Fibroblasts in myocardial infarction: a role in inflammation and repair

Circadian MicroRNAs in Cardioprotection

The most dramatic feature of life on Earth is our adaptation to the cycle of day and night. Throughout evolutionary time, almost all living organisms developed a molecular clock linked to the light-dark cycles of the sun. In present time, we know that this molecular clock is crucial to maintain metabolic and physiological homeostasis. Indeed, a dysregulated molecular clockwork is a major contributing factor to many metabolic diseases. In fact, the time of onset of acute myocardial infarction exhibits a circadian periodicity and recent studies have found that the light regulated circadian rhythm protein Period 2 (PER2) elicits endogenous cardioprotection from ischemia. Manipulating the molecular clockwork may prove beneficial during myocardial ischemia in humans. MicroRNAs are small non-coding RNA molecules capable of silencing messenger RNA (mRNA) targets. MicroRNA dysregulation has been linked to cancer development, cardiovascular and neurological diseases, lipid metabolism, and impaired immunity. Therefore, microRNAs are gaining interest as putative novel disease biomarkers and therapeutic targets. To identify circadian microRNA-based cardioprotective pathways, a recent study evaluated transcriptional changes of PER2 dependent microRNAs during myocardial ischemia. Out of 352 most abundantly expressed microRNAs, miR-21 was amongst the top PER2 dependent microRNAs and was shown to mediate PER2 elicited cardioprotection. Further analysis suggested circadian entrainment via intense light therapy to be a potential strategy to enhance miR-21 activity in humans. In this review, we will focus on circadian microRNAs in the context of cardioprotection and will highlight new discoveries, which could lead to novel therapeutic concepts to treat myocardial ischemia.

Pathophysiology and Nonsurgical Treatment of Chronic Subdural Hematoma: From Past to Present to Future

BACKGROUND

Chronic subdural hematoma (CSDH) is one of the more frequent pathologic entities in daily neurosurgical practice. Historically, CSDH was considered progressive recurrent bleeding with a traumatic cause. However, recent evidence has suggested a complex intertwined pathway of inflammation, angiogenesis, local coagulopathy, recurrent microbleeds, and exudates. The aim of the present review is to collect existing data on pathophysiology of CSDH to direct further research questions aiming to optimize treatment for the individual patient.

METHODS

We performed a thorough literature search in PubMed, Ovid, EMBASE, CINAHL, and Google scholar, focusing on any aspect of the pathophysiology and nonsurgical treatment of CSDH.

RESULTS

After a (minor) traumatic event, the dural border cell layer tears, which leads to the extravasation of cerebrospinal fluid and blood in the subdural space. A cascade of inflammation, impaired coagulation, fibrinolysis, and angiogenesis is set in motion. The most commonly used treatment is surgical drainage. However, because of the pathophysiologic mechanisms, the mortality and high morbidity associated with surgical drainage, drug therapy (dexamethasone, atorvastatin, tranexamic acid, or angiotensin-converting enzyme inhibitors) might be a beneficial alternative in many patients with CSDH.

CONCLUSIONS

Based on pathophysiologic mechanisms, animal experiments, and small patient studies, medical treatment may play a role in the treatment of CSDH. There is a lack of level I evidence in the nonsurgical treatment of CSDH. Therefore, randomized controlled trials, currently lacking, are needed to assess which treatment is most effective in each individual patient.

Perivascular fibrosis and the microvasculature of the heart. Still hidden secrets of pathophysiology?

Perivascular fibrosis, the deposition of connective tissue around the vessels, has been demonstrated crucially involved in the development of cardiac dysfunction. Although cardiac fibrosis has been shown to be reversible under certain experimental conditions, effective anti-fibrotic therapies remain largely elusive. Therefore, perivascular fibrosis currently represents a major therapeutic target for cardiovascular diseases. The main topic of this review will be to address the mechanisms underlying perivascular fibrosis of the vasculature within the myocardium, with a special focus on perivascular fibrosis of small vessels, microvascular dysfunction and disease.

Generation of induced cardiac progenitor cells via somatic reprogramming

It has been demonstrated that cardiac progenitor cells (CPCs) represent a more effective cell-based therapy for treatment of myocardial infarction. Unfortunately, their therapeutic application is limited by low yield of cell harvesting, declining quality and quantity during the ageing process, and the need for highly invasive heart biopsy. Therefore, there is an emerging interest in generating CPC-like stem cells from somatic cells via somatic reprogramming. This novel approach would provide an unlimited source of stem cells with cardiac differentiation potential. Here we would firstly discuss the different types of CPC and their importance in stem cell therapy for treatment of myocardial infarction; secondly, the necessity of generating induced CPC from somatic cells via somatic reprogramming; and finally the current progress of somatic reprogramming in cardiac cells, especially induced CPC generation.

p63 Silencing induces reprogramming of cardiac fibroblasts into cardiomyocyte-like cells

OBJECTIVE

Reprogramming of fibroblasts into induced cardiomyocytes represents a potential new therapy for heart failure. We hypothesized that inactivation of p63, a p53 gene family member, may help overcome human cell resistance to reprogramming.

METHODS

p63 Knockout (^-/-) and knockdown murine embryonic fibroblasts (MEFs), p63^-/- adult murine cardiac fibroblasts, and human cardiac fibroblasts were assessed for cardiomyocyte-specific feature changes, with or without treatment by the cardiac transcription factors Hand2-Myocardin (HM).

RESULTS

Flow cytometry revealed that a significantly greater number of p63^-/- MEFs expressed the cardiac-specific marker cardiac troponin T (cTnT) in culture compared with wild-type (WT) cells (38% ± 11% vs 0.9% ± 0.9%, P < .05). HM treatment of p63^-/- MEFs increased cTnT expression to 74% ± 3% of cells but did not induce cTnT expression in wild-type murine embryonic fibroblasts. shRNA-mediated p63 knockdown likewise yielded a 20-fold increase in cTnT microRNA expression compared with untreated MEFs. Adult murine cardiac fibroblasts demonstrated a 200-fold increase in cTnT gene expression after inducible p63 knockout and expressed sarcomeric α-actinin as well as cTnT. These p63^-/- adult cardiac fibroblasts exhibited calcium transients and electrically stimulated contractions when co-cultured with neonatal rat cardiomyocytes and treated with HM. Increased expression of cTnT and other marker genes was also observed in p63 knockdown human cardiac fibroblasts procured from patients undergoing procedures for heart failure.

CONCLUSIONS

Downregulation of p63 facilitates direct cardiac cellular reprogramming and may help overcome the resistance of human cells to reprogramming.

Wound healing related agents: Ongoing research and perspectives

Wound healing response plays a central part in chronic inflammation, affecting millions of people worldwide. It is a dynamic process that can lead to fibrosis, if tissue damage is irreversible and wound resolution is not attained. It is clear that there is a tight interconnection among wound healing, fibrosis and a variety of chronic disease conditions, demonstrating the heterogeneity of this pathology. Based on our further understanding of the cellular and molecular mechanisms underpinning tissue repair, new therapeutic approaches have recently been developed that target different aspects of the wound healing process and fibrosis. Nevertheless, several issues still need to be taken into consideration when designing modern wound healing drug delivery formulations. In this review, we highlight novel pharmacological agents that hold promise for targeting wound repair and fibrosis. We also focus on drug-delivery systems that may enhance current and future therapies.

Myocardial infarction remodeling that progresses to heart failure: a signaling misunderstanding

After myocardial infarction, remodeling of the left ventricle involves a wound-healing orchestra involving a variety of cell types. In order for wound healing to be optimal, appropriate communication must occur; these cells all need to come in at the right time, be activated at the right time in the right amount, and know when to exit at the right time. When this occurs, a new homeostasis is obtained within the infarct, such that infarct scar size and quality are sufficient to maintain left ventricular size and shape. The ideal scenario does not always occur in reality. Often, miscommunication can occur between infarct and remote spaces, across the temporal wound-healing spectrum, and across organs. When miscommunication occurs, adverse remodeling can progress to heart failure. This review discusses current knowledge gaps and recent development of the roles of inflammation and the extracellular matrix in myocardial infarction remodeling. In particular, the macrophage is one cell type that provides direct and indirect regulation of both the inflammatory and scar-forming responses. We summarize current research efforts focused on identifying biomarker indicators that reflect the status of each component of the wound-healing process to better predict outcomes.

