Fibroblasts in post-infarction inflammation and cardiac repair

Hypoxic-Normoxic Crosstalk Activates Pro-Inflammatory Signaling in Human Cardiac Fibroblasts and Myocytes in a Post-Infarct Myocardium on a Chip

Myocardial infarctions locally deprive myocardium of oxygenated blood and cause immediate cardiac myocyte necrosis. Irreparable myocardium is then replaced with a scar through a dynamic repair process that is an interplay between hypoxic cells of the infarct zone and normoxic cells of adjacent healthy myocardium. In many cases, unresolved inflammation or fibrosis occurs for reasons that are incompletely understood, increasing the risk of heart failure. Crosstalk between hypoxic and normoxic cardiac cells is hypothesized to regulate mechanisms of repair after a myocardial infarction. To test this hypothesis, microfluidic devices are fabricated on 3D printed templates for co-culturing hypoxic and normoxic cardiac cells. This system demonstrates that hypoxia drives human cardiac fibroblasts toward glycolysis and a pro-fibrotic phenotype, similar to the anti-inflammatory phase of wound healing. Co-culture with normoxic fibroblasts uniquely upregulates pro-inflammatory signaling in hypoxic fibroblasts, including increased secretion of tumor necrosis factor alpha (TNF-α). In co-culture with hypoxic fibroblasts, normoxic human induced pluripotent stem cell (hiPSC)-derived cardiac myocytes also increase pro-inflammatory signaling, including upregulation of interleukin 6 (IL-6) family signaling pathway and increased expression of IL-6 receptor. Together, these data suggest that crosstalk between hypoxic fibroblasts and normoxic cardiac cells uniquely activates phenotypes that resemble the initial pro-inflammatory phase of post-infarct wound healing.

Bone-marrow mononuclear cells and acellular human amniotic membrane improve global cardiac function without inhibition of the NLRP3 Inflammasome in a rat model of heart failure

Recent studies have suggested that therapies with stem cells and amniotic membrane can modulate the inflammation following an ischemic injury in the heart. This study evaluated the effects of bone-marrow mononuclear cells (BMMC) and acellular human amniotic membrane (AHAM) on cardiac function and NLRP3 complex in a rat model of heart failure.On the 30th day,the echocardiographic showed improvements on ejection fraction and decreased pathological ventricular remodeling on BMMC and AHAM groups.Oxidative stress analysis was similar between the three groups,and the NLRP3 inflammasome activity were not decreased with the therapeutic use of both BMMC and AHAM,in comparison to the control group.

Regenerative loss in the animal kingdom as viewed from the mouse digit tip and heart

The myriad regenerative abilities across the animal kingdom have fascinated us for centuries. Recent advances in developmental, molecular, and cellular biology have allowed us to unearth a surprising diversity of mechanisms through which these processes occur. Developing an all-encompassing theory of animal regeneration has thus proved a complex endeavor. In this chapter, we frame the evolution and loss of animal regeneration within the broad developmental constraints that may physiologically inhibit regenerative ability across animal phylogeny. We then examine the mouse as a model of regeneration loss, specifically the experimental systems of the digit tip and heart. We discuss the digit tip and heart as a positionally-limited system of regeneration and a temporally-limited system of regeneration, respectively. We delve into the physiological processes involved in both forms of regeneration, and how each phase of the healing and regenerative process may be affected by various molecular signals, systemic changes, or microenvironmental cues. Lastly, we also discuss the various approaches and interventions used to induce or improve the regenerative response in both contexts, and the implications they have for our understanding regenerative ability more broadly.

Human left ventricular cardiac fibroblasts undergo a dynamic shift in secretome and gene expression toward a cardiac myofibroblast phenotype during early passage in typical culture expansion conditions

Cardiac fibroblasts (CFs) are critical components of the cardiac niche and primarily responsible for assembly and maintenance of the cardiac extracellular matrix (ECM). CFs are increasingly of interest for tissue engineering and drug development applications, as they provide synergistic support to cardiomyocytes through direct cell-to-cell signaling and cell-to-ECM interactions via soluble factors, including cytokines, growth factors and extracellular vesicles. CFs can be activated to a cardiac myofibroblast (CMF) phenotype upon injury or stimulation with transforming growth factor beta 1. Once activated, CMFs assemble collagen-rich ECM, which is vitally important to stabilize scar formation following myocardial infarction, for example. Although there is greater experience with culture expansion of CFs among non-human strains, very little is known about human CF-to-CMF transitions and expression patterns during culture expansion. In this study, we evaluated for shifts in inflammatory and angiogenic expression profiles of human CFs in typical culture expansion conditions. Understanding shifts in cellular expression patterns during CF culture expansion is critically important to establish quality benchmarks and optimize large-scale manufacturing for future clinical applications.

Extracellular Matrix Protein-1 as a Mediator of Inflammation-Induced Fibrosis After Myocardial Infarction

Irreversible fibrosis is a hallmark of myocardial infarction (MI) and heart failure. Extracellular matrix protein-1 (ECM-1) is up-regulated in these hearts, localized to fibrotic, inflammatory, and perivascular areas. ECM-1 originates predominantly from fibroblasts, macrophages, and pericytes/vascular cells in uninjured human and mouse hearts, and from M1 and M2 macrophages and myofibroblasts after MI. ECM-1 stimulates fibroblast-to-myofibroblast transition, up-regulates key fibrotic and inflammatory pathways, and inhibits cardiac fibroblast migration. ECM-1 binds HuCFb cell surface receptor LRP1, and LRP1 inhibition blocks ECM-1 from stimulating fibroblast-to-myofibroblast transition, confirming a novel ECM-1-LRP1 fibrotic signaling axis. ECM-1 may represent a novel mechanism facilitating inflammation-fibrosis crosstalk.

Primary cardiac fibroblast cell culture: methodological considerations for physiologically relevant conditions

Primary cardiac fibroblast (CF) tissue culture is a necessary tool for interrogating specific signaling mechanisms that dictate the phenotypic heterogeneity observed in vivo in different disease states. Traditional approaches that use tissue culture plastic and nutrient-rich medium have been shown to induce CF activation and, therefore, alter CF subpopulation composition. This shift away from in vivo phenotypes complicate the interpretation of results through the lens of the animal model. As the field works to identify CF diversity, these methodological flaws have begun to be addressed and more studies are focused on the dynamic interaction of CFs with their environment. This review focuses on the aspects of tissue culture that impact CF activation and, therefore, require consideration when designing in vitro experiments. The complexity of CF biology overlaid onto diverse model systems highlight the need for study-specific optimization and validation.

Research progress in the cardiac lymphatic system and myocardial repair after myocardial infarction

The lymphatic system of the heart plays an important role in the repair process after myocardial injury and may regulate normal tissue homeostasis and natural regeneration via maintaining fluid homeostasis and controlling the inflammatory response. The lymphatic system in the heart is activated after myocardial injury and is involved in the scarring process of the heart. Recent studies on the lymphatic system and myocardial repair of the heart have developed rapidly, and the mechanisms for lymphangiogenesis and lymphatic endothelial cell secretion have been elucidated by different animal models. A deep understanding of the structural, molecular, and functional characteristics of the lymphatic system of the heart can help develop therapies that target the lymphatic system in the heart. Summarizing the progress in studies on targets related to myocardial repair and the cardiac lymphatic system is helpful to provide potential new targets and strategies for myocardial repair therapy after myocardial infarction.

