritis in a mouse model of collagen-induced arthritis (CIA). F. nucleatum outer membrane vesicles (OMVs) containing the virulence determinant FadA translocate into the joints, triggering local inflammatory responses. Specifically, FadA acts on synovial macrophages, resulting in the activation of the Rab5a GTPase involved in vesicle trafficking and inflammatory pathways and YB-1, a key regulator of inflammatory mediators. OMVs containing FadA and heightened Rab5a-YB-1 expression were observed in RA patients compared with controls. These findings suggest a causal role of F. nucleatum in aggravating RA and provide promising therapeutic targets for clinically ameliorating RA.

Piezo1 (Piezo-Type Mechanosensitive Ion Channel Component 1)-Mediated Mechanosensation in Macrophages Impairs Perfusion Recovery After Hindlimb Ischemia in Mice

BACKGROUND

Angiogenesis is a promising strategy for those with peripheral artery disease. Macrophage-centered inflammation is intended to govern the deficiency of the angiogenic response after hindlimb ischemia. However, little is known about the mechanism of macrophage activation beyond signals from cytokines and chemokines. We sought to identify a novel mechanical signal from the ischemic microenvironment that provokes macrophages and the subsequent inflammatory cascade and to investigate the potential role of Piezo-type mechanosensitive ion channels (Piezo) on macrophages during this process.

METHODS

Myeloid cell-specific Piezo1 (Piezo-type mechanosensitive ion channel component 1) knockout (Piezo1^ΔMΦ) mice were generated by crossing Piezo1^fl/fl (LysM-Cre^-/-; Piezo1 flox/flox) mice with LysM-Cre transgenic mice to assess the roles of Piezo1 in macrophages after hindlimb ischemia. Furthermore, in vitro studies were carried out in bone marrow-derived macrophages to decipher the underlying mechanism.

RESULTS

We found that tissue stiffness gradually increased after hindlimb ischemia, as indicated by Young's modulus. Compared to Piezo2, Piezo1 expression and activation were markedly upregulated in macrophages from ischemic tissues in concurrence with increased tissue stiffness. Piezo1^ΔMΦ mice exhibited improved perfusion recovery by enhancing angiogenesis. Matrigel tube formation assays revealed that Piezo1 deletion promoted angiogenesis by enhancing FGF2 (fibroblast growth factor-2) paracrine signaling in macrophages. Conversely, activation of Piezo1 by increased stiffness or the agonist Yoda1 led to reduced FGF2 production in bone marrow-derived macrophages, which could be blocked by Piezo1 silencing. Mechanistically, Piezo1 mediated extracellular Ca²⁺ influx and activated Ca²⁺-dependent CaMKII (calcium/calmodulin-dependent protein kinase II)/ETS1 (ETS proto-oncogene 1) signaling, leading to transcriptional inactivation of FGF2.

CONCLUSIONS

This study uncovers a crucial role of microenvironmental stiffness in exacerbating the macrophage-dependent deficient angiogenic response. Deletion of macrophage Piezo1 promotes perfusion recovery after hindlimb ischemia through CaMKII/ETS1-mediated transcriptional activation of FGF2. This provides a promising therapeutic strategy to enhance angiogenesis in ischemic diseases.

Multiomics uncover the proinflammatory role of Trpm4 deletion after myocardial infarction in mice

