Cardiac monocytes and macrophages after myocardial infarction

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.

Myeloid cell-specific deletion of epidermal growth factor receptor aggravates acute cardiac injury

Myeloid cells, including macrophages, play important roles as first responders to cardiac injury and stress. Epidermal growth factor receptor (EGFR) has been identified as a mediator of macrophage responsiveness to select diseases, though its impact on cardiac function or remodeling following acute ischemic injury is unknown. We aimed to define the role of myeloid cell-specific EGFR in the regulation of cardiac function and remodeling following acute myocardial infarction (MI)-induced injury. Floxed EGFR mice were bred with homozygous LysM-Cre (LMC) transgenic mice to yield myeloid-specific EGFR knockout (mKO) mice. Via echocardiography, immunohistochemistry, RNA sequencing and flow cytometry, the impact of myeloid cell-specific EGFR deletion on cardiac structure and function was assessed at baseline and following injury. Compared with LMC controls, myeloid cell-specific EGFR deletion led to an increase in cardiomyocyte hypertrophy at baseline. Bulk RNASeq analysis of isolated cardiac Cd11b+ myeloid cells revealed substantial changes in mKO cell transcripts at baseline, particularly in relation to predicted decreases in neovascularization. In response to myocardial infarction, mKO mice experienced a hastened decline in cardiac function with isolated cardiac Cd11b+ myeloid cells expressing decreased levels of the pro-reparative mediators Vegfa and Il10, which coincided with enhanced cardiac hypertrophy and decreased capillary density. Overall, loss of EGFR qualitatively alters cardiac resident macrophages that promotes a low level of basal stress and a more rapid decrease in cardiac function along with worsened repair following acute ischemic injury.

Splenic monocytes mediate inflammatory response and exacerbate myocardial ischemia/reperfusion injury in a mitochondrial cell-free DNA-TLR9-NLRP3-dependent fashion

The spleen contributes importantly to myocardial ischemia/reperfusion (MI/R) injury. Nucleotide-binding oligomerization domain-like receptor family pyrin domain containing 3 (NLRP3) recruits inflammasomes, initiating inflammatory responses and mediating tissue injury. We hypothesize that myocardial cell-free DNA (cfDNA) activates the splenic NLRP3 inflammasome during early reperfusion, increases systemic inflammatory response, and exacerbates myocardial infarct. Mice were subjected to 40 min of ischemia followed by 0, 1, 5, or 15 min, or 24 h of reperfusion. Splenic leukocyte adoptive transfer was performed by injecting isolated splenocytes to mice with splenectomy performed prior to left coronary artery occlusion. CY-09 (4 mg/kg) was administered 5 min before reperfusion. During post-ischemic reperfusion, splenic protein levels of NLRP3, cleaved caspase-1, and interleukin-1β (IL-1β) were significantly elevated and peaked (2.1 ± 0.2-, 3.4 ± 0.4-, and 3.2 ± 0.2-fold increase respectively, p < 0.05) within 5 min of reperfusion. In myocardial tissue, NLRP3 was not upregulated until 24 h after reperfusion. Suppression by CY09, a specific NLRP3 inflammasome inhibitor, or deficiency of NLRP3 significantly reduced myocardial infarct size (17.3% ± 4.2% and 33.2% ± 1.8% decrease respectively, p < 0.01). Adoptive transfer of NLRP3-/- splenocytes to WT mice significantly decreased infarct size compared to transfer of WT splenocytes (19.1% ± 2.8% decrease, p < 0.0001). NLRP3 was mainly activated at 5 min after reperfusion in CD11b+ and LY6G- splenocytes, which significantly increased during reperfusion (24.8% ± 0.7% vs.14.3% ± 0.6%, p < 0.0001). The circulating cfDNA level significantly increased in patients undergoing cardiopulmonary bypass (CPB) (43.3 ± 5.3 ng/mL, compared to pre-CPB 23.8 ± 3.5 ng/mL, p < 0.01). Mitochondrial cfDNA (mt-cfDNA) contributed to NLRP3 activation in macrophages (2.1 ± 0.2-fold increase, p < 0.01), which was inhibited by a Toll-like receptor 9(TLR9) inhibitor. The NLRP3 inflammasome in splenic monocytes is activated and mediates the inflammatory response shortly after reperfusion onset, exacerbating MI/R injury in mt-cfDNA/TLR9-dependent fashion. The schema reveals splenic NLRP3 mediates the inflammatory response in macrophages and exacerbates MI/R in a mitochondrial cfDNA/ TLR9-dependent fashion.

Macrophage colony-stimulating factor ameliorates myocardial injury in mice after myocardial infarction by regulating cardiac macrophages through the P2X7R/NLRP3/IL-1β signal pathway

Aims

To investigate the effects of M-CSF on myocardial injury in mice after MI by regulating different types of cardiac macrophages through the P2X7R/NLRP3/IL-1β signal pathway.

Methods

A total of 60 C57BL/6J WT mice were used, with the Sham Group subjected to ligation without ligation through the LAD, the MI model was prepared by ligation of the LAD in the MC Group and MM Group, with the M-CSF reagent (500 μg/kg/d) being given an intraperitoneal injection for the first 5 days after surgery in the MM Group. All mice were fed in a barrier environment for 1 week. After the study, myocardial tissues were collected and IL-4, IL-6, IL-10, TNF-α, MCP-1, IFN-α, ANP, BNP, β-MHC, Collage I, Collage III, P2X7R, NLRP3, IL-1β, Bax, Caspase 3, C-Casp 3, Bcl-2, M1/2 macrophage, the apoptosis of cardiomyocytes, and the collagen deposition were detected.

Results

The inflammatory response was significantly lower in the MM Group, the cardiomyocyte apoptosis, fibrosis, and hypertrophy were inhibited compared to the MC Group, and the levels of P2X7R, NLRP3, and IL-1β were also statistically lower in the MM Group. Additionally, the expression of M2 macrophages increased in the MM Group while the M1 macrophages statistically decreased compared to the MC Group.

Conclusion

M-CSF can significantly increase the expression of M2 macrophage and reduce the level of M1 macrophage by inhibiting the levels of NLRP3/IL-1β-related proteins, thereby inhibiting inflammation, ameliorating reducing myocardial hypertrophy, apoptosis, and fibrosis, improve myocardial injury in mice after MI.

Malat1 promotes macrophage-associated inflammation by increasing PPAR-γ methylation through binding to EZH2 in acute myocardial infarction

The inflammatory microenvironment of macrophage plays an important role in acute myocardial infarction (AMI), but the regulatory mechanism is unknown. Here, we aimed to investigate the role of Malat1 on inflammation microenvironment of macrophage in AMI. Our study found that Malat1 expression was increased in AMI, which mainly expressed in macrophages. Malat1 inhibition improved collagen deposition and inflammation in infarcted heart. In vitro, Malat1 inhibition evidently reduced macrophage-associated inflammation. The results from ribonucleic acid pull-down (RNA pull-down) and RNA Immunoprecipitation (RIP) assay demonstrated that Malat1 directly binds to EZH2. Malat1 and EZH2 complex could increase histone H3K27me3 expression and further inhibit the production of PPAR-γ. In vivo, inhibition of Malat1 also leaded to the down-regulation of both EZH2 and H3K27me3, as well as up-regulation of PPAR-γ in infarcted heart. Therefore, these findings demonstrate a novel mechanism of Malat1 on inflammation microenvironment of macrophage in AMI, which provide a new target for its treatment.

ANNEXIN A2 FACILITATES NEOVASCULARIZATION TO PROTECT AGAINST MYOCARDIAL INFARCTION INJURY VIA INTERACTING WITH MACROPHAGE YAP AND ENDOTHELIAL INTEGRIN Β3

ABSTRACT

Cardiac macrophages with different polarization phenotypes regulate ventricular remodeling and neovascularization after myocardial infarction (MI). Annexin A2 (ANXA2) promotes macrophage polarization to the repair phenotype and regulates neovascularization. However, whether ANXA2 plays any role in post-MI remodeling and its underlying mechanism remains obscure. In this study, we observed that expression levels of ANXA2 were dynamically altered in mouse hearts upon MI and peaked on the second day post-MI. Using adeno-associated virus vector-mediated overexpression or silencing of ANXA2 in the heart, we also found that elevation of ANXA2 in the infarcted myocardium significantly improved cardiac function, reduced cardiac fibrosis, and promoted peri-infarct angiogenesis, compared with controls. By contrast, reduction of cardiac ANXA2 exhibited opposite effects. Furthermore, using in vitro coculture system, we found that ANXA2-engineered macrophages promoted cardiac microvascular endothelial cell (CMEC) proliferation, migration, and neovascularization. Mechanistically, we identified that ANXA2 interacted with yes-associated protein (YAP) in macrophages and skewed them toward pro-angiogenic phenotype by inhibiting YAP activity. In addition, ANXA2 directly interacted with integrin β3 in CMECs and enhanced their growth, migration, and tubule formation. Our results indicate that increased expression of ANXA2 could confer protection against MI-induced injury by promoting neovascularization in the infarcted area, partly through the inhibition of YAP in macrophages and activation of integrin β3 in endothelial cells. Our study provides new therapeutic strategies for the treatment of MI injury.