Temporal changes in glucose metabolism reflect polarization in resident and monocyte-derived macrophages after myocardial infarction

Introduction

Metabolic reprogramming from glycolysis to the mitochondrial tricarboxylic acid (TCA) cycle and oxidative phosphorylation may mediate macrophage polarization from the pro-inflammatory M1 to the anti-inflammatory M2 phenotype. We hypothesized that changes in cardiac macrophage glucose metabolism would reflect polarization status after myocardial infarction (MI), ranging from the early inflammatory phase to the later wound healing phase.

Methods

MI was induced by permanent ligation of the left coronary artery in adult male C57BL/6J mice for 1 (D1), 3 (D3), or 7 (D7) days. Infarct macrophages were subjected to metabolic flux analysis or gene expression analysis. Monocyte versus resident cardiac macrophage metabolism was assessed using mice lacking the Ccr2 gene (CCR2 KO).

Results

By flow cytometry and RT-PCR, D1 macrophages exhibited an M1 phenotype while D7 macrophages exhibited an M2 phenotype. Macrophage glycolysis (extracellular acidification rate) was increased at D1 and D3, returning to basal levels at D7. Glucose oxidation (oxygen consumption rate) was decreased at D3, returning to basal levels at D7. At D1, glycolytic genes were elevated (Gapdh, Ldha, Pkm2), while TCA cycle genes were elevated at D3 (Idh1 and Idh2) and D7 (Pdha1, Idh1/2, Sdha/b). Surprisingly, Slc2a1 and Hk1/2 were increased at D7, as well as pentose phosphate pathway (PPP) genes (G6pdx, G6pd2, Pgd, Rpia, Taldo1), indicating increased PPP activity. Macrophages from CCR2 KO mice showed decreased glycolysis and increased glucose oxidation at D3, and decreases in Ldha and Pkm2 expression. Administration of dichloroacetate, a pyruvate dehydrogenase kinase inhibitor, robustly decreased pyruvate dehydrogenase phosphorylation in the non-infarcted remote zone, but did not affect macrophage phenotype or metabolism in the infarct zone.

Discussion

Our results indicate that changes in glucose metabolism and the PPP underlie macrophage polarization following MI, and that metabolic reprogramming is a key feature of monocyte-derived but not resident macrophages.

Experimental heart failure models in small animals

Heart failure (HF) is one of the most critical health and economic burdens worldwide, and its prevalence is continuously increasing. HF is a disease that occurs due to a pathological change arising from the function or structure of the heart tissue and usually progresses. Numerous experimental HF models have been created to elucidate the pathophysiological mechanisms that cause HF. An understanding of the pathophysiology of HF is essential for the development of novel efficient therapies. During the past few decades, animal models have provided new insights into the complex pathogenesis of HF. Success in the pathophysiology and treatment of HF has been achieved by using animal models of HF. The development of new in vivo models is critical for evaluating treatments such as gene therapy, mechanical devices, and new surgical approaches. However, each animal model has advantages and limitations, and none of these models is suitable for studying all aspects of HF. Therefore, the researchers have to choose an appropriate experimental model that will fully reflect HF. Despite some limitations, these animal models provided a significant advance in the etiology and pathogenesis of HF. Also, experimental HF models have led to the development of new treatments. In this review, we discussed widely used experimental HF models that continue to provide critical information for HF patients and facilitate the development of new treatment strategies.

Acellular biomaterial modulates myocardial inflammation and promotes endogenous mechanisms of postinfarct cardiac repair

OBJECTIVE

After myocardial infarction, we previously showed that epicardial implantation of porcine small intestinal submucosal extracellular matrix (SIS-ECM) improves postinfarct cardiac function through fibroblast-mediated angiogenic and antifibrotic pathways. Herein, we characterize how SIS-ECM also coordinates a reparative cardiac inflammatory response.

METHODS

RNA sequencing and multiplex characterized modulation of fibroblast transcriptional and paracrine activity by SIS-ECM. Inhibitors of fibroblast growth factor 2 and toll-like receptor 9 elucidated mechanism. Mice received coronary ligation (infarction) and either SIS-ECM implantation (treatment) or sham surgery (control). Flow cytometry of SIS-ECM and the murine myocardium quantified monocytes, neutrophils, and proangiogenic subtypes. Microscopy tracked fibroblasts and immune cells, and characterized myocardial angiogenesis.

RESULTS

SIS-ECM increased fibroblast transcription of inflammatory pathways and production of angiogenic vascular endothelial growth factor and inflammatory cytokines via fibroblast growth factor 2 and toll-like receptor 9-dependent pathways. Two-photon microscopy showed that SIS-ECM became engrafted by native fibroblasts and leukocytes, subsequently increasing release of inflammatory cytokines and angiogenic vascular endothelial growth factor. On flow cytometry, SIS-ECM implantation increased day-7 myocardial counts of neutrophils, inflammatory monocytes, and proangiogenic vascular endothelial growth factor recptor 1 subtypes. SIS-ECM has a higher proportion of proangiogenic leukocytes compared with the myocardium. Resonant confocal microscopy showed neovascularization near SIS-ECM.

CONCLUSIONS

SIS-ECM promotes engraftment by native fibroblasts and leukocytes, and modulates fibroblast activity via fibroblast growth factor 2 and toll-like receptor 9 to potentiate a proangiogenic inflammatory response. Subsequently, the material increases myocardial counts of reparative proangiogenic leukocytes that can induce neovascularization. This reparative inflammatory response may explain previously reported functional improvements. Fibroblast growth factor 2 and toll-like receptor 9 mechanisms can be leveraged to design next-generation materials for postinfarct cardiac repair.

3D-printed long-acting 5-fluorouracil implant to prevent conjunctival fibrosis in glaucoma

OBJECTIVES

To develop a sustained release 5-fluorouracil (5-FU) implant by three-dimensional (3D) printing to effectively prevent conjunctival fibrosis after glaucoma surgery.

METHODS

3D-printed implants composed of polycaprolactone (PCL) and chitosan (CS) were fabricated by heat extrusion technology and loaded with 1% 5-FU. Light microscopy and scanning electron microscopy were used to study the surface morphology. The 5-FU concentration released over 8 weeks was measured by ultraviolet visible spectroscopy. The effects on cell viability, fibroblast contractility and the expression of key fibrotic genes were assessed in human conjunctival fibroblasts.

KEY FINDINGS

The PCL-CS-5-FU implant sustainably released 5-FU over 8 weeks and the peak concentration was over 6.1 μg/ml during weeks 1 and 2. The implant had a smooth surface and its total weight decreased by 3.5% after 8 weeks. The PCL-CS-5-FU implant did not affect cell viability in conjunctival fibroblasts and sustainably suppressed fibroblast contractility and key fibrotic genes for 8 weeks.

CONCLUSIONS

The PCL-CS-5-FU implant was biocompatible and degradable with a significant effect in suppressing fibroblast contractility. The PCL-CS-5-FU implant could be used as a sustained release drug implant, replacing the need for repeated 5-FU injections in clinic, to prevent conjunctival fibrosis after glaucoma surgery.

The paired-related homeobox protein 1 promotes cardiac fibrosis via the Twist1-Prrx1-tenascin-C loop

Cardiac fibrosis is a common pathology in the advanced stage of cardiovascular diseases, which leads to cardiac systolic and diastolic dysfunction. It is important to prevent cardiac fibrosis during myocardial injury. The transcription factor Prrx1 is involved in cancer-associated fibrosis and other organ fibrosis. However, the role and mechanism of Prrx1 in cardiac fibrosis deserves further exploration. We identified that overexpressed Prrx1 promoted the proliferation and migration of cardiac fibroblasts, and transform cardiac fibroblasts to myofibroblasts in vitro. We demonstrated that the expression of Prrx1 is upregulated in TGF-β1-treated fibroblasts. And silencing Prrx1 could attenuate cardiac fibrosis induced by TGF-β1 in vitro. In addition, a Twist1-paired-related homeobox 1 (Prrx1)-tenascin-C (TNC) positive feedback loop (PFL) combined with Twist1, Prrx1, and TNC activated fibroblasts, which was the mechanism the Prrx1 in cardiac fibrosis. In conclusion, our findings showed that the deficiency of Prrx1 attenuated cardiac fibrosis in vitro and reveal a novel Twist1-Prrx1-TNC PFL in the regulation of cardiac fibrosis.