Upon myocardial infarction (MI), ischemia-induced cell death triggers an inflammatory response responsible for removing necrotic material and inducing tissue repair. TRPM4 is a Ca2+-activated ion channel permeable to monovalent cations. Although its role in cardiomyocyte-driven hypertrophy and arrhythmia post-MI has been established, no study has yet investigated its role in the inflammatory process orchestrated by endothelial cells, immune cells, and fibroblasts. This study aims to assess the role of TRPM4 in 1) survival and cardiac function, 2) inflammation, and 3) healing post-MI. We performed ligation of the left coronary artery or sham intervention on 154 Trpm4 WT or KO mice under isoflurane anesthesia. Survival and echocardiographic functions were monitored up to 5 wk. We collected serum during the acute post-MI phase to analyze proteomes and performed single-cell RNA sequencing on nonmyocytic cells of hearts after 24 and 72 h. Lastly, we assessed chronic fibrosis and angiogenesis. We observed no significant differences in survival or cardiac function, even though our proteomics data showed significantly decreased tissue injury markers (i.e., creatine kinase M and VE-cadherin) in KO serum after 12 h. On the other hand, inflammation, characterized by serum amyloid P component in the serum, higher number of recruited granulocytes, inflammatory monocytes, and macrophages, as well as expression of proinflammatory genes, was significantly higher in KO. This correlated with increased chronic cardiac fibrosis and angiogenesis. Since inflammation and fibrosis are closely linked to adverse remodeling, future therapeutic attempts at inhibiting TRPM4 will need to assess these parameters carefully before proceeding with translational studies.NEW & NOTEWORTHY Deletion of Trpm4 increases markers of cardiac and systemic inflammation within the first 24 h after MI, while inducing an earlier fibrotic transition at 72 h and more overall chronic fibrosis and angiogenesis at 5 wk. The descriptive, robust, and methodologically broad approach of this study sheds light on an important caveat that will need to be taken into account in all future therapeutic attempts to inhibit TRPM4 post-MI.

Diabetes Induces Cardiac Fibroblast Activation, Promoting a Matrix-Preserving Nonmyofibroblast Phenotype, Without Stimulating Pericyte to Fibroblast Conversion

Background Interstitial and perivascular fibrosis may contribute to diabetes-associated heart failure. Pericytes can convert to fibroblasts under conditions of stress and have been implicated in the pathogenesis of fibrotic diseases. We hypothesized that in diabetic hearts, pericytes may convert to fibroblasts, contributing to fibrosis and to the development of diastolic dysfunction. Methods and Results Using pericyte:fibroblast dual reporter (NG2^Dsred [neuron-glial antigen 2 red fluorescent protein variant]; PDGFRα^EGFP [platelet-derived growth factor receptor alpha enhanced green fluorescent protein]) mice in a type 2 diabetic db/db background, we found that diabetes does not significantly affect pericyte density but reduces the myocardial pericyte:fibroblast ratio. Lineage tracing using the inducible NG2^CreER driver, along with reliable labeling of fibroblasts with the PDGFRα reporter system, showed no significant pericyte to fibroblast conversion in lean and db/db hearts. In addition, db/db mouse cardiac fibroblasts did not undergo myofibroblast conversion and had no significant induction of structural collagens but exhibited a matrix-preserving phenotype, associated with increased expression of antiproteases, matricellular genes, matrix cross-linking enzymes, and the fibrogenic transcription factor cMyc. In contrast, db/db mouse cardiac pericytes had increased expression of Timp3, without any changes in expression of other fibrosis-associated genes. The matrix-preserving phenotype of diabetic fibroblasts was associated with induction of genes encoding oxidative (Ptgs2/cycloxygenase-2, and Fmo2) and antioxidant proteins (Hmox1, Sod1). In vitro, high glucose partially recapitulated the in vivo changes in diabetic fibroblasts. Conclusions Diabetic fibrosis is not mediated through pericyte to fibroblast conversion but involves acquisition of a matrix-preserving fibroblast program, which is independent of myofibroblast conversion and is only partially explained by the effects of the hyperglycemic environment.

Impact of Reperfusion on Temporal Immune Cell Dynamics After Myocardial Infarction

Excessive inflammation and impaired healing of cardiac tissue following a myocardial infarction (MI) can drive the development of heart failure. Cardiac repair begins immediately after the onset of MI and continues for months. The repair process can be divided into the following 3 overlapping phases, each having distinct functions and sequelae: the inflammatory phase, the proliferative phase, and the maturation phase. Macrophages, neutrophils, and lymphocytes are present in the myocardium throughout the repair process and govern the duration and function of each of these phases. However, changes in the functions of these cell types across each phase are poorly characterized. Numerous immunomodulatory therapies that specifically target inflammation have been developed for promoting cardiac repair and preventing heart failure after MI. However, these treatments have been largely unsuccessful in large-scale clinical randomized controlled trials. A potential explanation for this failure is the lack of a thorough understanding of the time-dependent evolution of the functions of immune cells after a major cardiovascular event. Failure to account for this temporal plasticity in cell function may reduce the efficacy of immunomodulatory approaches that target cardiac repair. This review is concerned with how the functions of different immune cells change with time following an MI. Improved understanding of the temporal changes in immune cell function is important for the future development of effective and targeted treatments for preventing heart failure after MI.

