Myofibroblast-mediated mechanisms of pathological remodelling of the heart. Nat Rev Cardiol. 2013;10:15-26. [PMID: 23207731 DOI: 10.1038/nrcardio.2012.158]

Tanshinone IIA from Salvia miltiorrhiza exerts anti-fibrotic effects on cardiac fibroblasts and rat heart tissues by suppressing the levels of pro-fibrotic factors: The key role of miR-618

Tanshinone IIA (TAN) is widely employed for handling cardiovascular disorders. The current study explored the potential role of miRs in the antifibrotic effect of TAN on heart. Fibrotic features were induced in cardiac fibroblasts (CFs) and in rat hearts, and then handled with TAN. MicroRNAs (miRs) responding to TAN were determined using a microarray assay. The selected miR was modulated to verify its role in antifibrotic effects of TAN. TAN suppressed the viability and the production of α-SMA in CFs, which was associated with 101 miR being upregulated and 223 miR being downregulated. MiR-618 was selected as the potential target of TAN. Ang II inhibited miR-618 level and resulted in the upregulation of pro-fibrosis factors, which was reversed by TAN. The antifibrotic effect of TAN was weakened by miR-618 inhibition. TAN inhibits hypertrophy and collagen deposition in heart tissues, which is associated with the increased level of miR-618. PRACTICAL APPLICATIONS: The findings outlined in the current study show that the antifibrotic function of TAN is closely related to the function of miRs: the induction of miR-618 is indispensable for the function of TAN against the fibrotic process after heart injury, which will promote the application of TAN as an adjuvant therapy for improving heart function.

Exosomal myeloperoxidase as a biomarker of deep venous thrombosis

BACKGROUND

Deep vein thrombosis (DVT) often occurs following major orthopedic surgery. In this study, we investigated specific exosomal proteins as potential diagnostic biomarkers of DVT.

METHODS

Proteomic analysis of exosomes from four DVT patients and healthy controls (n=4) was performed by mass spectrometry. The model animals were evaluated at 1 inferior vena cava ligation [(IVCL)-1D], 3 (IVCL-3D), and 7 (IVCL-7D) days after IVCL. Endothelial cells in the thrombus segment were examined using terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assays and hematoxylin and eosin (HE) staining. Myeloperoxidase (MPO) expression in the damaged vessel was detected by immunofluorescence staining. Exosomes were co-cultured with human umbilical vein endothelial cells (HUVECs) and cell proliferation was estimated using Cell Counting Kit-8 (CCK-8) assays.

RESULTS

A total of 78 differentially expressed proteins (DEPs; 38 downregulated and 40 upregulated) were identified in the DVT group. In the rat DVT model, endothelial cells were damaged continuously after thrombosis, with the most serious injury in the IVCL-3D group, after which signs of endothelial repair were apparent. The IVCL-1D group showed the highest levels of vascular endothelial cell apoptosis and MPO increased sharply in the IVCL-1D and IVCL-3D groups, but had almost disappeared in the IVCL-7D group. In co-culture, plasma exosomes isolated from DVT model rats were efficiently absorbed by HUVECs, with markedly lower HUVECs growth and higher levels of apoptosis in the IVCL-1D and IVCL-3D groups compared with the control group.

CONCLUSIONS

Our findings suggest that exosomes may be involved in endothelial cell injury during DVT. The exosomal protein MPO is a potential biomarker of early stage DVT.

Beyond Ejection Fraction: Novel Clinical Approaches Towards Sudden Cardiac Death Risk Stratification in Patients with Dilated Cardiomyopathy

Implantable Cardioverter-Defibrillator (ICD) therapy is indicated for patients at risk for sudden cardiac death due to ventricular tachyarrhythmia. The most commonly used risk stratification algorithms use Left Ventricular Ejection Fraction (LVEF) to determine which patients qualify for ICD therapy, even though LVEF is a better marker of total mortality than ventricular tachyarrhythmias mortality. This review evaluates imaging tools and novel biomarkers proposed for better risk stratifying arrhythmic substrate, thereby identifying optimal ICD therapy candidates.

Detection of early myocardial cell death in owl monkeys (Aotus nancymai) using complement component C9 immunohistochemistry in formalin-fixed paraffin-embedded heart tissues: A retrospective study

BACKGROUND

Owl monkeys are commonly used in biomedical research which is affected by the high incidence of cardiomyopathy in this species. Occasionally, owl monkeys with no clinical signs of heart disease are found dead and at necropsy show no, or very mild, cardiomyopathy. A possible explanation for sudden death is acute myocardial infarction; however, early myocardial changes may be difficult to assess by conventional stains and light microscopy.

METHODS

Complement component C9 immunohistochemistry was performed in paraffin-embedded heart tissue samples from owl monkeys who died suddenly, or were euthanized due to sickness, to determine whether these animals suffered from acute myocardial infarcts.

RESULTS AND CONCLUSION

C9 deposits were found in the myocardium of 19 out of 20 (95%) animals. The findings in this study suggest owl monkeys suffer from acute myocardial infarcts, and complement component C9 immunohistochemistry may be a useful diagnostic tool.

MiR-185-5p regulates the development of myocardial fibrosis

BACKGROUND

Cardiac fibrosis stiffens the ventricular wall, predisposes to cardiac arrhythmias and contributes to the development of heart failure. In the present study, our aim was to identify novel miRNAs that regulate the development of cardiac fibrosis and could serve as potential therapeutic targets for myocardial fibrosis.

METHODS AND RESULTS

Analysis for cardiac samples from sudden cardiac death victims with extensive myocardial fibrosis as the primary cause of death identified dysregulation of miR-185-5p. Analysis of resident cardiac cells from mice subjected to experimental cardiac fibrosis model showed induction of miR-185-5p expression specifically in cardiac fibroblasts. In vitro, augmenting miR-185-5p induced collagen production and profibrotic activation in cardiac fibroblasts, whereas inhibition of miR-185-5p attenuated collagen production. In vivo, targeting miR-185-5p in mice abolished pressure overload induced cardiac interstitial fibrosis. Mechanistically, miR-185-5p targets apelin receptor and inhibits the anti-fibrotic effects of apelin. Finally, analysis of left ventricular tissue from patients with severe cardiomyopathy showed an increase in miR-185-5p expression together with pro-fibrotic TGF-β1 and collagen I.

CONCLUSIONS

Our data show that miR-185-5p targets apelin receptor and promotes myocardial fibrosis.

Hopes and Hurdles of Employing Mesenchymal Stromal Cells in the Treatment of Cardiac Fibrosis

Excessive cardiac fibrosis plays a crucial role in almost all types of heart disease. Generally, cardiac fibrosis is a scarring process triggered in response to stress, injury, or aging and is characterized by the accumulation of activated myofibroblasts that deposit high levels of extracellular matrix proteins in the myocardium. While it is beneficial for cardiac repair in the short term, it can also result in pathological remodeling, tissue stiffening, and cardiac dysfunction, contributing to the progression of heart failure, arrhythmia, and sudden cardiac death. Despite its high prevalence, there is a lack of effective and safe therapies that specifically target myofibroblasts to inhibit or even reverse pathological cardiac fibrosis. In the past few decades, cell therapy has been under continuous evaluation as a potential treatment strategy, and several studies have shown that transplantation of mesenchymal stromal cells (MSCs) can reduce cardiac fibrosis and improve heart function. Mechanistically, it is believed that the heart benefits from MSC therapy by stimulating innate anti-fibrotic and regenerative reactions. The mechanisms of action include paracrine signaling and cell-to-cell interactions. In this review, we provide an overview of the anti-fibrotic properties of MSCs and approaches to enhance them and discuss future directions of MSCs for the treatment of cardiac fibrosis.

Dexmedetomidine Promotes Lipopolysaccharide-Induced Differentiation of Cardiac Fibroblasts and Collagen I/III Synthesis through α2A Adrenoreceptor-Mediated Activation of the PKC-p38-Smad2/3 Signaling Pathway in Mice

Dexmedetomidine (DEX), a selective α₂ adrenergic receptor (AR) agonist, is commonly used as a sedative drug during critical illness. In the present study, we explored a novel accelerative effect of DEX on cardiac fibroblast (CF) differentiation mediated by LPS and clarified its potential mechanism. LPS apparently increased the expression of α-SMA and collagen I/III and the phosphorylation of p38 and Smad-3 in the CFs of mice. These effects were significantly enhanced by DEX through increasing α_2A-AR expression in CFs after LPS stimulation. The CFs from α_2A-AR knockout mice were markedly less sensitive to DEX treatment than those of wild-type mice. Inhibition of protein kinase C (PKC) abolished the enhanced effects of DEX on LPS-induced differentiation of CFs. We also found that the α-SMA level in the second-passage CFs was much higher than that in the nonpassage and first-passage CFs. However, after LPS stimulation, the TNF-α released from the nonpassage CFs was much higher than that in the first- and second-passage CFs. DEX had no effect on LPS-induced release of TNF-α and IL-6 from CFs. Further investigation indicated that DEX promoted cardiac fibrosis and collagen I/III synthesis in mice exposed to LPS for four weeks. Our results demonstrated that DEX effectively accelerated LPS-induced differentiation of CFs to myofibroblasts through the PKC-p38-Smad2/3 signaling pathway by activating α_2A-AR.

