Fibroblasts in myocardial infarction: a role in inflammation and repair

Triptolide improves myocardial fibrosis in rats through inhibition of nuclear factor kappa B and NLR family pyrin domain containing 3 inflammasome pathway

Myocardial fibrosis (MF) is the result of persistent and repeated aggravation of myocardial ischemia and hypoxia, leading to the gradual development of heart failure of chronic ischemic heart disease. Triptolide (TPL) is identified to be involved in the treatment for MF. This study aims to explore the mechanism of TPL in the treatment of MF. The MF rat model was established, subcutaneously injected with isoproterenol and treated by subcutaneous injection of TPL. The cardiac function of each group was evaluated, including LVEF, LVFS, LVES, and LVED. The expressions of ANP, BNP, inflammatory related factors (IL-1β, IL-18, TNF-α, MCP-1, VCAM-1), NLRP3 inflammasome factors (NLRP3, ASC) and fibrosis related factors (TGF-β1, COL1, and COL3) in rats were dete cted. H&E staining and Masson staining were used to observe myocardial cell inflammation and fibrosis of rats. Western blot was used to detect the p-P65 and t-P65 levels in nucleoprotein of rat myocardial tissues. LVED and LVES of MF group were significantly upregulated, LVEF and LVFS were significantly downregulated, while TPL treatment reversed these trends; TPL treatment downregulated the tissue injury and improved the pathological damage of MF rats. TPL treatment downregulated the levels of inflammatory factors and fibrosis factors, and inhibited the activation of NLRP3 inflammasome. Activation of NLRP3 inflammasome or NF-κB pathway reversed the effect of TPL on MF. Collectively, TPL inhibited the activation of NLRP3 inflammasome by inhibiting NF-κB pathway, and improved MF in MF rats.

Relation of a novel fibrosis marker and post-myocardial infarction left ventricular ejection fraction in revascularized patients

Aim: To investigate the relationship between post-myocardial infarction (MI) left ventricular ejection fraction (LVEF) and fibrosis marker HE-4 in primarily revascularized patients with ST-segment elevation MI (STEMI). Patients & methods: In 94 consecutive STEMI patients (median age 57 [IQR: 50-69] years; 77.7% male), HE-4 values were measured at hospital admission and 4 days after STEMI. Transthoracic echocardiography was performed 4 days after STEMI (median 5 days [interquartile range: 4-6]). Results: HE-4 levels 4 days after STEMI were significantly higher in the low ejection fraction group (30.1 [26.0-46.5] pmol/l vs 48.5 [32.5-85.9] pmol/l, p = 0.004). In the multivariable analysis, HE-4 values (odds ratio: 1.029, 95% CI: 1.012-1.046, p = 0.001), troponin I levels, anterior MI and diabetes mellitus were independent predictors of low LVEF after STEMI. A negative correlation existed between ΔHE-4 levels and LVEF (r: -0.337, p = 0.001). Receiver operating characteristic analysis indicated 34.01 pmol/l HE-4 at 4 days after STEMI identified patients with low LVEF (AUC = 0.707; 95% CI: 0.601-0.813; p = 0.001). Conclusion: In revascularized STEMI patients, high HE-4 levels are associated with decreased LVEF. HE-4 may represent a diagnostic marker and treatment target for patients with heart failure or left ventricular systolic dysfunction after STEMI.

Regulatory T Cells in Chronic Heart Failure

Heart failure is a global problem with high hospitalization and mortality rates. Inflammation and immune dysfunction are involved in this disease. Owing to their unique function, regulatory T cells (Tregs) have reacquired attention recently. They participate in immunoregulation and tissue repair in the pathophysiology of heart failure. Tregs are beneficial in heart by suppressing excessive inflammatory responses and promoting stable scar formation in the early stage of heart injury. However, in chronic heart failure, the phenotypes and functions of Tregs changed. They transformed into an antiangiogenic and profibrotic cell type. In this review, we summarized the functions of Tregs in the development of chronic heart failure first. Then, we focused on the interactions between Tregs and their target cells. The target cells of Tregs include immune cells (such as monocytes/macrophages, dendritic cells, T cells, and B cells) and parenchymal cells (such as cardiomyocytes, fibroblasts, and endothelial cells). Next-generation sequencing and gene editing technology make immunotherapy of heart failure possible. So, prospective therapeutic approaches based on Tregs in chronic heart failure had also been evaluated.

Dye-Mediated Photo-Oxidation Biomaterial Fixation: Analysis of Bioinductivity and Mechanical Properties of Bovine Pericardium for Use in Cardiac Surgery

Extracellular matrix bioscaffolds can influence the cardiac microenvironment and modulate endogenous cellular mechanisms. These materials can optimize cardiac surgery for repair and reconstruction. We investigated the biocompatibility and bioinductivity of bovine pericardium fixed via dye-mediated photo-oxidation on human cardiac fibroblast activity. We compared a dye-mediated photo-oxidation fixed bioscaffold to glutaraldehyde-fixed and non-fixed bioscaffolds reported in contemporary literature in cardiac surgery. Human cardiac fibroblasts from consenting patients were seeded on to bioscaffold materials to assess the biocompatibility and bioinductivity. Human cardiac fibroblast gene expression, secretome, morphology and viability were studied. Dye-mediated photo-oxidation fixed acellular bovine pericardium preserves human cardiac fibroblast phenotype and viability; and potentiates a pro-vasculogenic paracrine response. Material tensile properties were compared with biomechanical testing. Dye-mediated photo-oxidation fixed acellular bovine pericardium had higher compliance compared to glutaraldehyde-fixed bioscaffold in response to tensile force. The biocompatibility, bioinductivity, and biomechanical properties of dye-mediated photo-oxidation fixed bovine pericardium demonstrate its feasibility as a bioscaffold for use in cardiac surgery. As a fixed yet bioinductive solution, this bioscaffold demonstrates enhanced compliance and retains bioinductive properties that may leverage endogenous reparative pathways. Dye-mediated photo-oxidation fixed bioscaffold warrants further investigation as a viable tool for cardiac repair and reconstruction.

Visualization of Fibroblast Activation After Myocardial Infarction Using 68Ga-FAPI PET

AIMS

The aim of this retrospective analysis was to examine the pattern of cardiac 68Ga-fibroblast-activation protein-α inhibitor (FAPI) uptake in patients after acute myocardial infarction (AMI) using PET and to investigate its association with results of coronary angiography. We correlated FAPI uptake with biomarkers of myocardial damage including left ventricular function.

METHODS AND RESULTS

A cohort of 10 patients with no history of coronary artery disease underwent PET 18 ± 20.6 days after AMI (ST-segment elevation myocardial infarction [n = 5] and non-ST-segment elevation infarction [n = 5]), respectively. SUVmax, SUVmean, and SUVpeak of localized tracer uptake were calculated; tracer uptake volume was reported as fibroblast activation volume (FAV), with imaging data being correlated with clinical parameters. Focal FAPI uptake was observed in all patients. Average uptake at 10 minutes postinjection was 8.9 ± 4.4 (SUVmax), 7.6 ± 4.0 (SUVpeak), and 5.3 ± 2.8 (SUVmean), respectively. Affected myocardium showed a partial to complete match between tracer uptake and confirmed culprit lesion by coronary angiography in 44.4% and 55.6% of patients, respectively. A strong correlation between FAV and peak creatine kinase level (r = 0.90, P < 0.01) and inverse correlation of FAV with left ventricular function (r = -0.69, P < 0.05) was observed.

CONCLUSIONS

This analysis demonstrates in vivo visualization of fibroblast activation after AMI. The uptake area showed a very good agreement with the affected coronary territory. A strong correlation of the de novo established parameter FAV with left ventricular function and peak creatine kinase was observed. This imaging modality may provide important insights into mechanisms of structural remodeling after AMI at an early stage.

RNA sequencing indicates age-dependent shifts in the cardiac fibroblast transcriptome between fetal, neonatal, and adult developmental ages

Cardiac fibroblasts are responsible for extracellular matrix turnover and repair in the cardiac environment and serve to help facilitate immune responses. However, it is well established that they have a significant phenotypic heterogeneity with respect to location, physiological conditions, and developmental age. The goal of this study was to provide an in-depth transcriptomic profile of cardiac fibroblasts derived from rat hearts at fetal, neonatal, and adult developmental ages to ascertain variations in gene expression that may drive functional differences in these cells at these specific stages of development. We performed RNA sequencing (RNA-seq) of cardiac fibroblasts isolated from fetal, neonatal, and adult rats and compared with the rat genome. Principal component analysis of RNA-seq data suggested that data variance was predominantly due to developmental age. Differential expression and gene set enrichment analysis against Gene Ontology and Kyoto Encyclopedia of Genes and Genomes datasets indicated an array of differences across developmental ages, including significant decreases in cardiac development and cardiac function-associated genes with age and a significant increase in immune- and inflammatory-associated functions, particularly immune cell signaling and cytokine and chemokine production, with respect to increasing developmental age. These results reinforce established evidence of diverse phenotypic heterogeneity of fibroblasts with respect to developmental age. Furthermore, based on our analysis of gene expression, age-specific alterations in cardiac fibroblasts may play a crucial role in observed differences in cardiac inflammation and immune response observed across developmental ages.