The Role of M1 and M2 Myocardial Macrophages in Promoting Proliferation and Healing via Activating Epithelial-to-Mesenchymal Transition

(1) Background: The activation of sequential processes for the formation of permanent fibrotic tissue following myocardial infarction (MI) is pivotal for optimal healing of heart tissue. M1 and M2 macrophages are known to play essential roles in wound healing by the activation of cardiac fibroblasts after an episode of MI. However, the molecular and cellular mechanisms mediated by these macrophages in cellular proliferation, fibrosis, and wound healing remain unclear. (2) Methods: In the present study, we aimed to explore the mechanisms by which M1 and M2 macrophages contribute to cellular proliferation, fibrosis, and wound healing. Using both in vivo and cellular models, we examined the remodeling effects of M1 and M2 macrophages on infarcted cardiac fibroblasts and their role in promoting cardiac healing post-MI. (3) Results: Our findings indicate that M1 macrophages induce a proliferative effect on infarcted cardiac fibroblasts by exerting an anti-apoptotic effect, thereby preventing cell death. Moreover, M1 macrophages were found to activate the mechanism of epithelial-to-mesenchymal transition (EMT), resulting in wound healing and inducing the fibrotic process. The present findings suggest that M1 macrophages play a crucial role in promoting cardiac remodeling post-MI, as they activate the EMT pathway and contribute to increased collagen production and fibrotic changes. (4) Conclusions: The present study provides insights into molecular and cellular mechanisms mediated by M1 and M2 macrophages in cellular proliferation, fibrosis, and wound healing post-MI. Our findings highlight the critical role of M1 macrophages in promoting cardiac remodeling by activating the EMT pathway. Understanding these mechanisms can potentially result in the development of targeted therapies aimed at enhancing the healing process and improving outcomes following MI.

M6A regulator methylation patterns and characteristics of immunity in acute ST-segment elevation myocardial infarction

M6A methylation is the most prevalent and abundant RNA modification in mammals. Although there are many studies on the regulatory role of m6A methylation in the immune response, the m6A regulators in the pathogenesis of acute ST-segment elevation myocardial infarction (STEMI) remain unclear. We comprehensively analysed the role of m6A regulators in STEMI and built a predictive model, revealing the relationship between m6A methylations and the immune microenvironment. Differential analysis revealed that 18 of 24 m6A regulators were significantly differentially expressed, and there were substantial interactions between the m6A regulator. Then, we established a classifier and nomogram model based on 6 m6A regulators, which can easily distinguish the STEMI and control samples. Finally, two distinct m6A subtypes were obtained and significantly differentially expressed in terms of infiltrating immunocyte abundance, immune reaction activity and human leukocyte antigen genes. Three hub m6A phenotype related genes (RAC2, RELA, and WAS) in the midnightblue module were identified by weighted gene coexpression network analysis, and were associated with immunity. These findings suggest that m6A modification and the immune microenvironment play a key role in the pathogenesis of STEMI.

Macrophages in the Inflammatory Phase following Myocardial Infarction: Role of Exogenous Ubiquitin

Cardiovascular disease (CVD) is one of the leading causes of death worldwide. One of the most common implications of CVD is myocardial infarction (MI). Following MI, the repair of the infarcted heart occurs through three distinct, yet overlapping phases of inflammation, proliferation, and maturation. Macrophages are essential to the resolution of the inflammatory phase due to their role in phagocytosis and efferocytosis. However, excessive and long-term macrophage accumulation at the area of injury and dysregulated function can induce adverse cardiac remodeling post-MI. Ubiquitin (UB) is a highly evolutionarily conserved small protein and is a normal constituent of plasma. Levels of UB are increased in the plasma during a variety of pathological conditions, including ischemic heart disease. Treatment of mice with UB associates with decreased inflammatory response and improved heart function following ischemia/reperfusion injury. This review summarizes the role of macrophages in the infarct healing process of the heart post-MI, and discusses the role of exogenous UB in myocardial remodeling post-MI and in the modulation of macrophage phenotype and function.

Application of locally responsive design of biomaterials based on microenvironmental changes in myocardial infarction

Morbidity and mortality caused by acute myocardial infarction (AMI) are on the rise, posing a grave threat to the health of the general population. Up to now, interventional, surgical, and pharmaceutical therapies have been the main treatment methods for AMI. Effective and timely reperfusion therapy decreases mortality, but it cannot stimulate myocardial cell regeneration or reverse ventricular remodeling. Cell therapy, gene therapy, immunotherapy, anti-inflammatory therapy, and several other techniques are utilized by researchers to improve patients' prognosis. In recent years, biomaterials for AMI therapy have become a hot spot in medical care. Biomaterials furnish a microenvironment conducive to cell growth and deliver therapeutic factors that stimulate cell regeneration and differentiation. Biomaterials adapt to the complex microenvironment and respond to changes in local physical and biochemical conditions. Therefore, environmental factors and material properties must be taken into account when designing biomaterials for the treatment of AMI. This article will review the factors that need to be fully considered in the design of biological materials.

hESC-Derived Epicardial Cells Promote Repair of Infarcted Hearts in Mouse and Swine

Myocardial infarction (MI) causes excessive damage to the myocardium, including the epicardium. However, whether pluripotent stem cell-derived epicardial cells (EPs) can be a therapeutic approach for infarcted hearts remains unclear. Here, the authors report that intramyocardial injection of human embryonic stem cell-derived EPs (hEPs) at the acute phase of MI ameliorates functional worsening and scar formation in mouse hearts, concomitantly with enhanced cardiomyocyte survival, angiogenesis, and lymphangiogenesis. Mechanistically, hEPs suppress MI-induced infiltration and cytokine-release of inflammatory cells and promote reparative macrophage polarization. These effects are blocked by a type I interferon (IFN-I) receptor agonist RO8191. Moreover, intelectin 1 (ITLN1), abundantly secreted by hEPs, interacts with IFN-β and mimics the effects of hEP-conditioned medium in suppression of IFN-β-stimulated responses in macrophages and promotion of reparative macrophage polarization, whereas ITLN1 downregulation in hEPs cancels beneficial effects of hEPs in anti-inflammation, IFN-I response inhibition, and cardiac repair. Further, similar beneficial effects of hEPs are observed in a clinically relevant porcine model of reperfused MI, with no increases in the risk of hepatic, renal, and cardiac toxicity. Collectively, this study reveals hEPs as an inflammatory modulator in promoting infarct healing via a paracrine mechanism and provides a new therapeutic approach for infarcted hearts.

Phloretin ameliorates heart function after myocardial infarction via NLRP3/Caspase-1/IL-1β signaling

OBJECTIVES/AIMS

Inflammation is crucial in structural and electrical remodeling after myocardial infarction (MI), affecting cardiac pump function and conduction pathways. Phloretin possesses an anti-inflammation role by inhibiting the NLRP3/Caspase-1/IL-1β pathway. However, the effects of Phloretin on cardiac contractile and electrical conduction function after MI remained unclear. Therefore, we aimed to investigate the potential role of Phloretin in a rat model of MI.

METHODS

Rats were assigned into four groups: Sham, Sham+Phloretin, MI and MI+Phloretin, with ad libitum food and water. In the MI and MI+Phloretin groups, the left anterior descending coronary artery was occluded for 4 weeks, while the Sham and Sham+Phloretin groups received sham operation. The Sham+Phloretin group and the MI+Phloretin group received oral administration of Phloretin. In vitro, H9c2 cells were subjected to hypoxic conditions to simulate an MI model, with Phloretin for 24 h. Cardiac electrophysiological properties were assessed following MI, including the effective refractory period (ERP), action potential duration (APD)90 and ventricular fibrillation (VF) incidence. Echocardiography evaluated left ventricular ejection fraction (LVEF), left ventricular fraction shortening (LVFS), left ventricular internal diameter at end-diastole (LVIDd), left ventricular internal diameter at end-systole (LVIDs), left ventricular end-systolic volume (LVESV) and left ventricular end-diastolic volume (LVEDV) to assess cardiac function. Serum type B natriuretic peptide (BNP) level was applied to evaluate the degree of Heart failure (HF). The fibrosis area and severity were assessed by Masson staining and protein expression levels of collagen 3, collagen 1, TGF-β and α-SMA. Western blot analysis estimated the protein expression levels of NLRP3, Pro Caspase-1, Caspase-1, ASC, IL-18, IL-1β, pp38, p38, and Connexin43(Cx43) to elucidate the influence of inflammation on electrical remodeling after MI.