Combined role for YAP-TEAD and YAP-RUNX2 signalling in substrate-stiffness regulation of cardiac fibroblast proliferation

Cardiac fibrosis is associated with increased stiffness of the myocardial extracellular matrix (ECM) in part mediated by increased cardiac fibroblast proliferation However, our understanding of the mechanisms regulating cardiac fibroblast proliferation are incomplete. Here we characterise a novel mechanism involving a combined activation of Yes-associated protein (YAP) targets RUNX Family Transcription Factor 2 (RUNX2) and TEA Domain Transcription Factor (TEAD). We demonstrate that cardiac fibroblast proliferation is enhanced by interaction with a stiff ECM compared to a soft ECM. This is associated with activation of the transcriptional co-factor, YAP. We demonstrate that this stiffness induced activation of YAP enhances the transcriptional activity of both TEAD and RUNX2 transcription factors. Inhibition of either TEAD or RUNX2, using gene silencing, expression of dominant-negative mutants or pharmacological inhibition, reduces cardiac fibroblast proliferation. Using mutants of YAP, defective in TEAD or RUNX2 activation ability, we demonstrate a dual role of YAP-mediated activation of TEAD and RUNX2 for substrate stiffness induced cardiac fibroblast proliferation. Our data highlights a previously unrecognised role of YAP mediated RUNX2 activation for cardiac fibroblast proliferation in response to increased ECM stiffness.

NLRP3 inflammasome: The rising star in cardiovascular diseases

Cardiovascular diseases (CVDs) are the prevalent cause of mortality around the world. Activation of inflammasome contributes to the pathological progression of cardiovascular diseases, including atherosclerosis, abdominal aortic aneurysm, myocardial infarction, dilated cardiomyopathy, diabetic cardiomyopathy, heart failure, and calcific aortic valve disease. The nucleotide oligomerization domain-, leucine-rich repeat-, and pyrin domain-containing protein 3 (NLRP3) inflammasome plays a critical role in the innate immune response, requiring priming and activation signals to provoke the inflammation. Evidence shows that NLRP3 inflammasome not only boosts the cleavage and release of IL-1 family cytokines, but also leads to a distinct cell programmed death: pyroptosis. The significance of NLRP3 inflammasome in the CVDs-related inflammation has been extensively explored. In this review, we summarized current understandings of the function of NLRP3 inflammasome in CVDs and discussed possible therapeutic options targeting the NLRP3 inflammasome.

The caspase-1 inhibitor VX765 upregulates connexin 43 expression and improves cell-cell communication after myocardial infarction via suppressing the IL-1β/p38 MAPK pathway

Connexin 43 (Cx43) is the most important protein in the gap junction channel between cardiomyocytes. Abnormalities of Cx43 change the conduction velocity and direction of cardiomyocytes, leading to reentry and conduction block of the myocardium, thereby causing arrhythmia. It has been shown that IL-1β reduces the expression of Cx43 in astrocytes and cardiomyocytes in vitro. However, whether caspase-1 and IL-1β affect connexin 43 after myocardial infarction (MI) is uncertain. In this study we investigated the effects of VX765, a caspase-1 inhibitor, on the expression of Cx43 and cell-to-cell communication after MI. Rats were treated with VX765 (16 mg/kg, i.v.) 1 h before the left anterior descending artery (LAD) ligation, and then once daily for 7 days. The ischemic heart was collected for histochemical analysis and Western blot analysis. We showed that VX765 treatment significantly decreased the infarct area, and alleviated cardiac dysfunction and remodeling by suppressing the NLRP3 inflammasome/caspase-1/IL-1β expression in the heart after MI. In addition, VX765 treatment markedly raised Cx43 levels in the heart after MI. In vitro experiments were conducted in rat cardiac myocytes (RCMs) stimulated with the supernatant from LPS/ATP-treated rat cardiac fibroblasts (RCFs). Pretreatment of the RCFs with VX765 (25 μM) reversed the downregulation of Cx43 expression in RCMs and significantly improved intercellular communication detected using a scrape-loading/dye transfer assay. We revealed that VX765 suppressed the activation of p38 MAPK signaling in the heart tissue after MI as well as in RCMs stimulated with the supernatant from LPS/ATP-treated RCFs. Taken together, these data show that the caspase-1 inhibitor VX765 upregulates Cx43 expression and improves cell-to-cell communication in rat heart after MI via suppressing the IL-1β/p38 MAPK pathway.

Mechanical Strain Drives Myeloid Cell Differentiation Toward Proinflammatory Subpopulations

Objective: After injury, humans and other mammals heal by forming fibrotic scar tissue with diminished function, and this healing process involves the dynamic interplay between resident cells within the skin and cells recruited from the circulation. Recent studies have provided mounting evidence that external mechanical forces stimulate intracellular signaling pathways to drive fibrotic processes. Innovation: While most studies have focused on studying mechanotransduction in fibroblasts, recent data suggest that mechanical stimulation may also shape the behavior of immune cells, referred to as "mechano-immunomodulation." However, the effect of mechanical strain on myeloid cell recruitment and differentiation remains poorly understood and has never been investigated at the single-cell level. Approach: In this study, we utilized a three-dimensional (3D) in vitro culture system that permits the precise manipulation of mechanical strain applied to cells. We cultured myeloid cells and used single-cell RNA-sequencing to interrogate the effects of strain on myeloid differentiation and transcriptional programming. Results: Our data indicate that myeloid cells are indeed mechanoresponsive, with mechanical stress influencing myeloid differentiation. Mechanical strain also upregulated a cascade of inflammatory chemokines, most notably from the Ccl family. Conclusion: Further understanding of how mechanical stress affects myeloid cells in conjunction with other cell types in the complicated, multicellular milieu of wound healing may lead to novel insights and therapies for the treatment of fibrosis.

Growth factors: avenues for the treatment of myocardial infarction and potential delivery strategies

Acute myocardial infarction (AMI) is one of the leading causes of death worldwide. Despite recent advances in clinical management, reoccurence of heart failure after AMI remains high, in part because of the limited capacity of cardiac tissue to repair after AMI-induced cell death. Growth factor-based therapy has emerged as an alternative AMI treatment strategy. Understanding the underlying mechanisms of growth factor cardioprotective and regenerative actions is important. This review focuses on the function of different growth factors at each stage of the cardiac repair process. Recent evidence for growth factor therapy in preclinical and clinical trials is included. Finally, different delivery strategies are reviewed with a view to providing workable strategies for clinical translation.

Cardiac Remodeling in Heart Failure: Role of Pyroptosis and Its Therapeutic Implications

Pyroptosis is a kind of programmed cell death closely related to inflammation. The pathways that mediate pyroptosis can be divided into the Caspase-1-dependent canonical pathway and the Caspase4/5/11-dependent non-canonical pathway. The most significant difference from other cell death is that pyroptosis rapidly causes rupture of the plasma membrane, cell expansion, dissolution and rupture of the cell membrane, the release of cell contents and a large number of inflammatory factors, and send pro-inflammatory signals to adjacent cells, recruit inflammatory cells and induce inflammatory responses. Cardiac remodeling is the basic mechanism of heart failure (HF) and the core of pathophysiological research on the underlying mechanism. A large number of studies have shown that pyroptosis can cause cardiac fibrosis, cardiac hypertrophy, cardiomyocytes death, myocardial dysfunction, excessive inflammation, and cardiac remodeling. Therefore, targeting pyroptosis has a good prospect in improving cardiac remodeling in HF. In this review, the basic molecular mechanism of pyroptosis is summarized, the relationship between pyroptosis and cardiac remodeling in HF is analyzed in-depth, and the potential therapy of targeting pyroptosis to improve adverse cardiac remodeling in HF is discussed, providing some ideas for improving the study of adverse cardiac remodeling in HF.