Inflammatory Response During Myocardial Infarction

The occlusion of a coronary artery by a thrombus generated on a ruptured atherosclerotic plaque has been pursued in the last decades as a determining event for the clinical outcome after myocardial infarction (MI). Yet, MI causes a cell death wave front, which triggers an inflammatory response to clear cellular debris, and which in excess can double the myocardial lesion and influence the clinical prognosis in the short and long term. Accordingly, proper, timely regulated inflammatory response has now been considered a second pivotal player in cardiac recovery after MI justifying the search for pharmacological strategies to modulate inflammatory effectors. This chapter reviews the key events and the main effectors of inflammation after myocardial ischemic insult, as well as the contribution of this phenomenon to the progression of atherosclerosis.

Curcumin administration suppresses collagen synthesis in the hearts of rats with experimental diabetes

Cardiac fibrosis is considered the initial change of diabetic cardiomyopathy (DCM). We have shown that curcumin alleviates collagen deposition in DCM, but the mechanism remains unknown. In this study we sought to investigate the effects of curcumin on cardiac fibrosis in vivo and in vitro and to elucidate the underlying mechanisms. Experimental diabetes was induced in rats by injection of low-dose streptozotocin (STZ) combined with high energy diet. The rats were orally treated with curcumin (300 mg·kg-1·d-1) for 16 weeks. Curcumin administration significantly suppressed the deposition of type I and type III collagens in the heart tissues of diabetic rats, accompanied by markedly reduced TGF-β1 production, suppressed TβR II levels and Smad2/3 phosphorylation, and increased Smad7 expression. Similar effects were observed in human cardiac fibroblasts exposed to high glucose (HG, 30 mmol/L) or exogenous TGF-β1 (5 ng/mL). Furthermore, TGF-β1 or HG treatment significantly increased the phosphorylation levels of AMPK and p38 MAPK in the fibroblasts. Application of curcumin (25 μmol/L) inhibited TGF-β1- or HG-induced AMPK/p38 MAPK activation and suppressed collagen synthesis in the fibroblasts. These effects were similar to those of the AMPK inhibitor compound C (10 μmol/L) but opposite to the effects of the AMPK activator metformin (2 mmol/L) in the fibroblasts. Our results demonstrate that curcumin suppresses diabetes-associated collagen synthesis in rat myocardium not only by inhibiting TGF-β1 production and canonical Smad signaling but also by blocking the non-canonical AMPK/p38 MAPK pathway.

Imaging transparent intact cardiac tissue with single-cell resolution

We developed a new method, SUT (Scheme Update on tissue Transparency), to view cardiac microstructures and unveil the molecular changes underlying cardiac diseases. SUT is an effective method to clear whole-hearts from different species. Over the course of 4 - 6 days we obtained transparent whole-layer left ventricular tissues from mice with only an approximate 1% protein loss. In addition, EAL (Electrophoretic Antibody Labeling) was used to achieve fast antibody labeling by electric force, which significantly reduced antibody incubation time from days to hours. SUT, together with EAL and modern imaging techniques, were successfully used to visualize three-dimensional spatial distribution of various molecules in cardiac tissue. We also observed changes in the number and phenotypes of fibroblasts during post-myocardial infarction in a stereoscopic pattern. We believe that our technique opens a new avenue to explore the mechanisms underlying cardiac diseases.

Macrophage overexpression of matrix metalloproteinase-9 in aged mice improves diastolic physiology and cardiac wound healing after myocardial infarction

Matrix metalloproteinase (MMP)-9 increases in the myocardium with advanced age and after myocardial infarction (MI). Because young transgenic (TG) mice overexpressing human MMP-9 only in macrophages show better outcomes post-MI, whereas aged TG mice show a worse aging phenotype, we wanted to evaluate the effect of aging superimposed on MI to see if the detrimental effect of aging counteracted the benefits of macrophage MMP-9 overexpression. We used 17- to 28-mo-old male and female C57BL/6J wild-type (WT) and TG mice ( n = 10-21 mice/group) to evaluate the effects of aging superimposed on MI. Despite similar infarct areas and mortality rates at day 7 post-MI, aging TG mice showed improved diastolic properties and remodeling index compared with WT mice (both P < 0.05). Macrophage numbers were higher in TG than WT mice at days 0 and 7 post-MI, and the post-MI increase was due to elevated cluster of differentiation 18 protein levels (all P < 0.05). RNA sequencing analysis of cardiac macrophages isolated from day 7 post-MI infarcts identified 1,276 statistically different (all P < 0.05) genes (994 increased and 282 decreased in TG mice). Reduced expression of vascular endothelial growth factor A, platelet-derived growth factor subunit A, and transforming growth factor-β3, along with elevated expression of tissue inhibitor of MMP-4, in macrophages revealed mechanisms of indirect downstream effects on fibroblasts and neovascularization. While collagen accumulation was enhanced in TG mice compared with WT mice at days 0 and 7 post-MI ( P < 0.05 for both), the post-MI collagen cross-linking ratio was higher in WT mice ( P < 0.05), consistent with increased diastolic volumes. Vessel numbers [by Griffonia ( Bandeiraea) simplicifolia lectin I staining] were decreased in TG mice compared with WT mice at days 0 and 7 post-MI ( P < 0.05 for both). In conclusion, macrophage-derived MMP-9 improved post-MI cardiac wound healing through direct and indirect mechanisms to improve diastolic physiology and remodeling. NEW & NOTEWORTHY Aging mice with macrophage overexpression of matrix metalloproteinase-9 have increased macrophage numbers 7 days after myocardial infarction, resulting in improved diastolic physiology and left ventricular remodeling through effects on cardiac wound healing.

Inflammation following acute myocardial infarction: Multiple players, dynamic roles, and novel therapeutic opportunities

Acute myocardial infarction (AMI) and the heart failure that often follows, are major causes of death and disability worldwide. As such, new therapies are required to limit myocardial infarct (MI) size, prevent adverse left ventricular (LV) remodeling, and reduce the onset of heart failure following AMI. The inflammatory response to AMI, plays a critical role in determining MI size, and a persistent pro-inflammatory reaction can contribute to adverse post-MI LV remodeling, making inflammation an important therapeutic target for improving outcomes following AMI. In this article, we provide an overview of the multiple players (and their dynamic roles) involved in the complex inflammatory response to AMI and subsequent LV remodeling, and highlight future opportunities for targeting inflammation as a therapeutic strategy for limiting MI size, preventing adverse LV remodeling, and reducing heart failure in AMI patients.

Regulation of macrophage migration in ischemic mouse hearts via an AKT2/NBA1/SPK1 pathway

The role of the AKT2/NBA1/SPK1 signaling cascade in macrophage migration regulation and post-ischemic cardiac remodeling was investigated. We determined that the AKT2/NBA1/SPK1 signaling cascade regulated macrophage migration. A novel role for NBA1 in macrophage migration was discovered. Elevated AKT2 phosphorylation, NBA1, SPK1 (along with phosphorylated SPK1) levels, macrophage recruitment, apoptosis, and fibrosis were found within the infarct area. Atorvastatin had a beneficial effect on cardiac remodeling following myocardial infarction by inhibiting AKT2/NBA1/SPK1-mediated macrophage recruitment, apoptosis, and collagen deposition while increasing angiogenesis in the infarct area. Atorvastatin-related protection of cardiac remodeling following myocardial infarction was abolished in SPK1-KO mice. The AKT2/NAB1/SPK1 pathway is a novel regulating factor of macrophage migration and cardiac remodeling after myocardial infarction.

GHK Peptide Inhibits Bleomycin-Induced Pulmonary Fibrosis in Mice by Suppressing TGFβ1/Smad-Mediated Epithelial-to-Mesenchymal Transition

Objective: Idiopathic pulmonary fibrosis is an irreversible and progressive fibrotic lung disease that leads to declines in pulmonary function and, eventually, respiratory failure and has no effective treatment. Gly-His-Lys (GHK) is a tripeptide involved in the processes of tissue regeneration and wound healing and has significant inhibitory effects on transforming growth factor (TGF)-β1 secretion. The effect of GHK on fibrogenesis in pulmonary fibrosis and the exact underlying mechanism have not been studied previously. Thus, this study investigated the effects of GHK on bleomycin (BLM)-induced fibrosis and identified the pathway that is potentially responsible for these effects.