Helium Conditioning Increases Cardiac Fibroblast Migration Which Effect Is Not Propagated via Soluble Factors or Extracellular Vesicles

Helium inhalation induces cardioprotection against ischemia/reperfusion injury, the cellular mechanism of which remains not fully elucidated. Extracellular vesicles (EVs) are cell-derived, nano-sized membrane vesicles which play a role in cardioprotective mechanisms, but their function in helium conditioning (HeC) has not been studied so far. We hypothesized that HeC induces fibroblast-mediated cardioprotection via EVs. We isolated neonatal rat cardiac fibroblasts (NRCFs) and exposed them to glucose deprivation and HeC rendered by four cycles of 95% helium + 5% CO2 for 1 h, followed by 1 h under normoxic condition. After 40 h of HeC, NRCF activation was analyzed with a Western blot (WB) and migration assay. From the cell supernatant, medium extracellular vesicles (mEVs) were isolated with differential centrifugation and analyzed with WB and nanoparticle tracking analysis. The supernatant from HeC-treated NRCFs was transferred to naïve NRCFs or immortalized human umbilical vein endothelial cells (HUVEC-TERT2), and a migration and angiogenesis assay was performed. We found that HeC accelerated the migration of NRCFs and did not increase the expression of fibroblast activation markers. HeC tended to decrease mEV secretion of NRCFs, but the supernatant of HeC or the control NRCFs did not accelerate the migration of naïve NRCFs or affect the angiogenic potential of HUVEC-TERT2. In conclusion, HeC may contribute to cardioprotection by increasing fibroblast migration but not by releasing protective mEVs or soluble factors from cardiac fibroblasts.

miR-4732-3p in Extracellular Vesicles From Mesenchymal Stromal Cells Is Cardioprotective During Myocardial Ischemia

Extracellular vesicles (EVs) derived from mesenchymal stromal cells (MSCs) are an emerging alternative to cell-based therapies to treat many diseases. However, the complexity of producing homogeneous populations of EVs in sufficient amount hampers their clinical use. To address these limitations, we immortalized dental pulp-derived MSC using a human telomerase lentiviral vector and investigated the cardioprotective potential of a hypoxia-regulated EV-derived cargo microRNA, miR-4732-3p. We tested the compared the capacity of a synthetic miR-4732-3p mimic with EVs to confer protection to cardiomyocytes, fibroblasts and endothelial cells against oxygen-glucose deprivation (OGD). Results showed that OGD-induced cardiomyocytes treated with either EVs or miR-4732-3p showed prolonged spontaneous beating, lowered ROS levels, and less apoptosis. Transfection of the miR-4732-3p mimic was more effective than EVs in stimulating angiogenesis in vitro and in vivo and in reducing fibroblast differentiation upon transforming growth factor beta treatment. Finally, the miR-4732-3p mimic reduced scar tissue and preserved cardiac function when transplanted intramyocardially in infarcted nude rats. Overall, these results indicate that miR-4732-3p is regulated by hypoxia and exerts cardioprotective actions against ischemic insult, with potential application in cell-free-based therapeutic strategies.

Near Complete Repair After Myocardial Infarction in Adult Mice by Altering the Inflammatory Response With Intramyocardial Injection of α-Gal Nanoparticles

Background: Neonatal mice, but not older mice, can regenerate their hearts after myocardial-infarction (MI), a process mediated by pro-reparative macrophages. α-Gal nanoparticles applied to skin wounds in adult-mice bind the anti-Gal antibody, activate the complement cascade and generate complement chemotactic peptides that recruit pro-reparative macrophages which are further activated by these nanoparticles. The recruited macrophages decrease wound healing time by ~50%, restore the normal skin structure and prevent fibrosis and scar formation in mice. Objectives: The objective of this study is to determine if α-gal nanoparticles injected into the reperfused myocardium after MI in adult-mice can induce myocardial repair that restores normal structure, similar to that observed in skin injuries. Methods and Results: MI was induced by occluding the mid-portion of the left anterior descending (LAD) coronary artery for 30 min. Immediately following reperfusion, each mouse received two 10 μl injections of 100 μg α-gal nanoparticles in saline into the LAD territory (n = 20), or saline for controls (n = 10). Myocardial infarct size was measured by planimetry following Trichrome staining and macrophage recruitment by hematoxylin-eosin staining. Left ventricular (LV) function was measured by echocardiography. Control mice displayed peak macrophage infiltration at 4-days, whereas treated mice had a delayed peak macrophage infiltration at 7-days. At 28-days, control mice demonstrated large transmural infarcts with extensive scar formation and poor contractile function. In contrast, mice treated with α-gal nanoparticles demonstrated after 28-days a marked reduction in infarct size (~10-fold smaller), restoration of normal myocardium structure and contractile function. Conclusions: Intramyocardial injection of α-gal nanoparticles post-MI in anti-Gal producing adult-mice results in near complete repair of the infarcted territory, with restoration of normal LV structure and contractile function. The mechanism responsible for this benefit likely involves alteration of the usual inflammatory response post-MI, as previously observed with regeneration of injured hearts in adult zebrafish, salamanders and neonatal mice.

Selective FPR2 Agonism Promotes a Proresolution Macrophage Phenotype and Improves Cardiac Structure-Function Post Myocardial Infarction

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MI leads to ischemic damage of myocardium and activation of inflammatory programs as part of the wound healing response.

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Selective activation of FPR2 on macrophages potentiates key cellular activities that enable wound healing.

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MI was induced in rodents to study the effects of treatment with BMS-986235, a selective small molecule agonist of FPR2.

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BMS-986235 stimulated proresolution macrophage activities, induced neutrophil apoptosis and clearance, improved LV and infarct structure, and preserved cardiac function post MI.

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The findings suggest that targeted activation of FPR2 can improve post-MI outcome and may diminish the development of HF.

Dysregulated inflammation following myocardial infarction (MI) leads to maladaptive healing and remodeling. The study characterized and evaluated a selective formyl peptide receptor 2 (FPR2) agonist BMS-986235 in cellular assays and in rodents undergoing MI. BMS-986235 activated G proteins and promoted β-arrestin recruitment, enhanced phagocytosis and neutrophil apoptosis, regulated chemotaxis, and stimulated interleukin-10 and monocyte chemoattractant protein-1 gene expression. Treatment with BMS-986235 improved mouse survival, reduced left ventricular area, reduced scar area, and preserved wall thickness. Treatment increased macrophage arginase-1 messenger RNA and CD206 receptor levels indicating a proresolution phenotype. In rats following MI, BMS-986235 preserved viable myocardium, attenuated left ventricular remodeling, and increased ejection fraction relative to control animals. Therefore, FPR2 agonism improves post-MI healing, limits remodeling and preserves function, and may offer an innovative therapeutic option to improve outcomes.

Fibrosis of the diabetic heart: Clinical significance, molecular mechanisms, and therapeutic opportunities

In patients with diabetes, myocardial fibrosis may contribute to the pathogenesis of heart failure and arrhythmogenesis, increasing ventricular stiffness and delaying conduction. Diabetic myocardial fibrosis involves effects of hyperglycemia, lipotoxicity and insulin resistance on cardiac fibroblasts, directly resulting in increased matrix secretion, and activation of paracrine signaling in cardiomyocytes, immune and vascular cells, that release fibroblast-activating mediators. Neurohumoral pathways, cytokines, growth factors, oxidative stress, advanced glycation end-products (AGEs), and matricellular proteins have been implicated in diabetic fibrosis; however, the molecular links between the metabolic perturbations and activation of a fibrogenic program remain poorly understood. Although existing therapies using glucose- and lipid-lowering agents and neurohumoral inhibition may act in part by attenuating myocardial collagen deposition, specific therapies targeting the fibrotic response are lacking. This review manuscript discusses the clinical significance, molecular mechanisms and cell biology of diabetic cardiac fibrosis and proposes therapeutic targets that may attenuate the fibrotic response, preventing heart failure progression.