Pectins from various sources inhibit galectin-3-related cardiac fibrosis

PURPOSE OF THE STUDY

A major challenge in cardiology remains in finding a therapy for cardiac fibrosis. Inhibition of galectin-3 with pectins attenuates fibrosis in animal models of heart failure. The purpose of this study is to identify pectins with the strongest galectin-3 inhibitory capacity. We evaluated the in vitro inhibitory capacity, identified potent pectins, and tested if this potency could be validated in a mouse model of myocardial fibrosis.

METHODS

Various pectin fractions were screened in vitro. Modified rhubarb pectin (EMRP) was identified as the most potent inhibitor of galectin-3 and compared to the well-known modified citrus pectin (MCP). Our findings were validated in a mouse model of myocardial fibrosis, which was induced by angiotensin II (Ang II) infusion.

RESULTS

Ang II infusion was associated with a 4-5-fold increase in fibrosis signal in the tissue of the left ventricle, compared to the control group (0•22±0•10 to 1•08±0•53%; P < 0•001). After treatment with rhubarb pectin, fibrosis was reduced by 57% vs. Ang II alone while this reduction was 30% with the well-known MCP (P = NS, P < 0•05). Treatment was associated with a reduced cardiac inflammatory response and preserved cardiac function.

CONCLUSION

The galectin-3 inhibitor natural rhubarb pectin has a superior inhibitory capacity over established pectins, substantially attenuates cardiac fibrosis, and preserves cardiac function in vivo. Bioactive pectins are natural sources of galectin-3 inhibitors and may be helpful in the prevention of heart failure or other diseases characterized by fibrosis.

FUNDING

Dr. Meijers is supported by the Mandema-Stipendium of the Junior Scientific Masterclass 2020-10, University Medical Center Groningen and by the Netherlands Heart Foundation (Dekkerbeurs 2021)Dr. de Boer is supported by the Netherlands Heart Foundation (CVON SHE-PREDICTS-HF, grant 2017-21; CVON RED-CVD, grant 2017-11; CVON PREDICT2, grant 2018-30; and CVON DOUBLE DOSE, grant 2020B005), by a grant from the leDucq Foundation (Cure PhosphoLambaN induced Cardiomyopathy (Cure-PLaN), and by a grant from the European Research Council (ERC CoG 818715, SECRETE-HF).

The role of microRNAs in diseases and related signaling pathways

MicroRNAs (miRNAs) are epigenetic regulators of the gene expression and act through posttranslational modification. They bind to 3'-UTR of target mRNAs to inhibit translation or increase the degradation mRNA in many tissues. Any alteration in the level of miRNA expression in many human diseases indicates their involvement in the pathogenesis of many diseases. On the other hand, the regulation of the signaling pathways is necessary for the maintenance of natural and physiological characteristics of any cell. It is worth mentioning that dysfunction of the signaling pathways manifests itself as a disorder or disease. The significant evidence report that miRNAs regulate the several signaling pathways in many diseases. Base on previous studies, miRNAs can be used for therapeutic or diagnostic purposes. According to the important role of miRNAs on the cell signaling pathways, this article reviews miRNAs involvement in incidence of diseases by changing signaling pathways.

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.

Fibrotic Remodeling during Persistent Atrial Fibrillation: In Silico Investigation of the Role of Calcium for Human Atrial Myofibroblast Electrophysiology

During atrial fibrillation, cardiac tissue undergoes different remodeling processes at different scales from the molecular level to the tissue level. One central player that contributes to both electrical and structural remodeling is the myofibroblast. Based on recent experimental evidence on myofibroblasts' ability to contract, we extended a biophysical myofibroblast model with Ca²⁺ handling components and studied the effect on cellular and tissue electrophysiology. Using genetic algorithms, we fitted the myofibroblast model parameters to the existing in vitro data. In silico experiments showed that Ca²⁺ currents can explain the experimentally observed variability regarding the myofibroblast resting membrane potential. The presence of an L-type Ca²⁺ current can trigger automaticity in the myofibroblast with a cycle length of 799.9 ms. Myocyte action potentials were prolonged when coupled to myofibroblasts with Ca²⁺ handling machinery. Different spatial myofibroblast distribution patterns increased the vulnerable window to induce arrhythmia from 12 ms in non-fibrotic tissue to 22 ± 2.5 ms and altered the reentry dynamics. Our findings suggest that Ca²⁺ handling can considerably affect myofibroblast electrophysiology and alter the electrical propagation in atrial tissue composed of myocytes coupled with myofibroblasts. These findings can inform experimental validation experiments to further elucidate the role of myofibroblast Ca²⁺ handling in atrial arrhythmogenesis.

Cardiac fibrosis and curcumin: a novel perspective on this natural medicine

BACKGROUND

According to WHO statistics, cardiovascular disease are the leading causes of death in the world. One of the main factors which is causing heart failure, systolic and diastolic dysfunction, and arrythmias is a condition named cardiac fibrosis. This condition is defined by the accumulation of fibroblast-produced ECM in myocardium layer of the heart.

OBJECTIVE

Accordingly, the current review aims to depict the role of curcumin in the regulation of different signaling pathways that are involved in cardiac fibrosis.

RESULTS

A great number of cellular and molecular mechanisms such as oxidative stress, inflammation, and mechanical stress are acknowledged to be involved in cardiac fibrosis. Despite the available therapeutic procedures which are designed to target these mechanisms in order to prevent cardiac fibrosis, still, effective therapeutic methods are needed. Curcumin is a natural Chinese medicine which currently has been declared to have therapeutic properties such as anti-oxidant and immunomodulatory activities. In this review, we have gathered several experimental studies in order to represent diverse impacts of this turmeric derivative on pathogenic factors of cardiac fibrosis.

CONCLUSION

Curcumin might open new avenues in the field of cardiovascular treatment.

Ivabradine Ameliorates Cardiac Function in Heart Failure with Preserved and Reduced Ejection Fraction via Upregulation of miR-133a

Heart failure (HF) is a clinical syndrome caused by impairment of ventricular filling, ejection of blood, or both and is categorized as HF with reduced ejection fraction (HFrEF) or HF with preserved ejection fraction (HFpEF) based on left ventricular function. Cardiac fibrosis contributes to left ventricular dysfunction and leads to the development of HF. Ivabradine, an If current selective specific inhibitor, has been shown to improve the prognosis of patients with HF. However, the effects of ivabradine on cardiac function and fibrosis in HFpEF and HFrEF and the underlying mechanism remain unclear. In the present study, we utilized mouse models to mimic HFpEF and HFrEF and evaluated the therapeutic effects of ivabradine. By treating mice with different doses (10 mg/kg/d and 20 mg/kg/d) of ivabradine for 4 or 8 weeks, we found that a high dose of ivabradine improved cardiac diastolic function in HFpEF mice and ameliorated cardiac diastolic and systolic function and ventricular tachycardia incidence in HFrEF mice. Moreover, ivabradine significantly reduced the activation of cardiac fibroblasts and myocardial fibrosis in mice. Mechanistically, microRNA-133a, which was upregulated by ivabradine, targeted connective tissue growth factor and collagen 1 in cardiac fibroblasts and might contribute to the protective role of ivabradine. Together, our work utilized mouse models to study HFpEF and HFrEF, demonstrated the protective role of ivabradine in HFpEF and HFrEF, and elucidated the potential underlying mechanism, which provides an effective strategy for related diseases.

Myocardial fibrosis: morphologic patterns and role of imaging in diagnosis and prognostication

Myocardial fibrosis is defined as an increased amount of collagen in the myocardium relative to cardiac myocytes. Two main morphologic patterns are recognized: 1) replacement fibrosis, which occurs in response to myocyte necrosis (myocardial scarring); and 2) interstitial fibrosis, which is usually a diffuse process and has been shown to be reversible and treatable. Replacement and interstitial fibrosis often coexist and are a constant feature of pathologic cardiac remodeling. In the last twenty years, there has been significant interest in developing objective non-invasive methods to identify and quantitatively assess myocardial fibrosis in vivo, both for diagnostic purposes and to improve stratification of patients. The present Review focuses on the morphologic patterns of myocardial fibrosis observed either at autopsy and heart transplant, or in vivo by non-invasive imaging techniques. Main aim is to provide clues for the differential diagnosis, with emphasis on entities whose diagnosis may be challenging. An update on the diagnostic and prognostic role of imaging, along with recent data on available biomarkers, is also proposed.