RESULTS

Our findings demonstrate that Phloretin inhibits the NLRP3/Caspase-1/IL-1β pathway, leading to the upregulation of Cx43 by limiting p38 phosphorylation, which further decreases susceptibility to ventricular arrhythmias (VAs). Additionally, Phloretin attenuated fibrosis by inhibiting inflammation to prevent HF. In vitro experiments also provided strong evidence supporting the inhibitory effects of Phloretin on the NLRP3/Caspase-1/IL-1β pathway.

CONCLUSION

Our results suggest that Phloretin could suppress the NLRP3/Caspase-1/IL-1β pathway to reverse structural and electrical remodeling after MI to prevent the occurrence of VAs and HF.

Nanowired human cardiac organoid transplantation enables highly efficient and effective recovery of infarcted hearts

Human cardiac organoids hold remarkable potential for cardiovascular disease modeling and human pluripotent stem cell-derived cardiomyocyte (hPSC-CM) transplantation. Here, we show cardiac organoids engineered with electrically conductive silicon nanowires (e-SiNWs) significantly enhance the therapeutic efficacy of hPSC-CMs to treat infarcted hearts. We first demonstrated the biocompatibility of e-SiNWs and their capacity to improve cardiac microtissue engraftment in healthy rat myocardium. Nanowired human cardiac organoids were then engineered with hPSC-CMs, nonmyocyte supporting cells, and e-SiNWs. Nonmyocyte supporting cells promoted greater ischemia tolerance of cardiac organoids, and e-SiNWs significantly improved electrical pacing capacity. After transplantation into ischemia/reperfusion-injured rat hearts, nanowired cardiac organoids significantly improved contractile development of engrafted hPSC-CMs, induced potent cardiac functional recovery, and reduced maladaptive left ventricular remodeling. Compared to contemporary studies with an identical injury model, greater functional recovery was achieved with a 20-fold lower dose of hPSC-CMs, revealing therapeutic synergy between conductive nanomaterials and human cardiac organoids for efficient heart repair.

Lnc-PXMP4-2-4 alleviates myocardial cell damage by activating the JAK2/STAT3 signaling pathway

PURPOSE

The aim of this study was to investigate the protective effect of long non-coding lnc-PXMP4-2-4 on myocardial cell damage caused by acute myocardial infarction (AMI).

METHODS

Peripheral blood mononuclear cells (PBMC) were collected from 24 patients with AMI on the day of admission, the first day after percutaneous coronary intervention (PCI) and the third day after surgery, and 24 patients with clinical control group. Real-time quantitative PCR(QRT-PCR) was used to detect the expression of related genes. Then in human cardiomyocytes (AC16), Cell Counting Kit-8 (CCK-8) was used to determine cell viability, lactate dehydrogenase release assay (LDH) was used to determine the release of lactate dehydrogenase, PCR was used to detect the expression of genes, cell death was detected by flow cytometry, and the expression of related proteins was measured by Western blot. The effect of lnc-PXMP4-2-4 was further studied by silencing and overexpressing lnc-PXMP4-2-4.

RESULTS

Compared with clinical control group, the expression of lnc-PXMP4-2-4 in PBMC of AMI patients was significantly higher than it. Compared with pre-operation, the expression of lnc-PXMP4-2-4 was significantly up-regulated on day 1 after PCI, and recovered to pre-operation level on day 3 after surgery. In AC16 cells, lnc-PXMP4-2-4 inhibited the proliferation of AC16, promoted the release of LDH and increased cell death, aggravated the cardiomyocyte injury caused by H2O2, and inhibited the expression of JAK2 and STAT3 mRNA and protein. The up-regulation of lnc-PXMP-4-2-4 had the opposite effect. In addition, the inhibition of the signal pathway by JAK2/STAT3 pathway inhibitor AG490 partially weakened the enhanced viability of AC16 cells, decreased LDH release and apoptosis induced by lnc-PXMP4-2-4 overexpression, increased Bcl-2 expression and down-regulated Bax expression.

CONCLUSION

Therefore, we conclude that lnc-PXMP4-2-4 protects cardiomyocytes from injury by activating the JAK2/STAT3 signaling pathway.

Disturbance of suprachiasmatic nucleus function improves cardiac repair after myocardial infarction by IGF2-mediated macrophage transition

Suprachiasmatic nucleus (SCN) in mammals functions as the master circadian pacemaker that coordinates temporal organization of physiological processes with the environmental light/dark cycles. But the causative links between SCN and cardiovascular diseases, specifically the reparative responses after myocardial infarction (MI), remain largely unknown. In this study we disrupted mouse SCN function to investigate the role of SCN in cardiac dysfunction post-MI. Bilateral ablation of the SCN (SCNx) was generated in mice by electrical lesion; myocardial infarction was induced via ligation of the mid-left anterior descending artery (LAD); cardiac function was assessed using echocardiography. We showed that SCN ablation significantly alleviated MI-induced cardiac dysfunction and cardiac fibrosis, and promoted angiogenesis. RNA sequencing revealed differentially expressed genes in the heart of SCNx mice from D0 to D3 post-MI, which were functionally associated with the inflammatory response and cytokine-cytokine receptor interaction. Notably, the expression levels of insulin-like growth factor 2 (Igf2) in the heart and serum IGF2 concentration were significantly elevated in SCNx mice on D3 post-MI. Stimulation of murine peritoneal macrophages in vitro with serum isolated from SCNx mice on D3 post-MI accelerated the transition of anti-inflammatory macrophages, while antibody-mediated neutralization of IGF2 receptor blocked the macrophage transition toward the anti-inflammatory phenotype in vitro as well as the corresponding cardioprotective effects observed in SCNx mice post-MI. In addition, disruption of mouse SCN function by exposure to a desynchronizing condition (constant light) caused similar protective effects accompanied by elevated IGF2 expression on D3 post-MI. Finally, mice deficient in the circadian core clock genes (Ckm-cre; Bmal1f/f mice or Per1/2 double knockout) did not lead to increased serum IGF2 concentration and showed no protective roles in post-MI, suggesting that the cardioprotective effect observed in this study was mediated particularly by the SCN itself, but not by self-sustained molecular clock. Together, we demonstrate that inhibition of SCN function promotes Igf2 expression, which leads to macrophage transition and improves cardiac repair post-MI.

TFRC in cardiomyocytes promotes macrophage infiltration and activation during the process of heart failure through regulating Ccl2 expression mediated by hypoxia inducible factor-1α

BACKGROUND

Cardiac hypertrophy is an initiating link to Heart failure (HF) which still seriously endangers human health. Transferrin receptor (TFRC), which promotes iron uptake through the transferrin cycle, is essential for cardiac function. However, whether TFRC is involved in the process of pathological cardiac hypertrophy is not clear.

METHODS

Transverse aortic constriction (TAC) mouse model and mice primary cardiomyocytes treated with isoproterenol (ISO) or phenylephrine (PHE) were used to mimic cardiac hypertrophy in vivo and in vitro. Single cell RNA sequence data from heart tissues of TAC-model mice was obtained from the Gene Expression Omnibus (GEO) database, and was analyzed with R package Seurat. TFRC expression and macrophage infiltration in the heart tissue were tested by immunofluorescent staining. Macrophage polarization was detected by Flow Cytometry. TFRC expressions were detected by qRT-PCR, Western blot, and ELISA.

RESULTS

TFRC expression is increased in the pathological cardiac hypertrophy of mice model and positively associated with macrophage infiltration. Furthermore, TFRC in cardiomyocytes recruits and activates macrophages by secreting C-C motif ligand 2 (Ccl2) in the mice heart tissue with TAC surgery or in the primary cardiomyocytes stimulated with ISO or PHE to induce myocardial hypertrophy in vitro. Moreover, we find that TFRC promotes Ccl2 expression in cardiomyocytes via regulating signal transducer and activator of transcription 3 (STAT3). In addition, we find that increased TFRC expression in the HF tissue is regulated by hypoxia-inducible factor-1α (HIF-1α).

CONCLUSION

This in-depth study shows that TFRC in cardiomyocytes promotes HF development through inducing macrophage infiltration and activation via the STAT3-Ccl2 signaling, and TFRC expression in cardiomyocytes is regulated by HIF-1α during HF. This study first uncovers the role of TFRC in cardiomyocytes on macrophage infiltration and activation during HF.