Metformin Attenuates Postinfarction Myocardial Fibrosis and Inflammation in Mice

Diabetes is a major risk factor for the development of cardiovascular disease with a higher incidence of myocardial infarction. This study explores the role of metformin, a first-line antihyperglycemic agent, in postinfarction fibrotic and inflammatory remodeling in mice. Three-month-old C57BI/6J mice were submitted to 30 min cardiac ischemia followed by reperfusion for 14 days. Intraperitoneal treatment with metformin (5 mg/kg) was initiated 15 min after the onset of reperfusion and maintained for 14 days. Real-time PCR was used to determine the levels of COL3A1, αSMA, CD68, TNF-α and IL-6. Increased collagen deposition and infiltration of macrophages in heart tissues are associated with upregulation of the inflammation-associated genes in mice after 14 days of reperfusion. Metformin treatment markedly reduced postinfarction fibrotic remodeling and CD68-positive cell population in mice. Moreover, metformin resulted in reduced expression of COL3A1, αSMA and CD68 after 14 days of reperfusion. Taken together, these results open new perspectives for the use of metformin as a drug that counteracts adverse myocardial fibroticand inflammatory remodeling after MI.

Galectin-3 Derived from HucMSC Exosomes Promoted Myocardial Fibroblast-to-Myofibroblast Differentiation Associated with β-catenin Upregulation

Background and Objectives

Galectin-3 promotes fibroblast-to-myofibroblast differentiation and facilitates injury repair. Previous studies have shown that exosomes derived from human umbilical cord mesenchymal stem cells (hucMSC-ex) promote the differentiation of myocardial fibroblasts into myofibroblasts under inflammatory environment. Whether hucMSC-ex derived Galectin-3 (hucMSC-ex-Galectin-3) plays an important role in fibroblast-to-myofibroblast differentiation is the focus of this study.

Methods and Results

Galectin-3 was knocked-down by siRNA in hucMSCs, and then exosomes were extracted. Fibroblasts were treated with LPS, LPS＋hucMSC-ex, LPS＋negative control-siRNA-ex (NC-ex), or LPS＋Galectin-3-siRNA-ex (si-ex) in vitro. The coronary artery of the left anterior descending (LAD) branch was permanently ligated, followed by intramyocardial injection with phosphate buffered saline(PBS), hucMSC-ex, hucMSC-NC-ex, or hucMSC-si-ex in vivo. Western blot, RT-PCR, and immunohistochemistry were used to detect the expression of markers related to fibroblast-to-myofibroblast differentiation and inflammatory factors. Migration and contraction functions of fibroblasts were evaluated using Transwell migration and collagen contraction assays, respectively. β-catenin expression was detected by western blot and immunofluorescence. The results showed that hucMSC-ex increased the protein expression of myofibroblast markers, anti-inflammatory factors, and β-catenin. HucMSC-ex also reduced the migration and promoted the contractility of fibroblasts. However, hucMSC-si-ex did not show these activities.

Conclusions

HucMSC-ex-Galectin-3 promoted the differentiation of cardiac fibroblasts into myofibroblasts in an inflammatory environment, which was associated with increased β-catenin levels.

Yap Promotes Noncanonical Wnt Signals From Cardiomyocytes for Heart Regeneration

[Figure: see text].

New perspectives of the cardiac cellular landscape: mapping cellular mediators of cardiac fibrosis using single-cell transcriptomics

Single-cell transcriptomics enables inference of context-dependent phenotypes of individual cells and determination of cellular diversity of complex tissues. Cardiac fibrosis is a leading factor in the development of heart failure and a major cause of morbidity and mortality worldwide with no effective treatment. Single-cell RNA-sequencing (scRNA-seq) offers a promising new platform to identify new cellular and molecular protagonists that may drive cardiac fibrosis and development of heart failure. This review will summarize the application scRNA-seq for understanding cardiac fibrosis and development of heart failure. We will also discuss some key considerations in interpreting scRNA-seq data and some of its limitations.

TUG1 knockdown suppresses cardiac fibrosis after myocardial infarction

Cardiac fibrosis is involved in myocardial remodeling following acute myocardial infarction (AMI), which can result in heart failure, arrhythmias and even sudden cardiac death. Investigating the molecular mechanisms of cardiac fibrosis in acute myocardial infarction (AMI) is essential for better understanding this pathology. The current study aims to investigate the effect of TUG1 on cardiac fibrosis after AMI and elucidated the underlying molecular mechanism of AMI. Rats were randomly divided into four groups (sham-operation group, myocardial infarction group (AMI group), si-NC treated group and si-TUG1 treated group). The biological behavior of cardiac fibroblasts treated with TGF-β1after being transfected by si-TUG1 or miR-590 mimic or miR-590 inhibitor or FGF1 mimic or a combination was evaluated using the cell counting kit-8 (CCK8) and Transwell assays. SatarBase v2.0 was used to predict the target microRNAs binding site candidates with TUG1 and FGF1. Western blot and recovery experiments were used to explore the potential mechanism. TUG1 expression was up-regulated and knockdown of TUG1 improved cardiac function in AMI rats. Knockdown of TUG1 suppressed cell viability and migration and improved collagen production of TGF-β1 treated cardiac fibroblasts. SatarBase v2.0 showed TUG1 served as a sponge for miR-590 and FGF1 is a direct target of miR-590. TUG1 expression was increased in AMI tissue and cardiac fibroblasts treated with TGF-β1. TUG1 knockdown suppressed the biological process of cardiac fibroblasts treated with TGF-β1 by sponging miR-590.

Preparation of Cell-Seeded Heart Patch In Vitro; Co-Culture of Adipose-Derived Mesenchymal Stem Cell and Cardiomyocytes in Amnion Bilayer Patch

INTRODUCTION

Cardiovascular disease is the second killer across the globe, while coronary disease is the major cause. Cell therapy is one alternative to regenerate the infarcted heart wall.

MATERIALS AND METHODS

In this study, the cardiomyogenesis capacity of human adipose stem cells (hAdSC) and human cardiomyocytes (hCardio) cultured in a 3-D biological scaffold (decellularised amnion bilayer) for nine days in a static condition was investigated. The cardiomyogenesis capacity of hAdSC were identified using immunohistochemistry and RT-PCR. The population of the cells isolated from the heart tissue expressed cTnT-1 (13.38 ± 11.38%), cKit (7.85 ± 4.2%), ICAM (85.53 ± 8.69%), PECAM (61.63 ± 7.18%) and VCAM (35.9 ± 9.11%), while from the fat tissue expressed the mesenchymal phenotypes (CD73, CD90, CD105, but not CD45, CD34, CD11b, CD19 and HLA-DR). Two age groups of hAdSC donors were compared, the youngsters (30-40yo) and the elderly (60-70 yo).

RESULTS

The co-culture showed that after 5-day incubation, the seeded graft in the hAdSC-30 group had a tube-like appearance while the hAdSC-60 group demonstrated a disorganised pattern, despite of the MSC expressions of the hAdSC-60 were significantly higher. Initial co-culture showed no difference of ATP counts among all groups, however the hAdSC-30 group had the highest ATP count after 9 days culture (p = 0.004). After normalising to the normal myocardium, only the hAdSC-60 group expressed cTnT and MHC, very low, seen during the initial cultivation, but then disappeared. Meanwhile, the hAdSC-30 group expressed α-actinin, MHC and cTnT in the Day-5. The PPAR also was higher in the Day-5 compared to the Day-9 (p < 0.005).

CONCLUSION

Cardiomyogenesis capacity of hAdSC co-cultured with hCardio in a 3-D scaffold taken from the 30-40yo donor showed better morphology and viability than the 60-70yo group, but maintained less than 5 days in this system.

Innate Immune Cells in Pressure Overload-Induced Cardiac Hypertrophy and Remodeling

Pressure overload and heart failure are among the leading causes of cardiovascular morbidity and mortality. Accumulating evidence suggests that inflammatory cell activation and release of inflammatory mediators are of vital importance during the pathogenesis of these cardiac diseases. Yet, the roles of innate immune cells and subsequent inflammatory events in these processes remain poorly understood. Here, we outline the possible underlying mechanisms of innate immune cell participation, including mast cells, macrophages, monocytes, neutrophils, dendritic cells, eosinophils, and natural killer T cells in these pathological processes. Although these cells accumulate in the atrium or ventricles at different time points after pressure overload, their cardioprotective or cardiodestructive activities differ from each other. Among them, mast cells, neutrophils, and dendritic cells exert detrimental function in experimental models, whereas eosinophils and natural killer T cells display cardioprotective activities. Depending on their subsets, macrophages and monocytes may exacerbate cardiodysfunction or negatively regulate cardiac hypertrophy and remodeling. Pressure overload stimulates the secretion of cytokines, chemokines, and growth factors from innate immune cells and even resident cardiomyocytes that together assist innate immune cell infiltration into injured heart. These infiltrates are involved in pro-hypertrophic events and cardiac fibroblast activation. Immune regulation of cardiac innate immune cells becomes a promising therapeutic approach in experimental cardiac disease treatment, highlighting the significance of their clinical evaluation in humans.