Beneficial effect of TLR4 blockade by a specific aptamer antagonist after acute myocardial infarction

Experimental evidence indicates that the control of the inflammatory response after myocardial infarction is a key strategy to reduce cardiac injury. Cellular damage after blood flow restoration in the heart promotes sterile inflammation through the release of molecules that activate pattern recognition receptors, among which TLR4 is the most prominent. Transient regulation of TLR4 activity has been considered one of the potential therapeutic interventions with greater projection towards the clinic. In this regard, the characterization of an aptamer (4FT) that acts as a selective antagonist for human TLR4 has been investigated in isolated macrophages from different species and in a rat model of cardiac ischemia/reperfusion (I/R). The binding kinetics and biological responses of murine and human macrophages treated with 4FT show great affinity and significant inhibition of TLR4 signaling including the NF-κB pathway and the LPS-dependent increase in the plasma membrane currents (Kv currents). In the rat model of I/R, administration of 4FT following reoxygenation shows amelioration of cardiac injury function and markers, a process that is significantly enhanced when the second dose of 4FT is administered 24 h after reperfusion of the heart. Parameters such as cardiac injury biomarkers, infiltration of circulating inflammatory cells, and the expression of genes associated with the inflammatory onset are significantly reduced. In addition, the expression of anti-inflammatory genes, such as IL-10, and pro-resolution molecules, such as resolvin D1 are enhanced after 4FT administration. These results indicate that targeting TLR4 with 4FT offers new therapeutic opportunities to prevent cardiac dysfunction after infarction.

Role of mitochondrial metabolic disorder and immune infiltration in diabetic cardiomyopathy: new insights from bioinformatics analysis

BACKGROUND

Diabetic cardiomyopathy (DCM) is one of the common cardiovascular complications of diabetes and a leading cause of death in diabetic patients. Mitochondrial metabolism and immune-inflammation are key for DCM pathogenesis, but their crosstalk in DCM remains an open issue. This study explored the separate roles of mitochondrial metabolism and immune microenvironment and their crosstalk in DCM with bioinformatics.

METHODS

DCM chip data (GSE4745, GSE5606, and GSE6880) were obtained from NCBI GEO, while mitochondrial gene data were downloaded from MitoCarta3.0 database. Differentially expressed genes (DEGs) were screened by GEO2R and processed for GSEA, GO and KEGG pathway analyses. Mitochondria-related DEGs (MitoDEGs) were obtained. A PPI network was constructed, and the hub MitoDEGs closely linked to DCM or heart failure were identified with CytoHubba, MCODE and CTD scores. Transcription factors and target miRNAs of the hub MitoDEGs were predicted with Cytoscape and miRWalk database, respectively, and a regulatory network was established. The immune infiltration pattern in DCM was analyzed with ImmuCellAI, while the relationship between MitoDEGs and immune infiltration abundance was investigated using Spearman method. A rat model of DCM was established to validate the expression of hub MitoDEGs and their relationship with cardiac function.

RESULTS

MitoDEGs in DCM were significantly enriched in pathways involved in mitochondrial metabolism, immunoregulation, and collagen synthesis. Nine hub MitoDEGs closely linked to DCM or heart failure were obtained. Immune analysis revealed significantly increased infiltration of B cells while decreased infiltration of DCs in immune microenvironment of DCM. Spearman analysis demonstrated that the hub MitoDEGs were positively associated with the infiltration of pro-inflammatory immune cells, but negatively associated with the infiltration of anti-inflammatory or regulatory immune cells. In the animal experiment, 4 hub MitoDEGs (Pdk4, Hmgcs2, Decr1, and Ivd) showed an expression trend consistent with bioinformatics analysis result. Additionally, the up-regulation of Pdk4, Hmgcs2, Decr1 and the down-regulation of Ivd were distinctly linked to reduced cardiac function.