Methods: Intratracheal injections of 3 mg/kg BLM were administered to induce pulmonary fibrosis in C57BL/6 mice. GHK was administered intraperitoneally at doses of 2.6, 26, and 260 μg/ml/day every other day from the 4th to the 21st day after BLM instillation. Three weeks after BLM instillation, pulmonary injury and pulmonary fibrosis was evaluated by the hematoxylin-eosin (HE) and Masson’s trichrome (MT) staining. Chronic inflammation index was used for the histological assessments by two pathologists blindly to each other. Tumor necrosis factor (TNF)-α and IL-6 levels in BALF and myeloperoxidase (MPO) activity in lung extracts were measured. For the pulmonary fibrosis evaluation, the fibrosis index calculated based on MT staining, collagen deposition and active TGF-β1 expression detected by ELISA, and the expression of TGF-β1, α-smooth muscle actin (SMA), fibronectin, MMP-9, and TIMP-1 by western blotting. The epithelial mesenchymal transition index, E-cadherin, and vimentin was also detected by western blot. The statistical analysis was performed by one-way ANOVA and the comparison between different groups were performed.

Results: Treatment with GHK at all three doses reduced inflammatory cell infiltration and interstitial thickness and attenuated BLM-induced pulmonary fibrosis in mice. GHK treatment significantly improved collagen deposition, and MMP-9/TIMP-1 imbalances in lung tissue and also reduced TNF-α, IL-6 expression in bronchoalveolar lavage fluid (BALF) and MPO in lung extracts. Furthermore, GHK reversed BLM-induced increases in TGF-β1, p-Smad2, p-Smad-3 and insulin-like growth factor-1 (IGF-1) expression.

Conclusion: GHK inhibits BLM-induced fibrosis progression, the inflammatory response and EMT via the TGF-β1/Smad 2/3 and IGF-1 pathway. Thus, GHK may be a potential treatment for pulmonary fibrosis.

Erythropoietin reduces collagen deposition after myocardial infarction but does not improve cardiac function

Myocardial remodeling includes inappropriate collagen deposition in the interstitium. Erythropoietin (EPO) may have cardioprotective effects. We aimed to assess the role of EPO on myocardial remodeling during the chronic phase. We studied 60 Wistar rats divided into the following groups: control (CT), control + EPO (CT + EPO), myocardial infarction + EPO (MI + EPO), and myocardial infarction (MI). The interstitial collagen volume fraction (ICVF) was quantified and echocardiography was performed. We quantified asymmetric dimethylarginine and glutathione by ELISA, and used real-time PCR to assess apoptosis and inflammation. Western blotting was used to evaluate inflammatory proteins and tissue inhibitors of metalloproteinases (TIMPs), and TUNEL staining was used to detect apoptosis. For matrix metalloproteinases (MMPs), we performed zymography. Parametric and nonparametric analyses were performed according to normality testing. ICVF was greater in MI groups (p < 0.001) and was attenuated by EPO (p = 0.05). The MMP-2 did not show any difference between groups. The TIMP-1 and TIMP-2 did not have difference between groups. The MI groups had worse fraction shortening (p < 0.001), without EPO protection (p = 0.666). The MI groups had increased left ventricle diastolic dimension (p < 0.001) without EPO attenuation (p = 0.79). EPO did not act on oxidative stress. Apoptosis and inflammation were not modulated by EPO. We concluded that EPO attenuated interstitial collagen accumulation, but did not protect from heart dilation or dysfunction.

Serum levels of Growth Arrest-Specific 6 protein and soluble AXL in patients with ST-segment elevation myocardial infarction

BACKGROUND

Serum soluble AXL (sAXL) and its ligand, Growth Arrest-Specific 6 protein (GAS6), intervene in tissue repair processes. AXL is increased in end-stage heart failure, but the role of GAS6 and sAXL in ST-segment elevation myocardial infarction (STEMI) is unknown.

OBJECTIVES

To study the association of sAXL and GAS6 acutely and six months following STEMI with heart failure and left ventricular remodelling.

METHODS

GAS6 and sAXL were measured by enzyme-linked immunosorbent assay at one day, seven days and six months in 227 STEMI patients and 20 controls. Contrast-enhanced magnetic resonance was performed during admission and at six months to measure infarct size and left ventricular function.

RESULTS

GAS6, but not sAXL, levels during admission were significantly lower in STEMI than in controls. AXL increased progressively over time (p<0.01), while GAS6 increased only from day 7. GAS6 or sAXL did not correlate with brain natriuretic peptide or infarct size. However, patients with heart failure (Killip >1) had higher values of sAXL at day 1 (48.9±11.9 vs. 44.0±10.7 ng/ml; p<0.05) and at six months (63.3±15.4 vs. 55.9±13.7 ng/ml; p<0.05). GAS6 levels were not different among subjects with heart failure or left ventricular remodelling. By multivariate analysis including infarct size, Killip class and sAXL at seven days, only the last two were independent predictors of left ventricular remodelling (odds ratio 2.24 (95% confidence interval: 1.08-4.63) and odds ratio 1.04 (95% confidence interval: 1.00-1.08) respectively).

CONCLUSION

sAXL levels increased following STEMI. Patients with heart failure and left ventricular remodelling have higher sAXL levels acutely and at six month follow-up. These findings suggest a potential role of the GAS6-AXL system in the pathophysiology of left ventricular remodelling following STEMI.

Early treatment with Resolvin E1 facilitates myocardial recovery from ischaemia in mice

BACKGROUND AND PURPOSE

An appropriate inflammatory response is necessary for cardiac healing after acute myocardial infarction (MI). Resolvin E1 (RvE1) is an anti-inflammatory and pro-resolution lipid mediator derived from eicosapentaenoic acid. Here we have investigated the effects of RvE1 on the recovery of cardiac function after MI in mice.

EXPERIMENTAL APPROACH

Acute MI was induced by surgical ligation of the left anterior descending artery in male C57BL/6 mice. RvE1 (5 ng·g^-1 ·day^-1 ; i.p.) was given to mice at different times following MI. Cardiac function was monitored by transthoracic echocardiography at days 3, 7 and 14 after MI. Effects of RvE1 on the migration of subpopulations of monocytes/macrophages (Mos/Mps, Ly6C^hi and Ly6C^low ) were examined by flow cytometry and transwell assay.

KEY RESULTS

RvE1 administration from days 1 to 7 post-MI improved cardiac function, whereas treatment from days 7 to 14 markedly inhibited recovery of cardiac function. Early treatment with RvE1 post-MI suppressed the infiltration of dominant Ly6C^hi Mos/Mps and secretion of pro-inflammatory cytokines in injured hearts, which protected cardiomyocytes against apoptosis in the peri-infarct zones. Contrastingly, treatment with RvE1 1 week after MI decreased infiltration of Ly6C^low Mos/Mps and expression of pro-angiogenic factors in cardiac tissue, consequently reducing neovascularization in the peri-infarct zones. Additionally, RvE1 inhibited Mp migration by activating ChemR23 receptors.

CONCLUSION AND IMPLICATIONS

Treatment with RvE1 during the initial 7 days after MI facilitated cardiac healing by suppressing pro-inflammatory cytokine secretion, indicating that RvE1 may serve as an early therapeutic agent for acute MI.

LINKED ARTICLES

This article is part of a themed section on Spotlight on Small Molecules in Cardiovascular Diseases. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v175.8/issuetoc.

Platelet-derived growth factor-C and -D in the cardiovascular system and diseases

The cardiovascular system is among the first organs formed during development and is pivotal for the formation and function of the rest of the organs and tissues. Therefore, the function and homeostasis of the cardiovascular system are finely regulated by many important molecules. Extensive studies have shown that platelet-derived growth factors (PDGFs) and their receptors are critical regulators of the cardiovascular system. Even though PDGF-C and PDGF-D are relatively new members of the PDGF family, their critical roles in the cardiovascular system as angiogenic and survival factors have been amply demonstrated. Understanding the functions of PDGF-C and PDGF-D and the signaling pathways involved may provide novel insights into both basic biomedical research and new therapeutic possibilities for the treatment of cardiovascular diseases.