Fibrosis, the Bad Actor in Cardiorenal Syndromes: Mechanisms Involved

Cardiorenal syndrome is a term that defines the complex bidirectional nature of the interaction between cardiac and renal disease. It is well established that patients with kidney disease have higher incidence of cardiovascular comorbidities and that renal dysfunction is a significant threat to the prognosis of patients with cardiac disease. Fibrosis is a common characteristic of organ injury progression that has been proposed not only as a marker but also as an important driver of the pathophysiology of cardiorenal syndromes. Due to the relevance of fibrosis, its study might give insight into the mechanisms and targets that could potentially be modulated to prevent fibrosis development. The aim of this review was to summarize some of the pathophysiological pathways involved in the fibrotic damage seen in cardiorenal syndromes, such as inflammation, oxidative stress and endoplasmic reticulum stress, which are known to be triggers and mediators of fibrosis.

Engineering the Cellular Microenvironment of Post-infarct Myocardium on a Chip

Myocardial infarctions are one of the most common forms of cardiac injury and death worldwide. Infarctions cause immediate necrosis in a localized region of the myocardium, which is followed by a repair process with inflammatory, proliferative, and maturation phases. This repair process culminates in the formation of scar tissue, which often leads to heart failure in the months or years after the initial injury. In each reparative phase, the infarct microenvironment is characterized by distinct biochemical, physical, and mechanical features, such as inflammatory cytokine production, localized hypoxia, and tissue stiffening, which likely each contribute to physiological and pathological tissue remodeling by mechanisms that are incompletely understood. Traditionally, simplified two-dimensional cell culture systems or animal models have been implemented to elucidate basic pathophysiological mechanisms or predict drug responses following myocardial infarction. However, these conventional approaches offer limited spatiotemporal control over relevant features of the post-infarct cellular microenvironment. To address these gaps, Organ on a Chip models of post-infarct myocardium have recently emerged as new paradigms for dissecting the highly complex, heterogeneous, and dynamic post-infarct microenvironment. In this review, we describe recent Organ on a Chip models of post-infarct myocardium, including their limitations and future opportunities in disease modeling and drug screening.

Platelet derived growth factor-A (Pdgf-a) gene transfer modulates scar composition and improves left ventricular function after myocardial infarction

BACKGROUND

Novel therapies that can limit or reverse damage caused by myocardial infarction (MI) could ease the increasing burden of heart failure. In this regard Platelet Derived Growth Factor (PDGF) has been previously shown to contribute to cardiac repair after MI. Here, we use a rodent model of MI and recombinant adeno-associated virus 9 (rAAV9)-mediated gene transfer to overexpress Pdgf-a in the injured heart and assess its therapeutic potential.

METHODS AND RESULTS

Sprague Dawley rats underwent temporary occlusion of the left anterior descending coronary artery, followed immediately by systemic delivery of 1 × 10^11 vector genomes of either rAAV9 Pdgf-a or rAAV9 Empty vector (control). At day 28 post-MI echocardiography showed significantly improved left ventricular (LV) function (fractional shortening) after rAAV9 Pdgf-a (0.394 ± 0.019%) treatment vs control (0.304 ± 0.018%). Immunohistochemical analysis demonstrated significantly increased capillary and arteriolar density in the infarct border zone of rAAV9 Pdgf-a treated hearts together with a significant reduction in infarct scar size (rAAV9 Pdgf-a 6.09 ± 0.94% vs Empty 12.45 ± 0.92%). Western blot and qPCR analyses confirmed overexpression of PDGF-A and showed upregulation of smooth muscle alpha actin (Acta2), collagen type III alpha 1 (Col3a1) and lysyl oxidase (Lox) genes in rAAV9 Pdgf-a treated infarcts.

CONCLUSION

Overexpression of Pdgf-a in the post-MI heart can modulate scar composition and improve LV function. Our study highlights the potential of rAAV gene transfer of Pdgf-a as a cardio-reparative therapy.

Pulsed field ablation prevents chronic atrial fibrotic changes and restrictive mechanics after catheter ablation for atrial fibrillation

Aims

Pulsed field ablation (PFA), a non-thermal ablative modality, may show different effects on the myocardial tissue compared to thermal ablation. Thus, this study aimed to compare the left atrial (LA) structural and mechanical characteristics after PFA vs. thermal ablation.

Methods and results

Cardiac magnetic resonance was performed pre-ablation, acutely (<3 h), and 3 months post-ablation in 41 patients with paroxysmal atrial fibrillation (AF) undergoing pulmonary vein (PV) isolation with PFA (n = 18) or thermal ablation (n = 23, 16 radiofrequency ablations, 7 cryoablations). Late gadolinium enhancement (LGE), T2-weighted, and cine images were analysed. In the acute stage, LGE volume was 60% larger after PFA vs. thermal ablation (P < 0.001), and oedema on T2 imaging was 20% smaller (P = 0.002). Tissue changes were more homogeneous after PFA than after thermal ablation, with no sign of microvascular damage or intramural haemorrhage. In the chronic stage, the majority of acute LGE had disappeared after PFA, whereas most LGE persisted after thermal ablation. The maximum strain on PV antra, the LA expansion index, and LA active emptying fraction declined acutely after both PFA and thermal ablation but recovered at the chronic stage only with PFA.

Conclusion

Pulsed field ablation induces large acute LGE without microvascular damage or intramural haemorrhage. Most LGE lesions disappear in the chronic stage, suggesting a specific reparative process involving less chronic fibrosis. This process may contribute to a preserved tissue compliance and LA reservoir and booster pump functions.

Targeting fibrosis in the failing heart with nanoparticles

Heart failure (HF) is a clinical syndrome characterized by typical symptoms and signs caused by a structural and/or functional cardiac abnormality, resulting in a reduced cardiac output and/or elevated intracardiac pressures at rest or during stress. Due to increasing incidence, prevalence and, most importantly mortality, HF is a healthcare burden worldwide, despite the improvement of treatment options and effectiveness. Acute and chronic cardiac injuries trigger the activation of neurohormonal, inflammatory, and mechanical pathways ultimately leading to fibrosis, which plays a key role in the development of cardiac dysfunction and HF. The use of nanoparticles for targeted drug delivery would greatly improve therapeutic options to identify, prevent and treat cardiac fibrosis. In this review we will highlight the mechanisms of cardiac fibrosis development to depict the pathophysiological features for passive and active targeting of acute and chronic cardiac fibrosis with nanoparticles. Then we will discuss how cardiomyocytes, immune and inflammatory cells, fibroblasts and extracellular matrix can be targeted with nanoparticles to prevent or restore cardiac dysfunction and to improve the molecular imaging of cardiac fibrosis.

Hydrostatic pressure promotes migration and filamin-A activation in fibroblasts with increased p38 phosphorylation and TGF-β production

Fibroblast migration is closely regulated by the mechanical characteristics in surrounding microenvironment. While increased interstitial hydrostatic pressure (HP) is a hallmark in many pathological and physiological conditions, little is known about how the HP affects fibroblast motility. Using cell-culture chips with elevated HP conditions, we showed that 20 cmH₂O HP significantly accelerated fibroblast migration. The HP-induced migration acceleration was dependent on the augmentation of transforming growth factor-β₁, and correlated with the activation of filamin A via the phosphorylation of p38 mitogen-activated protein kinase. Our results suggest that interstitial HP elevation associated with various pathological states could significantly regulate fibroblast migration.

Direct Reprogramming of Cardiac Fibroblasts to Repair the Injured Heart

Coronary heart disease is a leading cause of mortality and morbidity. Those that survive acute myocardial infarction are at significant risk of subsequent heart failure due to fibrotic remodelling of the infarcted myocardium. By applying knowledge from the study of embryonic cardiovascular development, modern medicine offers hope for treatment of this condition through regeneration of the myocardium by direct reprogramming of fibrotic scar tissue. Here, we will review mechanisms of cell fate specification leading to the generation of cardiovascular cell types in the embryo and use this as a framework in which to understand direct reprogramming. Driving expression of a network of transcription factors, micro RNA or small molecule epigenetic modifiers can reverse epigenetic silencing, reverting differentiated cells to a state of induced pluripotency. The pluripotent state can be bypassed by direct reprogramming in which one differentiated cell type can be transdifferentiated into another. Transdifferentiating cardiac fibroblasts to cardiomyocytes requires a network of transcription factors similar to that observed in embryonic multipotent cardiac progenitors. There is some flexibility in the composition of this network. These studies raise the possibility that the failing heart could one day be regenerated by directly reprogramming cardiac fibroblasts within post-infarct scar tissue.