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.

Connecting different heart diseases through intercellular communication

Well-orchestrated intercellular communication networks are pivotal to maintaining cardiac homeostasis and to ensuring adaptative responses and repair after injury. Intracardiac communication is sustained by cell-cell crosstalk, directly via gap junctions (GJ) and tunneling nanotubes (TNT), indirectly through the exchange of soluble factors and extracellular vesicles (EV), and by cell-extracellular matrix (ECM) interactions. GJ-mediated communication between cardiomyocytes and with other cardiac cell types enables electrical impulse propagation, required to sustain synchronized heart beating. In addition, TNT-mediated organelle transfer has been associated with cardioprotection, whilst communication via EV plays diverse pathophysiological roles, being implicated in angiogenesis, inflammation and fibrosis. Connecting various cell populations, the ECM plays important functions not only in maintaining the heart structure, but also acting as a signal transducer for intercellular crosstalk. Although with distinct etiologies and clinical manifestations, intercellular communication derailment has been implicated in several cardiac disorders, including myocardial infarction and hypertrophy, highlighting the importance of a comprehensive and integrated view of complex cell communication networks. In this review, I intend to provide a critical perspective about the main mechanisms contributing to regulate cellular crosstalk in the heart, which may be considered in the development of future therapeutic strategies, using cell-based therapies as a paradigmatic example. This Review has an associated Future Leader to Watch interview with the author.

Cardiac Fibrosis: Cellular Effectors, Molecular Pathways, and Exosomal Roles

Cardiac fibrosis, a common pathophysiologic process in most heart diseases, refers to an excess of extracellular matrix (ECM) deposition by cardiac fibroblasts (CFs), which can lead to cardiac dysfunction and heart failure subsequently. Not only CFs but also several other cell types including macrophages and endothelial cells participate in the process of cardiac fibrosis via different molecular pathways. Exosomes, ranging in 30-150 nm of size, have been confirmed to play an essential role in cellular communications by their bioactive contents, which are currently a hot area to explore pathobiology and therapeutic strategy in multiple pathophysiologic processes including cardiac fibrosis. Cardioprotective factors such as RNAs and proteins packaged in exosomes make them an excellent cell-free system to improve cardiac function without significant immune response. Emerging evidence indicates that targeting selective molecules in cell-derived exosomes could be appealing therapeutic treatments in cardiac fibrosis. In this review, we summarize the current understandings of cellular effectors, molecular pathways, and exosomal roles in cardiac fibrosis.

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.

Bottom-up proteomic analysis of human adult cardiac tissue and isolated cardiomyocytes

The heart is composed of multiple cell types, each with a specific function. Cell-type-specific approaches are necessary for defining the intricate molecular mechanisms underlying cardiac development, homeostasis, and pathology. While single-cell RNA-seq studies are beginning to define the chamber-specific cellular composition of the heart, our views of the proteome are more limited because most proteomics studies have utilized homogenized human cardiac tissue. To promote future cell-type specific analyses of the human heart, we describe the first method for cardiomyocyte isolation from cryopreserved human cardiac tissue followed by flow cytometry for purity assessment. We also describe a facile method for preparing isolated cardiomyocytes and whole cardiac tissue homogenate for bottom-up proteomic analyses. Prior experience in dissociating cardiac tissue or proteomics is not required to execute these methods. We compare different sample preparation workflows and analysis methods to demonstrate how these can impact the depth of proteome coverage achieved. We expect this how-to guide will serve as a starting point for investigators interested in general and cell-type-specific views of the cardiac proteome.

Comparative and Combinatorial Effects of Resveratrol and Sacubitril/Valsartan alongside Valsartan on Cardiac Remodeling and Dysfunction in MI-Induced Rats

The development and progression of heart failure (HF) due to myocardial infarction (MI) is a major concern even with current optimal therapy. Resveratrol is a plant polyphenol with cardioprotective properties. Sacubitril/valsartan is known to be beneficial in chronic HF patients. In this study, we investigated the comparative and combinatorial benefits of resveratrol with sacubitril/valsartan alongside an active comparator valsartan in MI-induced male Sprague Dawley rats. MI-induced and sham-operated animals received vehicle, resveratrol, sacubitril/valsartan, valsartan alone or sacubitril/valsartan + resveratrol for 8 weeks. Echocardiography was performed at the endpoint to assess cardiac structure and function. Cardiac oxidative stress, inflammation, fibrosis, brain natriuretic peptide (BNP), creatinine and neutrophil gelatinase associated lipocalin were measured. Treatment with resveratrol, sacubitril/valsartan, valsartan and sacubitril/valsartan + resveratrol significantly prevented left ventricular (LV) dilatation and improved LV ejection fraction in MI-induced rats. All treatments also significantly reduced myocardial tissue oxidative stress, inflammation and fibrosis, as well as BNP. Treatment with the combination of sacubitril/valsartan and resveratrol did not show additive effects. In conclusion, resveratrol, sacubitril/valsartan, and valsartan significantly prevented cardiac remodeling and dysfunction in MI-induced rats. The reduction in cardiac remodeling and dysfunction in MI-induced rats was mediated by a reduction in cardiac oxidative stress, inflammation and fibrosis.

A Retinoic Acid Receptor β 2 Agonist Improves Cardiac Function in a Heart Failure Model

We previously demonstrated that the selective retinoic acid receptor (RAR) β ₂ agonist AC261066 reduces oxidative stress in an ex vivo murine model of ischemia/reperfusion. We hypothesized that by decreasing oxidative stress and consequent fibrogenesis, AC261066 could attenuate the development of contractile dysfunction in post-ischemic heart failure (HF). We tested this hypothesis in vivo using an established murine model of myocardial infarction (MI), obtained by permanent occlusion of the left anterior descending coronary artery. Treating mice with AC261066 in drinking water significantly attenuated the post-MI deterioration of echocardiographic indices of cardiac function, diminished remodeling, and reduced oxidative stress, as evidenced by a decrease in malondialdehyde level and p38 mitogen-activated protein kinase expression in cardiomyocytes. The effects of AC261066 were also associated with a decrease in interstitial fibrosis, as shown by a marked reduction in collagen deposition and α-smooth muscle actin expression. In cardiac murine fibroblasts subjected to hypoxia, AC261066 reversed hypoxia-induced decreases in superoxide dismutase 2 and angiopoietin-like 4 transcriptional levels as well as the increase in NADPH oxidase 2 mRNA, demonstrating that the post-MI cardioprotective effects of AC261066 are associated with an action at the fibroblast level. Thus, AC261066 alleviates post-MI cardiac dysfunction by modulating a set of genes involved in the oxidant/antioxidant balance. These AC261066 responsive genes diminish interstitial fibrogenesis and remodeling. Since MI is a recognized major cause of HF, our data identify RARβ ₂ as a potential pharmacological target in the treatment of HF. SIGNIFICANCE STATEMENT: A previous report showed that the selective retinoic acid receptor (RAR) β ₂ agonist AC261066 reduces oxidative stress in an ex vivo murine model of ischemia/reperfusion. This study shows that AC261066 attenuates the development of contractile dysfunction and maladaptive remodeling in post-ischemic heart failure (HF) by modulating a set of genes involved in oxidant/antioxidant balance. Since myocardial infarction is a recognized major cause of HF, these data identify RARβ ₂ as a potential pharmacological target in the treatment of HF.

Concurrent cardiac transthyretin and brain β amyloid accumulation among the older adults: The Hisayama study

Previous studies have revealed risk for cognitive impairment in cardiovascular diseases. We investigated the relationship between degenerative changes of the brain and heart, with reference to Alzheimer's disease (AD) pathologies, cardiac transthyretin amyloid (ATTR) deposition, and cardiac fibrosis. A total of 240 consecutive autopsy cases of a Japanese population‐based study were examined. β amyloid (Aβ) of senile plaques, phosphorylated tau protein of neurofibrillary tangles, and ATTR in the hearts were immunohistochemically detected and graded according to the NIH‐AA guideline for AD pathology and as Tanskanen reported, respectively. Cerebral amyloid angiopathy (CAA) was graded according to the Vonsattel scale. Cardiac fibrosis was detected by picrosirius red staining, followed by image analysis. Cardiac ATTR deposition occurred after age 75 years and increased in an age‐dependent manner. ATTR deposition was more common, and of higher grades, in the dementia cases. We subdivided the cases into two age groups: ≤90 years old (n = 173) and >90 years old (n = 67), which was the mean and median age at death of the AD cases. When adjusted for age and sex, TTR deposition grades correlated with Aβ phase score (A2–3), the Consortium to Establish a Registry for AD score (sparse to frequent), and high Braak stage (V–VI) only in those aged ≤90 years at death. No significant correlation was observed between the cardiac ATTR deposition and CAA stages, or between cardiac fibrosis and AD pathologies. Collectively, AD brain pathology correlated with cardiac TTR deposition among the older adults ≤90 years.