Deciphering Cardiac Biology and Disease by Single-Cell Transcriptomic Profiling

By detecting minute molecular changes in hundreds to millions of single cells, single-cell RNA sequencing allows for the comprehensive characterization of the diversity and dynamics of cells in the heart. Our understanding of the heart has been transformed through the recognition of cellular heterogeneity, the construction of regulatory networks, the building of lineage trajectories, and the mapping of intercellular crosstalk. In this review, we introduce cardiac progenitors and their transcriptional regulation during embryonic development, highlight cellular heterogeneity and cell subtype functions in cardiac health and disease, and discuss insights gained from the study of pluripotent stem-cell-derived cardiomyocytes.

Fibroblast mechanotransduction network predicts targets for mechano-adaptive infarct therapies

Regional control of fibrosis after myocardial infarction is critical for maintaining structural integrity in the infarct while preventing collagen accumulation in non-infarcted areas. Cardiac fibroblasts modulate matrix turnover in response to biochemical and biomechanical cues, but the complex interactions between signaling pathways confound efforts to develop therapies for regional scar formation. We employed a logic-based ordinary differential equation model of fibroblast mechano-chemo signal transduction to predict matrix protein expression in response to canonical biochemical stimuli and mechanical tension. Functional analysis of mechano-chemo interactions showed extensive pathway crosstalk with tension amplifying, dampening, or reversing responses to biochemical stimuli. Comprehensive drug target screens identified 13 mechano-adaptive therapies that promote matrix accumulation in regions where it is needed and reduce matrix levels in regions where it is not needed. Our predictions suggest that mechano-chemo interactions likely mediate cell behavior across many tissues and demonstrate the utility of multi-pathway signaling networks in discovering therapies for context-specific disease states.

Gut bacterial metabolite Urolithin A inhibits myocardial fibrosis through activation of Nrf2 pathway in vitro and in vivo

Background

Myocardial fibrosis after myocardial infarction (MI) is one of the leading causes of cardiovascular diseases. Cardiac fibroblasts (CFs) are activated and promoted by MI to undergo myofibroblast transformation (CMT). Urolithin A (UA) is an active and effective gut metabolite derived from polyphenolics of berries and pomegranate fruits, which has been reported to have anti-inflammatory and anti-oxidant functions. However, whether UA affects the CMT process during myocardial fibrosis remains unclear.

Methods

TGF-β1-treated primary rat cardiac fibroblasts were used for in vitro study. Cell proliferation ability was evaluated by MTT assay. Cell migration and invasion abilities were tested by wound healing and Transwell assays. The expression of CMT process-related markers were measured by qRT-PCR and western blot. The rat MI model was established by left anterior descending coronary artery (LAD) ligation and evaluated by H&E and Masson staining.

Results

Our data demonstrated that UA treatment could inhibit the CMT process in TGF-β1-induced CFs, including cell proliferation, migration and invasion abilities. Knocking down of Nrf2, which was activated by UA treatment, could mitigate the effects of UA treatment on CMT process. Moreover, in vivo administration of UA in rat MI model successfully up-regulated Nrf2 expression and improved the myocardial damage and fibrosis.

Conclusions

The study discovered the function and mechanism of UA on myocardial fibrosis and demonstrated the protective effects of UA administration through activation of Nrf2 pathway.

Cardiac fibroblasts secrete exosome microRNA to suppress cardiomyocyte pyroptosis in myocardial ischemia/reperfusion injury

Molecular mechanisms underlying myocardial ischemia/reperfusion (MI/R) injury and effective strategies to treat MI/R injury are both in shortage. Although pyroptosis of cardiomyocytes and the protective role of cardiac fibroblasts (CFs) have been well recognized as targets to reduce MI/R injury and sudden cardiac death (SCD), the connection has not yet been established. Here, we showed that CFs protected cardiomyocytes against MI/R-induced injury through suppression of pyroptosis. A novel molecular mechanism underpinning this effect was further identified. Under hypoxia/reoxygenation condition, CFs were found to secrete exosomes, which contain increased level of microRNA-133a (miR-133a). These exosomes then delivered miR-133a into cardiomyocytes to target ELAVL1 and repressed cardiomyocyte pyroptosis. Based on this finding, we successfully developed a new strategy that used exosomes derived from CFs with overexpressed miR-133a to enhance the therapeutic outcomes for the MI/R injury. Overall, our results provide a novel molecular basis for understanding and treating MI/R injury, and our study also provides novel insight for the postmortem diagnosis of MI/R injury induced SCD by using exosome biomarker in forensic.

Exosomes in cardiovascular diseases: a blessing or a sin for the mankind

Cardiovascular diseases (CVDs) comprises disorders of blood vessels and heart. Multiple cells in the heart suggests that hetero-cellular communication, which is an important aspect in heart functioning and there is a need to elucidate the way in which this inter-cellular communication occurs. Now a days, exosomal research has gained much attention. Exosomes, nano-shuttles, are EVs with diameters ranging from 40 to 160 nm (average 100 nm), secreted by body cells. These vesicles act as cell-to-cell communicators and are carriers of important biomolecules such as RNAs, miRNAs, Proteins and lipids. Exosomes can change the gene expression of the recipient cells, thereby, changes the cellular characteristics. Exosomes have known to play an essential role in protection as well as progression of various cardiovascular diseases. In the present review, role of exosomes in various CVDs have been discussed.

NP202 treatment improves left ventricular systolic function and attenuates pathological remodelling following chronic myocardial infarction

AIMS

Myocardial injury is a major contributor to left ventricular (LV) remodelling activating neurohormonal and inflammatory processes that create an environment of enhanced oxidative stress. This results in geometric and structural alterations leading to reduced LV systolic function. In this study we evaluated the efficacy of NP202, a synthetic flavonol, on cardiac remodelling in a chronic model of myocardial infarction (MI).

MAIN METHODS

A rat model of chronic MI was induced by permanent surgical ligation of the coronary artery. NP202 treatment was commenced 2 days post-MI for 6 weeks at different doses (1, 10 and 20 mg/kg/day) to determine efficacy. Cardiac function was assessed by echocardiography prior to treatment and at week 6, and pressure-volume measurements were performed prior to tissue collection. Tissues were analysed for changes in fibrotic and inflammatory markers using immunohistochemistry and gene expression analysis.

KEY FINDINGS

Rats treated with NP202 demonstrated improved LV systolic function and LV geometry compared to vehicle treated animals. Furthermore, measures of hypertrophy and interstitial fibrosis were attenuated in the non-infarct region of the myocardium with NP202 at the higher dose of 20 mg/kg (P < 0.05). At the tissue level, NP202 reduced monocyte chemoattractant protein-1 expression (P < 0.05) and tended to attenuate active caspase-3 expression to similar levels observed in sham animals (P = 0.075).

SIGNIFICANCE

Improved LV function and structural changes observed with NP202 may be mediated through inhibition of inflammatory and apoptotic processes in the MI setting. NP202 could therefore prove a useful addition to standard therapy in patients with post-MI LV dysfunction.