Myocardial ischemia-reperfusion injury and the influence of inflammation

Acute myocardial infarction is caused by a sudden coronary artery occlusion and leads to ischemia in the corresponding myocardial territory which generally results in myocardial necrosis. Without restoration of coronary perfusion, myocardial scar formation will cause adverse remodelling of the myocardium and heart failure. Successful introduction of percutaneous coronary intervention and surgical coronary artery bypass grafting made it possible to achieve early revascularisation/reperfusion, hence limiting the ischemic zone of myocardium. However, reperfusion by itself paradoxically triggers an exacerbated and accelerated injury in the myocardium, called ischemia-reperfusion (I/R) injury. This mechanism is partially driven by inflammation through multiple interacting pathways. In this review we summarize the current insights in mechanisms of I/R injury and the influence of altered inflammation. Multiple pharmacological and interventional therapeutic strategies (ischemic conditioning) have proven to be beneficial during I/R in preclinical models but were notoriously unsuccessful upon clinical translation. In this review we focus on common mechanisms of I/R injury, altered inflammation and potential therapeutic strategies. We hypothesize that a dual approach may be of value because I/R injury patients are predestined with multiple comorbidities and systemic low-grade inflammation, which requires targeted intervention before other strategies can be fully effective.

Circulating macrophages as the mechanistic link between mosaic loss of Y-chromosome and cardiac disease

BACKGROUND

Genetics evidences have long linked mosaic loss of Y-chromosome (mLOY) in peripheral leukocytes with a wide range of male age-associated diseases. However, a lack of cellular and molecular mechanistic explanations for this link has limited further investigation into the relationship between mLOY and male age-related disease. Excitingly, Sano et al. have provided the first piece of evidence directly linking mLOY to cardiac fibrosis through mLOY enriched profibrotic transforming growth factor β1 (TGF-β1) regulons in hematopoietic macrophages along with suppressed interleukin-1β (IL-1β) proinflammatory regulons. The results of this novel finding can be extrapolated to other disease related to mLOY, such as cancer, cardiac disease, and age-related macular degeneration.

RESULTS

Sano et al. used a CRISPR-Cas9 gRNAs gene editing induced Y-chromosome ablation mouse model to assess results of a UK biobank prospective analysis implicating the Y-chromosome in male age-related disease. Using this in vivo model, Sano et al. showed that hematopoietic mLOY accelerated cardiac fibrosis and heart failure in male mice through profibrotic pathways. This process was linked to monocyte-macrophage differentiation during hematopoietic development. Mice confirmed to have mLOY in leukocytes, by loss of Y-chromosome genes Kdm5d, Uty, Eif2s3y, and Ddx3y, at similar percentages to the human population were shown to have accelerated rates of interstitial and perivascular fibrosis and abnormal echocardiograms. These mice also recovered poorly from the transverse aortic constriction (TAC) model of heart failure and developed left ventricular dysfunction at higher rates. This was attributed to aberrant proliferation of cardiac MEF-SK4 + fibroblasts promoted by mLOY macrophages enriched in profibrotic regulons and lacking in proinflammatory regulons. These pro-fibrotic macrophages localized to heart and eventually resulted in cardiac fibrosis via enhanced TGF-β1 and suppressed IL-1β signaling. Furthermore, treatment of mLOY mice with TGFβ1 neutralizing antibody was able to improve their cardiac function. This study by Sano et al. was able to provide a causative link between the known association between mLOY and male cardiac disease morbidity and mortality for the first time, and thereby provide a new target for improving human health.

CONCLUSIONS

Using a CRISPR-Cas9 induced Y-chromosome ablation mouse model, Sano et al. has proven mosaic loss of Y-chromosome in peripheral myeloid cells to have a causative effect on male mobility and mortality due to male age-related cardiac disease. They traced the mechanism of this effect to hyper-expression of the profibrotic TGF-β1 and reduced pro-inflammatory IL-1β signaling, attenuation of which could provide another potential strategy in improving outcomes against age-related diseases in men.

Behind the monocyte's mystique: uncovering their developmental trajectories and fates

Monocytes are circulating myeloid cells that are derived from dedicated progenitors in the bone marrow. Originally thought of as mere precursors for the replacement of tissue macrophages, it is increasingly clear that monocytes execute distinct effector functions and may give rise to monocyte-derived cells with unique properties from tissue-resident macrophages. Recently, the advent of novel experimental approaches such as single-cell analysis and fate-mapping tools has uncovered an astonishing display of monocyte plasticity and heterogeneity, which we believe has emerged as a key theme in the field of monocyte biology in the last decade. Monocyte heterogeneity is now recognized to develop as early as the progenitor stage through specific imprinting mechanisms, giving rise to specialized effector cells in the tissue. At the same time, monocytes must overcome their susceptibility towards cellular death to persist as monocyte-derived cells in the tissues. Environmental signals that preserve their heterogenic phenotypes and govern their eventual fates remain incompletely understood. In this review, we will summarize recent advances on the developmental trajectory of monocytes and discuss emerging concepts that contributes to the burgeoning field of monocyte plasticity and heterogeneity.

Triptolide with hepatotoxicity and nephrotoxicity used in local delivery treatment of myocardial infarction by thermosensitive hydrogel

Myocardial infarction (MI) resulting from coronary artery occlusion is the leading global cause of cardiovascular disability and mortality. Anti-inflammatory treatment plays an important role in MI treatment. Triptolide (TPL), as a Chinese medicine monomer, has a variety of biological functions, including anti-inflammatory, anti-tumor, and immunoregulation. However, it has been proved that TPL is poorly water soluble, and has clear hepatotoxicity and nephrotoxicity, which seriously limits its clinical application. Herein, we designed a long-acting hydrogel platform (TPL@PLGA@F127) for MI treatment by intramyocardial injection. First, we found that the inflammatory response and immune regulation might be the main mechanisms of TPL against MI by network pharmacology. Subsequently, we prepared the hydrogel platform (TPL@PLGA@F127) and tested its effects and toxicity on normal organs in the early stage of MI (3 days after MI-operation). The results showed that TPL@PLGA@F127 could not only promote "repair" macrophages polarization (to M2 macrophage) by day 3 after MI, but also has a long-lasting anti-inflammatory effect in the later stage of MI (28 days after MI-operation). Additionally, we proved that TPL@PLGA@F127 could attenuate the toxicity of TPL by releasing it more slowly and stably. Finally, we observed the long-term effects of TPL@PLGA@F127 on MI and found that it could improve cardiac function, depress the myocardial fibrosis and protect the cardiomyocytes. In summary, this study indicated that TPL@PLGA@F127 could not only enhance the therapeutic effects of TPL on MI, but also attenuate the hepatotoxicity and nephrotoxicity, which established a strong foundation for the clinical application of TPL for MI.

Control of the post-infarct immune microenvironment through biotherapeutic and biomaterial-based approaches

Ischemic heart failure (IHF) is a leading cause of morbidity and mortality worldwide, for which heart transplantation remains the only definitive treatment. IHF manifests from myocardial infarction (MI) that initiates tissue remodeling processes, mediated by mechanical changes in the tissue (loss of contractility, softening of the myocardium) that are interdependent with cellular mechanisms (cardiomyocyte death, inflammatory response). The early remodeling phase is characterized by robust inflammation that is necessary for tissue debridement and the initiation of repair processes. While later transition toward an immunoregenerative function is desirable, functional reorientation from an inflammatory to reparatory environment is often lacking, trapping the heart in a chronically inflamed state that perpetuates cardiomyocyte death, ventricular dilatation, excess fibrosis, and progressive IHF. Therapies can redirect the immune microenvironment, including biotherapeutic and biomaterial-based approaches. In this review, we outline these existing approaches, with a particular focus on the immunomodulatory effects of therapeutics (small molecule drugs, biomolecules, and cell or cell-derived products). Cardioprotective strategies, often focusing on immunosuppression, have shown promise in pre-clinical and clinical trials. However, immunoregenerative therapies are emerging that often benefit from exacerbating early inflammation. Biomaterials can be used to enhance these therapies as a result of their intrinsic immunomodulatory properties, parallel mechanisms of action (e.g., mechanical restraint), or by enabling cell or tissue-targeted delivery. We further discuss translatability and the continued progress of technologies and procedures that contribute to the bench-to-bedside development of these critically needed treatments.

The Role of Innate Immune Cells in Cardiac Injury and Repair: A Metabolic Perspective

PURPOSE OF REVIEW

Recent technological advances have identified distinct subpopulations and roles of the cardiac innate immune cells, specifically macrophages and neutrophils. Studies on distinct metabolic pathways of macrophage and neutrophil in cardiac injury are expanding. Here, we elaborate on the roles of cardiac macrophages and neutrophils in concomitance with their metabolism in normal and diseased hearts.

RECENT FINDINGS

Single-cell techniques combined with fate mapping have identified the clusters of innate immune cell subpopulations present in the resting and diseased hearts. We are beginning to know about the presence of cardiac resident macrophages and their functions. Resident macrophages perform cardiac homeostatic roles, whereas infiltrating neutrophils and macrophages contribute to tissue damage during cardiac injury with eventual role in repair. Prior studies show that metabolic pathways regulate the phenotypes of the macrophages and neutrophils during cardiac injury. Profiling the metabolism of the innate immune cells, especially of resident macrophages during chronic and acute cardiac diseases, can further the understanding of cardiac immunometabolism.