Signaling pathways in cancer-associated fibroblasts and targeted therapy for cancer

To flourish, cancers greatly depend on their surrounding tumor microenvironment (TME), and cancer-associated fibroblasts (CAFs) in TME are critical for cancer occurrence and progression because of their versatile roles in extracellular matrix remodeling, maintenance of stemness, blood vessel formation, modulation of tumor metabolism, immune response, and promotion of cancer cell proliferation, migration, invasion, and therapeutic resistance. CAFs are highly heterogeneous stromal cells and their crosstalk with cancer cells is mediated by a complex and intricate signaling network consisting of transforming growth factor-beta, phosphoinositide 3-kinase/AKT/mammalian target of rapamycin, mitogen-activated protein kinase, Wnt, Janus kinase/signal transducers and activators of transcription, epidermal growth factor receptor, Hippo, and nuclear factor kappa-light-chain-enhancer of activated B cells, etc., signaling pathways. These signals in CAFs exhibit their own special characteristics during the cancer progression and have the potential to be targeted for anticancer therapy. Therefore, a comprehensive understanding of these signaling cascades in interactions between cancer cells and CAFs is necessary to fully realize the pivotal roles of CAFs in cancers. Herein, in this review, we will summarize the enormous amounts of findings on the signals mediating crosstalk of CAFs with cancer cells and its related targets or trials. Further, we hypothesize three potential targeting strategies, including, namely, epithelial-mesenchymal common targets, sequential target perturbation, and crosstalk-directed signaling targets, paving the way for CAF-directed or host cell-directed antitumor therapy.

Recent Advances in Single-Cell Profiling and Multispecific Therapeutics: Paving the Way for a New Era of Precision Medicine Targeting Cardiac Fibroblasts

PURPOSE OF REVIEW

Cardiac fibroblast activation contributes to fibrosis, maladaptive remodeling and heart failure progression. This review summarizes the latest findings on cardiac fibroblast activation dynamics derived from single-cell transcriptomic analyses and discusses how this information may aid the development of new multispecific medicines.

RECENT FINDINGS

Advances in single-cell gene expression technologies have led to the discovery of distinct fibroblast subsets, some of which are more prevalent in diseased tissue and exhibit temporal changes in response to injury. In parallel to the rapid development of single-cell platforms, the advent of multispecific therapeutics is beginning to transform the biopharmaceutical landscape, paving the way for the selective targeting of diseased fibroblast subpopulations. Insights gained from single-cell technologies reveal critical cardiac fibroblast subsets that play a pathogenic role in the progression of heart failure. Combined with the development of multispecific therapeutic agents that have enabled access to previously "undruggable" targets, we are entering a new era of precision medicine.

Long Noncoding RNA Small Nuclear RNA Host Gene 7 Knockdown Protects Mouse Cardiac Fibroblasts Against Myocardial Infarction by Regulating miR-455-3p/Platelet-Activating Factor Receptor Axis

ABSTRACT

Myocardial infarction (MI) is a leading cause of heart failure all over the world. Long noncoding RNAs have been reported to be associated with the development of MI. In this article, we aimed to explore the effects of long noncoding RNA small nuclear RNA host gene 7 (SNHG7) on MI and the possible mechanism. In this study, an MI model was established by ligating the left anterior descending coronary artery of mice. Cardiac fibroblasts (CFs) derived from neonatal mice were activated by angiotensin II (Ang-II) treatment. The expression of SNHG7 and miR-455-3p was examined by quantitative real-time polymerase chain reaction, and protein levels of platelet-activating factor receptor (PTAFR) and fibrosis-related proteins were analyzed by western blot assay. Cell apoptosis of CFs was monitored by flow cytometry. Enzyme-linked immunosorbent assay was performed to evaluate inflammatory responses in CFs. Moreover, dual-luciferase reporter assay was used to confirm the target relationship between miR-455-3p and SNHG7 or PTAFR. LncRNA SNHG7 and PTAFR were upregulated, whereas miR-455-3p was downregulated in cardiac tissues of mice with MI and Ang-II-induced CFs. SNHG7 depletion or miR-455-3p overexpression attenuated Ang-II-induced apoptosis, fibrosis, and inflammation in CFs, which was severally weakened by miR-455-3p inhibition or PTAFR upregulation. LncRNA SNHG7 targeted miR-455-3p, and PTAFR was a target of miR-455-3p. LncRNA SNHG7 depletion exerted protective roles in apoptosis, fibrosis, and inflammation in Ang-II-induced CFs by regulating miR-455-3p/PTAFR axis, providing a potential molecular target for MI therapy.

Time-Series Transcriptome Analysis Reveals the miR-27a-5p-Ppm1l Axis as a New Pathway Regulating Macrophage Alternative Polarization After Myocardial Infarction

BACKGROUND

Timely differentiation of monocytes into M2-like macrophages is important in the cardiac healing process after myocardial infarction (MI), but molecular mechanisms governing M2-like macrophage differentiation at the transcriptional level after MI have not been fully understood.

METHODS AND RESULTS

A time-series microarray analysis of mRNAs and microRNAs in macrophages isolated from the infarcted myocardium was performed to identify the microRNAs involved in regulating the process of differentiation to M2-like macrophages. Correlation analysis revealed 7 microRNAs showing negative correlations with the progression of polarity changes towards M2-like subsets. Next, correlation coefficients for the changes in expression of mRNAs and miRNAs over time were calculated for all combinations. As a result, miR-27a-5p was extracted as a possible regulator of the largest number of genes in the pathway for the M2-like polarization. By selecting mouse mRNAs and human mRNAs possessing target sequences of miR-27a-5p and showing expression patterns inversely correlated with that of miR-27a-5p, 8 potential targets of miR-27a-5p were identified, includingPpm1l. Using the mouse bone marrow-derived macrophages undergoing differentiation into M2-like subsets by interleukin 4 stimulation, we confirmed that miR-27a-5p suppressed M2-related genes by negatively regulatingPpm1lexpression.

CONCLUSIONS

Ppm1land miR-27a-5p may be the key molecules regulating M2-like polarization, with miR-27a-5p inhibiting the M2-like polarization through downregulation ofPpm1lexpression.

Dimethyl fumarate preserves left ventricular infarct integrity following myocardial infarction via modulation of cardiac macrophage and fibroblast oxidative metabolism

Myocardial infarction (MI) is one of the leading causes of mortality and cardiovascular disease worldwide. MI is characterized by a substantial inflammatory response in the infarcted left ventricle (LV), followed by transition of quiescent fibroblasts to active myofibroblasts, which deposit collagen to form the reparative scar. Metabolic shifting between glycolysis and mitochondrial oxidative phosphorylation (OXPHOS) is an important mechanism by which these cell types transition towards reparative phenotypes. Thus, we hypothesized that dimethyl fumarate (DMF), a clinically approved anti-inflammatory agent with metabolic actions, would improve post-MI remodeling via modulation of macrophage and fibroblast metabolism. Adult male C57BL/6J mice were treated with DMF (10 mg/kg) for 3-7 days after MI. DMF attenuated LV infarct and non-infarct wall thinning at 3 and 7 days post-MI, and decreased LV dilation and pulmonary congestion at day 7. DMF improved LV infarct collagen deposition, myofibroblast activation, and angiogenesis at day 7. DMF also decreased pro-inflammatory cytokine expression (Tnf) 3 days after MI, and decreased inflammatory markers in macrophages isolated from the infarcted heart (Hif1a, Il1b). In fibroblasts extracted from the infarcted heart at day 3, RNA-Seq analysis demonstrated that DMF promoted an anti-inflammatory/pro-reparative phenotype. By Seahorse analysis, DMF did not affect glycolysis in either macrophages or fibroblasts at day 3, but enhanced macrophage OXPHOS while impairing fibroblast OXPHOS. Our results indicate that DMF differentially affects macrophage and fibroblast metabolism, and promotes anti-inflammatory/pro-reparative actions. In conclusion, targeting cellular metabolism in the infarcted heart may be a promising therapeutic strategy.

GDF15 Promotes Cardiac Fibrosis and Proliferation of Cardiac Fibroblasts via the MAPK/ERK1/2 Pathway after Irradiation in Rats

Ionizing radiation exposure is associated with a risk of cardiac fibrosis; however, the underlying molecular mechanism remains unclear. Growth/differentiation factor-15 (GDF15), a fibroblast factor, is a divergent member of the transforming growth factor β superfamily. Next-generation sequencing analyses has revealed that Gdf15 is increased in cardiac fibroblasts during radiation-induced fibrosis. However, the role of Gdf15 in cardiac fibrosis remains unclear. In this study, we demonstrated that the upregulated expression of GDF15 in newborn rat cardiac fibroblasts and adult rats after irradiation could induce fibrosis, which was confirmed by the increased cell proliferation rate and the increased expression of fibrosis markers (Col1α and αSMA) in newborn rat cardiac fibroblasts after transfection with Gdf15 in vitro. Conversely, the downregulation of GDF15 inhibited cardiac fibrosis, as confirmed by G2/M-cell cycle arrest, suppression of cell proliferation, and low levels of Col1α and αSMA expression. We also found that suppressing the expression of Gdf15 in cardiac fibroblasts could lead to a decrease in CDK1 and inhibit phosphorylation of ERK1/2. Thus, GDF15 might promote cardiac fibroblast fibrosis through the MAPK/ERK1/2 pathway and thus contribute to the pathogenesis of radiation-induced heart disease.