Exercise Training Protects Against Heart Failure Via Expansion of Myeloid-Derived Suppressor Cells Through Regulating IL-10/STAT3/S100A9 Pathway

BACKGROUND

Exercise training (ET) has a protective effect on the progression of heart failure, however, the specific mechanism has not been fully explored. Myeloid-derived suppressor cells (MDSCs) are a group of myeloid-derived immunosuppressive cells, which showed a protective effect in the progression of heart failure. Thus, we hypothesized that the protective effect of ET on heart failure may be related to the infiltration of MDSCs.

METHODS

C57BL/6 mice were made to run on a treadmill 6× a week for 4 weeks followed by isoproterenol injection from third week. Heart function was evaluated by echocardiography and the proportion of MDSCs was detected by flow cytometry. Hypertrophic markers, cardiac fibrosis, and inflammatory factors were detected by real-time PCR, ELISA, histological staining, and Western blot.

RESULTS

ET treatment in isoproterenol-induced heart failure mice (n=7) enhanced cardiac function (57% increase in FS%, P=0.002) and improved morphological changes compared with isoproterenol mice (n=17). ET further caused 79% increasing in cardiac MDSCs in isoproterenol mice (P<0.001). In addition, depletion of MDSCs by 5-Fluorouracil blunted the cardio-protective effect of ET. T-cell proliferation assay showed that ET did not affect the suppressive activity of MDSCs. Furthermore, we found that ET activated the secretion of IL (interleukin)-10 by macrophages in isoproterenol mice. MDSCs expansion and cardio protection was not present in tamoxifen-inducible macrophage-specific IL-10 knockout mice. Western blot results confirmed that IL-10 regulated the differentiation of MDSCs through the translocation of p-STAT3 (signal transducer and activator of transcription 3)/S100A9 (S100 calcium-binding protein A9) to the nucleus.

CONCLUSIONS

ET could increase MDSCs by stimulating the secretion of IL-10 from macrophage, which was through IL-10/STAT3/S100A9 signaling pathway, thereby achieving the role of heart protection.

Quantitative Evaluation of Cardiac Cell Interactions and Responses to Cyclic Strain

The heart has a dynamic mechanical environment contributed by its unique cellular composition and the resultant complex tissue structure. In pathological heart tissue, both the mechanics and cell composition can change and influence each other. As a result, the interplay between the cell phenotype and mechanical stimulation needs to be considered to understand the biophysical cell interactions and organization in healthy and diseased myocardium. In this work, we hypothesized that the overall tissue organization is controlled by varying densities of cardiomyocytes and fibroblasts in the heart. In order to test this hypothesis, we utilized a combination of mechanical strain, co-cultures of different cell types, and inhibitory drugs that block intercellular junction formation. To accomplish this, an image analysis pipeline was developed to automatically measure cell type-specific organization relative to the stretch direction. The results indicated that cardiac cell type-specific densities influence the overall organization of heart tissue such that it is possible to model healthy and fibrotic heart tissue in vitro. This study provides insight into how to mimic the dynamic mechanical environment of the heart in engineered tissue as well as providing valuable information about the process of cardiac remodeling and repair in diseased hearts.

The Role of the Inflammasome in Heart Failure

Inflammation promotes the development of heart failure (HF). The inflammasome is a multimeric protein complex that plays an essential role in the innate immune response by triggering the cleavage and activation of the proinflammatory cytokines interleukins (IL)-1β and IL-18. Blocking IL-1β with the monoclonal antibody canakinumab reduced hospitalizations and mortality in HF patients, suggesting that the inflammasome is involved in HF pathogenesis. The inflammasome is activated under various pathologic conditions that contribute to the progression of HF, including pressure overload, acute or chronic overactivation of the sympathetic system, myocardial infarction, and diabetic cardiomyopathy. Inflammasome activation is responsible for cardiac hypertrophy, fibrosis, and pyroptosis. Besides inflammatory cells, the inflammasome in other cardiac cells initiates local inflammation through intercellular communication. Some inflammasome inhibitors are currently being investigated in clinical trials in patients with HF. The current evidence suggests that the inflammasome is a critical mediator of cardiac inflammation during HF and a promising therapeutic target. The present review summarizes the recent advances in both basic and clinical research on the role of the inflammasome in HF.

Coagulation Factor Xa Induces Proinflammatory Responses in Cardiac Fibroblasts via Activation of Protease-Activated Receptor-1

Coagulation factor (F) Xa induces proinflammatory responses through activation of protease-activated receptors (PARs). However, the effect of FXa on cardiac fibroblasts (CFs) and the contribution of PARs in FXa-induced cellular signalling in CF has not been fully characterised. To answer these questions, human and rat CFs were incubated with FXa (or TRAP-14, PAR-1 agonist). Gene expression of pro-fibrotic and proinflammatory markers was determined by qRT-PCR after 4 and 24 h. Gene silencing of F2R (PAR-1) and F2RL1 (PAR-2) was achieved using siRNA. MCP-1 protein levels were measured by ELISA of FXa-conditioned media at 24 h. Cell proliferation was assessed after 24 h of incubation with FXa ± SCH79797 (PAR-1 antagonist). In rat CFs, FXa induced upregulation of Ccl2 (MCP-1; >30-fold at 4 h in atrial and ventricular CF) and Il6 (IL-6; ±7-fold at 4 h in ventricular CF). Increased MCP-1 protein levels were detected in FXa-conditioned media at 24 h. In human CF, FXa upregulated the gene expression of CCL2 (>3-fold) and IL6 (>4-fold) at 4 h. Silencing of F2R (PAR-1 gene), but not F2RL1 (PAR-2 gene), downregulated this effect. Selective activation of PAR-1 by TRAP-14 increased CCL2 and IL6 gene expression; this was prevented by F2R (PAR-1 gene) knockdown. Moreover, SCH79797 decreased FXa-induced proliferation after 24 h. In conclusion, our study shows that FXa induces overexpression of proinflammatory genes in human CFs via PAR-1, which was found to be the most abundant PARs isoform in this cell type.

Increased release of serotonin from rat primary isolated adult cardiac myofibroblasts

Elevated blood serotonin levels have been observed in patients with heart failure and serotonin has a role in pathological cardiac function. The serotonin receptor system was examined in adult rat isolated cardiac fibroblast and myofibroblast cells. This is one of the first studies that has investigated serotonin receptors and other proteins involved in the serotonin receptor system in rat cardiac fibroblast and myofibroblast cells. Rat primary cardiac fibroblasts were isolated and transformed into myofibroblasts using 5 ng/ml TGF-β1. Transformation of cells to myofibroblasts was confirmed with the presence of α-smooth muscle actin using Western blot. Serotonin metabolism and receptor protein expression was assessed using Western blot techniques and serotonin levels measured using ELISA. The 5-HT_1A, 5-HT_2A and 5-HT_2B receptors were found to be present in both rat cardiac fibroblasts and myofibroblast cells, however no significance in protein expression between the two cell types was found (P > 0.05). In this study a significant increase in the serotonin transporter (SERT), tryptophan hydroxylase 1 and extracellular serotonin levels was observed in rat cardiac myofibroblasts when compared to fibroblasts (P < 0.05). These results suggest that serotonin levels may rise in parallel with cardiac myofibroblast populations and contribute to the pathogenesis of heart failure via serotonin receptors.

Does the Heart Want What It Wants? A Case for Self-Adapting, Mechano-Sensitive Therapies After Infarction

There is a critical need for interventions to control the development and remodeling of scar tissue after myocardial infarction. A significant hurdle to fibrosis-related therapy is presented by the complex spatial needs of the infarcted ventricle, namely that collagenous buildup is beneficial in the ischemic zone but detrimental in the border and remote zones. As a new, alternative approach, we present a case to develop self-adapting, mechano-sensitive drug targets in order to leverage local, microenvironmental mechanics to modulate a therapy's pharmacologic effect. Such approaches could provide self-tuning control to either promote fibrosis or reduce fibrosis only when and where it is beneficial to do so.