Polarizing Macrophage Functional Phenotype to Foster Cardiac Regeneration

There is an increasing interest in understanding the connection between the immune and cardiovascular systems, which are highly integrated and communicate through finely regulated cross-talking mechanisms. Recent evidence has demonstrated that the immune system does indeed have a key role in the response to cardiac injury and in cardiac regeneration. Among the immune cells, macrophages appear to have a prominent role in this context, with different subtypes described so far that each have a specific influence on cardiac remodeling and repair. Similarly, there are significant differences in how the innate and adaptive immune systems affect the response to cardiac damage. Understanding all these mechanisms may have relevant clinical implications. Several studies have already demonstrated that stem cell-based therapies support myocardial repair. However, the exact role that cardiac macrophages and their modulation may have in this setting is still unclear. The current need to decipher the dual role of immunity in boosting both heart injury and repair is due, at least for a significant part, to unresolved questions related to the complexity of cardiac macrophage phenotypes. The aim of this review is to provide an overview on the role of the immune system, and of macrophages in particular, in the response to cardiac injury and to outline, through the modulation of the immune response, potential novel therapeutic strategies for cardiac regeneration.

Mechanism of fibroblast growth factor 21 in cardiac remodeling

Cardiac remodeling is a basic pathological process that enables the progression of multiple cardiac diseases to heart failure. Fibroblast growth factor 21 is considered a regulator in maintaining energy homeostasis and shows a positive role in preventing damage caused by cardiac diseases. This review mainly summarizes the effects and related mechanisms of fibroblast growth factor 21 on pathological processes associated with cardiac remodeling, based on a variety of cells of myocardial tissue. The possibility of Fibroblast growth factor 21 as a promising treatment for the cardiac remodeling process will also be discussed.

IL-27 promotes cardiac fibroblast activation and aggravates cardiac remodeling post myocardial infarction

Excessive and chronic inflammation post myocardial infarction (MI) causes cardiac fibrosis and progressive ventricular remodeling, which leads to heart failure. We previously found high levels of IL-27 in the heart and serum until day 14 in murine cardiac ischemia‒reperfusion injury models. However, whether IL-27 is involved in chronic inflammation-mediated ventricular remodeling remains unclear. In the present study, we found that MI triggered high IL-27 expression in murine cardiac macrophages. The increased expression of IL-27 in serum is correlated with cardiac dysfunction and aggravated fibrosis after MI. Furthermore, the addition of IL-27 significantly activated the JAK/STAT signaling pathway in cardiac fibroblasts (CFs). Meanwhile, IL-27 treatment promoted the proliferation, migration and extracellular matrix (ECM) production of CFs induced by angiotensin II (Ang II). Collectively, high levels of IL-27 mainly produced by cardiac macrophages post MI contribute to the activation of CFs and aggravate cardiac fibrosis.

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.

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.

The phagocytic role of macrophage following myocardial infarction

Myocardial infarction (MI) is one of the cardiovascular diseases with high morbidity and mortality. MI causes large amounts of apoptotic and necrotic cells that need to be efficiently and instantly engulfed by macrophage to avoid second necrosis. Phagocytic macrophages can dampen or resolve inflammation to protect infarcted heart. Phagocytosis of macrophages is modulated by various factors including proteins, receptors, lncRNA and cytokines. A better understanding of mechanisms in phagocytosis will be beneficial to regulate macrophage phagocytosis capability towards a desired direction in cardioprotection after MI. In this review, we describe the phagocytosis effect of macrophages and summarize the latest reported signals regulating phagocytosis after MI, which will provide a new thinking about phagocytosis-dependent cardiac protection after MI.

New insights into the molecular mechanisms of SGLT2 inhibitors on ventricular remodeling

Ventricular remodeling is a pathological process of ventricular response to continuous stimuli such as pressure overload, ischemia or ischemia-reperfusion, which can lead to the change of cardiac structure and function structure, which is central to the pathophysiology of heart failure (HF) and is an established prognostic factor in patients with HF. Sodium glucose cotransporter 2 inhibitors (SGLT2i) get a new hypoglycemic drug that inhibit sodium glucose coconspirator on renal tubular epithelial cells. Recently, clinical trials increasingly and animal experiments increasingly have shown that SGLT2 inhibitors have been largely applied in the fields of cardiovascular diseases, forinstance heart failure, myocardial ischemia-reperfusion injury, myocardial infarction, atrial fibrillation, metabolic diseases such as obesity, diabetes cardiomyopathy and other diseases play a cardiovascular protective role in addition to hypoglycemic. These diseases are association with ventricular remodeling. Inhibiting ventricular remodeling can improve the readmission rate and mortality of patients with heart failure. So far, clinical trials and animal experiments demonstrate that the protective effect of SGLT2 inhibitors in the cardiovascular field is bound to inhibit ventricular remodeling. Therefore, this review briefly investigates the molecular mechanisms of SGLT2 inhibitors on ameliorating ventricular remodeling, and further explore the mechanisms of cardiovascular protection of SGLT2 inhibitors, in order to establish strategies for ventricular remodeling to prevent the progress of heart failure.

M2 Macrophage-Derived sEV Regulate Pro-Inflammatory CCR2+ Macrophage Subpopulations to Favor Post-AMI Cardiac Repair

Tissue-resident cardiac macrophage subsets mediate cardiac tissue inflammation and repair after acute myocardial infarction (AMI). CC chemokine receptor 2 (CCR2)-expressing macrophages have phenotypical similarities to M1-polarized macrophages, are pro-inflammatory, and recruit CCR2+ circulating monocytes to infarcted myocardium. Small extracellular vesicles (sEV) from CCR2̶ macrophages, which phenotypically resemble M2-polarized macrophages, promote anti-inflammatory activity and cardiac repair. Here, the authors harvested M2 macrophage-derived sEV (M2EV ) from M2-polarized bone-marrow-derived macrophages for intramyocardial injection and recapitulation of sEV-mediated anti-inflammatory activity in ischemic-reperfusion (I/R) injured hearts. Rats and pigs received sham surgery; I/R without treatment; or I/R with autologous M2EV treatment. M2EV rescued cardiac function and attenuated injury markers, infarct size, and scar size. M2EV inhibited CCR2+ macrophage numbers, reduced monocyte-derived CCR2+ macrophage recruitment to infarct sites, induced M1-to-M2 macrophage switching and promoted neovascularization. Analysis of M2EV microRNA content revealed abundant miR-181b-5p, which regulated macrophage glucose uptake, glycolysis, and mitigated mitochondrial reactive oxygen species generation. Functional blockade of miR-181b-5p is detrimental to beneficial M2EV actions and resulted in failure to inhibit CCR2+ macrophage numbers and infarct size. Taken together, this investigation showed that M2EV rescued myocardial function, improved myocardial repair, and regulated CCR2+ macrophages via miR-181b-5p-dependent mechanisms, indicating an option for cell-free therapy for AMI.

An immunometabolic patch facilitates mesenchymal stromal/stem cell therapy for myocardial infarction through a macrophage-dependent mechanism

Mesenchymal stromal/stem cells (MSCs) have emerged as a promising approach against myocardial infarction. Due to hostile hyperinflammation, however, poor retention of transplanted cells seriously impedes their clinical applications. Proinflammatory M1 macrophages, which rely on glycolysis as their main energy source, aggravate hyperinflammatory response and cardiac injury in ischemic region. Here, we showed that the administration of an inhibitor of glycolysis, 2-deoxy-d-glucose (2-DG), blocked the hyperinflammatory response within the ischemic myocardium and subsequently extended effective retention of transplanted MSCs. Mechanistically, 2-DG blocked the proinflammatory polarization of macrophages and suppressed the production of inflammatory cytokines. Selective macrophage depletion abrogated this curative effect. Finally, to avoid potential organ toxicity caused by systemic inhibition of glycolysis, we developed a novel chitosan/gelatin-based 2-DG patch that directly adhered to the infarcted region and facilitated MSC-mediated cardiac healing with undetectable side effects. This study pioneered the application of an immunometabolic patch in MSC-based therapy and provided insights into the therapeutic mechanism and advantages of this innovative biomaterial.