Biotherapeutic-loaded injectable hydrogels as a synergistic strategy to support myocardial repair after myocardial infarction

Myocardial infarction (MI) has been considered as the leading cause of cardiovascular-related deaths worldwide. Although traditional therapeutic agents including various bioactive species such as growth factors, stem cells, and nucleic acids have demonstrated somewhat usefulness for the restoration of cardiac functions, the therapeutic efficiency remains unsatisfactory most likely due to the off-target-associated side effects and low localized retention of the used therapeutic agents in the infarcted myocardium, which constitutes a substantial barrier for the effective treatment of MI. Injectable hydrogels are regarded as a minimally invasive technology that can overcome the clinical and surgical limitations of traditional stenting by a modulated sol-gel transition and localized transport of a variety of encapsulated cargoes, leading to enhanced therapeutic efficiency and improved patient comfort and compliance. However, the design of injectable hydrogels for myocardial repair and the mechanism of action of bioactive substance-loaded hydrogels for MI repair remain unclear. To elucidate these points, we summarized the recent progresses made on the use of injectable hydrogels for encapsulation of various therapeutic substances for MI treatment with an emphasis on the mechanism of action of hydrogel systems for myocardial repair. Specifically, the pathogenesis of MI and the rational design of injectable hydrogels for myocardial repair were presented. Next, the mechanisms of various biotherapeutic substance-loaded injectable hydrogels for myocardial repair was discussed. Finally, the potential challenges and future prospects for the use of injectable hydrogels for MI treatment were proposed for the purpose of drawing theoretical guidance on the development of novel therapeutic strategies for efficient treatment of MI.

Pharmacological inhibition of GLUT1 as a new immunotherapeutic approach after myocardial infarction

Myocardial infarction (MI) is one of the major contributors to cardiovascular morbidity and mortality. Excess inflammation significantly contributes to cardiac remodeling and heart failure after MI. Accumulating evidence has shown the central role of cellular metabolism in regulating the differentiation and function of cells. Metabolic rewiring is particularly relevant for proinflammatory responses induced by ischemia. Hypoxia reduces mitochondrial oxidative phosphorylation (OXPHOS) and induces increased reliance on glycolysis. Moreover, activation of a proinflammatory transcriptional program is associated with preferential glucose metabolism in leukocytes. An improved understanding of the mechanisms that regulate metabolic adaptations holds the potential to identify new metabolic targets and strategies to reduce ischemic cardiac damage, attenuate excess local inflammation and ultimately prevent the development of heart failure. Among possible drug targets, glucose transporter 1 (GLUT1) gained considerable interest considering its pivotal role in regulating glucose availability in activated leukocytes and the availability of small molecules that selectively inhibit it. Therefore, we summarize current evidence on the role of GLUT1 in leukocytes (focusing on macrophages and T cells) and non-leukocytes, including cardiomyocytes, endothelial cells and fibroblasts regarding ischemic heart disease. Beyond myocardial infarction, we can foresee the role of GLUT1 blockers as a possible pharmacological approach to limit pathogenic inflammation in other conditions driven by excess sterile inflammation.

Nanomedicine for the treatment of diabetes-associated cardiovascular diseases and fibrosis

Cardiomyopathy and fibrosis are the main causes of heart failure in diabetes patients. For therapeutic purposes, a delivery system is required to enhance antidiabetic drug efficacy and specifically target profibrotic pathways in cardiomyocytes. Nanoparticles (NPs) have distinct advantages, including biocompatibility, bioavailability, targeting efficiency, and minimal toxicity, which make them ideal for antidiabetic treatment. In this review, we overview the latest information on the pathogenesis of cardiomyopathy and fibrosis in diabetes patients. We summarize how NP applications improve insulin and liraglutide efficacy and their sustained release upon oral administration. We provide a comprehensive review of the results of NP clinical trials in diabetes patients and of animal studies investigating the effects of NP-mediated anti-fibrotic treatments. Collectively, the application of advanced NP delivery systems in the treatment of cardiomyopathy and fibrosis in diabetes patients is a promising and innovative therapeutic strategy.

Novel Targets of Metformin in Cardioprotection: Beyond the Effects Mediated by AMPK

Ischemic heart disease is the main cause of death globally. In the heart, the ischemia/reperfusion injury gives rise to a complex cascade of molecular signals, called cardiac remodeling, which generates harmful consequences for the contractile function of the myocardium and consequently heart failure. Metformin is the drug of choice in the treatment of type 2 diabetes mellitus. Clinical data suggest the direct effects of this drug on cardiac metabolism and studies in animal models showed that metformin activates the classical pathway of AMP-activated protein kinase (AMPK), generating cardioprotective effects during cardiac remodeling, hypertrophy and fibrosis. Furthermore, new studies have emerged about other targets of metformin with a potential role in cardioprotection. This state of the art review shows the available scientific evidence of the cardioprotective potential of metformin and its possible effects beyond AMPK. Targeting of autophagy, mitochondrial function and miRNAs are also explored as cardioprotective approaches along with a therapeutic potential. Further advances related to the biological effects of metformin and cardioprotective approaches may provide new therapies to protect the heart and prevent cardiac remodeling and heart failure.

Adipose-Derived Mesenchymal Stem Cells-Derived Exosomes Carry MicroRNA-671 to Alleviate Myocardial Infarction Through Inactivating the TGFBR2/Smad2 Axis

Mesenchymal stem cells (MSCs) and their derived extracellular vesicles have been reported as promising tools for the management of heart disease. The aim of this study was to explore the function of adipose-derived MSCs (adMSCs)-derived exosomes (Exo) in the progression of myocardial infarction (MI) and the molecules involved. Mouse cardiomyocytes were treated with oxygen-glucose deprivation (OGD) to mimic an MI condition in vitro. The adMSCs-derived Exo were identified and administrated into the OGD-treated cardiomyocytes, and then the viability and apoptosis of cells, and the secretion of fibrosis- and inflammation-related cytokines in cells were determined. Differentially expressed microRNAs (miRNAs) in cells after Exo treatment were screened using a microarray analysis. The downstream molecules regulated by miR-671 were explored through bioinformatic analysis. Involvements of miR-671 and transforming growth factor beta receptor 2 (TGFBR2) in the exosome-mediated events were confirmed by rescue experiments. A murine model with MI was induced and treated with Exo for functional experiments in vivo. Compared to phosphate-buffered saline treatment, the Exo treatment significantly enhanced viability while reduced apoptosis of cardiomyocytes, and in reduced myocardial fibrosis and inflammation both in vitro and in vivo. miR-671 was significantly upregulated in cells after Exo treatment. Downregulation of miR-671 blocked the protective functions of Exo. miR-671 targeted TGFBR2 and suppressed phosphorylation of Smad2. Artificial downregulation of TGFBR2 enhanced viability of the OGD-treated cardiomyocytes. This study suggested that adMSC-derived exosomal miR-671 directly targets TGFBR2 and reduces Smad2 phosphorylation to alleviate MI-like symptoms both in vivo and in vitro.

Periplocymarin protects against myocardial fibrosis induced by β-adrenergic activation in mice

Periplocymarin is an effective component of Periplocae Cortex, which was wildly used as an ingredient in Traditional Chinese Medicine. Our group previously reported that periplocymarin exerted cardiotonic role via promoting calcium influx. However, its exact role in the pathogenesis of myocardial fibrosis has not been elucidated yet. The present study was aimed at determining the potential effect and underlying mechanism of periplocymarin in isoproterenol (ISO)-induced myocardial fibrosis. C57BL/6 mice were subcutaneously injected with ISO (5 mg/kg/day) or saline for 1 week. The early-to-atrial wave ratio (E/A ratio) measured by echocardiography revealed that ISO-induced heart stiffness was remarkably reversed by administration of periplocymarin (5 mg/kg/day). Masson trichrome staining exhibited that treatment of periplocymarin reduced the excessive deposition of extracellular matrix (ECM). Further investigations employing real-time PCR and western blot demonstrated that periplocymarin suppressed the expression of fibrosis related genes (Col1a1, Col3a1, Acta2 and Tgfb1) and proteins (Collagen I, Collagen III, α-SMA and TGF-β1) induced by ISO. Metabolomics analysis demonstrated that periplocymarin ameliorated the disorders triggered by ISO and many of the differential metabolic substances were involved in amino acid, glucose and lipid metabolism. Further analysis using network pharmacology revealed that three key genes, namely NOS2, NOS3 and Ptgs2, may be the potential targets of periplocymarin and responsible for the disorders. Validation using heart tissues showed that the mRNA expression of NOS3 was decreased while Ptgs2 was increased upon ISO treatment, which were reversed by periplocymarin. Moreover, the expression of COX-2 (Ptgs2 encoded protein) was consistent with the aspect of Ptgs2 mRNA, while eNOS (NOS3 encoded protein) expression was unchanged. In vitro studies exhibited that periplocymarin exerts anti-fibrotic function via regulating at least eNOS and COX-2 in cardiomyocyte. Taken together, periplocymarin protects against myocardial fibrosis induced by β-adrenergic activation, the potential mechanism was that periplocymarin targeted on, at least eNOS and COX-2, to improve the metabolic processes of cardiomyocyte and thus attenuated the myocardial fibrosis. Our study highlighted that periplocymarin is a potential therapeutic agent for the prevention of myocardial fibrosis.

