Crosstalk Between Cardiac Cells and Macrophages Postmyocardial Infarction: Insights from In Vitro Studies

Cardiomyocyte-derived Galectin-9 induces macrophage M2 polarization via the TIM3 pathway to attenuate myocardial remodeling post-myocardial infarction

M2 macrophages play a key role in tissue repair during the late stages of myocardial infarction (MI). This study highlights the influence of cardiomyocyte-derived Galectin-9 on macrophage function post-MI. Using a murine model with left anterior descending (LAD) artery ligation, we examined the effects of Galectin-9 deficiency, exogenous Galectin-9 supplementation, and macrophage depletion on myocardial macrophage polarization and tissue remodeling. Our results showed increased Galectin-9 expression in infarcted myocardial tissue. Galectin-9 deficiency impaired cardiac recovery and reduced M2 macrophage presence in the infarcted area. Supplementation with exogenous Galectin-9 improved tissue remodeling in Galectin-9-deficient mice and increased M2 macrophage levels. However, macrophage depletion negated the benefits of Galectin-9 supplementation, exacerbating cardiac dysfunction. In vitro, Galectin-9 enhanced the M2 phenotype in macrophage-like RAW264.7 cells after hypoxic preconditioning of cardiomyocytes. This effect was diminished when cardiomyocytes lacked Galectin-9. TIM3 knockdown in RAW264.7 cells reversed the M2 polarization induced by recombinant Galectin-9 and inhibited the PI3K/Akt signaling pathway. These findings suggest that injured cardiomyocytes release Galectin-9 after MI, which binds to TIM3 on macrophages, activating the PI3K/Akt pathway to promote M2 polarization. This cardiomyocyte-macrophage interaction mitigates myocardial remodeling and helps preserve cardiac function after MI.

Cardiac fibroblast-derived mitochondria-enriched sEVs regulate tissue inflammation and ventricular remodeling post-myocardial infarction through NLRP3 pathway

Resident cardiac fibroblasts (CFs) play crucial roles in sensing injury signals and regulating inflammatory responses post-myocardial infarction (MI). Damaged mitochondria can be transferred extracellularly via various mechanisms, including extracellular vesicles (EVs). In this study, we aimed to investigate whether CFs could transfer damaged mitochondrial components via small EVs (sEVs) and elucidate their role in regulating inflammatory responses post-MI. Left anterior descending coronary artery ligation was performed in mice. Mitochondrial components in sEVs were detected using nanoflow cytometry. Differential protein expression in sEVs from normoxia and normoglycemia CFs (CFs-Nor-sEVs) and CFs post oxygen-glucose deprivation (CFs-OGD-sEVs) was identified using label-free proteomics. CFs-sEVs were co-cultured with mouse bone marrow-derived macrophages (BMDMs) to assess macrophage inflammatory responses. Effects of intramyocardial injection of CFs-sEVs were assessed in MI mice in the absence or presence of NLRP3 inhibitor CY-09. Results demonstrated that mitochondrial components were detected in CFs-derived sEVs post-MI. Damaged mitochondrial components were enriched in CFs-OGD-sEVs (CFs-mt-sEVs), which promoted pro-inflammatory phenotype activation of BMDMs in vitro. Myocardial injection of CFs-mt-sEVs enhanced tissue inflammation, aggravated cardiac dysfunction, and exacerbated maladaptive ventricular remodeling post-MI in vivo. Mechanistically, above effects were achieved via activation of NLRP3 and above effects could be reversed by NLRP3 inhibitor CY-09. This study indicates that CFs could transfer damaged mitochondrial components via the sEVs post-MI, promote macrophage inflammatory activation and exacerbate maladaptive ventricular remodeling post MI by activating NLRP3. Our findings highlight the potential therapeutic effects of inhibiting CFs-mt-sEVs and NLRP3 to improve cardiac function and attenuate ventricular remodeling post-MI.

Enhancing cardiac repair post-myocardial infarction: a study on GATM/Gel hydrogel therapeutics

BACKGROUND AND PURPOSE

Significant advancements in therapeutic approaches are imperative to address the prevalent impact of myocardial infarction (MI) on morbidity and mortality rates worldwide. This study explores the therapeutic potential of GATM/Gel hydrogel, focusing on its ability to enhance cardiac repair and functionality after MI through modulation of inflammatory and repair pathways.