Targeting immunometabolism during cardiorenal injury: roles of conventional and alternative macrophage metabolic fuels

Macrophages play critical roles in mediating and resolving tissue injury as well as tissue remodeling during cardiorenal disease. Altered immunometabolism, particularly macrophage metabolism, is a critical underlying mechanism of immune dysfunction and inflammation, particularly in individuals with underlying metabolic abnormalities. In this review, we discuss the critical roles of macrophages in cardiac and renal injury and disease. We also highlight the roles of macrophage metabolism and discuss metabolic abnormalities, such as obesity and diabetes, which may impair normal macrophage metabolism and thus predispose individuals to cardiorenal inflammation and injury. As the roles of macrophage glucose and fatty acid metabolism have been extensively discussed elsewhere, we focus on the roles of alternative fuels, such as lactate and ketones, which play underappreciated roles during cardiac and renal injury and heavily influence macrophage phenotypes.

Characteristics, prognostic determinants of monocytes, macrophages and T cells in acute coronary syndrome: protocol for a multicenter, prospective cohort study

BACKGROUND

Acute coronary syndrome(ACS) is the leading cause of mortality and disability worldwide. Immune response has been confirmed to play a vital role in the occurrence and development of ACS. The objective of this prospective, multicenter, observational study is to define immune response and their relationship to the occurrence and progressive of ACS.

METHODS

This is a multicenter, prospective, observational longitudinal cohort study. The primary outcome is the incidence of major adverse cardiovascular events (MACE) including in-stent restenosis, severe ventricular arrhythmia, heart failure, recurrent angina pectoris, and sudden cardiac death, and stroke one year later after ACS. Demographic characteristics, clinical data, treatments, and outcomes are collected by local investigators. Furthermore, freshly processed samples will be stained and assessed by flow cytometry. The expression of S100A4, CD47, SIRPα and Tim-3 on monocytes, macrophages and T cells in ACS patients were collected.

FOLLOW-UP

during hospitalization, 3, 6 and 12 months after discharge.

DISCUSSION

It is expected that this study will reveal the possible targets to improve the prognosis or prevent from occurrence of MACE in ACS patients. Since it's a multicenter study, the enrollment rate of participants will be accelerated and it can ensure that the collected data are more symbolic and improve the richness and credibility of the test basis.

ETHICS AND DISSEMINATION

This study has been registered in Chinese Clinical Trial Registry Center. Ethical approval was obtained from the Affiliated Hospital of Guizhou Medical University. The dissemination will occur through the publication of articles in international peer-reviewed journals.

TRIAL REGISTRATION

Chinese Clinical Trial Registry: ChiCTR2200066382.

Cardiac Reverse Remodeling in Ischemic Heart Disease with Novel Therapies for Heart Failure with Reduced Ejection Fraction

Despite the improvements in the treatment of coronary artery disease (CAD) and acute myocardial infarction (MI) over the past 20 years, ischemic heart disease (IHD) continues to be the most common cause of heart failure (HF). In clinical trials, over 70% of patients diagnosed with HF had IHD as the underlying cause. Furthermore, IHD predicts a worse outcome for patients with HF, leading to a substantial increase in late morbidity, mortality, and healthcare costs. In recent years, new pharmacological therapies have emerged for the treatment of HF, such as sodium-glucose cotransporter-2 inhibitors, angiotensin receptor-neprilysin inhibitors, selective cardiac myosin activators, and oral soluble guanylate cyclase stimulators, demonstrating clear or potential benefits in patients with HF with reduced ejection fraction. Interventional strategies such as cardiac resynchronization therapy, cardiac contractility modulation, or baroreflex activation therapy might provide additional therapeutic benefits by improving symptoms and promoting reverse remodeling. Furthermore, cardiac regenerative therapies such as stem cell transplantation could become a new therapeutic resource in the management of HF. By analyzing the existing data from the literature, this review aims to evaluate the impact of new HF therapies in patients with IHD in order to gain further insight into the best form of therapeutic management for this large proportion of HF patients.

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.

CTRP1: A novel player in cardiovascular and metabolic diseases

Cardiovascular diseases (CVDs) are a series of diseases induced by inflammation and lipid metabolism disorders, among others. Metabolic diseases can cause inflammation and abnormal lipid metabolism. C1q/TNF-related proteins 1 (CTRP1) is a paralog of adiponectin that belongs to the CTRP subfamily. CTRP1 is expressed and secreted in adipocytes, macrophages, cardiomyocytes, and other cells. It promotes lipid and glucose metabolism but has bidirectional effects on the regulation of inflammation. Inflammation can also inversely stimulate CTRP1 production. A vicious circle may exist between the two. This article introduces CTRP1 from the structure, expression, and different roles of CTRP1 in CVDs and metabolic diseases, to summarize the role of CTRP1 pleiotropy. Moreover, the proteins which may interact with CTRP1 are predicted through GeneCards and STRING, speculating their effects, to provide new ideas for the study of CTRP1.

Transcriptional regulation of macrophages in heart failure

Adverse cardiac remodeling after acute myocardial infarction is the most important pathological mechanism of heart failure and remains a major problem in clinical practice. Cardiac macrophages, derived from tissue resident macrophages and circulating monocyte, undergo significant phenotypic and functional changes following cardiac injury and play crucial roles in inflammatory response and tissue repair response. Currently, numerous studies indicate that epigenetic regulatory factors and transcription factors can regulate the transcription of inflammatory and reparative genes and timely conversion of inflammatory macrophages into reparative macrophages and then alleviate cardiac remodeling. Accordingly, targeting transcriptional regulation of macrophages may be a promising option for heart failure treatment. In this review, we not only summarize the origin and function of cardiac macrophages, but more importantly, describe the transcriptional regulation of macrophages in heart failure, aiming to provide a potential therapeutic target for heart failure.

The Protective Role of TREM2 in the Heterogenous Population of Macrophages during Post-Myocardial Infarction Inflammation

Advances in interventions after myocardial infarction (MI) have dramatically increased survival, but MI remains the leading cause of heart failure due to maladaptive ventricular remodeling following ischemic damage. Inflammation is crucial in both the initial response to ischemia and subsequent wound healing in the myocardium. To date, preclinical and clinical efforts have been made to elucidate the deleterious effects of immune cells contributing to ventricular remodeling and to identify therapeutic molecular targets. The conventional concept classifies macrophages or monocytes into dichotomous populations, while recent studies support their diverse subpopulations and spatiotemporal dynamicity. The single-cell and spatial transcriptomic landscapes of macrophages in infarcted hearts successfully revealed the heterogeneity of cell types and their subpopulations post-MI. Among them, subsets of Trem2hi macrophages were identified that were recruited to infarcted myocardial tissue in the subacute phase of MI. The upregulation of anti-inflammatory genes was observed in Trem2hi macrophages, and an in vivo injection of soluble Trem2 during the subacute phase of MI significantly improved myocardial function and the remodeling of infarcted mice hearts, suggesting the potential therapeutic role of Trem2 in LV remodeling. Further investigation of the reparative role of Trem2 in LV remodeling would provide novel therapeutic targets for MI.

Ginaton reduces M1-polarized macrophages in hypertensive cardiac remodeling via NF-κB signaling

Introduction: Macrophages play a critical role in cardiac remodeling, and dysregulated macrophage polarization between the proinflammatory M1 and anti-inflammatory M2 phenotypes promotes excessive inflammation and cardiac damage. Ginaton is a natural extract extracted from Ginkgo biloba. Because of its anti-inflammatory properties, it has long been used to treat a variety of diseases. However, the role of Ginaton in modulating the diverse macrophage functional phenotypes brought on by Ang II-induced hypertension and cardiac remodeling is unknown.

Methods: In the present study, we fed C57BL/6J mice in the age of eight weeks with Ginaton (300 mg/kg/day) or PBS control, and then injected Ang II (1000 ng/kg/min) or saline for 14 days to investigate the specific efficacy of Ginaton. Systolic blood pressure was recorded, cardiac function was detected by echocardiography, and pathological changes in cardiac tissue were assessed by histological staining. Different functional phenotypes of the macrophages were assessed by immunostaining. The mRNA expression of genes was assessed by qPCR analysis. Protein levels were detected by immunoblotting.

Results: Our results showed that Ang II infusion significantly enhanced the activation and infiltration of macrophages with hypertension, cardiac insufficiency, myocardial hypertrophy, fibrosis and M1 phenotype macrophages compared with the saline group. Instead, Ginaton attenuated these effects. In addition, in vitro experiments showed that Ginaton inhibited Ang II-induced activation, adhesion and migration of M1 phenotype macrophages.

Conclusion: Our study showed that Ginaton treatment inhibits Ang II-induced M1 phenotype macrophage activation, macrophage adhesion, and mitigation, as well as the inflammatory response leading to impaired and dysfunctional hypertension and cardiac remodeling. Gianton may be a powerful treatment for heart disease.

Activating α7nAChR helps post-myocardial infarction healing by regulating macrophage polarization via the STAT3 signaling pathway

BACKGROUND

Monocytes/macrophages play critical roles in inflammation and cardiac remodeling following myocardial infarction (MI). The cholinergic anti-inflammatory pathway (CAP) modulates local and systemic inflammatory responses by activating α7 nicotinic acetylcholine receptors (α7nAChR) in monocytes/macrophages. We investigated the effect of α7nAChR on MI-induced monocyte/macrophage recruitment and polarization and its contribution to cardiac remodeling and dysfunction.