Vincristine attenuates cardiac fibrosis through the inhibition of NLRP3 inflammasome activation

Vincristine (VCR) is widely used in cancer therapies, although its benefits on cardiac fibrosis remain unknown. Here, we investigated VCR's efficacy on cardiac fibrosis and elucidated the underlying mechanism of action. Network pharmacology was employed to predict the mechanism of VCR action on cardiac fibrosis. We induced cardiac fibrosis in adult male Sprague-Dawley (SD) rats via isoproterenol (ISO) injection, followed by treatment with VCR or vehicle. After 10 days of treatment, VCR-treated rats exhibited a significantly lower heart/body weight ratio relative to those treated with the vehicle. Moreover, cardiac fibrosis was alleviated in VCR-treated rats relative to vehicle-treated rats. The results revealed the down-regulation of mature caspase-1, interleukin (IL)-1β, and IL-18 in VCR-treated rats relative to vehicle-treated rats. We also observed less colocalization between the nucleotide-binding domain, leucine-rich repeat, and pyrin domain-containing protein 3 (NLRP3) and apoptosis-associated speck-like protein containing a CARD (ASC) in VCR-treated rats compared with vehicle-treated rats. We then cultured neonatal rat cardiac fibroblasts (NRCFs) and exposed them to lipopolysaccharide (LPS) and adenosine triphosphate (ATP) in the presence or absence of VCR. The results indicated that VCR mediated the down-regulation of caspase-1, IL-1β, and IL-18 and the colocalization of NLRP3 and ASC in LPS+ATP-stimulated cardiac fibroblasts (CFs). We found evidence that VCR attenuates cardiac fibrosis by directly suppressing the activation of the NLRP3 inflammasome. These findings provide novel insights into VCR's mechanism of action in alleviating cardiac fibrosis.

Toll-Like Receptor 4 Activation Prevents Rat Cardiac Fibroblast Death Induced by Simulated Ischemia/Reperfusion

Death of cardiac fibroblasts (CFs) by ischemia/reperfusion (I/R) has major implications for cardiac wound healing. In in vivo models of myocardial infarction, toll-like receptor 4 (TLR4) activation has been reported as a cardioprotector; however, it remains unknown whether TLR4 activation can prevent CF death triggered by simulated I/R (sI/R). In this study, we analyzed TLR4 activation in neonate CFs exposed to an in vitro model of sI/R and explored the participation of the pro-survival kinases Akt and ERK1/2. Simulated ischemia was performed in a free oxygen chamber in an ischemic medium, whereas reperfusion was carried out in normal culture conditions. Cell viability was analyzed by trypan blue exclusion and the MTT assay. Necrotic and apoptotic cell populations were evaluated by flow cytometry. Protein levels of phosphorylated forms of Akt and ERK1/2 were analyzed by Western blot. We showed that sI/R triggers CF death by necrosis and apoptosis. In CFs exposed only to simulated ischemia or only to sI/R, blockade of the TLR4 with TAK-242 further reduced cell viability and the activation of Akt and ERK1/2. Preconditioning with lipopolysaccharide (LPS) or treatment with LPS in ischemia or reperfusion was not protective. However, LPS incubation during both ischemia and reperfusion periods prevented CF viability loss induced by sI/R. Furthermore, LPS treatment reduced the sub-G1 population, but not necrosis of CFs exposed to sI/R. On the other hand, the protective effects exhibited by LPS were abolished when TLR4 was blocked and Akt and ERK1/2 were inhibited. In conclusion, our results suggest that TLR4 activation protects CFs from apoptosis induced by sI/R through the activation of Akt and ERK1/2 signaling pathways.

Non-coding RNAs in cardiac inflammation: key drivers in the pathophysiology of heart failure

Heart failure is among the most progressive diseases and a leading cause of morbidity. Despite several advances in cardiovascular therapies, pharmacological treatments are limited to relieve symptoms without curing cardiac injury. Multiple observations point to the involvement of immune cells as key drivers in the pathophysiology of heart failure. In particular, there is a growing recognition that heart failure is related to a prolonged and insufficiently repressed inflammatory response leading to molecular, cellular, and functional cardiac alterations. Over the last decades, non-coding RNAs are recognized as prominent mediators of the cardiac inflammation, affecting the function of several immune cells. In the current review, we explore the contribution of the diverse immune cells in the progression of heart failure, revealing mechanistic functions for non-coding RNAs in cardiac immune cells as a new and exciting field of investigation.

Mechano-chemo signaling interactions modulate matrix production by cardiac fibroblasts

Extracellular matrix remodeling after myocardial infarction occurs in a dynamic environment in which local mechanical stresses and biochemical signaling species stimulate the accumulation of collagen-rich scar tissue. It is well-known that cardiac fibroblasts regulate post-infarction matrix turnover by secreting matrix proteins, proteases, and protease inhibitors in response to both biochemical stimuli and mechanical stretch, but how these stimuli act together to dictate cellular responses is still unclear. We developed a screen of cardiac fibroblast-secreted proteins in response to combinations of biochemical agonists and cyclic uniaxial stretch in order to elucidate the relationships between stretch, biochemical signaling, and cardiac matrix turnover. We found that stretch significantly synergized with biochemical agonists to inhibit the secretion of matrix metalloproteinases, with stretch either amplifying protease suppression by individual agonists or antagonizing agonist-driven upregulation of protease expression. Stretch also modulated fibroblast sensitivity towards biochemical agonists by either sensitizing cells towards agonists that suppress protease secretion or de-sensitizing cells towards agonists that upregulate protease secretion. These findings suggest that the mechanical environment can significantly alter fibrosis-related signaling in cardiac fibroblasts, suggesting caution when extrapolating in vitro data to predict effects of fibrosis-related cytokines in situations like myocardial infarction where mechanical stretch occurs.

Dexmedetomidine attenuates myocardial ischemia-reperfusion injury in vitro by inhibiting NLRP3 Inflammasome activation

Background

Myocardial ischemia-reperfusion injury (MIRI) is the most common cause of death worldwide. The NOD-, LRR- and pyrin domain-containing protein 3 (NLRP3) inflammasome plays an important role in the inflammatory response to MIRI. Dexmedetomidine (DEX), a specific agonist of α2-adrenergic receptor, is commonly used for sedation and analgesia in anesthesia and critically ill patients. Several studies have shown that dexmedetomidine has a strong anti-inflammatory effect in many diseases. Here, we investigated whether dexmedetomidine protects against MIRI by inhibiting the activation of the NLRP3 inflammasome in vitro.

Methods

We established an MIRI model in cardiomyocytes (CMs) alone and in coculture with cardiac fibroblasts (CFs) by hypoxia/reoxygenation (H/R) in vitro. The cells were treated with dexmedetomidine with or without MCC950 (a potent selective NLRP3 inhibitor). The beating rate and cell viability of cardiomyocytes, NLRP3 localization, the expression of inflammatory cytokines and NLRP3 inflammasome-related proteins, and the expression of apoptosis-related proteins, including Bcl2 and BAX, were determined.