The Processes and Mechanisms of Cardiac and Pulmonary Fibrosis

Fibrosis is the formation of fibrous connective tissue in response to injury. It is characterized by the accumulation of extracellular matrix components, particularly collagen, at the site of injury. Fibrosis is an adaptive response that is a vital component of wound healing and tissue repair. However, its continued activation is highly detrimental and a common final pathway of numerous disease states including cardiovascular and respiratory disease. Worldwide, fibrotic diseases cause over 800,000 deaths per year, accounting for ~45% of total deaths. With an aging population, the incidence of fibrotic disease and subsequently the number of fibrosis-related deaths will rise further. Although, fibrosis is a well-recognized cause of morbidity and mortality in a range of disease states, there are currently no viable therapies to reverse the effects of chronic fibrosis. Numerous predisposing factors contribute to the development of fibrosis. Biological aging in particular, interferes with repair of damaged tissue, accelerating the transition to pathological remodeling, rather than a process of resolution and regeneration. When fibrosis progresses in an uncontrolled manner, it results in the irreversible stiffening of the affected tissue, which can lead to organ malfunction and death. Further investigation into the mechanisms of fibrosis is necessary to elucidate novel, much needed, therapeutic targets. Fibrosis of the heart and lung make up a significant proportion of fibrosis-related deaths. It has long been established that the heart and lung are functionally and geographically linked when it comes to health and disease, and thus exploring the processes and mechanisms that contribute to fibrosis of each organ, the focus of this review, may help to highlight potential avenues of therapeutic investigation.

Serelaxin inhibits differentiation and fibrotic behaviors of cardiac fibroblasts by suppressing ALK-5/Smad2/3 signaling pathway

Serelaxin, a recombinant form of human relaxin-2, is currently regarded as a novel drug for treatment of acute heart failure. However, whether therapeutic effects of serelaxin are achieved by inhibiting cardiac fibrosis remains unclear. In this study, we investigate effects of serelaxin on inhibiting cardiac fibrosis. Cardiac fibroblasts (CFs) were isolated from the hearts of adult rats. Effects of serelaxin on differentiation of CFs towards myofibroblasts (MFs) and their fibrotic behaviors after induction with TGF-β1 were examined. Synthesis and degradation of collagens, secretion of IL-10, and expression of ALK-5 and p-Smad2/3 of TGF-β1-induced cells were assessed after treatment with serelaxin. Serelaxin inhibited differentiation of TGF-β1-induced CFs towards MFs, and reduced proliferation and migration of the induced cells. Moreover, serelaxin down-regulated expression of collagen I/III and TIMP-2, and up-regulated expression of MMP-2 and MMP-9 in the cells. After treatment with serelaxin, activity of MMP-2 and MMP-9 and secretion of IL-10 increased, expression of ALK-5 and the level of Smad2/3 phosphorylation was reduced significantly. These results suggest that serelaxin can inhibit differentiation of TGF-β1-induced CFs towards MFs, reduce production of collagens by suppressing ALK-5/Smad2/3 signaling pathway, and enhance extracellular matrix degradation by increasing MMP-2/TIMP-2 ratio and IL-10 secretion. Serelaxin may be a potential therapeutic drug for inhibiting cardiac fibrosis.

Loss of β-catenin in resident cardiac fibroblasts attenuates fibrosis induced by pressure overload in mice

Cardiac fibrosis is characterized by excessive extracellular matrix deposition that contributes to compromised cardiac function and potentially heart failure. Cardiac pressure overload resulting from trans-aortic constriction in mice leads to cardiac fibrosis and increased Wnt/β-catenin signaling in cardiac fibroblasts. Here, we conditionally induce β-catenin loss of function in resident cardiac fibroblasts using Tcf21 MerCreMer or in activated cardiac fibroblasts using periostin (Postn) MerCreMer . We show that β-catenin loss of function in cardiac fibroblasts after trans-aortic constriction significantly preserves cardiac function, and reduces interstitial fibrosis but does not alter the numbers of activated or differentiated cardiac fibroblasts in vivo. However, β-catenin is specifically required in resident cardiac fibroblasts for fibrotic excessive extracellular matrix gene expression and binds Col3a1 and Postn gene sequences in cultured cardiac fibroblasts after induction of Wnt signaling. Moreover, cardiomyocyte hypertrophy is blunted with cardiac fibroblast-specific loss of β-catenin after trans-aortic constriction in vivo. Thus, Wnt/β-catenin signaling in resident cardiac fibroblasts is required for excessive extracellular matrix gene expression and collagen deposition after trans-aortic constriction.Understanding the mechanisms causing cardiac fibrosis is key to prevention and therapy development of many heart diseases. Here, the authors show that Wnt/β-catenin signaling in resident cardiac fibroblasts is required for deposition of fibrotic extracellular matrix and the regulation of cardiomyocyte hypertrophy in a mouse model of heart fibrosis.

Sesamin prevents apoptosis and inflammation after experimental myocardial infarction by JNK and NF-κB pathways

Myocardial infarction is a devastating event, especially when reperfusion is not performed. The inflammatory response has been associated with the pathogenesis of left ventricular remodeling after myocardial infarction. This study focused on the anti-apoptotic and anti-inflammatory effects of sesamin on ligation of the left anterior descending artery in an experimental mouse model and the potential mechanism underlying the activation of JNK and NF-κB pathways. Mice with MI induced by surgical left anterior descending coronary artery ligation were treated with sesamin by gavage for 1 week. Results showed that after treatment with sesamin, MI-induced cardiac damage was alleviated significantly, indicated by the histopathological examination. The myocardial apoptosis in the border zone was dramatically reduced by sesamin, resulting from the altered expression of apoptosis factors. Moreover, treatment with sesamin also mitigated the inflammatory response, decreased expression of cytokines and the inactivation of NF-κB (nuclear factor κB) signaling. Sesamin decreased the levels of p-JNK protein, which in turn inactivated pro-apoptotic signaling events by restoring the balance between mitochondrial pro-apoptotic Bcl-2 and Bax proteins. Thus, our study suggests that sesamin could alleviate MI-induced cardiac dysfunction through decrease of myocardial apoptosis and inflammatory response.

IL-4 as a Repurposed Biological Drug for Myocardial Infarction through Augmentation of Reparative Cardiac Macrophages: Proof-of-Concept Data in Mice

Recent research has shown that reparative (alternatively activated or M2) macrophages play a role in repair of damaged tissues, including the infarcted hearts. Administration of IL-4 is known to augment M2 macrophages. This translational study thus aimed to investigate whether IL-4 administration is useful for the treatment of myocardial infarction. Long-acting IL-4 complex (IL-4c; recombinant IL-4 mixed with anti-IL-4 monoclonal antibody as a stabilizer) was administered after coronary artery ligation in mice. It was observed that IL-4c administration increased accumulation of CD206+F4/80+ M2-like macrophages predominantly in the injured myocardium, compared to the control. Sorted cardiac M2-like macrophages highly expressed wide-ranging tissue repair-related genes. Indeed, IL-4c administration enhanced cardiac function in association with reduced infarct size and enhanced tissue repair (strengthened connective tissue formation, improved microvascular formation and attenuated cardiomyocyte hypertrophy). Experiments using Trib1 -/- mice that had a depleted ability to develop M2 macrophages and other in-vitro studies supported that these IL-4-mediated effects were induced via M2-like macrophages. On the other hand, when administered at Day 28 post-MI, the effects of IL-4c were diminished, suggesting a time-frame for IL-4 treatment to be effective. These data represent proof-of-concept of efficacy of IL-4 treatment for acute myocardial infarction, encouraging its further development.

IL-1β Inhibition in Cardiovascular Complications Associated to Diabetes Mellitus

Diabetes mellitus (DM) is a chronic disease that affects nowadays millions of people worldwide. In adults, type 2 diabetes mellitus (T2DM) accounts for the majority of all diagnosed cases of diabetes. The course of the T2DM is characterized by insulin resistance and a progressive loss of β-cell mass. DM is associated with a number of related complications, among which cardiovascular complications and atherosclerosis are the main cause of morbidity and mortality in patients suffering from the disease. DM is acknowledged as a low-grade chronic inflammatory state characterized by the over-secretion of pro-inflammatory cytokines, including interleukin (IL)-1β, which reinforce inflammatory signals thus contributing to the development of complications. In this context, the pharmacological approaches to treat diabetes should not only correct hyperglycaemia, but also attenuate inflammation and prevent the development of metabolic and cardiovascular complications. Over the last years, novel biological drugs have been developed to antagonize the pathophysiological actions of IL-1β. The drugs currently used in clinical practice are anakinra, a recombinant form of the naturally occurring IL-1 receptor antagonist, the soluble decoy receptor rilonacept and the monoclonal antibodies canakinumab and gevokizumab. This review will summarize the main experimental and clinical findings obtained with pharmacological IL-1β inhibitors in the context of the cardiovascular complications of DM, and discuss the perspectives of IL-1β inhibitors as novel therapeutic tools for treating these patients.