METHODS

Adult male Sprague Dawley rats underwent coronary ligation and were intraperitoneally injected with the α7nAChR-selective agonist PNU282987 or the antagonist methyllycaconitine (MLA). RAW264.7 cells were stimulated with lipopolysaccharide (LPS) + interferon-gamma (IFN-γ) and treated with PNU282987, MLA, and S3I-201 (a STAT3 inhibitor). Cardiac function was evaluated by echocardiography. Masson's trichrome and immunofluorescence were used to detect cardiac fibrosis, myocardial capillary density, and M1/M2 macrophages. Western blotting was used to detect protein expression, and the proportion of monocytes was measured using flow cytometry.

RESULTS

Activating the CAP with PNU282987 significantly improved cardiac function and reduced cardiac fibrosis and 28-day mortality after MI. On days 3 and 7 post-MI, PNU282987 reduced the percentage of peripheral CD172a + CD43low monocytes and the infiltration of M1 macrophages in the infarcted hearts, whereas it increased the recruitment of peripheral CD172a + CD43high monocytes and M2 macrophages. Conversely, MLA exerted the opposite effects. In vitro, PNU282987 inhibited M1 macrophage polarization and promoted M2 macrophage polarization in LPS + IFN-γ-stimulated RAW264.7 cells. These PNU282987-induced changes in LPS + IFN-γ-stimulated RAW264.7 cells were reversed by administering S3I-201.

CONCLUSION

Activating α7nAChR inhibits the early recruitment of pro-inflammatory monocytes/macrophages during MI and improves cardiac function and remodeling. Our findings suggest a promising therapeutic target for regulating monocyte/macrophage phenotypes and promoting healing after MI.

High-resolution mapping of sensory fibers at the healthy and post-myocardial infarct whole transgenic hearts

The sensory nervous system is critical to maintain cardiac function. As opposed to efferent innervation, less is known about cardiac afferents. For this, we mapped the VGLUT2-expressing cardiac afferent fibers of spinal and vagal origin by using the VGLUT2::tdTomato double transgenic mouse as an approach to visualize the whole hearts both at the dorsal and ventral sides. For comparison, we colabeled mixed-sex transgenic hearts with either TUJ1 protein for global cardiac innervation or tyrosine hydroxylase for the sympathetic network at the healthy state or following ischemic injury. Interestingly, the nerve density for global and VGLUT2-expressing afferents was found significantly higher on the dorsal side compared to the ventral side. From the global nerve innervation detected by TUJ1 immunoreactivity, VGLUT2 afferent innervation was detected to be 15-25% of the total network. The detailed characterization of both the atria and the ventricles revealed a remarkable diversity of spinal afferent nerve ending morphologies of flower sprays, intramuscular endings, and end-net branches that innervate distinct anatomical parts of the heart. Using this integrative approach in a chronic myocardial infarct model, we showed a significant increase in hyperinnervation in the form of axonal sprouts for cardiac afferents at the infarct border zone, as well as denervation at distal sites of the ischemic area. The functional and physiological consequences of the abnormal sensory innervation remodeling post-ischemic injury should be further evaluated in future studies regarding their potential contribution to cardiac dysfunction.

Ultrasonic Microbubble Cavitation Deliver Gal-3 shRNA to Inhibit Myocardial Fibrosis after Myocardial Infarction

Galectin-3 (Gal-3) participates in myocardial fibrosis (MF) in a variety of ways. Inhibiting the expression of Gal-3 can effectively interfere with MF. This study aimed to explore the value of Gal-3 short hairpin RNA (shRNA) transfection mediated by ultrasound-targeted microbubble destruction (UTMD) in anti-myocardial fibrosis and its mechanism. A rat model of myocardial infarction (MI) was established and randomly divided into control and Gal-3 shRNA/cationic microbubbles + ultrasound (Gal-3 shRNA/CMBs + US) groups. Echocardiography measured the left ventricular ejection fraction (LVEF) weekly, and the heart was harvested to analyze fibrosis, Gal-3, and collagen expression. LVEF in the Gal-3 shRNA/CMB + US group was improved compared with the control group. On day 21, the myocardial Gal-3 expression decreased in the Gal-3 shRNA/CMBs + US group. Furthermore, the proportion of the myocardial fibrosis area in the Gal-3 shRNA/CMBs + US group was 6.9 ± 0.41% lower than in the control group. After inhibition of Gal-3, there was a downregulation in collagen production (collagen I and III), and the ratio of Col I/Col III decreased. In conclusion, UTMD-mediated Gal-3 shRNA transfection can effectively silence the expression of Gal-3 in myocardial tissue, reduce myocardial fibrosis, and protect the cardiac ejection function.

NEDD4 ameliorates myocardial reperfusion injury by preventing macrophages pyroptosis

OBJECTIVES

The inflammatory cascade and cell death post-myocardial ischemia reperfusion (MI/R) are very complex. Despite the understanding that macrophage inflammation has a pivotal role in the pathophysiology of MI/R, the contribution of macrophage inflammatory signals in tailoring the function of vascular endothelium remains unknown.

MATERIALS AND METHODS

In the present study, we analyzed the effects of NEDD4 on the NLRP3 inflammasome activation-mediated pyroptosis in vitro after an acute pro-inflammatory stimulus and in vivo in a MI/R mouse model. TTC and Evan's blue dye, Thioflavin S, immunohistochemistry staining, and ELISA were performed in wild-type and NEDD4 deficiency mice. THP-1 cells were transfected with si-NEDD4 or si-SF3A2. HEK293T cells were transfected with NEDD4 or SF3A2 overexpression plasmid. ELISA analyzed the inflammatory cytokines in the cell supernatant. The levels of NEDD4, SF3A2, and NLRP3/GSDMD pathway were determined by Western blot. Protein interactions were evaluated by immunoprecipitation. The protein colocalization in cells was monitored using a fluorescence microscope.

RESULTS

NEDD4 inhibited NLRP3 inflammasome activation and pyroptosis in THP-1 cells treated with lipopolysaccharide (LPS) and nigericin (Nig). Mechanistically, NEDD4 maintained the stability of NLRP3 through direct interaction with the SF3A2, whereas the latter association with NLRP3 indirectly interacted with NEDD4 promoting proteasomal degradation of NLRP3. Deletion of NLRP3 expression further inhibited the caspase cascade to induce pyroptosis. Interestingly, inhibiting NLRP3 inflammasome activation in THP-1 cells could prevent cardiac microvascular endothelial cells (CMECs) injury. In addition, NEDD4 deficiency decreased animal survival and increased myocardial infarct size, no-reflow area, and promoted macrophages infiltration post-MI/R.

CONCLUSIONS

NEDD4 could be a potential therapeutic target in microvascular injury following myocardial reperfusion. Video Abstract.

Single-cell transcriptome sequencing of macrophages in common cardiovascular diseases

Macrophages are strategically located throughout the body at key sites in the immune system. A key feature in atherosclerosis is the uptake and accumulation of lipoproteins by arterial macrophages, leading to the formation of foam cells. After myocardial infarction, macrophages derived from monocytes infiltrate the infarcted heart. Macrophages are also closely related to adverse remodeling after heart failure. An in-depth understanding of the functions and characteristics of macrophages is required to study heart health and pathophysiological processes; however, the heterogeneity and plasticity explained by the classic M1/M2 macrophage paradigm are too limited. Single-cell sequencing is a high-throughput sequencing technique that enables the sequencing of the genome or transcriptome of a single cell. It effectively complements the heterogeneity of gene expression in a single cell that is ignored by conventional sequencing and can give valuable insights into the development of complex diseases. In the present review, we summarize the available research on the application of single-cell transcriptome sequencing to study the changes in macrophages during common cardiovascular diseases, such as atherosclerosis, myocardial infarction, and heart failure. This article also discusses the contribution of this knowledge to understanding the pathogenesis, development, diagnosis, and treatment of heart diseases.

Propionate alleviated post-infarction cardiac dysfunction by macrophage polarization in a rat model

BACKGROUND

The propionate (C3), the important components of short-chain fatty acids (SCFAs), had the effect of inhibiting pro-inflammatory macrophages. Earlier macrophages phenotypic transition from pro-inflammatory M1 to reparative M2 in early stage was a central juncture of cardiac dysfunction mitigation after myocardial infarction (MI).