Results

Dexmedetomidine treatment increased the beating rates and viability of cardiomyocytes cocultured with cardiac fibroblasts. The expression of the NLRP3 protein was significantly upregulated in cardiac fibroblasts but not in cardiomyocytes after H/R and was significantly attenuated by dexmedetomidine treatment. Expression of the inflammatory cytokines IL-1β, IL-18 and TNF-α was significantly increased in cardiac fibroblasts after H/R and was attenuated by dexmedetomidine treatment. NLRP3 inflammasome activation induced the increased expression of cleaved caspase1, mature IL-1β and IL-18, while dexmedetomidine suppressed H/R-induced NLRP3 inflammasome activation in cardiac fibroblasts. In addition, dexmedetomidine reduced the expression of Bcl2 and BAX in cocultured cardiomyocytes by suppressing H/R-induced NLRP3 inflammasome activation in cardiac fibroblasts.

Conclusion

Dexmedetomidine treatment can suppress H/R-induced NLRP3 inflammasome activation in cardiac fibroblasts, thereby alleviating MIRI by inhibiting the inflammatory response.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12871-021-01334-5.

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.

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.

Pathological cardiac remodeling seen by the eyes of proteomics

Cardiac remodeling involves cellular and structural changes that occur as consequence of multifactorial events to maintain the homeostasis. The progression of pathological cardiac remodeling involves a transition from adaptive to maladaptive changes that eventually leads to impairment of ventricular function and heart failure. In this scenario, proteins are key elements that orchestrate molecular events as increased expression of fetal genes, neurohormonal and second messengers' activation, contractile dysfunction, rearrangement of the extracellular matrix and alterations in heart geometry. Mass spectrometry based-proteomics has emerged as a sound method to study protein dysregulation and identification of cardiac diseases biomarkers in plasma. In this review, we summarize the main findings related to large-scale proteome modulation of cardiac cells and extracellular matrix occurred during pathological cardiac remodeling. We describe the recent proteomic progresses in the selection of protein targets and introduce the renin-angiotensin system as an interesting target for the treatment of pathological cardiac remodeling.

Mechanobiological Principles Influence the Immune Response in Regeneration: Implications for Bone Healing

A misdirected or imbalanced local immune composition is often one of the reasons for unsuccessful regeneration resulting in scarring or fibrosis. Successful healing requires a balanced initiation and a timely down-regulation of the inflammation for the re-establishment of a biologically and mechanically homeostasis. While biomaterial-based approaches to control local immune responses are emerging as potential new treatment options, the extent to which biophysical material properties themselves play a role in modulating a local immune niche response has so far been considered only occasionally. The communication loop between extracellular matrix, non-hematopoietic cells, and immune cells seems to be specifically sensitive to mechanical cues and appears to play a role in the initiation and promotion of a local inflammatory setting. In this review, we focus on the crosstalk between ECM and its mechanical triggers and how they impact immune cells and non-hematopoietic cells and their crosstalk during tissue regeneration. We realized that especially mechanosensitive receptors such as TRPV4 and PIEZO1 and the mechanosensitive transcription factor YAP/TAZ are essential to regeneration in various organ settings. This indicates novel opportunities for therapeutic approaches to improve tissue regeneration, based on the immune-mechanical principles found in bone but also lung, heart, and skin.

CGRP derived from cardiac fibroblasts is an endogenous suppressor of cardiac fibrosis

AIMS

Aberrant activation of cardiac fibroblasts leads to cardiac fibrosis, and evolving evidences suggest that endogenous bioactive substances derived from cardiac fibroblasts regulate cardiac fibroblasts activation in an autocrine/paracrine manner. Here we first presented evidence that cardiac fibroblasts can synthesize and secrete calcitonin gene-related peptide (CGRP), therefore, this study aimed to investigate the role of cardiac fibroblasts-derived CGRP in cardiac fibroblasts activation and its regulative mechanism.

METHODS AND RESULTS

The abundantly expression of CGRP in rat, mouse, and human myocardium allowed us to explore the cellular origin of CGRP, and found that the cardiac CGRP was mainly derived from cardiac fibroblasts. Activating TRPA1 with a specific agonist allyl isothiocyanate promoted the synthesis and secretion of CGRP, as well as intracellular Ca2+. These effects were reversed by TRPA1-specific antagonist HC030031 and Ca2+ chelator BAPTA-AM. TGF-β1 was applied to induce the activation of cardiac fibroblasts, and found that TGF-β1 can increase the mRNA expression and secretion levels of CGRP in cardiac fibroblasts. Either CGRP8-37 (CGRP receptor antagonist) or α-CGRP small interfering RNA (siRNA) aggravated TGF-β1-induced proliferation, differentiation, collagen production, and instigated inflammation in cardiac fibroblasts. Moreover, TGF-β1-induced NF-κB activation including IκBα phosphorylation and p65 nuclear translocation were also promoted by CGRP8-37 and α-CGRP siRNA. NF-κB inhibitor pyrrolidinedithiocarbamate ammonium (PDTC) reversed the effects of CGRP8-37 on NF-κB activation. The promotive effects of CGRP8-37 on TGF-β1-induced activation of cardiac fibroblasts were all reversed by PDTC. Monocrotaline (MCT) induces pulmonary arterial hypertension, progressively leading to right ventricular fibrosis. This model of cardiac fibrosis was developed here to test the potentially beneficial effects of TRPA1 activation in vivo. The non-toxic TRPA1 agonist Cinnamaldehyde (CA) inhibited MCT-induced elevation in right ventricle systolic pressure, RV/LV + S, and right ventricular collagen accumulation, as well as down-regulation of CGRP. CA increased the synthesis and secretion of CGRP, and inhibited TGF-β1-induced activation in cardiac fibroblasts.

CONCLUSION

Our data suggested an autocrine role for cardiac fibroblasts-derived CGRP in suppressing activation of cardiac fibroblasts through inhibiting NF-κB activation. Increasing autocrine CGRP by activating TRPA1 can ameliorate cardiac fibrosis. These findings support the notion that CGRP derived from cardiac fibroblasts is an endogenous suppressor of cardiac fibrosis.

NLRP3 Inflammasome Biomarker-Could Be the New Tool for Improved Cardiometabolic Syndrome Outcome

Metabolomics, the research area studying chemical processes involving metabolites, finds its utility in inflammasome biomarker discovery, thus representing a novel approach for cardiometabolic syndrome pathogeny acknowledgements. Metabolite biomarkers discovery is expected to improve the disease evolution and outcome. The activation of abundantly expressed NLRP3 inflammasome represents the background process of the diabetes mellitus disturbances like hyperglycemia and insulin resistance, as well as for myocardial cell death and fibrosis, all of them being features characteristic for cardiometabolic syndrome. Many molecules like troponins, brain natriuretic protein (BNP), ST2/IL-33, C-reactive protein (CRP), TNF, IL-1β, and IL-18 cytokines have been already examined as molecular markers for diagnosing or predicting different cardiac disturbances like myocardial infarction, heart failure, or myocarditis. In addition, metabolomics research comes with new findings arguing that NLRP3 inflammasome becomes a promising molecular tool to use for clinical and therapeutical management providing new targets for therapies in cardiometabolic syndrome. Inflammasome markers analyses, along with other molecular or genetic biomarkers, will result in a better understanding of cardiometabolic syndrome pathogenesis and therapeutic targets. Screening, diagnostic, and prognostic biomarkers resulted from inflammasome biomarker research will become standard of care in cardiometabolic syndrome management, their utility becoming the first magnitude.