EDIL3 deficiency ameliorates adverse cardiac remodeling by neutrophil extracellular traps (NET)-mediated macrophage polarization

AIMS

After myocardial infarction (MI), injured cardiomyocytes recruit neutrophils and monocytes/macrophages to myocardium, which in turn initiates inflammatory and reparative cascades, respectively. Either insufficient or excessive inflammation impairs cardiac healing. As an endogenous inhibitor of neutrophil adhesion, EDIL3 plays a crucial role in inflammatory regulation. However, the role of EDIL3 in MI remains obscure. We aimed to define the role of EDIL3 in cardiac remodeling after MI.

METHODS AND RESULTS

Serum EDIL3 levels in MI patients were negatively associated with MI biomarkers. Consistently, WT mice after MI showed low levels of cardiac EDIL3. Compared with WT mice, Edil3-/- mice showed improvement of post-MI adverse remodeling, as they exhibited lower mortality, better cardiac function, shorter scar length and smaller LV cavity. Accordingly, infarcted hearts of Edil3-/- mice contained fewer cellular debris and lower amounts of fibrosis content, with decreased collagen I/III expression and the percentage of α-smooth muscle actin (α-SMA) myofibroblasts. Mechanistically, EDIL3 deficiency did not affect the recruitment of monocytes or T cells, but enhanced neutrophil recruitment and following expansion of pro-inflammatory Mertk-MHC-IIlo-int (myeloid-epithelial-reproductive tyrosine kinase/major histocompatibility complex II) macrophages. The injection of neutrophil-specific C-X-C motif chemokine receptor 2 (CXCR2) antagonist eliminated the differences in macrophage polarization and cardiac function between WT and Edil3-/- mice after MI. Neutrophil extracellular traps (NETs), which were more abundant in the hearts of Edil3-/- mice, contributed to Mertk-MHC-IIlo-int polarization via toll-like receptor 9 pathway. The inhibition of NET formation by treatment of neutrophil elastase inhibitor or DNase I impaired macrophage polarization, increased cellular debris and aggravated cardiac adverse remodeling, thus removed the differences of cardiac function between WT and Edil3-/- mice. Totally, EDIL3 plays an important role in NET-primed macrophage polarization and cardiac remodeling during MI.

CONCLUSION

We not only reveal that EDIL3 deficiency ameliorates adverse cardiac healing via NET-mediated pro-inflammatory macrophage polarization but also discover a new crosstalk between neutrophil and macrophage after MI.

TRANSLATIONAL PERSPECTIVE

We established EDIL3 as a critical regulator of neutrophil recruitment and macrophage polarization during post-MI cardiac remodeling. EDIL3 may be a candidate prognostic biomarker and drug target for cardiovascular diseases. The novel pathways and mechanisms revealed in this study has renewed our understanding of the role of leukocyte adhesion inhibitors in cardiovascular disease. Meanwhile, our study reaffirmed the indispensable role of inflammation in the healing process, thereby prompting the reevaluation of post-MI anti-inflammatory treatments.

Traditional Chinese medicine as a therapeutic option for cardiac fibrosis: Pharmacology and mechanisms

Cardiovascular diseases are one of the leading causes of death worldwide and cardiac fibrosis is a common pathological process for cardiac remodeling in cardiovascular diseases. Cardiac fibrosis not only accelerates the deterioration progress of diseases but also becomes a pivotal contributor for futile treatment in clinical cardiovascular trials. Although cardiac fibrosis is common and prevalent, effective medicines to provide sufficient clinical intervention for cardiac fibrosis are still unavailable. Traditional Chinese medicine (TCM) is the natural essence experienced boiling, fry, and other processing methods, including active ingredients, extracts, and herbal formulas, which have been applied to treat human diseases for a long history. Recently, research has increasingly focused on the great potential of TCM for the prevention and treatment of cardiac fibrosis. Here, we aim to clarify the identified pro-fibrotic mechanisms and intensively summarize the application of TCM in improving cardiac fibrosis by working on these mechanisms. Through comprehensively analyzing, TCM mainly regulates the following pathways during ameliorating cardiac fibrosis: attenuation of inflammation and oxidative stress, inhibition of cardiac fibroblasts activation, reduction of extracellular matrix accumulation, modulation of the renin-angiotensin-aldosterone system, modulation of autophagy, regulation of metabolic-dependent mechanisms, and targeting microRNAs. We also discussed the deficiencies and the development direction of anti-fibrotic therapies on cardiac fibrosis. The data reviewed here demonstrates that TCM shows a robust effect on alleviating cardiac fibrosis, which provides us a rich source of new drugs or drug candidates. Besides, we also hope this review may give some enlightenment for treating cardiac fibrosis in clinical practice.

8-Gingerol Ameliorates Myocardial Fibrosis by Attenuating Reactive Oxygen Species, Apoptosis, and Autophagy via the PI3K/Akt/mTOR Signaling Pathway

8-gingerol (8-Gin) is the series of phenolic substance that is extracted from ginger. Although many studies have revealed that 8-Gin has multiple pharmacological properties, the possible underlying mechanisms of 8-Gin against myocardial fibrosis (MF) remains unclear. The study examined the exact role and potential mechanisms of 8-Gin against isoproterenol (ISO)-induced MF. Male mice were intraperitoneally injected with 8-Gin (10 and 20 mg/kg/d) and concurrently subcutaneously injected with ISO (10 mg/kg/d) for 2 weeks. Electrocardiography, pathological heart morphology, myocardial enzymes, reactive oxygen species (ROS) generation, degree of apoptosis, and autophagy pathway-related proteins were measured. Our study observed 8-Gin significantly reduced J-point elevation and heart rate. Besides, 8-Gin caused a marked decrease in cardiac weight index and left ventricle weight index, serum levels of creatine kinase and lactate dehydrogenase (CK and LDH, respectively), ROS generation, and attenuated ISO-induced pathological heart damage. Moreover, treatment with 8-Gin resulted in a marked decrease in the levels of collagen types I and III and TGF-β in the heart tissue. Our results showed 8-Gin exposure significantly suppressed ISO-induced autophagosome formation. 8-Gin also could lead to down-regulation of the activities of matrix metalloproteinases-9 (MMP-9), Caspase-9, and Bax protein, up-regulation of the activity of Bcl-2 protein, and alleviation of cardiomyocyte apoptosis. Furthermore, 8-Gin produced an obvious increase in the expressions of the PI3K/Akt/mTOR signaling pathway-related proteins. Our data showed that 8-Gin exerted cardioprotective effects on ISO-induced MF, which possibly occurred in connection with inhibition of ROS generation, apoptosis, and autophagy via modulation of the PI3K/Akt/mTOR signaling pathway.

Conophylline Suppresses Angiotensin II-Induced Myocardial Fibrosis In Vitro via the BMP4/JNK Pathway

We studied the effects and mechanisms of action of conophylline in different concentrations in the original in vitro model of myocardial fibrosis (treatment of cardiac fibroblasts isolated form the hearts of newborn rats with angiotensin II). Viability, collagen content, and expression of related protein in cardiac fibroblasts were assessed using the MTT-test, Sircol assay, and Western blotting, respectively. Conophylline markedly protected the cultured cells against the development of angiotensin II-induced fibrosis, which was seen from reduced viability of fibroblasts, decreased collagen content, and down-regulation of the expression of α-smooth muscle actin (α-SMA). Conophylline did not affect the TGF-β pathway altered by angiotensin II, but markedly decreased the level of bone morphogenetic protein-4 (BMP4) enhanced by angiotensin II and BMP4 itself. Conophylline produced no effect on phosphorylation of α-SMA and Smad homologue-1/5/8, the classic BMP4 downstream pathway elements, but reduced the level of c-Jun N-terminal kinase (JNK) elevated by BMP4. Conophylline did not inhibit the development of myocardial fibrosis in the presence of JNK activator anisomycin. Thus, conophylline inhibited angiotensin II-provoked myocardial fibrosis via the BMP4/JNK pathway.

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.