CONCLUSIONS

This study unraveled the interaction between mitochondrial metabolism and immune microenvironment in DCM, providing new insights into the research on potential pathogenesis of DCM and the exploration of novel targets for medical interventions.

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.

Central role of cardiac fibroblasts in myocardial fibrosis of diabetic cardiomyopathy

Diabetic cardiomyopathy (DCM), a main cardiovascular complication of diabetes, can eventually develop into heart failure and affect the prognosis of patients. Myocardial fibrosis is the main factor causing ventricular wall stiffness and heart failure in DCM. Early control of myocardial fibrosis in DCM is of great significance to prevent or postpone the progression of DCM to heart failure. A growing body of evidence suggests that cardiomyocytes, immunocytes, and endothelial cells involve fibrogenic actions, however, cardiac fibroblasts, the main participants in collagen production, are situated in the most central position in cardiac fibrosis. In this review, we systematically elaborate the source and physiological role of myocardial fibroblasts in the context of DCM, and we also discuss the potential action and mechanism of cardiac fibroblasts in promoting fibrosis, so as to provide guidance for formulating strategies for prevention and treatment of cardiac fibrosis in DCM.

Immune cells drive new immunomodulatory therapies for myocardial infarction: From basic to clinical translation

The high incidence of heart failure secondary to myocardial infarction (MI) has been difficult to effectively address. MI causes strong aseptic inflammation, and infiltration of different immune cells and changes in the local inflammatory microenvironment play a key regulatory role in ventricular remodeling. Therefore, the possibility of improving the prognosis of MI through targeted immunity has been of interest and importance in MI. However, previously developed immune-targeted therapies have not achieved significant success in clinical trials. Here, we propose that the search for therapeutic targets from different immune cells may be more precise and lead to better clinical translation. Specifically, this review summarizes the role and potential therapeutic targets of various immune cells in ventricular remodeling after MI, especially monocytes/macrophages and neutrophils, as a way to demonstrate the importance and potential of immunomodulatory therapies for MI. In addition, we analyze the reasons for the failure of previous immunomodulatory therapies and the issues that need to be addressed, as well as the prospects and targeting strategies of using immune cells to drive novel immunomodulatory therapies, hoping to advance the development of immunomodulatory therapies by providing evidence and new ideas.

TRIM21 aggravates cardiac injury after myocardial infarction by promoting M1 macrophage polarization

Macrophage polarization followed by myocardial infarction (MI) is essential for wound healing. Tripartite motif-containing protein 21 (TRIM21), a member of E3 ubiquitin ligases, is emerging as a mediator in cardiac injury and heart failure. However, its function in modulating post-MI macrophage polarization remains elusive. Here, we detected that the levels of TRIM21 significantly increased in macrophages of wild-type (WT) mice after MI. In contrast, MI was ameliorated in TRIM21 knockout (TRIM21-/-) mice with improved cardiac remodeling, characterized by a marked decrease in mortality, decreased infarct size, and improved cardiac function compared with WT-MI mice. Notably, TRIM21 deficiency impeded the post-MI apoptosis and DNA damage in the hearts of mice. Consistently, the accumulation of M1 phenotype macrophages in the infarcted tissues was significantly reduced with TRIM21 deletion. Mechanistically, the deletion of TRIM21 orchestrated the process of M1 macrophage polarization at least partly via a PI3K/Akt signaling pathway. Overall, we identify TRIM21 drives the inflammatory response and cardiac remodeling by stimulating M1 macrophage polarization through a PI3K/Akt signaling pathway post-MI.

Pan-cancer single-cell analysis reveals the heterogeneity and plasticity of cancer-associated fibroblasts in the tumor microenvironment

Cancer-associated fibroblasts (CAFs) are the predominant components of the tumor microenvironment (TME) and influence cancer hallmarks, but without systematic investigation on their ubiquitous characteristics across different cancer types. Here, we perform pan-cancer analysis on 226 samples across 10 solid cancer types to profile the TME at single-cell resolution, illustrating the commonalities/plasticity of heterogenous CAFs. Activation trajectory of the major CAF types is divided into three states, exhibiting distinct interactions with other cell components, and relating to prognosis of immunotherapy. Moreover, minor CAF components represent the alternative origin from other TME components (e.g., endothelia and macrophages). Particularly, the ubiquitous presentation of endothelial-to-mesenchymal transition CAF, which may interact with proximal SPP1⁺ tumor-associated macrophages, is implicated in endothelial-to-mesenchymal transition and survival stratifications. Our study comprehensively profiles the shared characteristics and dynamics of CAFs, and highlight their heterogeneity and plasticity across different cancer types. Browser of integrated pan-cancer single-cell information is available at https://gist-fgl.github.io/sc-caf-atlas/ .