EXPERIMENTAL APPROACH

The effects of GATM/Gel hydrogel on cardiac recovery were studied in a murine MI model. HA-CHO and gelatin solutions were mixed in situ using a dual syringe with a static mixing needle, and the resulting hydrogel was applied directly to the epicardium during MI modeling, followed by repositioning of the heart and closure of the thorax. Comprehensive in vivo assessments-including echocardiography, electrocardiography, and histopathological analysis-were combined with molecular techniques such as RT-qPCR, Western blotting, and immunofluorescence to elucidate the underlying mechanisms. Key cellular and molecular changes were tracked, focusing on macrophage polarization, angiogenesis, and modulation of the TNF/TNFR2 signaling pathway.

KEY RESULTS

Employing the GATM/Gel hydrogel led to a substantial improvement in heart function, shown through enhanced ejection fraction and fractional shortening, and reduced infarction size compared to control groups. Mechanistically, the hydrogel promoted the polarization of anti-inflammatory M2 macrophages and stimulated angiogenesis. Moreover, treatment with GATM/Gel hydrogel altered the TNF/TNFR2 pathway, pivotal in mediating inflammatory responses and facilitating myocardial repair. The discoveries highlight the possibility of GATM/Gel hydrogels as an innovative remedy for MI, providing a twofold role in regulating inflammation and fostering recovery.

Cardiac macrophages in maintaining heart homeostasis and regulating ventricular remodeling of heart diseases

Macrophages are most important immune cell population in the heart. Cardiac macrophages have broad-spectrum and heterogeneity, with two extreme polarization phenotypes: M1 pro-inflammatory macrophages (CCR2-ly6Chi) and M2 anti-inflammatory macrophages (CCR2-ly6Clo). Cardiac macrophages can reshape their polarization states or phenotypes to adapt to their surrounding microenvironment by altering metabolic reprogramming. The phenotypes and polarization states of cardiac macrophages can be defined by specific signature markers on the cell surface, including tumor necrosis factor α, interleukin (IL)-1β, inducible nitric oxide synthase (iNOS), C-C chemokine receptor type (CCR)2, IL-4 and arginase (Arg)1, among them, CCR2+/- is one of most important markers which is used to distinguish between resident and non-resident cardiac macrophage as well as macrophage polarization states. Dedicated balance between M1 and M2 cardiac macrophages are crucial for maintaining heart development and cardiac functional and electric homeostasis, and imbalance between macrophage phenotypes may result in heart ventricular remodeling and various heart diseases. The therapy aiming at specific target on macrophage phenotype is a promising strategy for treatment of heart diseases. In this article, we comprehensively review cardiac macrophage phenotype, metabolic reprogramming, and their role in maintaining heart health and mediating ventricular remodeling and potential therapeutic strategy in heart diseases.

The Influence of Metabolic Risk Factors on the Inflammatory Response Triggered by Myocardial Infarction: Bridging Pathophysiology to Treatment

Myocardial infarction (MI) sets off a complex inflammatory cascade that is crucial for effective cardiac healing and scar formation. Yet, if this response becomes excessive or uncontrolled, it can lead to cardiovascular complications. This review aims to provide a comprehensive overview of the tightly regulated local inflammatory response triggered in the early post-MI phase involving cardiomyocytes, (myo)fibroblasts, endothelial cells, and infiltrating immune cells. Next, we explore how the bone marrow and extramedullary hematopoiesis (such as in the spleen) contribute to sustaining immune cell supply at a cardiac level. Lastly, we discuss recent findings on how metabolic cardiovascular risk factors, including hypercholesterolemia, hypertriglyceridemia, diabetes, and hypertension, disrupt this immunological response and explore the potential modulatory effects of lifestyle habits and pharmacological interventions. Understanding how different metabolic risk factors influence the inflammatory response triggered by MI and unraveling the underlying molecular and cellular mechanisms may pave the way for developing personalized therapeutic approaches based on the patient's metabolic profile. Similarly, delving deeper into the impact of lifestyle modifications on the inflammatory response post-MI is crucial. These insights may enable the adoption of more effective strategies to manage post-MI inflammation and improve cardiovascular health outcomes in a holistic manner.

LncRNA CCRR Attenuates Postmyocardial Infarction Inflammatory Response by Inhibiting the TLR Signalling Pathway

BACKGROUND

Timely and proper suppression of inflammation can effectively reduce myocardial injury and promote the postmyocardial infarction (post-MI) wound-healing process. We have previously found that cardiac conduction regulatory RNA (CCRR), a long noncoding RNA (lncRNA) transcribed by the gene located on chromosome 9, with abundant expression in the heart, elicits antiarrhythmic effects in heart failure, and this is a continuing study on the role of CCRR in MI.