Senolytic Agent Navitoclax Inhibits Angiotensin II-Induced Heart Failure in Mice

Navitoclax, which is a type of senolytic drug, selectively eliminates senescent cells. This study aimed to evaluate the therapeutic potential of navitoclax in treatment of angiotensin II (Ang II)-induced heart failure in mice. Navitoclax or vehicle was administrated in mice with Ang II-induced heart failure. Cardiac function and electrophysiology were assessed before and after administration of navitoclax. Cardiac remodeling, including morphological changes, fibrosis, and inflammatory responses, was analyzed in myocardial tissue. Cellular effects of navitoclax were validated in isolated primary cardiomyocytes and cardiac fibroblasts in vitro. Echocardiography of mice showed that navitoclax improved cardiac dysfunction by improving the left ventricular ejection fraction (vehicle: 45.88 ± 2.19%; navitoclax: 54.70 ± 1.65%, P < 0.01). In cardiac electrophysiological testing, navitoclax increased conduction velocity (vehicle: 1.37 ± 0.05 mm/ms; navitoclax: 1.69 ± 0.08 mm/ms, P < 0.05) and decreased susceptibility to ventricular tachyarrhythmia induced by programmed electrical stimulation. Histopathological staining, immunofluorescence, and western blotting examinations showed that navitoclax ameliorated Ang II-induced cardiac fibrosis, hypertrophy, and the inflammatory response. Moreover, navitoclax eliminated senescent cells by inducing apoptosis. Therefore, navitoclax improved cardiac function and electrophysiological characteristics through decreasing cardiac fibrosis, hypertrophy, and inflammation in mice with heart failure. Pharmacological clearance of senescent cells may be a potential therapeutic approach in heart failure with reduced ejection fraction.

In vivo reprogramming as a new approach to cardiac regenerative therapy

Cardiovascular diseases are a common cause of death worldwide. Adult cardiomyocytes have limited regenerative capacity after injury, and there is growing interest in cardiac regeneration as a new therapeutic strategy. There are several limitations of induced pluripotent stem cell-based transplantation therapy with respect to efficiency and risks of tumorigenesis. Direct reprogramming enables the conversion of terminally differentiated cells into target cell types using defined factors. In most cardiac diseases, activated fibroblasts proliferate in the damaged heart and contribute to the progression of heart failure. In vivo cardiac reprogramming, in which resident cardiac fibroblasts are converted into cardiomyocytes in situ, is expected to become a new cardiac regenerative therapy. Indeed, we and other groups have demonstrated that in vivo reprogramming improves cardiac function and reduces fibrosis after myocardial infarction. In this review, we summarize recent discoveries and developments related to in vivo reprogramming. In addition, issues that need to be resolved for clinical application are described.

Prognostic significance of liver stiffness assessed by fibrosis-4 index in patients with heart failure

BACKGROUND

Heart failure (HF)-related congestive hepatopathy is a well-recognized problem in management of HF. The fibrosis-4 (FIB4) index calculated by [age × aspartate aminotransferase (IU/L)/platelet count (10⁹ /L) × square root of alanine aminotransferase (IU/L)] is useful for evaluating liver stiffness. We aimed to investigate the impact of the FIB4 index on prognosis in patients with HF.

METHODS AND RESULTS

Consecutive HF patients referred for hospitalization at Kumamoto University Hospital, Japan, were registered between 2006 and 2015. We observed cardiovascular outcomes in each type of HF [HF with reduced left ventricular ejection fraction (LVEF) (HFrEF), HF with mid-range LVEF (HFmrEF) and with preserved LVEF (HFpEF)] according to their FIB4 index; Group 1 (FIB4 index <1.3), Group 2 (FIB4 index: 1.3-2.67), and Group 3 (FIB4 index >2.67). This study enrolled 83 HFrEF patients, 117 HFmrEF patients, and 504 HFpEF patients. In HFpEF patients, the Kaplan-Meier curve revealed that Group 3 had a significantly higher rate of total cardiovascular events compared with the other two groups. By contrast, the occurrences of total cardiovascular events were not different among three groups in HFrEF and HFmrEF patients. Multivariate Cox proportional hazard analysis with significant factors in univariate analysis identified that the FIB4 index as an independent and significant predictor for future total cardiovascular events in HFpEF patients (hazard ratio: 1.09, 95% confidence interval: 1.03-1.15, P = 0.001).

CONCLUSIONS

The FIB4 index was a significant predictor for total cardiovascular events in HFpEF.

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.

Cardiac morphological and functional changes induced by C-type natriuretic peptide are different in normotensive and spontaneously hypertensive rats

OBJECTIVE

Inflammation and fibrosis are key mechanisms in cardiovascular remodeling. C-type natriuretic peptide (CNP) is an endothelium-derived factor with a cardiovascular protective role, although its in-vivo effect on cardiac remodeling linked to hypertension has not been investigated. The aim of this study was to determine the effects of chronic administration of CNP on inflammatory and fibrotic cardiac mechanisms in normotensive Wistar rats and spontaneously hypertensive rats (SHR).

METHODS

Twelve-week-old male SHR and normotensive rats were infused with CNP (0.75 μg/h/100 g) or isotonic saline (NaCl 0.9%) for 14 days (subcutaneous micro-osmotic pumps). Echocardiograms and electrocardiograms were performed, and SBP was measured. After treatment, transforming growth factor-beta 1, Smad proteins, tumor necrosis factor-alpha, interleukin-1 and interleukin-6, nitric oxide (NO) system and 2-thiobarbituric acid-reactive substances were evaluated in left ventricle. Histological studies were also performed.

RESULTS

SHR showed lower cardiac output with signs of fibrosis and hypertrophy in left ventricle, higher NO-system activity and more oxidative damage, as well as higher pro-inflammatory and pro-fibrotic markers than normotensive rats. Chronic CNP treatment-attenuated hypertension and ventricular hypertrophy in SHR, with no changes in normotensive rats. In left ventricle, CNP induced an anti-inflammatory and antifibrotic response, decreasing both pro-fibrotic and pro-inflammatory cytokines in SHR. In addition, CNP reduced oxidative damage as well as collagen content, and upregulated the NO system in both groups.

CONCLUSION

Chronic CNP treatment appears to attenuate hypertension and associated end-organ damage in the heart by reducing inflammation and fibrosis.

PU.1 inhibition attenuates atrial fibrosis and atrial fibrillation vulnerability induced by angiotensin-II by reducing TGF-β1/Smads pathway activation

Fibrosis serves a critical role in driving atrial remodelling‐mediated atrial fibrillation (AF). Abnormal levels of the transcription factor PU.1, a key regulator of fibrosis, are associated with cardiac injury and dysfunction following acute viral myocarditis. However, the role of PU.1 in atrial fibrosis and vulnerability to AF remain unclear. Here, an in vivo atrial fibrosis model was developed by the continuous infusion of C57 mice with subcutaneous Ang‐II, while the in vitro model comprised atrial fibroblasts that were isolated and cultured. The expression of PU.1 was significantly up‐regulated in the Ang‐II‐induced group compared with the sham/control group in vivo and in vitro. Moreover, protein expression along the TGF‐β1/Smads pathway and the proliferation and differentiation of atrial fibroblasts induced by Ang‐II were significantly higher in the Ang‐II‐induced group than in the sham/control group. These effects were attenuated by exposure to DB1976, a PU.1 inhibitor, both in vivo and in vitro. Importantly, in vitro treatment with small interfering RNA against Smad3 (key protein of TGF‐β1/Smads signalling pathway) diminished these Ang‐II‐mediated effects, and the si‐Smad3‐mediated effects were, in turn, antagonized by the addition of a PU.1‐overexpression adenoviral vector. Finally, PU.1 inhibition reduced the atrial fibrosis induced by Ang‐II and attenuated vulnerability to AF, at least in part through the TGF‐β1/Smads pathway. Overall, the study implicates PU.1 as a potential therapeutic target to inhibit Ang‐II‐induced atrial fibrosis and vulnerability to AF.

Left atrial fibrosis progression detected by LGE-MRI after ablation of atrial fibrillation

BACKGROUND

Left atrial (LA) fibrosis is thought to be a substrate for atrial fibrillation (AF) and can be quantified by late gadolinium enhancement magnetic resonance imaging (LGE-MRI). Fibrosis formation in LA is a dynamic process and may either progress or regress following AF ablation. We examined the impact of postablation progression in LA fibrosis on AF recurrence.

METHODS

LA enhancement in LGE-MRI was quantified in 127 consecutive patients who underwent first time AF ablation. Serial LGE-MRIs were done prior to AF ablation, 3 months postablation and at least 12 months after second LGE-MRI. Transient postablation lesion (TL) was defined as atrial enhancement caused by ablation lesions that was detected on the first (3 month) but not on the second postablation LGE-MRI. New fibrosis (NF) was defined as atrial enhancement detected on the most recent LGE-MRI, at least 15 months after the ablation procedure. AF recurrence and its correlation with TL and NF was assessed in all patients during the follow-up period.

RESULTS

An increase of 1% NF increased the chance of postablation AF recurrence by 3% (hazard ratio [HR] 1.03, 95% CI 1-1.06, P = .05). TL had no significant impact on recurrence (P = .057). After adjusting for cardiovascular risk factors, HR increased as NF became greater. Greater volume of NF (≥21%) corresponded with lower arrhythmia-free survival (37% vs 62%, P = .01).