Oxygen–Glucose Deprivation Promoted Fibroblast Senescence and Collagen Expression via IL11

Cell senescence is one of the most important forms of injury induced by cardiovascular and other ischemic diseases. Fibroblasts are important participants in tissue repair after ischemic injury and the main source of IL11 secretion. However, the roles of oxygen–glucose deprivation (OGD) and IL11 in promoting fibroblast senescence and their regulatory mechanisms remain unclear. This study selected the NIH3T3 and L929 fibroblast cell lines as research objects. We found that OGD could induce the expression of p53, P16, p21, and collagen in fibroblasts. In the condition of OGD, when IL11 intervened, fibroblasts’ senescence and collagen expression were changed. Some studies have found that changes in kynurenine (KYN) metabolism are related to aging diseases, and indoleamine 2,3-dioxygenase 1 (IDO1) is a key rate-limiting enzyme in the KYN metabolic pathway. We found that KYN secretion decreased after OGD increased fibroblast senescence, and inhibition of IL11 promoted IDO1 and increased KYN secretion. These results suggest that OGD may promote fibroblast senescence and collagen expression via IL11 inhibition of the IDO1/KYN metabolic pathway. Therefore, the revealed mechanism of OGD-promoted fibroblast senescence could provide an effective theoretical basis for the clinical treatment of aging-related ischemic diseases.

Macrophages in myocardial infarction

The heart contains a population of resident macrophages that markedly expands following injury through recruitment of monocytes and through proliferation of macrophages. In myocardial infarction, macrophages have been implicated in both injurious and reparative responses. In coronary atherosclerotic lesions, macrophages have been implicated in disease progression and in the pathogenesis of plaque rupture. Following myocardial infarction, resident macrophages contribute to initiation and regulation of the inflammatory response. Phagocytosis and efferocytosis are major functions of macrophages during the inflammatory phase of infarct healing, and mediate phenotypic changes, leading to acquisition of an anti-inflammatory macrophage phenotype. Infarct macrophages respond to changes in the cytokine content and extracellular matrix composition of their environment and secrete fibrogenic and angiogenic mediators, playing a central role in repair of the infarcted heart. Macrophages may also play a role in scar maturation and may contribute to chronic adverse remodeling of noninfarcted segments. Single cell studies have revealed a remarkable heterogeneity of macrophage populations in infarcted hearts; however, the relations between transcriptomic profiles and functional properties remain poorly defined. This review manuscript discusses the fate, mechanisms of expansion and activation, and role of macrophages in the infarcted heart. Considering their critical role in injury, repair, and remodeling, macrophages are important, but challenging, targets for therapeutic interventions in myocardial infarction.

New insights into fibrosis from the ECM degradation perspective: the macrophage-MMP-ECM interaction

Fibrosis is a pathological feature of a variety of chronic inflammatory diseases that can affect almost all organs, which can cause severe consequences and even lead to death. Fibrosis is characterized by the excessive accumulation of extracellular matrix (ECM) due to disruption of the balance between ECM production and degradation. Although overabundance of ECM proteins has long been the focus of studies on fibrosis, another facet of the problem—impaired degradation of the ECM—is gaining increasing attention. Matrix metalloproteinase (MMP) and the tissue inhibitor of metalloproteinase (TIMP) system is the main molecular system contributing to ECM degradation, and macrophages are the major regulators of ECM. However, the relationship among macrophages, the MMP/TIMP system and the ECM is not fully understood in the context of fibrosis. Here, we discuss in detail the role played by the ECM in the development of fibrosis and highlight the macrophage-MMP-ECM interaction that is involved in fibrogenesis and may be a potential therapeutic target for fibrosis.