Role of the immune system in cardiac tissue damage and repair following myocardial infarction

INTRODUCTION

The immune system plays a crucial role in the initiation, development, and resolution of inflammation following myocardial infarction (MI). The lack of oxygen and nutrients causes the death of cardiomyocytes and leads to the exposure of danger-associated molecular patterns that are recognized by the immune system to initiate inflammation.

RESULTS

At the initial stage of post-MI inflammation, the immune system further damages cardiac tissue to clear cell debris. The excessive production of reactive oxygen species (ROS) by immune cells and the inability of the anti-oxidant system to neutralize ROS cause oxidative stress that further aggravates inflammation. On the other hand, the cells of both innate and adaptive immune system and their secreted factors are critically instrumental in the very dynamic and complex processes of regulating inflammation and mediating cardiac repair.

CONCLUSIONS

It is important to decipher the balance between detrimental and beneficial effects of the immune system in MI. This enables us to identify better therapeutic targets for reducing the infarct size, sustaining the cardiac function, and minimizing the likelihood of heart failure. This review discusses the role of both innate and adaptive immune systems in cardiac tissue damage and repair in experimental models of MI.

11β-HSD1 suppresses cardiac fibroblast CXCL2, CXCL5 and neutrophil recruitment to the heart post MI

We have previously demonstrated that neutrophil recruitment to the heart following myocardial infarction (MI) is enhanced in mice lacking 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) that regenerates active glucocorticoid within cells from intrinsically inert metabolites. The present study aimed to identify the mechanism of regulation. In a mouse model of MI, neutrophil mobilization to blood and recruitment to the heart were higher in 11β-HSD1-deficient (Hsd11b1^-/- ) relative to wild-type (WT) mice, despite similar initial injury and circulating glucocorticoid. In bone marrow chimeric mice, neutrophil mobilization was increased when 11β-HSD1 was absent from host cells, but not when absent from donor bone marrow-derived cells. Consistent with a role for 11β-HSD1 in 'host' myocardium, gene expression of a subset of neutrophil chemoattractants, including the chemokines Cxcl2 and Cxcl5, was selectively increased in the myocardium of Hsd11b1^-/- mice relative to WT. SM22α-Cre directed disruption of Hsd11b1 in smooth muscle and cardiomyocytes had no effect on neutrophil recruitment. Expression of Cxcl2 and Cxcl5 was elevated in fibroblast fractions isolated from hearts of Hsd11b1^-/- mice post MI and provision of either corticosterone or of the 11β-HSD1 substrate, 11-dehydrocorticosterone, to cultured murine cardiac fibroblasts suppressed IL-1α-induced expression of Cxcl2 and Cxcl5 These data identify suppression of CXCL2 and CXCL5 chemoattractant expression by 11β-HSD1 as a novel mechanism with potential for regulation of neutrophil recruitment to the injured myocardium, and cardiac fibroblasts as a key site for intracellular glucocorticoid regeneration during acute inflammation following myocardial injury.

Platelet "first responders" in wound response, cancer, and metastasis

Platelets serve as "first responders" during normal wounding and homeostasis. Arising from bone marrow stem cell lineage megakaryocytes, anucleate platelets can influence inflammation and immune regulation. Biophysically, platelets are optimized due to size and discoid morphology to distribute near vessel walls, monitor vascular integrity, and initiate quick responses to vascular lesions. Adhesion receptors linked to a highly reactive filopodia-generating cytoskeleton maximizes their vascular surface contact allowing rapid response capabilities. Functionally, platelets normally initiate rapid clotting, vasoconstriction, inflammation, and wound biology that leads to sterilization, tissue repair, and resolution. Platelets also are among the first to sense, phagocytize, decorate, or react to pathogens in the circulation. These platelet first responder properties are commandeered during chronic inflammation, cancer progression, and metastasis. Leaky or inflammatory reaction blood vessel genesis during carcinogenesis provides opportunities for platelet invasion into tumors. Cancer is thought of as a non-healing or chronic wound that can be actively aided by platelet mitogenic properties to stimulate tumor growth. This growth ultimately outstrips circulatory support leads to angiogenesis and intravasation of tumor cells into the blood stream. Circulating tumor cells reengage additional platelets, which facilitates tumor cell adhesion, arrest and extravasation, and metastasis. This process, along with the hypercoagulable states associated with malignancy, is amplified by IL6 production in tumors that stimulate liver thrombopoietin production and elevates circulating platelet numbers by thrombopoiesis in the bone marrow. These complex interactions and the "first responder" role of platelets during diverse physiologic stresses provide a useful therapeutic target that deserves further exploration.

The Soft- and Hard-Heartedness of Cardiac Fibroblasts: Mechanotransduction Signaling Pathways in Fibrosis of the Heart

Cardiac fibrosis, the excessive accumulation of extracellular matrix (ECM), remains an unresolved problem in most forms of heart disease. In order to be successful in preventing, attenuating or reversing cardiac fibrosis, it is essential to understand the processes leading to ECM production and accumulation. Cardiac fibroblasts are the main producers of cardiac ECM, and harbor great phenotypic plasticity. They are activated by the disease-associated changes in mechanical properties of the heart, including stretch and increased tissue stiffness. Despite much remaining unknown, an interesting body of evidence exists on how mechanical forces are translated into transcriptional responses important for determination of fibroblast phenotype and production of ECM constituents. Such mechanotransduction can occur at multiple cellular locations including the plasma membrane, cytoskeleton and nucleus. Moreover, the ECM functions as a reservoir of pro-fibrotic signaling molecules that can be released upon mechanical stress. We here review the current status of knowledge of mechanotransduction signaling pathways in cardiac fibroblasts that culminate in pro-fibrotic gene expression.

The Biological Basis for Cardiac Repair After Myocardial Infarction: From Inflammation to Fibrosis

In adult mammals, massive sudden loss of cardiomyocytes after infarction overwhelms the limited regenerative capacity of the myocardium, resulting in the formation of a collagen-based scar. Necrotic cells release danger signals, activating innate immune pathways and triggering an intense inflammatory response. Stimulation of toll-like receptor signaling and complement activation induces expression of proinflammatory cytokines (such as interleukin-1 and tumor necrosis factor-α) and chemokines (such as monocyte chemoattractant protein-1/ chemokine (C-C motif) ligand 2 [CCL2]). Inflammatory signals promote adhesive interactions between leukocytes and endothelial cells, leading to extravasation of neutrophils and monocytes. As infiltrating leukocytes clear the infarct from dead cells, mediators repressing inflammation are released, and anti-inflammatory mononuclear cell subsets predominate. Suppression of the inflammatory response is associated with activation of reparative cells. Fibroblasts proliferate, undergo myofibroblast transdifferentiation, and deposit large amounts of extracellular matrix proteins maintaining the structural integrity of the infarcted ventricle. The renin-angiotensin-aldosterone system and members of the transforming growth factor-β family play an important role in activation of infarct myofibroblasts. Maturation of the scar follows, as a network of cross-linked collagenous matrix is formed and granulation tissue cells become apoptotic. This review discusses the cellular effectors and molecular signals regulating the inflammatory and reparative response after myocardial infarction. Dysregulation of immune pathways, impaired suppression of postinfarction inflammation, perturbed spatial containment of the inflammatory response, and overactive fibrosis may cause adverse remodeling in patients with infarction contributing to the pathogenesis of heart failure. Therapeutic modulation of the inflammatory and reparative response may hold promise for the prevention of postinfarction heart failure.

Intense light-elicited upregulation of miR-21 facilitates glycolysis and cardioprotection through Per2-dependent mechanisms

A wide search for ischemic preconditioning (IPC) mechanisms of cardioprotection identified the light elicited circadian rhythm protein Period 2 (Per2) to be cardioprotective. Studies on cardiac metabolism found a key role for light elicited Per2 in mediating metabolic dependence on carbohydrate metabolism. To profile Per2 mediated pathways following IPC of the mouse heart, we performed a genome array and identified 352 abundantly expressed and well-characterized Per2 dependent micro RNAs. One prominent result of our in silico analysis for cardiac Per2 dependent micro RNAs revealed a selective role for miR-21 in the regulation of hypoxia and metabolic pathways. Based on this Per2 dependency, we subsequently found a diurnal expression pattern for miR-21 with higher miR-21 expression levels at Zeitgeber time (ZT) 15 compared to ZT3. Gain or loss of function studies for miR-21 using miRNA mimics or miRNA inhibitors and a Seahorse Bioanalyzer uncovered a critical role of miR-21 for cellular glycolysis, glycolytic capacity, and glycolytic reserve. Exposing mice to intense light, a strategy to induce Per2, led to a robust induction of cardiac miR-21 tissue levels and decreased infarct sizes, which was abolished in miR-21-/- mice. Similarly, first translational studies in humans using intense blue light exposure for 5 days in healthy volunteers resulted in increased plasma miR-21 levels which was associated with increased phosphofructokinase activity, the rate-limiting enzyme in glycolysis. Together, we identified miR-21 as cardioprotective downstream target of Per2 and suggest intense light therapy as a potential strategy to enhance miR-21 activity and subsequent carbohydrate metabolism in humans.