METHODS

CCRR was overexpressed in CCRR transgenic mice or after injection of adeno-associated virus-9 (AAV-9). MI surgery was performed, and cardiac function was assessed in vivo by echocardiography, followed by histologic analyses. Western blot analysis and qRT-PCR were performed to investigate the effects of CCRR on macrophages, cardiomyocytes, and cardiomyocytes cocultured with macrophages. Through microarray analysis and RNA-binding protein immunoprecipitation (RIP) and other related techniques were also employed to study the effects of CCRR on Toll-like receptor (TLR)2 and TLR4.

RESULTS

We found that CCRR level was significantly decreased with increases in proinflammatory cytokines and activation of the TLR signalling pathway in the heart of the 3-day MI mice. CCRR overexpression downregulated TLR2 and TLR4 in MI and effectively inhibited the inflammatory responses in primary cardiomyocytes and macrophages cultured under hypoxic conditions. Downregulation of CCRR induced excessive inflammatory responses by activating the TLR signalling pathway. CCRR acted by suppressing TLR2 and TLR4 to inhibit the secretion of proinflammatory factors to reduce infarct size, thereby improving cardiac function.

CONCLUSIONS

CCRR protected cardiomyocytes against MI injury by suppressing inflammatory response through targeting the TLR signalling pathway.

Interferon-β decreases LPS-induced neutrophil recruitment to cardiac fibroblasts

Introduction: Cardiac fibroblasts (CF) are crucial cells in damaged heart tissues, expressing TLR4, IFN-receptor and responding to lipopolysaccharide (LPS) and interferon-β (IFN-β) respectively. While CF interact with immune cells; however, their relationship with neutrophils remains understudied. Additionally, theimpact of LPS and IFN-β on CF-neutrophil interaction is poorly understood. Methods: Isolated CF from adult rats were treated with LPS, with or without IFN-β. This study examined IL-8 secretion, ICAM-1 and VCAM-1 expression, and neutrophil recruitment, as well as their effects on MMPs activity. Results: LPS triggered increased IL-8 expression and secretion, along with elevated ICAM-1 and VCAM-1 expression, all of which were blocked by TAK-242. Pre-treatment with IFN-β countered these LPS effects. LPS treated CF showed higher neutrophil recruitment (migration and adhesion) compared to unstimulated CF, an effect prevented by IFN-β. Ruxolitinib blocked these IFN-β anti-inflammatory effects, implicating JAK signaling. Analysis of culture medium zymograms from CF alone, and CF-neutrophils interaction, revealed that MMP2 was mainly originated from CF, while MMP9 could come from neutrophils. LPS and IFN-β boosted MMP2 secretion by CF. MMP9 activity in CF was low, and LPS or IFN-β had no significant impact. Pre-treating CF with LPS, IFN-β, or both before co-culture with neutrophils increased MMP2. Neutrophil co-culture increased MMP9 activity, with IFN-β pre-treatment reducing MMP9 compared to unstimulated CF. Conclusion: In CF, LPS induces the secretion of IL-8 favoring neutrophils recruitment and these effects were blocked by IFN-. The results highlight that CF-neutrophil interaction appears to influence the extracellular matrix through MMPs activity modulation.

Construction of cardiac fibrosis for biomedical research

Cardiac remodeling is critical for effective tissue recuperation, nevertheless, excessive formation and deposition of extracellular matrix components can result in the onset of cardiac fibrosis. Despite the emergence of novel therapies, there are still no lifelong therapeutic solutions for this issue. Understanding the detrimental cardiac remodeling may aid in the development of innovative treatment strategies to prevent or reverse fibrotic alterations in the heart. Further combining the latest understanding of disease pathogenesis with cardiac tissue engineering has provided the conversion of basic laboratory studies into the therapy of cardiac fibrosis patients as an increasingly viable prospect. This review presents the current main mechanisms and the potential tissue engineering of cardiac fibrosis. Approaches using biomedical materials-based cardiac constructions are reviewed to consider key issues for simulating in vitro cardiac fibrosis, outlining a future perspective for preclinical applications.

The Characteristic of Resident Macrophages and their Therapeutic Potential for Myocardial Infarction

Resident macrophages (R-mac) are a subset of macrophages with self-renewal functions, which play a pivotal role in the homeostasis, inflammation, injury, and repair of the heart. In this paper, we summarize the knowledge related to cardiac R-mac and describe their dominating functions in myocardial infarction, such as inhibiting fibrosis and adverse remodeling, promoting revascularization and improving arrhythmia, etc. In the last, we sketch out the extended application of R-mac in tissue engineering, providing a novel direction of research and application for the therapy in the future.