METHODS

160 Sprague-Dawley rats were assigned to 4 groups: sham group (n = 40), sham + C3 group (n = 40), MI group (n = 40) and MI + C3 group (n = 40). The rats in sham + C3 and MI + C3 group were treated with oral sodium propionate (200 mM), and equivalent concentration of sodium chloride was administered in sham and MI group as control. After 7 days of propionate adaptive feeding, rats were anesthetized and induced the MI by coronary occlusion. The classification of macrophages, the level of inflammatory factors and inflammatory signaling were estimated at 3rd days after thoracotomy, and the extent of myocardial fibrosis was evaluated at 7th and 28th days after operation. Echocardiography was estimated on 28th day after surgery. RAW264.7 cells, stimulated by LPS + IFN-γ with or without propionate, were harvested for western blot and supernatants were collected for cytokine analysis by ELISA.

RESULTS

Propionate administration reduced the MI-induced myocardial fibrosis in infarcted border and attenuated cardiac function deterioration compared with MI group. In comparison with MI group, propionate promoted macrophages reduction, macrophage M2-like polarization, and inflammatory cytokines decrease in infarcted border zone following MI, which partly depends on the inhibition of JNK/P38/NFκB signaling pathways.

CONCLUSIONS

Oral propionate in early stage, as a nutritional intervention, alleviated post-MI chronic cardiac remodeling and cardiac dysfunction at least in part by modulating macrophages polarization and pro-inflammatory cytokine, which were associated with reduction of JNK/P38/NFκB phosphorylation.

The role of serial cardiac biomarkers in prognostication and risk prediction of chronic heart failure: additional scientific insights with hemodynamic feedback

INTRODUCTION

Heart failure (HF) is considered as a chronic long-term and lethal disease and will continue to be a major public health problem. Studying (circulating) biomarkers is a promising field of research and could be the first step toward HF tailored prognostic strategies as well as understanding the response to HF drugs in CHF patients.

AREAS COVERED

In literature, there has been considerable research on elevated biomarker levels that are related to a poor prognosis for HF. Since biomarker levels change over time, it is important to study serial (repeated) biomarker measurements which may help us better understand the dynamic course of HF illness. However, the majority of research focuses predominantly on baseline values of biomarkers. Additionally, remote monitoring devices, like sensors, can be used to link hemodynamic information to freshen biomarker data in order to further ameliorate the management of HF.

EXPERT OPINION

Novel biomarkers and additional scientific insights with hemodynamic feedback strongly aid in the prognostication and risk prediction of chronic HF.

Blood Milieu in Acute Myocardial Infarction Reprograms Human Macrophages for Trauma Repair

Acute myocardial infarction (AMI) is accompanied by a systemic trauma response that impacts the whole body, including blood. This study addresses whether macrophages, key players in trauma repair, sense and respond to these changes. For this, healthy human monocyte-derived macrophages are exposed to 20% human AMI (n = 50) or control (n = 20) serum and analyzed by transcriptional and multiparameter functional screening followed by network-guided data interpretation and drug repurposing. Results are validated in an independent cohort at functional level (n = 47 AMI, n = 25 control) and in a public dataset. AMI serum exposure results in an overt AMI signature, enriched in debris cleaning, mitosis, and immune pathways. Moreover, gene networks associated with AMI and with poor clinical prognosis in AMI are identified. Network-guided drug screening on the latter unveils prostaglandin E2 (PGE2) signaling as target for clinical intervention in detrimental macrophage imprinting during AMI trauma healing. The results demonstrate pronounced context-induced macrophage reprogramming by the AMI systemic environment, to a degree decisive for patient prognosis. This offers new opportunities for targeted intervention and optimized cardiovascular disease risk management.

Monocytes presenting a pro-inflammatory profile persist in patients submitted to a long-term pharmacological treatment after acute myocardial infarction

Introduction: Although it is broadly known that monocyte recruitment is involved in atherosclerosis development and that, in accordance with the microenvironment, these cells can be modulated into three well-known subpopulations: Classical (CD14++CD16-), intermediate (CD14++CD16+), and non-classical (CD14+CD16++), the effects of treatment with different pharmacological strategies (based on lipid-lowering and antiplatelets) after acute myocardial infarction upon the monocytes modulation and the role of the chemokine receptors CCR2, CCR5 and CX3CR1 in this context, are poorly understood. Methods: In this study, patients [n = 148, both men (n = 105, 71%) and women (n = 43, 29%)] submitted to treatment with a 2×2 factorial design, in which they received rosuvastatin 20 mg or simvastatin 40 mg plus ezetimibe 10 mg, as well as ticagrelor 90 mg or clopidogrel 75 mg were enrolled. Monocyte subsets were analyzed by flow cytometry at baseline (BL), and after one (1-M) and 6 months (6-M) of treatment. Results: Firstly, our results showed that, regardless of the treatment received, higher percentages of classical monocytes and lower of non-classical monocytes were found at the 6-M time point than BL values, whilst the percentage of intermediate monocytes was higher in all time points assessed than the other subsets. There were reductions in the CCR2 expression by non-classical and intermediate monocytes, without differences for the classical subtype. Concerning the CCR5 expression, there were reductions in the three monocyte subtypes, whereas the CX3CR1 expression increased both in intermediate and classical monocytes, without differences for non-classical monocytes. In relation to the treatment received, a higher percentage of intermediate monocytes at the 6-M time point than the values BL was observed in the group treated with simvastatin + ezetimibe + clopidogrel. No significant differences were found concerning non-classical, intermediate, and classical monocytes, for CCR2, CCR5, and CX3CR1 in the four treatment arms. Conclusion: Taken together, our results demonstrated that even under lipid-lowering and antiplatelet therapy for 6 months, the inflammatory phenotype of monocytes still persisted in the patients enrolled in this study.

Scavenger Receptors in Myocardial Infarction and Ischemia/Reperfusion Injury: The Potential for Disease Evaluation and Therapy

Scavenger receptors (SRs) are a structurally heterogeneous superfamily of evolutionarily conserved receptors that are divided into classes A to J. SRs can recognize multiple ligands, such as modified lipoproteins, damage-associated molecular patterns, and pathogen-associated molecular patterns, and regulate lipid metabolism, immunity, and homeostasis. According to the literature, SRs may play a critical role in myocardial infarction and ischemia/reperfusion injury, and the soluble types of SRs may be a series of promising biomarkers for the diagnosis and prognosis of patients with acute coronary syndrome or acute myocardial infarction. In this review, we briefly summarize the structure and function of SRs and discuss the association between each SR and ischemic cardiac injury in patients and animal models in detail. A better understanding of the effect of SRs on ischemic cardiac injury will inspire novel ideas for therapeutic drug discovery and disease evaluation in patients with myocardial infarction.

Cardiac repair after myocardial infarction: A two-sided role of inflammation-mediated

Myocardial infarction is the leading cause of death and disability worldwide, and the development of new treatments can help reduce the size of myocardial infarction and prevent adverse cardiovascular events. Cardiac repair after myocardial infarction can effectively remove necrotic tissue, induce neovascularization, and ultimately replace granulation tissue. Cardiac inflammation is the primary determinant of whether beneficial cardiac repair occurs after myocardial infarction. Immune cells mediate inflammatory responses and play a dual role in injury and protection during cardiac repair. After myocardial infarction, genetic ablation or blocking of anti-inflammatory pathways is often harmful. However, enhancing endogenous anti-inflammatory pathways or blocking endogenous pro-inflammatory pathways may improve cardiac repair after myocardial infarction. A deficiency of neutrophils or monocytes does not improve overall cardiac function after myocardial infarction but worsens it and aggravates cardiac fibrosis. Several factors are critical in regulating inflammatory genes and immune cells' phenotypes, including DNA methylation, histone modifications, and non-coding RNAs. Therefore, strict control and timely suppression of the inflammatory response, finding a balance between inflammatory cells, preventing excessive tissue degradation, and avoiding infarct expansion can effectively reduce the occurrence of adverse cardiovascular events after myocardial infarction. This article reviews the involvement of neutrophils, monocytes, macrophages, and regulatory T cells in cardiac repair after myocardial infarction. After myocardial infarction, neutrophils are the first to be recruited to the damaged site to engulf necrotic cell debris and secrete chemokines that enhance monocyte recruitment. Monocytes then infiltrate the infarct site and differentiate into macrophages and they release proteases and cytokines that are harmful to surviving myocardial cells in the pre-infarct period. As time progresses, apoptotic neutrophils are cleared, the recruitment of anti-inflammatory monocyte subsets, the polarization of macrophages toward the repair phenotype, and infiltration of regulatory T cells, which secrete anti-inflammatory factors that stimulate angiogenesis and granulation tissue formation for cardiac repair. We also explored how epigenetic modifications regulate the phenotype of inflammatory genes and immune cells to promote cardiac repair after myocardial infarction. This paper also elucidates the roles of alarmin S100A8/A9, secreted frizzled-related protein 1, and podoplanin in the inflammatory response and cardiac repair after myocardial infarction.