Redefining the identity of cardiac fibroblasts

Cardiac fibroblasts deposit and maintain extracellular matrix during organogenesis and under physiological conditions. In the adult heart, activated cardiac fibroblasts also participate in the healing response after acute myocardial infarction and during chronic disease states characterized by augmented interstitial fibrosis and ventricular remodelling. However, delineation of the characteristics, plasticity, and origins of cardiac fibroblasts is an area of ongoing investigation and controversy. A set of genetic mouse models has been developed that specifically addresses the nature of these cells, in terms of both their origins and their response during cardiac disease and ventricular remodelling. As our understanding of cardiac fibroblasts becomes more defined and refined, so does the potential to develop new therapeutic strategies to control fibrosis and adverse ventricular remodelling.

Mechanisms of Fibroblast Activation in the Remodeling Myocardium

PURPOSE OF REVIEW

Activated fibroblasts are critically implicated in repair and remodeling of the injured heart. This manuscript discusses recent progress in the cell biology of fibroblasts in the infarcted and remodeling myocardium, highlighting advances in understanding the origin, function and mechanisms of activation of these cells.

RECENT FINDINGS

Following myocardial injury, fibroblasts undergo activation and myofibroblast transdifferentiation. Recently published studies have suggested that most activated myofibroblasts in the infarcted and pressure-overloaded hearts are derived from resident fibroblast populations. In the healing infarct, fibroblasts undergo dynamic phenotypic alterations in response to changes in the cytokine milieu and in the composition of the extracellular matrix. Fibroblasts do not simply serve as matrix-producing cells, but may also regulate inflammation, modulate cardiomyocyte survival and function, mediate angiogenesis, and contribute to phagocytosis of dead cells.

SUMMARY

In the injured myocardium, fibroblasts are derived predominantly from resident populations and serve a wide range of functions.

The role of air pollution in myocardial remodeling

Background

Excessive air pollution in urban environments can impact morbidity and mortality. The authors evaluated the role of particulate matter_2.5 (PM_2.5) in structural, geometric, and functional remodeling in hearts, using an experimental model of myocardial infarction.

Methods and findings

Seventy-five rats were divided into 5 groups: control (CG), CG exposed to PM_2.5 pollution (CGP), myocardial infarcted group (MI), infarcted group immediately exposed to pollution (IGP-I), and infarcted group previously exposed to pollution and kept exposed after infarction (IGP-II). Greater deposition of interstitial collagen occurred in the left ventricle in CGP, MI, IGP-I, and IGP-II groups compared with that in controls (p = 0.002 CG vs CGP and p<0.0001 CG vs MI, IGP-I, and IGP-II). In the right ventricle, greater collagen deposition existed in CGP, MI, IGP-I, and IGP-II compared with that in CG (p<0.021 CG vs CGP and p<0.0001 CG vs MI, IGP-I, and IGP-II). At the end of the study, CG had a higher mean shortening fraction than the other groups had (p≤0.03). Left ventricular systolic diameter was lower in CG than in infarcted groups (p≤0.003). The infarcted groups had greater expression of TGF-β (p≤0.04). PM_2.5 increased the expression of TGF-β in the IGP-II compared with the MI group (p = 0.004). The TNF-α gene was overexpressed in the IGP-II compared with the CGP group (p = 0.012). INF-γ gene expression was greater in IGP-II (p≤0.01). Oxidative stress analysis showed a higher glutathione concentration in CGP (p = 0.03), MI (p = 0.014), and IGP-I (p = 0.008) compared with that in CG.

Conclusions

PM_2.5 stimulates the deposition of fibrosis in the myocardium of healthy hearts, but not in infarcted hearts. PM_2.5 modulates the inflammatory response, which was greater in the IGP-II group. It also modulates oxidative stress in healthy hearts but not in infarcted hearts.

Cardiac Fibroblast Activation Post-Myocardial Infarction: Current Knowledge Gaps

In response to myocardial infarction (MI), the wound healing response of the left ventricle (LV) comprises overlapping inflammatory, proliferative, and maturation phases, and the cardiac fibroblast is a key cell type involved in each phase. It has recently been appreciated that, early post-MI, fibroblasts transform to a proinflammatory phenotype and secrete cytokines and chemokines as well as matrix metalloproteinases (MMPs). Later post-MI, fibroblasts are activated to anti-inflammatory and proreparative phenotypes and generate anti-inflammatory and proangiogenic factors and extracellular matrix (ECM) components that form the infarct scar. Additional studies are needed to systematically examine how fibroblast activation shifts over the timeframe of the MI response and how modulation at different activation stages could alter wound healing and LV remodeling in distinct ways. This review summarizes current fibroblast knowledge as the foundation for a discussion of existing knowledge gaps.

The role of miR‑370 in fibrosis after myocardial infarction

In the present study, we investigated the expression of miR-370 in the border area of infarction after myocardial infarction and its role in the process of post-infarction fibrosis. A myocardial infarction model in Sprague-Dawley rats was established. After two weeks, the mRNA levels of transforming growth factor-β1 (TGFβ1), TGFβRII, ColIa1, ColIIIa1 and miR-370 and the expression of TGFβ1, TGFβRII and α-smooth muscle actin (α-SMA) proteins in the border area of infarction were detected by real-time fluorescence quantitative polymerase chain reaction (qRT-PCR) and western blot analysis. Cardiac fibroblasts in neonatal rat were isolated and cultured, and the changes in the above indicators were detected after AngII and miR-370 intervention. Luciferase reporter gene assay was conducted to verify whether TGFβRII was a target gene of miR-370. In the border area after myocardial infarction, the expression of miR-370 decreased, while mRNA levels of TGFβ1, TGFβRII, ColIa1 and ColIIIa1 and levels of TGFβ1, TGFβRII and α-SMA proteins were all increased. Luciferase reporter gene assay confirmed that TGFβRII was the target gene of miR-370. miR-370 reduced the expression of TGFβRII and inhibited the increased expression of TGFβRII and collagen protein caused by AngII. As well, its inhibited the differentiation effect of muscle fibroblasts while it did not inhibit the expression of TGFβ1. miR-370 inhibited the expression of TGFβRII protein by combining with TGFβRII mRNA. miR-370 also partially blocked TGFβ1-TGFβRII and induced the downstream signal transduction pathways, thus exerting anti-fibrotic effects.

Transforming growth factor β and its role in heart disease

Myocardial infarction (MI) is a major form of heart disease that leads to immediate cardiomyocyte death due to ischemia and eventually fibrosis and scar formation and further dysfunction of myocardium and heart failure. Extracellular matrix (ECM) production and tissue repair is conducted by myofibroblasts, which are formed from the normal quiescent cardiac fibroblasts following transformational changes, through the active participation of transforming growth factor β (TGFβ) and its signaling pathways. TGFβ appears to be a ‘Master of all trades’, with respect to cardiac fibrosis, as it can promote cardiomyocyte apoptosis and cardiac hypertrophy. TGFβ signaling involves its binding to TGFβ receptor type II (TGFβRII), which recruits TGFβ receptor type I (TGFβRI), which are also known as activin receptor-like kinase (ALK) in five different isoforms. In canonical signaling pathways, ALK5 activates Smads 2 and 3, and ALK1 activates Smads 1 and 5. These pairs of Smads form a corresponding complex and then bind to Smad 4, to translocate into the nucleus, where transcriptional reprogramming is carried out to promote myofibroblast formation and ECM production, eventually leading to cardiac fibrosis. TGFβ levels are elevated in MI, thereby aggravating the myocardial injury further. Several microRNAs are involved in the regulation of TGFβ signaling at different steps, affecting different components. Therapeutic targeting of TGFβ signaling at ALK1-5 receptor activity level has met with limited success and extensive research is needed to develop therapies based on the components of TGFβ signaling pathway, for instance cardiac dysfunction and heart failure.