CONCLUSION

NF formation postablation of AF is a novel marker of long-term procedural outcome. Extensive NF is associated with significantly higher risk of atrial arrhythmia recurrence.

Cardiac fibrosis: Myofibroblast-mediated pathological regulation and drug delivery strategies

Cardiac fibrosis remains an unresolved problem in heart diseases. After initial injury, cardiac fibroblasts (CFs) are activated and subsequently differentiate into myofibroblasts (myoFbs) that are major mediator cells in the pathological remodeling. MyoFbs exhibit proliferative and secretive characteristics, and contribute to extracellular matrix (ECM) turnover, collagen deposition. The persistent functions of myoFbs lead to fibrotic scars and cardiac dysfunction. The anti-fibrotic treatment is hindered by the elusive mechanism of fibrosis and lack of specific targets on myoFbs. In this review, we will outline the progress of cardiac fibrosis and its contributions to the heart failure. We will also shed light on the role of myoFbs in the regulation of adverse remodeling. The communication between myoFbs and other cells that are involved in the heart injury and repair respectively will be reviewed in detail. Then, recently developed therapeutic strategies to treat fibrosis will be summarized such as i) chimeric antigen receptor T cell (CAR-T) therapy with an optimal target on myoFbs, ii) direct reprogramming from stem cells to quiescent CFs, iii) "off-target" small molecular drugs. The application of nano/micro technology will be discussed as well, which is involved in the construction of cell-based biomimic platforms and "pleiotropic" drug delivery systems.

Cardiac fibroblast activation detected by Ga-68 FAPI PET imaging as a potential novel biomarker of cardiac injury/remodeling

BACKGROUND

Fibroblast activation protein (FAP) as a specific marker of activated fibroblasts can be visualized by positron emission tomography (PET) using Ga-68-FAP inhibitors (FAPI). Gallium-68-labeled FAPI is increasingly used in the staging of various cancers. In addition, the first cases of theranostic approaches have been reported. In this work, we describe the phenomenon of myocardial FAPI uptake in patients who received a Ga-68 FAPI PET for tumor staging.

METHOD AND RESULTS

Ga-68 FAPI PET examinations for cancer staging were retrospectively analyzed with respect to cardiac tracer uptake. Standardized uptake values (SUV) were correlated to clinical covariates in a univariate regression model. From 09/2018 to 11/2019 N = 32 patients underwent FAPI PET at our institution. Six out of 32 patients (18.8%) demonstrated increased localized myocardial tracer accumulation, with remote FAPI uptake being significantly higher in patients with vs without localized focal myocardial uptake (SUVmax 2.2 ± .6 vs 1.5 ± .4, P < .05 and SUVmean 1.6 ± .4 vs 1.2 ± .3, P < .05, respectively). Univariate regression demonstrated a significant correlation of coronary artery disease (CAD), age and left ventricular ejection fraction (LVEF) with remote SUVmean uptake, the latter with a very strong correlation with remote uptake (R2 = .74, P < .01).

CONCLUSION

Our study indicates an association of CAD, age, and LVEF with FAPI uptake. Further studies are warranted to assess if fibroblast activation can be reliably measured and may be used for risk stratification regarding early detection or progression of CAD and left ventricular remodeling.

Sex-Specific Differences of the Inflammatory State in Experimental Autoimmune Myocarditis

Increasing evidence suggests male sex as a potential risk factor for a higher incidence of cardiac fibrosis, stronger cardiac inflammation, and dilated cardiomyopathy (DCM) in human myocarditis. Chronic activation of the immune response in myocarditis may trigger autoimmunity. The experimental autoimmune myocarditis (EAM) model has been well established for the study of autoimmune myocarditis, however the role of sex in this pathology has not been fully explored. In this study, we investigated sex differences in the inflammatory response in the EAM model. We analyzed the cardiac function, as well as the inflammatory stage and fibrosis formation in the heart of EAM male and female rats. 21 days after induction of EAM, male EAM rats showed a decreased ejection fraction, stroke volume and cardiac output, while females did not. A significantly elevated number of infiltrates was detected in myocardium in both sexes, indicating the activation of macrophages following EAM induction. The level of anti-inflammatory macrophages (CD68+ ArgI+) was only significantly increased in female hearts. The expression of Col3A1 and fibrosis formation were more prominent in males. Furthermore, prominent pro-inflammatory factors were increased only in male rats. These findings indicate sex-specific alterations in the inflammatory stage of EAM, with a pro-inflammatory phenotype appearing in males and an anti-inflammatory phenotype in females, which both significantly affect cardiac function in autoimmune myocarditis.

An overview of human pericardial space and pericardial fluid

The pericardium is a double-layered fibro-serous sac that envelops the majority of the surface of the heart as well as the great vessels. Pericardial fluid is also contained within the pericardial space. Together, the pericardium and pericardial fluid contribute to a homeostatic environment that facilitates normal cardiac function. Different diseases and procedural interventions may disrupt this homeostatic space causing an imbalance in the composition of immune mediators or by mechanical stress. Inflammatory cells, cytokines, and chemokines are present in the pericardial space. How these specific mediators contribute to different diseases is the subject of debate and research. With the advent of highly specialized assays that can identify and quantify various mediators we can potentially establish specific and sensitive biomarkers that can be used to differentiate pathologies, and aid clinicians in improving clinical outcomes for patients.

Repurposing Nintedanib for pathological cardiac remodeling and dysfunction

Heart Failure (HF) is the leading cause of death worldwide. Myocardial fibrosis, one of the clinical manifestations implicated in almost every form of heart disease, contributes significantly to HF development. However, there is no approved drug specifically designed to target cardiac fibrosis. Nintedanib (NTB) is an FDA approved tyrosine kinase inhibitor for idiopathic pulmonary fibrosis (IPF) and chronic fibrosing interstitial lung diseases (ILD). The favorable clinical outcome of NTB in IPF patients is well established. Furthermore, NTB is well tolerated in IPF patients irrespective of cardiovascular comorbidities. However, there is a lack of direct evidence to support the therapeutic efficacy and safety of NTB in cardiac diseases. In this study we examined the effects of NTB treatment on cardiac fibrosis and dysfunction using a murine model of HF. Specifically, 10 weeks old C57BL/6J male mice were subjected to Transverse Aortic Constriction (TAC) surgery. NTB was administered once daily by oral gavage (50 mg/kg) till 16 weeks post-TAC. Cardiac function was monitored by serial echocardiography. Histological analysis and morphometric studies were performed at 16 weeks post-TAC. In the control group, systolic dysfunction started developing from 4 weeks post-surgery and progressed till 16 weeks. However, NTB treatment prevented TAC-induced cardiac functional decline. In another experiment, NTB treatment was stopped at 8 weeks, and animals were followed till 16 weeks post-TAC. Surprisingly, NTB's beneficial effect on cardiac function was maintained even after treatment interruption. NTB treatment remarkably reduced cardiac fibrosis as confirmed by Masson's trichrome staining and decreased expression of collagen genes (COL1A1, COL3A1). Compared to the TAC group, NTB treated mice showed a lower HW/TL ratio and cardiomyocyte cross-sectional area. NTB treatment reduced myocardial and systemic inflammation by inhibiting pro-inflammatory subsets and promoting regulatory T cells (Tregs). Our in vitro studies demonstrated that NTB prevents myofibroblast transformation, TGFβ1-induced SMAD3 phosphorylation, and the production of fibrogenic proteins (Fibronectin-1, α-SMA). However, NTB promoted immunosuppressive phenotype in Tregs, and altered vital signaling pathways in isolated cardiac fibroblast and cardiomyocytes, suggesting that its biological effect and underlying cardiac protection mechanisms are not limited to fibroblast and fibrosis alone. Our findings provide a proof of concept for repurposing NTB to combat adverse myocardial fibrosis and encourage the need for further validation in large animal models and subsequent clinical development for HF patients.

Ameliorative Effects of Osthole on Experimental Renal Fibrosis in vivo and in vitro by Inhibiting IL-11/ERK1/2 Signaling

Objectives: Natural product, osthole, has been proven to have a protective effect on organ fibrosis, including renal fibrosis. All of these studies are mainly focused on the regulation of TGF-β/Smad signaling pathway. However, due to the pleiotropic roles of TGF-β/Smad signaling, direct TGF-β-targeted treatments are unlikely to be therapeutically feasible in clinic. Recently, the downstream IL-11/ERK1/2 signaling of TGF-β has become an attractive therapeutic target without upstream disadvantages. Based on that, this study was designed to identify the potential effects of osthole on IL-11/ERK1/2 signaling pathway in renal fibrosis.