Isolation and culture of adult murine cardiac atrial and ventricular fibroblasts and myofibroblasts

Cardiac fibroblasts play a critical role in extracellular matrix homeostasis, wound healing, and cardiac interstitial fibrosis: the latter being a pathophysiological response to a chronic increase in afterload. Using a standard protocol to isolate cardiac fibroblasts and maintain them in their quiescent phenotype in vitro will enable a better understanding of cardiac fibroblast biology and their role in the response to profibrotic stimuli. Here, we describe an enzymatic method for isolating cardiac fibroblasts. The resulting cells are maintained on either a collagen-coated hydrogel-bound polystyrene (compliant) substrate or standard polystyrene culture dishes (non-compliant) to obtain quiescent fibroblasts and activated fibroblasts (myofibroblasts), respectively. Fibroblasts maintained on a non-compliant substrate developed a myofibroblast phenotype, in which the αSMA immunoreactivity was markedly elevated and incorporated into the stress fibers. In contrast, ventricular and atrial fibroblasts retain their quiescent phenotype for up to 3 passages when maintained on a compliant substrate. Hence, the methodology described herein provides a simple and reproducible way to isolate adult murine atrial and ventricular cardiac fibroblasts from a single animal and, by selecting a substrate with the appropriate compliance, examine the mediators of fibroblast activation or inactivation.

Cardiac Fibrosis: Key Role of Integrins in Cardiac Homeostasis and Remodeling

Cardiac fibrosis is a common finding that is associated with the progression of heart failure (HF) and impacts all chambers of the heart. Despite intense research, the treatment of HF has primarily focused upon strategies to prevent cardiomyocyte remodeling, and there are no targeted antifibrotic strategies available to reverse cardiac fibrosis. Cardiac fibrosis is defined as an accumulation of extracellular matrix (ECM) proteins which stiffen the myocardium resulting in the deterioration cardiac function. This occurs in response to a wide range of mechanical and biochemical signals. Integrins are transmembrane cell adhesion receptors, that integrate signaling between cardiac fibroblasts and cardiomyocytes with the ECM by the communication of mechanical stress signals. Integrins play an important role in the development of pathological ECM deposition. This review will discuss the role of integrins in mechano-transduced cardiac fibrosis in response to disease throughout the myocardium. This review will also demonstrate the important role of integrins as both initiators of the fibrotic response, and modulators of fibrosis through their effect on cardiac fibroblast physiology across the various heart chambers.

Myocardial Infarction Induces Cardiac Fibroblast Transformation within Injured and Noninjured Regions of the Mouse Heart

Heart failure (HF) is associated with pathological remodeling of the myocardium, including the initiation of fibrosis and scar formation by activated cardiac fibroblasts (CFs). Although early CF-dependent scar formation helps prevent cardiac rupture by maintaining the heart's structural integrity, ongoing deposition of the extracellular matrix in the remote and infarct regions can reduce tissue compliance, impair cardiac function, and accelerate progression to HF. In our study, we conducted mass spectrometry (MS) analysis to identify differentially altered proteins and signaling pathways between CFs isolated from 7 day sham and infarcted murine hearts. Surprisingly, CFs from both the remote and infarct regions of injured hearts had a wide number of similarly altered proteins and signaling pathways that were consistent with fibrosis and activation into pathological myofibroblasts. Specifically, proteins enriched in CFs isolated from MI hearts were involved in pathways pertaining to cell-cell and cell-matrix adhesion, chaperone-mediated protein folding, and collagen fibril organization. These results, together with principal component analyses, provided evidence of global CF activation postinjury. Interestingly, however, direct comparisons between CFs from the remote and infarct regions of injured hearts identified 15 differentially expressed proteins between MI remote and MI infarct CFs. Eleven of these proteins (Gpc1, Cthrc1, Vmac, Nexn, Znf185, Sprr1a, Specc1, Emb, Limd2, Pawr, and Mcam) were higher in MI infarct CFs, whereas four proteins (Gstt1, Gstm1, Tceal3, and Inmt) were higher in MI remote CFs. Collectively, our study shows that MI injury induced global changes to the CF proteome, with the magnitude of change reflecting their relative proximity to the site of injury.

Cardiac Fibroblasts and Myocardial Regeneration

The billions of cardiomyocytes lost to acute myocardial infarction (MI) cannot be replaced by the limited regenerative capacity of adult mammalian hearts, and despite decades of research, there are still no clinically effective therapies for remuscularizing and restoring damaged myocardial tissue. Although the majority of the cardiac mass is composed of cardiomyocytes, cardiac fibroblasts (CFs) are one type of most numerous cells in the heart and the primary drivers of fibrosis, which prevents ventricular rupture immediately after MI but the fibrotic scar expansion and LV dilatation can eventually lead to heart failure. However, embryonic CFs produce cytokines that can activate proliferation in cultured cardiomyocytes, and the structural proteins produced by CFs may regulate cardiomyocyte cell-cycle activity by modulating the stiffness of the extracellular matrix (ECM). CFs can also be used to generate induced-pluripotent stem cells and induced cardiac progenitor cells, both of which can differentiate into cardiomyocytes and vascular cells, but cardiomyocytes appear to be more readily differentiated from iPSCs that have been reprogrammed from CFs than from other cell types. Furthermore, the results from recent studies suggest that cultured CFs, as well as the CFs present in infarcted hearts, can be reprogrammed directly into cardiomyocytes. This finding is very exciting as should we be able to successfully increase the efficiency of this reprogramming, we could remuscularize the injured ventricle and restore the LV function without need the transplantation of cells or cell products. This review summarizes the role of CFs in the innate response to MI and how their phenotypic plasticity and involvement in ECM production might be manipulated to improve cardiac performance in injured hearts.

The common characteristics and mutual effects of heart failure and atrial fibrillation: initiation, progression, and outcome of the two aging-related heart diseases

Atrial fibrillation (AF) and heart failure (HF) are common chronic diseases noted in humans. AF and HF share several risk factors, such as age, hypertension, obesity, diabetes, and dyslipidemia. They can interact with each other, while both their morbidity and mortality have been considerably increased. And AF and HF often occur together, suggesting a strong association between the two. However, the underlying mechanism behind this association is not well understood. Among them, aging is the most significant common risk factor, which represents an aging heart and is characterized by fibrosis and decreased number of cardiomyocytes, known as senescence-related cardiac remodeling for both atria and ventricles. Finally, it is proposed that cardiac remodeling is the key link between AF and HF.

LncRNA-mRNA co-expression analysis discovered the diagnostic and prognostic biomarkers and potential therapeutic agents for myocardial infarction

Currently, the role of lncRNA in myocardial infarction (MI) is poorly understood. 17 co-expression modules were determined, specifically, the greenyellow, saddlebrown, grey60, royalblue, lightgreen, white, and pink modules were specifically expressed in the acute phase of MI, and brown, darkred, and royalblue, while greenyellow modules were specifically expressed in MI compared with CAD. 12 time-dependent of lncRNA/mRNA clusters with consistent expression trends were also identified. MI-associated modules were mainly enriched to immune, cell cycle, and metabolic pathways. We further obtained a network of 1816 lncRNA-mRNAs with higher expression correlations among these lncRNAs by analyzing the topological properties of the network. Herein, lncRNA RP11-847H18.2 and KLHL28, SPRTN, and EPM2AIP1 were determined as gene markers specifically expressed in MI, and they demonstrated a high predictive performance for MI diagnosis and prognosis. Three drugs, namely, Calcium citrate, Calcium Phosphate, and Calcium phosphate dihydrate, were identified as potential precursors of MI. Finally, gene and lncRNA diagnostic models were developed based on these genes and lncRNAs, with their AUCs averaged above 0.89 in both training and validation datasets. The findings of this study improve the diagnosis and prognosis of MI and personalized treatment of MI.