IL-33 induces type-2-cytokine phenotype but exacerbates cardiac remodeling post-myocardial infarction with eosinophil recruitment, worsened systolic dysfunction, and ventricular wall rupture

Myocardial infarction (MI) is the leading cause of mortality worldwide. Interleukin (IL)-33 (IL-33) is a cytokine present in most cardiac cells and is secreted on necrosis where it acts as a functional ligand for the ST2 receptor. Although IL-33/ST2 axis is protective against various forms of cardiovascular diseases, some studies suggest potential detrimental roles for IL-33 signaling. The aim of the present study was to examine the effect of IL-33 administration on cardiac function post-MI in mice. MI was induced by coronary artery ligation. Mice were treated with IL-33 (1 μg/day) or vehicle for 4 and 7 days. Functional and molecular changes of the left ventricle (LV) were assessed. Single cell suspensions were obtained from bone marrow, heart, spleen, and peripheral blood to assess the immune cells using flow cytometry at 1, 3, and 7 days post-MI in IL-33 or vehicle-treated animals. The results of the present study suggest that IL-33 is effective in activating a type 2 cytokine milieu in the damaged heart, consistent with reduced early inflammatory and pro-fibrotic response. However, IL-33 administration was associated with worsened cardiac function and adverse cardiac remodeling in the MI mouse model. IL-33 administration increased infarct size, LV hypertrophy, cardiomyocyte death, and overall mortality rate due to cardiac rupture. Moreover, IL-33-treated MI mice displayed a significant myocardial eosinophil infiltration at 7 days post-MI when compared with vehicle-treated MI mice. The present study reveals that although IL-33 administration is associated with a reparative phenotype following MI, it worsens cardiac remodeling and promotes heart failure.

Glycogen synthase kinase-3β inhibition alleviates activation of the NLRP3 inflammasome in myocardial infarction

Inflammasome-promoted sterile inflammation following cardiac damage is critically implicated in heart dysfunction after myocardial infarction (MI). Glycogen synthase kinase-3 (GSK-3β) is a prominent mediator of the inflammatory response, and high GSK-3 activity is associated with various heart diseases. We investigated the regulatory mechanisms of GSK-3β in activation of the nod-like receptor family pyrin domain containing 3 (NLRP3) inflammasome in a rat model with successful induction of MI on days 2-28. An in vitro investigation was performed using newborn rat/human cardiomyocytes and fibroblast cultures under typical inflammasome stimulation and hypoxia treatment. GSK-3β inhibition markedly improved myocardial dysfunction and prevented remodeling, with parallel reduction in the parameters of NLRP3 inflammasome activation after MI. GSK-3β inhibition reduced NLRP3 inflammasome activation in cardiac fibroblasts, but not in cardiomyocytes. GSK-3β's interaction with activating signal cointegrator (ASC) as well as GSK-3β inhibition reduced ASC phosphorylation and oligomerization at the tissues and cellular levels. Taken together, these data show that GSK-3β directly mediates NLRP3 inflammasome activation, causing cardiac dysfunction in MI.

Role of Muscle-Specific Histone Methyltransferase (Smyd1) in Exercise-Induced Cardioprotection against Pathological Remodeling after Myocardial Infarction

Pathological remodeling is the main detrimental complication after myocardial infarction (MI). Overproduction of reactive oxygen species (ROS) in infarcted myocardium may contribute to this process. Adequate exercise training after MI may reduce oxidative stress-induced cardiac tissue damage and remodeling. SET and MYND domain containing 1 (Smyd1) is a muscle-specific histone methyltransferase which is upregulated by resistance training, may strengthen sarcomere assembly and myofiber folding, and may promote skeletal muscles growth and hypertrophy. However, it remains elusive if Smyd1 has similar functions in post-MI cardiac muscle and participates in exercise-induced cardioprotection. Accordingly, we investigated the effects of interval treadmill exercise on cardiac function, ROS generation, Smyd1 expression, and sarcomere assembly of F-actin in normal and infarcted hearts. Adult male rats were randomly divided into five groups (n = 10/group): control (C), exercise alone (EX), sham-operated (S), MI induced by permanent ligation of left anterior descending coronary artery (MI), and MI with interval exercise training (MI + EX). Exercise training significantly improved post-MI cardiac function and sarcomere assembly of F-actin. The cardioprotective effects were associated with increased Smyd1, Trx1, cTnI, and α-actinin expression as well as upregulated ratio of phosphorylated AMP-activated protein kinase (AMPK)/AMPK, whereas Hsp90, MuRF1, brain natriuretic peptide (BNP) expression, ROS generation, and myocardial fibrosis were attenuated. The improved post-MI cardiac function was associated with increased Smyd1 expression. In cultured H9C2 cardiomyoblasts, in vitro treatment with H₂O₂ (50 µmol/L) or AMP-activated protein kinase (AMPK) agonist (AICAR, 1 mmol/L) or their combination for 4 h simulated the effects of exercise on levels of ROS and Smyd1. In conclusion, we demonstrated a novel role of Smyd1 in association with post-MI exercise-induced cardioprotection. The moderate level of ROS-induced upregulation of Smyd1 may be an important target for modulating post-MI cardiac function and remodeling.

Inhibition of MyD88 by a novel inhibitor reverses two-thirds of the infarct area in myocardial ischemia and reperfusion injury

Cardiomyocytes, macrophages, and fibroblasts play important roles in inflammation and repair during myocardial ischemia/reperfusion injury (MIRI). Myeloid differentiation primary response 88 (MyD88) is upregulated in immunocytes, cardiomyocytes, and fibroblasts during MIRI. MyD88 induces the secretion of proinflammatory cytokines, including interleukin (IL)-1β, IL-6, and tumor necrosis factor alpha (TNF-α), while fibroblasts are recruited and activated to mediate cardiac remodeling. The aim of this study was to assess the anti-MIRI effect and mode of action of the novel MyD88 inhibitor TJ-M2010-5. We synthesized TJ-M2010-5 and identified its target by co-immunoprecipitation, after which we established a murine MIRI model and tested the protective effect of TJ-M2010-5 by immunohistochemistry, flow cytometry, real-time PCR, and western blotting. Neonatal rat cardiomyocytes subjected to anoxia/reoxygenation were also isolated and their supernatants used to stimulate cardiac macrophagocytes and fibroblasts in vitro. MyD88 was found upregulated during the early and late phases after MIRI. The MyD88 inhibitor considerably improved cardiac function, reduced cardiomyocyte apoptosis, reduced IL-1β, IL-6, and TNF-α secretion, and inhibited CD80+CD86+MHCII+ macrophage and fibroblast migration. Moreover, TJ-M2010-5 markedly inhibited Toll-like receptor/MyD88 signaling in vivo and in vitro. Thus, our findings highlight TJ-M2010-5 as a potential therapeutic agent for MIRI treatment.

Biomarkers for the identification of cardiac fibroblast and myofibroblast cells

Experimental research has recognized the importance of cardiac fibroblast and myofibroblast cells in heart repair and function. In a normal healthy heart, the cardiac fibroblast plays a central role in the structural, electrical, and chemical aspects within the heart. Interestingly, the transformation of cardiac fibroblast cells to cardiac myofibroblast cells is suspected to play a vital part in the development of heart failure. The ability to differentiate between the two cells types has been a challenge. Myofibroblast cells are only expressed in the stressed or failing heart, so a better understanding of cell function may identify therapies that aid repair of the damaged heart. This paper will provide an outline of what is currently known about cardiac fibroblasts and myofibroblasts, the physiological and pathological roles within the heart, and causes for the transition of fibroblasts into myoblasts. We also reviewed the potential markers available for characterizing these cells and found that there is no single-cell specific marker that delineates fibroblast or myofibroblast cells. To characterize the cells of fibroblast origin, vimentin is commonly used. Cardiac fibroblasts can be identified using discoidin domain receptor 2 (DDR2) while α-smooth muscle actin is used to distinguish myofibroblasts. A known cytokine TGF-β₁ is well established to cause the transformation of cardiac fibroblasts to myofibroblasts. This review will also discuss clinical treatments that inhibit or reduce the actions of TGF-β₁ and its contribution to cardiac fibrosis and heart failure.