Methods: The renal fibrosis model was established in vivo and in vitro, we investigated the effects of osthole on unilateral ureteral obstruction (UUO)-induced renal fibrosis and TGF-β-induced HK-2 cells. After preliminarily confirming the antifibrogenic effects of osthole and the link between its antifibrogenic effects and the inhibition of IL-11/ERK1/2 signaling, we applied a direct IL-11-induced HK-2 cells fibrosis model to further explore the inhibitory effects of osthole on IL-11/ERK1/2 signaling pathway.

Results: Our results confirmed that osthole can decrease the secretion of fibrosis proteins, such as α-smooth muscle actin (α-SMA), collagen I, and fibronectin, ameliorate experimental renal fibrosis in vivo and in vitro, and the effect was associated with suppressing TGF-β1/Smad signaling. More importantly, we found that IL-11/ERK1/2 signaling in UUO-induced renal fibrosis and TGF-β-induced HK-2 cell model was obviously upregulated, and osthole treatment also significantly inhibited the abnormal IL-11/ERK1/2 signaling activation. Given the direct link between TGF-β/Smad signaling and IL-11/ERK1/2 signaling pathway, we have verified that osthole has a direct inhibitory effect on IL-11/ERK1/2 signaling independent of TGF-β signaling by using an IL-11-induced HK-2 cells fibrosis model. Osthole treatment decreased the protein expression of α-SMA, collagen I and fibronectin without changing their mRNA levels in IL-11-induced HK-2 cells. Moreover, it was observed that the IL-11/ERK1/2 inhibitor, U0126, partly blocked the antifibrogenic effects of osthole.

Conclusion: In this study, we found that osthole has a previously unrecognized role in inhibiting IL-11/ERK1/2 signaling pathway. Our work demonstrated that the antifibrogenic effect of osthole is not only mediated by TGF-β/Smad2/3 signaling, but also directly mediated by IL-11/ERK1/2 signaling pathway independent of TGF-β1 signaling.

Preclinical rodent models of cardiac fibrosis

Cardiac fibrosis (scarring), characterised by an increased deposition of extracellular matrix (ECM) proteins, is a hallmark of most types of cardiovascular disease and plays an essential role in heart failure progression. Inhibition of cardiac fibrosis could improve outcomes in patients with cardiovascular diseases and particularly heart failure. However, pharmacological treatment of the ECM build-up is still lacking. In this context, preclinical models of heart disease are important tools for understanding the complex pathogenesis involved in the development of cardiac fibrosis which in turn could identify new therapeutic targets and the facilitation of antifibrotic drug discovery. Many preclinical models have been used to study cardiac fibrosis and each model provides mechanistic insights into the many factors that contribute to cardiac fibrosis. This review discusses the most frequently used rodent models of cardiac fibrosis and also provides context for the use of particular models of heart failure.

MicroRNA-99b-3p promotes angiotensin II-induced cardiac fibrosis in mice by targeting GSK-3β

Cardiac fibrosis is a typical pathological change in various cardiovascular diseases. Although it has been recognized as a crucial risk factor responsible for heart failure, there is still a lack of effective treatment. Recent evidence shows that microRNAs (miRNAs) play an important role in the development of cardiac fibrosis and represent novel therapeutic targets. In this study we tried to identify the cardiac fibrosis-associated miRNA and elucidate its regulatory mechanisms in mice. Cardiac fibrosis was induced by infusion of angiotensin II (Ang II, 2 mg·kg-1·d-1) for 2 weeks via osmotic pumps. We showed that Ang II infusion induced cardiac disfunction and fibrosis accompanied by markedly increased expression level of miR-99b-3p in heart tissues. Upregulation of miR-99b-3p and fibrotic responses were also observed in cultured rat cardiac fibroblasts (CFs) treated with Ang II (100 nM) in vitro. Transfection with miR-99b-3p mimic resulted in the overproduction of fibronectin, collagen I, vimentin and α-SMA, and facilitated the proliferation and migration of CFs. On the contrary, transfection with specific miR-99b-3p inhibitor attenuated Ang II-induced fibrotic responses. Similarly, intravenous injection of specific miR-99b-3p antagomir could prevent Ang II-infused mice from cardiac dysfunction and fibrosis. We identified glycogen synthase kinase-3 beta (GSK-3β) as a direct target of miR-99b-3p. In CFs, miR-99b-3p mimic significantly reduced the expression of GSK-3β, leading to activation of its downstream profibrotic effector Smad3, whereas miR-99b-3p inhibitor caused anti-fibrotic effects. GSK-3β knockdown ameliorated the anti-fibrotic role of miR-99b-3p inhibitor. These results suggest that miR-99b-3p contributes to Ang II-induced cardiac fibrosis at least partially through GSK-3β. The modulation of miR-99b-3p may provide a new approach for tackling fibrosis-related cardiomyopathy.

Adaptable hydrogel with reversible linkages for regenerative medicine: Dynamic mechanical microenvironment for cells

Hydrogels are three-dimensional platforms that serve as substitutes for native extracellular matrix. These materials are starting to play important roles in regenerative medicine because of their similarities to native matrix in water content and flexibility. It would be very advantagoues for researchers to be able to regulate cell behavior and fate with specific hydrogels that have tunable mechanical properties as biophysical cues. Recent developments in dynamic chemistry have yielded designs of adaptable hydrogels that mimic dynamic nature of extracellular matrix. The current review provides a comprehensive overview for adaptable hydrogel in regenerative medicine as follows. First, we outline strategies to design adaptable hydrogel network with reversible linkages according to previous findings in supramolecular chemistry and dynamic covalent chemistry. Next, we describe the mechanism of dynamic mechanical microenvironment influence cell behaviors and fate, including how stress relaxation influences on cell behavior and how mechanosignals regulate matrix remodeling. Finally, we highlight techniques such as bioprinting which utilize adaptable hydrogel in regenerative medicine. We conclude by discussing the limitations and challenges for adaptable hydrogel, and we present perspectives for future studies.

Long-term, Time-course Evaluation of Ligamentum Flavum Hypertrophy Induced by Mechanical Stress: An Experimental Animal Study

STUDY DESIGN

Experimental animal study.

OBJECTIVE

The aim of this study was to clarify chronological effects of mechanical stress on ligamentum flavum (LF) using a long-term fusion rabbit model.

SUMMARY OF BACKGROUND DATA

LF hypertrophy is a major pathology of lumbar spinal stenosis (LSS), but its mechanism remains unclear. We previously demonstrated mechanical-stress-induced LF hypertrophy with a rabbit model. However, we only investigated LFs at a single time point in the short-term; the effects of long-term mechanical stress have not been elucidated.

METHODS

Eighteen-week-old male New Zealand White rabbits were randomly divided into two groups: the mechanical stress group underwent L2-3 and L4-5 posterolateral fusion and resection of the L3-4 supraspinal muscle, whereas the control group underwent only surgical exposure. Rabbits were sacrificed 16 and 52 weeks after the procedure. Axial specimens of LFs at L3-4 were evaluated histologically. Immunohistochemistry for alpha-smooth muscle actin (α-SMA) was performed to assess the numbers of vessels and myofibroblasts.

RESULTS

In the mechanical stress group, LFs at the L3-4 level exhibited hypertrophy with elastic fiber disruption and cartilage matrix production at 16 and 52 weeks. A trend test indicated that mechanical stress induced LF hypertrophy, elastic fiber disruption, and cartilage matrix production in a time-dependent manner, with the lowest levels before treatment and the highest at 52 weeks. Immunostaining for α-SMA showed similar numbers of vessels in both groups, whereas the percentage of myofibroblasts was significantly larger at 16 and 52 weeks in the mechanical stress group than in the control group.

CONCLUSION

We demonstrated that long-term mechanical stress caused LF hypertrophy with progressive elastic fiber disruption and cartilage matrix production accompanied by enhanced myofibroblasts. In addition, the reported rabbit model could be extended to elucidate the mechanism of LF hypertrophy and to develop new therapeutic strategies for LSS by preventing LF hypertrophy.Level of Evidence: SSSSS.

The relationship between miRNA-26b and connective tissue growth factor in rat models of aortic banding and debanding

BACKGROUND/AIMS

Connective tissue growth factor (CTGF) is a profibrotic factor implicated in pressure overload-mediated myocardial fibrosis. In this study, we determined the role of predicted CTGF-targeting microRNAs (miRNAs) in rat models of aortic stenosis and reverse cardiac remodeling.