Limb-bud and Heart (LBH) mediates proliferation, fibroblast-to-myofibroblast transition and EMT-like processes in cardiac fibroblasts

Cardiac fibrosis is an important pathological change after myocardial infarction (MI). Its progression is essential for post-MI infarct healing, during which transforming growth factor beta1 (TGF-β1) plays a critical role. Limb-bud and Heart (LBH), a newly discovered target gene of TGF-β1, was shown to promote normal cardiogenesis. αB-crystallin (CRYAB), an LBH-interacting protein, was demonstrated to be involved in TGF-β1-induced fibrosis. The roles and molecular mechanisms of LBH and CRYAB during cardiac fibrosis remain largely unexplored. In this study, we investigated the alterations of LBH and CRYAB expression in mouse cardiac tissue after MI. LBH and CRYAB were upregulated in activated cardiac fibroblasts (CFs), while in vitro TGF-β1 stimulation induced the upregulation of LBH, CRYAB, and fibrogenic genes in primary CFs of neonatal rats. The results of the ectopic expression of LBH proved that LBH accelerated CF proliferation under hypoxia, mediated the expression of CRYAB and fibrogenic genes, and promoted epithelial-mesenchymal transition (EMT)-like processes in rat CFs, while subsequent CRYAB silencing reversed the effects induced by elevated LBH expression. We also verified the protein-protein interaction (PPI) between LBH and CRYAB in fibroblasts. In summary, our work demonstrated that LBH promotes the proliferation of CFs, mediates TGF-β1-induced fibroblast-to-myofibroblast transition and EMT-like processes through CRYAB upregulation, jointly functioning in post-MI infarct healing. These findings suggest that LBH could be a promising potential target for the study of cardiac repair and cardiac fibrosis.

Wound Healing-related Functions of the p160 Steroid Receptor Coactivator Family

Multicellular organisms have evolved sophisticated mechanisms to recover and maintain original tissue functions following injury. Injury responses require a robust transcriptomic response associated with cellular reprogramming involving complex gene expression programs critical for effective tissue repair following injury. Steroid receptor coactivators (SRCs) are master transcriptional regulators of cell-cell signaling that is integral for embryogenesis, reproduction, normal physiological function, and tissue repair following injury. Effective therapeutic approaches for facilitating improved tissue regeneration and repair will likely involve temporal and combinatorial manipulation of cell-intrinsic and cell-extrinsic factors. Pleiotropic actions of SRCs that are critical for wound healing range from immune regulation and angiogenesis to maintenance of metabolic regulation in diverse organ systems. Recent evidence derived from studies of model organisms during different developmental stages indicates the importance of the interplay of immune cells and stromal cells to wound healing. With SRCs being the master regulators of cell-cell signaling integral to physiologic changes necessary for wound repair, it is becoming clear that therapeutic targeting of SRCs provides a unique opportunity for drug development in wound healing. This review will provide an overview of wound healing-related functions of SRCs with a special focus on cellular and molecular interactions important for limiting tissue damage after injury. Finally, we review recent findings showing stimulation of SRCs following cardiac injury with the SRC small molecule stimulator MCB-613 can promote cardiac protection and inhibit pathologic remodeling after myocardial infarction.

Polymers and Nanoparticles for Statin Delivery: Current Use and Future Perspectives in Cardiovascular Disease

Atherosclerosis-related coronary artery disease (CAD) is one of the leading sources of mortality and morbidity in the world. Primary and secondary prevention appear crucial to reduce CAD-related complications. In this scenario, statin treatment was shown to be clinically effective in the reduction of adverse events, but systemic administration provides suboptimal results. As an attempt to improve bioavailability and effectiveness, polymers and nanoparticles for statin delivery were recently investigated. Polymers and nanoparticles can help statin delivery and their effects by increasing oral bioavailability or enhancing target-specific interaction, leading to reduced vascular endothelial dysfunction, reduced intimal hyperplasia, reduced ischemia-reperfusion injury, increased cardiac regeneration, positive remodeling in the extracellular matrix, reduced neointimal growth and increased re-endothelization. Moreover, some innovative aspects described in other cardiovascular fields could be translated into the CAD scenario. Recent preclinical studies are underlining the effect of statins in the stimulation and differentiation of endogenous cardiac stem cells, as well as in targeting of local adverse conditions implicated in atherosclerosis, and statin delivery through poly-lactic-co-glycolic acid (PLGA) appears the most promising aspect of current research to enhance drug activity. The present review intends to summarize the current evidence about polymers and nanoparticles for statin delivery in the field of cardiovascular disease, trying to shed light on this topic and identify new avenues for future studies.

Macrophage migration inhibitory factor activates the inflammatory response in joint capsule fibroblasts following post-traumatic joint contracture

Objectives: Joint capsule fibrosis caused by excessive inflammation leading to post-traumatic joint contracture (PTJC). Fibroblasts trigger inflammation under the challenge of various proinflammatory cytokines. Macrophage migration inhibitory factor (MIF) is a prominent proinflammatory cytokine involved in inflammation- and fibrosis-associated pathophysiology, we investigated the role of MIF in PTJC.

Methods: Using rat PTJC model and fibroblast inflammation model, we detected MIF expression in posterior joint capsule. Primary joint capsule fibroblasts (JFs) were used to investigate the effects of MIF on cell proliferation, migration and proinflammatory cytokines production. The mechanism of JF-mediated events was evaluated by qRT-PCR, western blot and immunoprecipitation. We screened the mRNA expression profile to identify gene candidates that mediate the effect of MIF on JFs.

Results: MIF increased in posterior joint capsule following PTJC and co-localized with fibroblasts. Injection of MIF inhibitor significantly suppressed joint capsule inflammation and fibrosis. In vitro, MIF promoted JF proliferation, migration, and inflammation by regulating mitogen-activated protein kinase/nuclear factor-κB pathway through coupling with CD74. Transcriptome analysis revealed that lipid metabolism-related factors Pla2g2a, Angptl4, and Sgpp2, downstream of MIF/CD74, were potentially implicated in JF inflammation.

Conclusion: MIF/CD74 axis elicited JF inflammation and may provide new therapeutic targets for joint capsule fibrosis in PTJC.

Dynamic modulation of gut microbiota improves post-myocardial infarct tissue repair in rats via butyric acid-mediated histone deacetylase inhibition

The complex and dynamic population of gut microbiota exerts a marked influence on the host during homeostasis and disease. Imbalance of gut microbiota metabolites may lead to cardiac dysfunction in patients with heart failure, which is related to myocardial infarction(MI) severity. However, the role of gut microbiota in the repair process after MI has rarely been reported. To explore the role of gut microbiota in MI repair and its underlying mechanism, we mixed antibiotics in drinking water to interfere with gut microbiota in rats. Hematoxylin and eosin staining, Sirius red staining, western blotting, and immunohistochemistry were used to detect tissue repair and fibrosis. We found that the expressions of alpha-smooth muscle actin, collagen, and histone deacetylase (HDAC) activities were significantly increased. We detected gut microbiota at different time points after MI using 16S ribosomal RNA sequencing and detected that Prevotellaceae, Clostridiaceae, and Lachnospiraceae were significantly altered among the butyric acid producers. We administered sodium butyrate via drinking water and discovered that sodium butyrate reduced HDAC activities and adverse repair. Therefore, we speculated that gut microbiota influences the acetylation level and tissue repair process after MI by affecting butyric acid production.

Leonurine Attenuates Myocardial Fibrosis Through Upregulation of miR-29a-3p in Mice Post-myocardial Infarction

ABSTRACT

Myocardial fibrosis (MF) is a pathological process that accelerates cardiac remodeling in myocardial infarction (MI), and miR-29 has become one of the foci of research into MF. As an alkaloid extracted from Herba leonuri, leonurine (LE) has been found to be an effective natural active ingredient for inhibiting fibrosis in many preclinical experiments. However, whether LE protects against MF after MI through modifying miR-29 remains unclear. The present study aimed to investigate the therapeutic effects of LE on MF, and to elucidate the underlying mechanisms involved. A mouse model of MI was established, followed by administration of LE for 4 weeks. We found that LE effectively improved cardiac function, and attenuated fibrosis and cardiac remodeling in mice post-MI. In vitro, LE simultaneously inhibited proliferation and migration of neonatal mouse cardiac fibroblasts (CFs) exposed to angiotensin II (Ang II), and the activation of collagen synthesis and myofibroblast generation was markedly suppressed by LE. Notably, we found that all mature miR-29 family members were downregulated in the myocardial tissues of mice post-MI, whereas LE significantly upregulated miR-29a-3p expression, and such upregulation was also detected in LE-treated CFs under Ang II stimulation. Knockdown of miR-29a-3p by a specific miRNA inhibitor upregulated the protein levels of TGF-β, collagen III, and collagen I in CFs, and completely reversed the antifibrotic effects of LE on CFs. Our study suggests that LE exerts cardioprotective effects against MF, possibly through the upregulation of miR-29a-3p.