Human cardiac fibroblasts adaptive responses to controlled combined mechanical strain and oxygen changes in vitro

Upon cardiac pathological conditions such as ischemia, microenvironmental changes instruct a series of cellular responses that trigger cardiac fibroblasts-mediated tissue adaptation and inflammation. A comprehensive model of how early environmental changes may induce cardiac fibroblasts (CF) pathological responses is far from being elucidated, partly due to the lack of approaches involving complex and simultaneous environmental stimulation. Here, we provide a first analysis of human primary CF behavior by means of a multi-stimulus microdevice for combined application of cyclic mechanical strain and controlled oxygen tension. Our findings elucidate differential human CFs responses to different combinations of the above stimuli. Individual stimuli cause proliferative effects (PHH3⁺ mitotic cells, YAP translocation, PDGF secretion) or increase collagen presence. Interestingly, only the combination of hypoxia and a simulated loss of contractility (2% strain) is able to additionally induce increased CF release of inflammatory and pro-fibrotic cytokines and matrix metalloproteinases.

DOI:http://dx.doi.org/10.7554/eLife.22847.001

When the supply of oxygen to the heart is reduced, its cells start to die within hours, the heart muscle becomes less able to contract, and the area becomes inflamed. This inflammation is accompanied by an influx of immune cells. It also activates other cells known as cardiac fibroblasts that help to break down the framework of molecules that supported the damaged heart tissue and replace it with a scar. This response is part of the normal repair process, but it can lead to the formation of scar tissue in non-damaged areas of the heart. Excess scar tissue makes the heart muscle less able to contract and increases the affected individual’s chance of dying.

Understanding how this repair process works is an important step in developing strategies to minimise the damage caused by coronary artery disease or heart attacks. However, existing laboratory models are only partly able to recreate the conditions seen in real heart tissue. To properly understand the response at the level of living cells, a more complete model is needed.

Ugolini et al. now report improvements to a small device, referred to as a lab-on-chip, that can subject cells to mechanical strain. The improvements mean the device could also recreate other conditions seen early on in damaged heart tissue, specifically the reduced supply of oxygen. Replicating combinations of mechanical changes and oxygen supplies meant that the impact of these conditions on human cardiac fibroblasts could be directly observed in the laboratory for the first time. Ugolini et al. found that a lack of contraction and low oxygen levels triggered the cardiac fibroblasts to produce inflammatory molecules and molecules associated with the formation of scar tissue. This resembles the response seen in living hearts.

The next step is to improve the lab-on-chip device further by adding other cell types, including heart muscle cells and immune cells. A more complete model may aid future research into how our hearts operate in both health and disease.

DOI:http://dx.doi.org/10.7554/eLife.22847.002

Pathophysiological Fundamentals of Diabetic Cardiomyopathy

Diabetic cardiomyopathy (DCM) was first recognized more than four decades ago and occurred independent of cardiovascular diseases or hypertension in both type 1 and type 2 diabetic patients. The exact mechanisms underlying this disease remain incompletely understood. Several pathophysiological bases responsible for DCM have been proposed, including the presence of hyperglycemia, nonenzymatic glycosylation of large molecules (e.g., proteins), energy metabolic disturbance, mitochondrial damage and dysfunction, impaired calcium handling, reactive oxygen species formation, inflammation, cardiac cell death, and cardiac hypertrophy and fibrosis, leading to impairment of cardiac contractile functions. Increasing evidence also indicates the phenomenon called "metabolic memory" for diabetes-induced cardiovascular complications, for which epigenetic modulation seemed to play an important role, suggesting that the aforementioned pathogenic bases may be regulated by epigenetic modification. Therefore, this review aims at briefly summarizing the current understanding of the pathophysiological bases for DCM. Although how epigenetic mechanisms play a role remains incompletely understood now, extensive clinical and experimental studies have implicated its importance in regulating the cardiac responses to diabetes, which are believed to shed insight into understanding of the pathophysiological and epigenetic mechanisms for the development of DCM and its possible prevention and/or therapy. © 2017 American Physiological Society. Compr Physiol 7:693-711, 2017.

A peptide vaccine targeting angiotensin II attenuates the cardiac dysfunction induced by myocardial infarction

A peptide vaccine targeting angiotensin II (Ang II) was recently developed as a novel treatment for hypertension to resolve the problem of noncompliance with pharmacotherapy. Ang II plays a crucial role in the pathogenesis of cardiac remodeling after myocardial infarction (MI), which causes heart failure. In the present study, we examined whether the Ang II vaccine is effective in preventing heart failure. The injection of the Ang II vaccine in a rat model of MI attenuated cardiac dysfunction in association with an elevation in the serum anti-Ang II antibody titer. Furthermore, any detrimental effects of the Ang II vaccine were not observed in the rats that underwent sham operations. Treatment with immunized serum from Ang II vaccine-injected rats significantly suppressed post-MI cardiac dysfunction in MI rats and Ang II-induced remodeling-associated signaling in cardiac fibroblasts. Thus, our present study demonstrates that the Ang II vaccine may provide a promising novel therapeutic strategy for preventing heart failure.

The role of transforming growth factor (TGF)-β in the infarcted myocardium

The adult mammalian heart has negligible regenerative capacity. Following myocardial infarction, sudden necrosis of cardiomyocytes triggers an intense inflammatory reaction that clears the wound from dead cells and matrix debris, while activating a reparative program. A growing body of evidence suggests that members of the transforming growth factor (TGF)-β family critically regulate the inflammatory and reparative response following infarction. Although all three TGF-β isoforms (TGF-β1, -β2 and -β3) are markedly upregulated in the infarcted myocardium, information on isoform-specific actions is limited. Experimental studies have suggested that TGF-β exerts a wide range of actions on cardiomyocytes, fibroblasts, immune cells, and vascular cells. The findings are often conflicting, reflecting the context-dependence of TGF-β-mediated effects; conclusions are often based exclusively on in vitro studies and on associative evidence. TGF-β has been reported to modulate cardiomyocyte survival responses, promote monocyte recruitment, inhibit macrophage pro-inflammatory gene expression, suppress adhesion molecule synthesis by endothelial cells, promote myofibroblast conversion and extracellular matrix synthesis, and mediate both angiogenic and angiostatic effects. This review manuscript discusses our understanding of the cell biological effects of TGF-β in myocardial infarction. We discuss the relative significance of downstream TGF-β-mediated Smad-dependent and -independent pathways, and the risks and challenges of therapeutic TGF-β targeting. Considering the high significance of TGF-β-mediated actions in vivo, study of cell-specific effects and dissection of downstream signaling pathways are needed in order to design safe and effective therapeutic approaches.

Canstatin stimulates migration of rat cardiac fibroblasts via secretion of matrix metalloproteinase-2

Type IV collagen, a nonfibrillar type, is ubiquitously expressed in the basement membrane around cardiomyocytes. Canstatin, a cleaved product of α2 chain of type IV collagen, is an antiangiogenic factor. Because it has not been clarified whether canstatin exerts other biological activities in heart, we investigated the effects of canstatin on adult rat cardiac fibroblasts. Cell migration was determined by Boyden chamber assay. Western blotting was performed to detect secretion of matrix metalloproteinase-2 (MMP-2) and MMP-9 and phosphorylation of extracellular signal-regulated kinase (ERK). Localization of MMP-2 was detected by immunofluorescence staining. Canstatin (250 ng/ml) significantly increased migration, secretion, and activity of MMP-2 but not MMP-9. CTTHWGFTLC peptide, an MMP inhibitor and small interfering RNA (siRNA) against MMP-2 suppressed the canstatin-induced (250 ng/ml, 24 h) migration. Canstatin (250 ng/ml, 30 min) significantly increased phosphorylation of ERK. PD98059, a MEK inhibitor, significantly suppressed the canstatin-induced (250 ng/ml, 24 h) migration but not secretion of MMP-2. An increase in MMP-2 expression was observed in cytoplasm of the canstatin-treated (250 ng/ml) cardiac fibroblasts (within 30 min). Canstatin induced actin stress fiber formation, which was inhibited by Y-27632, a Rho-associated kinase inhibitor. Y-27632 also suppressed the canstatin-induced (250 ng/ml, 24 h) MMP-2 secretion. Canstatin (250 ng/ml, 30 min) failed to induce ERK phosphorylation in MMP-2 siRNA-treated cardiac fibroblasts. In conclusion, this study revealed a novel function of canstatin for inducing cell migration of adult rat cardiac fibroblasts at least in part by ERK phosphorylation through MMP-2 secretion, possibly via actin cytoskeletal change.