METHODS

Minimally invasive ascending aortic banding was performed in 24 7-week-old male Sprague-Dawley rats, which were divided into three groups. The banding group consisted of eight rats that were sacrificed immediately after 6 weeks of aortic constriction. The debanding group underwent aortic constriction for 4 weeks and was sacrificed 2 weeks after band removal. The third group underwent sham surgery. We investigated the expression of CTGF, transforming growth factor-β1 (TGFβ1), and matrix metalloproteinase-2 using ELISA and examined miRNA-26b, miRNA-133a, and miRNA-19b as predicted CTGF-targeting miRNAs based on miRNA databases in 24-hour TGFβ-stimulated and TGFβ- washed fibroblasts and myocardial tissues from all subjects.

RESULTS

CTGF was elevated in 24-hour TGFβ-stimulated fibroblasts and decreased in 24-hour TGFβ-washed fibroblasts. miRNA-26b was significantly increased in TGFβ-washed fibroblasts compared with control and TGFβ-stimulated fibroblasts (p < 0.05). CTGF expression was significantly higher in the banding group than that in the sham and debanding groups. The relative expression levels of miRNA-26b were higher in the debanding group than in the banding group.

CONCLUSION

The results of our study using models of aortic banding and debanding suggested that miRNA-26b was significantly increased after aortic debanding. The in vitro model yielded the same results: miRNA-26b was upregulated after removal of TGFβ from fibroblasts.

Bioengineering approaches to mature induced pluripotent stem cell-derived atrial cardiomyocytes to model atrial fibrillation

Induced pluripotent stem cells (iPSCs) serve as a robust platform to model several human arrhythmia syndromes including atrial fibrillation (AF). However, the structural, molecular, functional, and electrophysiological parameters of patient-specific iPSC-derived atrial cardiomyocytes (iPSC-aCMs) do not fully recapitulate the mature phenotype of their human adult counterparts. The use of physiologically inspired microenvironmental cues, such as postnatal factors, metabolic conditioning, extracellular matrix (ECM) modulation, electrical and mechanical stimulation, co-culture with non-parenchymal cells, and 3D culture techniques can help mimic natural atrial development and induce a more mature adult phenotype in iPSC-aCMs. Such advances will not only elucidate the underlying pathophysiological mechanisms of AF, but also identify and assess novel mechanism-based therapies towards supporting a more 'personalized' (i.e. patient-specific) approach to pharmacologic therapy of AF.

Investigating the Effect of Substrate Stiffness on the Redox State of Cardiac Fibroblasts Using Scanning Electrochemical Microscopy

Cardiac fibrosis, in which cardiac fibroblasts differentiate into myofibroblasts, leads to oversecretion of the extracellular matrix, results in increased stiffness, and facilitates disequilibrium of cellular redox state, further leading to oxidative stress and various degrees of cell death. However, the relationship between the matrix stiffness and the redox status of cardiac fibroblasts remains unclear. In this work, we constructed an in vitro cardiac fibrosis model by culturing cardiac fibroblasts on polyacrylamide gels with tunable stiffness and characterized the differentiation of cardiac fibroblasts to myofibroblasts by immunofluorescence staining of α-smooth muscle actin. We then applied scanning electrochemical microscopy (SECM) with a depth scan mode to in situ and quantitatively assess the redox status by monitoring the glutathione (GSH) efflux rate (k) through the redox reaction between GSH (a typical indicator of cellular redox level) released from cardiac fibroblasts and SECM probe-oxidized ferrocenecarboxylic acid ([FcCOOH]⁺). The SECM results demonstrate that the GSH efflux from the cardiac fibroblasts decreased with increasing substrate stiffness (i.e., mimicking the increased fibrosis degree), indicating that a more oxidizing microenvironment facilitates the cell differentiation and GSH may serve as a biomarker to predict the degree of cardiac fibrosis. This work provides an SECM approach to quantify the redox state of cardiac fibroblasts by recording the GSH efflux rate. In addition, the newly established relationship between the redox balance and the substrate stiffness would help to better understand the redox state of cardiac fibroblasts during cardiac fibrosis.

Targeting 5-HT2B Receptor Signaling Prevents Border Zone Expansion and Improves Microstructural Remodeling After Myocardial Infarction

BACKGROUND

Myocardial infarction (MI) induces an intense injury response that ultimately generates a collagen-dominated scar. Although required to prevent ventricular rupture, the fibrotic process is often sustained in a manner detrimental to optimal recovery. Cardiac myofibroblasts are the cells tasked with depositing and remodeling collagen and are a prime target to limit the fibrotic process after MI. Serotonin 2B receptor (5-HT2B) signaling has been shown to be harmful in a variety of cardiopulmonary pathologies and could play an important role in mediating scar formation after MI.

METHODS

We used 2 pharmacological antagonists to explore the effect of 5-HT2B inhibition on outcomes after MI and characterized the histological and microstructural changes involved in tissue remodeling. Inducible 5-HT2B ablation driven by Tcf21MCM and PostnMCM was used to evaluate resident cardiac fibroblast- and myofibroblast-specific contributions of 5-HT2B, respectively. RNA sequencing was used to motivate subsequent in vitro analyses to explore cardiac fibroblast phenotype.

RESULTS

5-HT2B antagonism preserved cardiac structure and function by facilitating a less fibrotic scar, indicated by decreased scar thickness and decreased border zone area. 5-HT2B antagonism resulted in collagen fiber redistribution to thinner collagen fibers that were more anisotropic, enhancing left ventricular contractility, whereas fibrotic tissue stiffness was decreased, limiting the hypertrophic response of uninjured cardiomyocytes. Using a tamoxifen-inducible Cre, we ablated 5-HT2B from Tcf21-lineage resident cardiac fibroblasts and saw similar improvements to the pharmacological approach. Tamoxifen-inducible Cre-mediated ablation of 5-HT2B after onset of injury in Postn-lineage myofibroblasts also improved cardiac outcomes. RNA sequencing and subsequent in vitro analyses corroborate a decrease in fibroblast proliferation, migration, and remodeling capabilities through alterations in Dnajb4 expression and Src phosphorylation.

CONCLUSIONS

Together, our findings illustrate that 5-HT2B expression in either cardiac fibroblasts or activated myofibroblasts directly contributes to excessive scar formation, resulting in adverse remodeling and impaired cardiac function after MI.

Fibrosis after Myocardial Infarction: An Overview on Cellular Processes, Molecular Pathways, Clinical Evaluation and Prognostic Value

The ischemic injury caused by myocardial infarction activates a complex healing process wherein a powerful inflammatory response and a reparative phase follow and balance each other. An intricate network of mediators finely orchestrate a large variety of cellular subtypes throughout molecular signaling pathways that determine the intensity and duration of each phase. At the end of this process, the necrotic tissue is replaced with a fibrotic scar whose quality strictly depends on the delicate balance resulting from the interaction between multiple actors involved in fibrogenesis. An inflammatory or reparative dysregulation, both in term of excess and deficiency, may cause ventricular dysfunction and life-threatening arrhythmias that heavily affect clinical outcome. This review discusses cellular process and molecular signaling pathways that determine fibrosis and the imaging technique that can characterize the clinical impact of this process in-vivo.

Sall4 and Myocd Empower Direct Cardiac Reprogramming From Adult Cardiac Fibroblasts After Injury

Direct conversion of fibroblasts into induced cardiomyocytes (iCMs) holds promising potential to generate functional cardiomyocytes for drug development and clinical applications, especially for direct in situ heart regeneration by delivery of reprogramming genes into adult cardiac fibroblasts in injured hearts. For a decade, many cocktails of transcription factors have been developed to generate iCMs from fibroblasts of different tissues in vitro and some were applied in vivo. Here, we aimed to develop genetic cocktails that induce cardiac reprogramming directly in cultured cardiac fibroblasts isolated from adult mice with myocardial infarction (MICFs), which could be more relevant to heart diseases. We found that the widely used genetic cocktail, Gata4, Mef2c, and Tbx5 (GMT) were inefficient in reprogramming cardiomyocytes from MICFs. In a whole well of a 12-well plate, less than 10 mCherry+ cells (<0.1%) were observed after 2 weeks of GMT infection with Myh6-reporter transgenic MICFs. By screening 22 candidate transcription factors predicted through analyzing the gene regulatory network of cardiac development, we found that five factors, GMTMS (GMT plus Myocd and Sall4), induced more iCMs expressing the cardiac structural proteins cTnT and cTnI at a frequency of about 22.5 ± 2.7% of the transduced MICFs at day 21 post infection. What is more, GMTMS induced abundant beating cardiomyocytes at day 28 post infection. Specifically, Myocd contributed mainly to inducing the expression of cardiac proteins, while Sall4 accounted for the induction of functional properties, such as contractility. RNA-seq analysis of the iCMs at day 28 post infection revealed that they were reprogrammed to adopt a cardiomyocyte-like gene expression profile. Overall, we show here that Sall4 and Myocd play important roles in cardiac reprogramming from MICFs, providing a cocktail of genetic factors that have potential for further applications in in vivo cardiac reprogramming.