The Structural and the Functional Aspects of Intercellular Communication in iPSC-Cardiomyocytes

Recent advances in the technology of producing novel cardiomyocytes from induced pluripotent stem cells (iPSC-cardiomyocytes) fuel new hope for future clinical applications. The use of iPSC-cardiomyocytes is particularly promising for the therapy of cardiac diseases such as myocardial infarction, where these cells could replace scar tissue and restore the functionality of the heart. Despite successful cardiogenic differentiation, medical applications of iPSC-cardiomyocytes are currently limited by their pronounced immature structural and functional phenotype. This review focuses on gap junction function in iPSC-cardiomyocytes and portrays our current understanding around the structural and the functional limitations of intercellular coupling and viable cardiac graft formation involving these novel cardiac muscle cells. We further highlight the role of the gap junction protein connexin 43 as a potential target for improving cell–cell communication and electrical signal propagation across cardiac tissue engineered from iPSC-cardiomyocytes. Better insight into the mechanisms that promote functional intercellular coupling is the foundation that will allow the development of novel strategies to combat the immaturity of iPSC-cardiomyocytes and pave the way toward cardiac tissue regeneration.

Mitochondrial DNA on Tumor-Associated Macrophages Polarization and Immunity

As the richest immune cells in most tumor microenvironments (TMEs), tumor-associated macrophages (TAMs) play an important role in tumor development and treatment sensitivity. The phenotypes and functions of TAMs vary according to their sources and tumor progression. Different TAM phenotypes display distinct behaviors in terms of tumor immunity and are regulated by intracellular and exogenous molecules. Additionally, dysfunctional and oxidatively stressed mitochondrial-derived mitochondrial DNA (mtDNA) plays an important role in remodeling the phenotypes and functions of TAMs. This article reviews the interactions between mtDNA and TAMs in the TME and further discusses the influence of their performance on tumor genesis and development.

Fibrin, Bone Marrow Cells and Macrophages Interactively Modulate Cardiomyoblast Fate

Interactions between macrophages, cardiac cells and the extracellular matrix are crucial for cardiac repair following myocardial infarction (MI). We hypothesized that cell-based treatments might modulate these interactions. After validating that bone marrow cells (BMC) associated with fibrin lowered the infarct extent and improved cardiac function, we interrogated the influence of fibrin, as a biologically active scaffold, on the secretome of BMC and the impact of their association on macrophage fate and cardiomyoblast proliferation. In vitro, BMC were primed with fibrin (F-BMC). RT-PCR and proteomic analyses showed that fibrin profoundly influenced the gene expression and the secretome of BMCs. Consequently, the secretome of F-BMC increased the spreading of cardiomyoblasts and showed an alleviated immunomodulatory capacity. Indeed, the proliferation of anti-inflammatory macrophages was augmented, and the phenotype of pro-inflammatory switched as shown by downregulated Nos2, Il6 and IL1b and upregulated Arg1, CD163, Tgfb and IL10. Interestingly, the secretome of F-BMC educated-macrophages stimulated the incorporation of EdU in cardiomyoblasts. In conclusion, our study provides evidence that BMC/fibrin-based treatment improved cardiac structure and function following MI. In vitro proofs-of-concept reveal that the F-BMC secretome increases cardiac cell size and promotes an anti-inflammatory response. Thenceforward, the F-BMC educated macrophages sequentially stimulated cardiac cell proliferation.

Human Placental Allograft Membranes: Promising Role in Cardiac Surgery and Repair

Despite the immense investment in research devoted to cardiovascular diseases, mechanisms of progression and potential treatments, it remains one of the leading causes of death in the world. Cellular based strategies have been explored for decades, having mixed results, while more recently inflammation and its role in healing, regeneration and disease progression has taken center stage. Placental membranes are immune privileged tissues whose native function is acting as a protective barrier during fetal development, a state which fosters regeneration and healing. Their unique properties stem from a complex composition of extracellular matrix, growth factors and cytokines involved in cellular growth, survival, and inflammation modulation. Placental allograft membranes have been used successfully in complex wound applications but their potential in cardiac wounds has only begun to be explored. Although limited, pre-clinical studies demonstrated benefits when using placental membranes compared to other standard of care options for pericardial repair or infarct wound covering, facilitating cardiomyogenesis of stem cell populations in vitro and supporting functional performance in vivo. Early clinical evidence also suggested use of placental allograft membranes as a cardiac wound covering with the potential to mitigate the predominantly inflammatory environment such as pericarditis and prevention of new onset post-operative atrial fibrillation. Together, these studies demonstrate the promising translational potential of placental allograft membranes as post-surgical cardiac wound coverings. However, the small number of publications on this topic highlights the need for further studies to better understand how to support the safe and efficient use of placenta allograft membranes in cardiac surgery.