Blockade to pathological remodeling of infarcted heart tissue using a porcupine antagonist

The secreted Wnt signaling molecules are essential to the coordination of cell-fate decision making in multicellular organisms. In adult animals, the secreted Wnt proteins are critical for tissue regeneration and frequently contribute to cancer. Small molecules that disable the Wnt acyltransferase Porcupine (Porcn) are candidate anticancer agents in clinical testing. Here we have systematically assessed the effects of the Porcn inhibitor (WNT-974) on the regeneration of several tissue types to identify potentially unwanted chemical effects that could limit the therapeutic utility of such agents. An unanticipated observation from these studies is proregenerative responses in heart muscle induced by systemic chemical suppression of Wnt signaling. Using in vitro cultures of several cell types found in the heart, we delineate the Wnt signaling apparatus supporting an antiregenerative transcriptional program that includes a subunit of the nonfibrillar collagen VI. Similar to observations seen in animals exposed to WNT-974, deletion of the collagen VI subunit, COL6A1, has been shown to decrease aberrant remodeling and fibrosis in infarcted heart tissue. We demonstrate that WNT-974 can improve the recovery of heart function after left anterior descending coronary artery ligation by mitigating adverse remodeling of infarcted tissue. Injured heart tissue exposed to WNT-974 exhibits decreased scarring and reduced Col6 production. Our findings support the development of Porcn inhibitors as antifibrotic agents that could be exploited to promote heart repair following injury.

Macrophage-Derived mir-155-Containing Exosomes Suppress Fibroblast Proliferation and Promote Fibroblast Inflammation during Cardiac Injury

Inflammation plays an important role in cardiac injuries. Here, we examined the role of miRNA in regulating inflammation and cardiac injury during myocardial infarction. We showed that mir-155 expression was increased in the mouse heart after myocardial infarction. Upregulated mir-155 was primarily presented in macrophages and cardiac fibroblasts of injured hearts, while pri-mir-155 was only expressed in macrophages. mir-155 was also presented in exosomes derived from macrophages, and it can be transferred into cardiac fibroblasts by macrophage-derived exosomes. A mir-155 mimic or mir-155 containing exosomes inhibited cardiac fibroblast proliferation by downregulating Son of Sevenless 1 expression and promoted inflammation by decreasing Suppressor of Cytokine Signaling 1 expression. These effects were reversed by the addition of a mir-155 inhibitor. In vivo, mir-155-deficient mice showed a significant reduction of the incidence of cardiac rupture and an improved cardiac function compared with wild-type mice. Moreover, transfusion of wild-type macrophage exosomes to mir-155-/- mice exacerbated cardiac rupture. Finally, the mir-155-deficient mice exhibited elevated fibroblast proliferation and collagen production, along with reduced cardiac inflammation in injured heart. Taken together, our results demonstrate that activated macrophages secrete mir-155-enriched exosomes and identify macrophage-derived mir-155 as a paracrine regulator for fibroblast proliferation and inflammation; thus, a mir-155 inhibitor (i.e., mir-155 antagomir) has the potential to be a therapeutic agent for reducing acute myocardial-infarction-related adverse events.

Getting to the heart of intracellular glucocorticoid regeneration: 11β-HSD1 in the myocardium

Corticosteroids influence the development and function of the heart and its response to injury and pressure overload via actions on glucocorticoid (GR) and mineralocorticoid (MR) receptors. Systemic corticosteroid concentration depends largely on the activity of the hypothalamic-pituitary-adrenal (HPA) axis, but glucocorticoid can also be regenerated from intrinsically inert metabolites by the enzyme 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1), selectively increasing glucocorticoid levels within cells and tissues. Extensive studies have revealed the roles for glucocorticoid regeneration by 11β-HSD1 in liver, adipose, brain and other tissues, but until recently, there has been little focus on the heart. This article reviews the evidence for glucocorticoid metabolism by 11β-HSD1 in the heart and for a role of 11β-HSD1 activity in determining the myocardial growth and physiological function. We also consider the potential of 11β-HSD1 as a therapeutic target to enhance repair after myocardial infarction and to prevent the development of cardiac remodelling and heart failure.

Astragaloside IV enhances cardioprotection of remote ischemic conditioning after acute myocardial infarction in rats

BACKGROUND

Remote ischemic conditioning (RIC) has been shown to be a practical method for protecting the heart from ischemic/reperfusion (I/R) injury. In the present study, we investigated whether or not the combination of RIC and Astragaloside IV (AS-IV) could improve cardioprotection against acute myocardial infarction (AMI)-induced heart failure (HF) when compared with individual treatments.

MATERIAL AND METHODS

A rat model of AMI was established via permanent ligation of the left anterior descending coronary artery (LAD). Postoperatively, the rats were randomly grouped into a sham group (n=10), a model group (n=15), an AS-IV alone group (n=15), an RIC alone group (n=15) and a combined treatment group (AS-IV+RIC; n=15). All treatments were administered for 2 weeks.

RESULTS

After treatment for 2 weeks, the survival rate was improved, the cardiac function was preserved and the infarcted size was limited in AS-IV alone and RIC alone treatment groups compared to the model group, whereas the combined treatment yielded the most optimal protective effects. Additional studies suggested that AS-IV enhanced the cardioprotective effects of RIC by alleviating myocardial fibrosis, suppressing inflammation, attenuating apoptosis and ameliorating impairment of the myocardial ultrastructural.

CONCLUSION

AS-IV enhances the cardioprotective effects of RIC against AMI-induced HF and ventricular remodeling, which represents a potential therapeutic approach for preserving cardiac function and improving the prognosis of AMI.

ADP-Induced Ca2+ Signaling and Proliferation of Rat Ventricular Myofibroblasts Depend on Phospholipase C-Linked TRP Channels Activation Within Lipid Rafts

Nucleotides released during heart injury affect myocardium electrophysiology and remodeling through P2 purinoceptors activation in cardiac myofibroblasts. ATP and UTP endorse [Ca²⁺ ]_i accumulation and growth of DDR-2/α-SMA-expressing myofibroblasts from adult rat ventricles via P2Y₄ and P2Y₂ receptors activation, respectively. Ventricular myofibroblasts also express ADP-sensitive P2Y₁ , P2Y₁₂ , and P2Y₁₃ receptors as demonstrated by immunofluorescence confocal microscopy and western blot analysis, but little information exists on ADP effects in these cells. ADP (0.003-3 mM) and its stable analogue, ADPßS (100 μM), caused fast [Ca²⁺ ]_i transients originated from thapsigargin-sensitive internal stores, which partially declined to a plateau sustained by capacitative Ca²⁺ entry through transient receptor potential (TRP) channels inhibited by 2-APB (50 μM) and flufenamic acid (100 μM). Hydrophobic interactions between G_q/11 -coupled P2Y purinoceptors and TRP channels were suggested by prevention of the ADP-induced [Ca²⁺ ]_i plateau following PIP₂ depletion with LiCl (10 mM) and cholesterol removal from lipid rafts with methyl-ß-cyclodextrin (2 mM). ADP [Ca²⁺ ]_i transients were insensitive to P2Y₁ , P2Y₁₂ , and P2Y₁₃ receptor antagonists, MRS2179 (10μM), AR-C66096 (0.1 μM), and MRS2211 (10μM), respectively, but were attenuated by suramin and reactive blue-2 (100 μM) which also blocked P2Y₄ receptors activation by UTP. Cardiac myofibroblasts growth and type I collagen production were favored upon activation of MRS2179-sensitive P2Y₁ receptors with ADP or ADPßS (30 μM). In conclusion, ADP exerts a dual role on ventricular myofibroblasts: [Ca²⁺ ]_i transients are mediated by fast-desensitizing P2Y₄ receptors, whereas the pro-fibrotic effect of ADP involves the P2Y₁ receptor activation. Data also show that ADP-induced capacitative Ca²⁺ influx depends on phospholipase C-linked TRP channels opening in lipid raft microdomains. J. Cell. Physiol. 232: 1511-1526, 2017. © 2016 Wiley Periodicals, Inc.