TGF-β1 prevents simulated ischemia/reperfusion-induced cardiac fibroblast apoptosis by activation of both canonical and non-canonical signaling pathways

Regulation of cardiac fibroblast cell death by unfolded protein response signaling

The endoplasmic reticulum (ER) is a tightly regulated organelle that requires specific environmental properties to efficiently carry out its function as a major site of protein synthesis and folding. Embedded in the ER membrane, ER stress sensors inositol-requiring enzyme 1 (IRE1), protein kinase R (PKR)-like endoplasmic reticulum kinase (PERK), and activating transcription factor 6 (ATF6) serve as a sensitive quality control system collectively known as the unfolded protein response (UPR). In response to an accumulation of misfolded proteins, the UPR signals for protective mechanisms to cope with the cellular stress. Under prolonged unstable conditions and an inability to regain homeostasis, the UPR can shift from its original adaptive response to mechanisms leading to UPR-induced apoptosis. These UPR signaling pathways have been implicated as an important feature in the development of cardiac fibrosis, but identifying effective treatments has been difficult. Therefore, the apoptotic mechanisms of UPR signaling in cardiac fibroblasts (CFs) are important to our understanding of chronic fibrosis in the heart. Here, we summarize the maladaptive side of the UPR, activated downstream pathways associated with cell death, and agents that have been used to modify UPR-induced apoptosis in CFs.

Epigenetic signatures in cardiac fibrosis: Focusing on noncoding RNA regulators as the gatekeepers of cardiac fibroblast identity

Cardiac fibroblasts play a pivotal role in cardiac fibrosis by transformation of fibroblasts into myofibroblasts, which synthesis and secrete a large number of extracellular matrix proteins. Ultimately, this will lead to cardiac wall stiffness and impaired cardiac performance. The epigenetic regulation and fate reprogramming of cardiac fibroblasts has been advanced considerably in recent decades. Non coding RNAs (microRNAs, lncRNAs, circRNAs) regulate the functions and behaviors of cardiac fibroblasts, including proliferation, migration, phenotypic transformation, inflammation, pyroptosis, apoptosis, autophagy, which can provide the basis for novel targeted therapeutic treatments that abrogate activation and inflammation of cardiac fibroblasts, induce different death pathways in cardiac fibroblasts, or make it sensitive to established pathogenic cells targeted cytotoxic agents and biotherapy. This review summarizes our current knowledge in this field of ncRNAs function in epigenetic regulation and fate determination of cardiac fibroblasts as well as the details of signaling pathways contribute to cardiac fibrosis. Moreover, we will comment on the emerging landscape of lncRNAs and circRNAs function in regulating signal transduction pathways, gene translation processes and post-translational regulation of gene expression in cardiac fibroblast. In the end, the prospect of cardiac fibroblasts targeted therapy for cardiac fibrosis based on ncRNAs is discussed.

Dynamic and static biomechanical traits of cardiac fibrosis

Cardiac fibrosis is a common pathology in cardiovascular diseases which are reported as the leading cause of death globally. In recent decades, accumulating evidence has shown that the biomechanical traits of fibrosis play important roles in cardiac fibrosis initiation, progression and treatment. In this review, we summarize the four main distinct biomechanical traits (i.e., stretch, fluid shear stress, ECM microarchitecture, and ECM stiffness) and categorize them into two different types (i.e., static and dynamic), mainly consulting the unique characteristic of the heart. Moreover, we also provide a comprehensive overview of the effect of different biomechanical traits on cardiac fibrosis, their transduction mechanisms, and in-vitro engineered models targeting biomechanical traits that will aid the identification and prediction of mechano-based therapeutic targets to ameliorate cardiac fibrosis.

Alamandine alleviated heart failure and fibrosis in myocardial infarction mice

Alamandine (Ala) is the newest identified peptide of the renin-angiotensin system and has protective effect on myocyte hypertrophy. However, it is still unclear whether Ala can alleviate heart failure (HF). The aim of this study was to explore the effects of Ala on HF and the related cardiac fibrosis, and to probe the mechanism. HF model was induced by myocardial infarction (MI) in mice. Four weeks after MI, Ala was administrated by intraperitoneal injection for two weeks. Ala injection significantly improved cardiac dysfunction of MI mice in vivo. The cardiac fibrosis and the related biomarkers were attenuated after Ala administration in HF mice in vivo. The increases of collagen I, alpha-smooth muscle actin and transforming growth factor-beta induced by oxygen–glucose deprivation (OGD) in neonatal rat cardiac fibroblasts (NRCFs) were inhibited by Ala treatment in vitro. The biomarkers of apoptosis were elevated in NRCFs induced by OGD, which were attenuated after treating with Ala in vitro. The enhancement of oxidative stress in the heart of MI mice or in the NRCFs treated with OGD was suppressed by treating with Ala in vivo and in vitro. These effects of Ala were reversed by tBHP, an exogenous inducer of oxidative stress in vitro. These results demonstrated that Ala could alleviate cardiac dysfunction and attenuate cardiac fibrosis via inhibition of oxidative stress.

Tangshen Formula Improves Diabetes-Associated Myocardial Fibrosis by Inhibiting TGF-β/Smads and Wnt/β-Catenin Pathways

Cardiovascular disease has become the main cause of death among complications of diabetes. Myocardial fibrosis is a crucial pathological change of cardiovascular disease. Tangshen Formula (TSF) shows a good clinical effect in the treatment of diabetic kidney disease (DKD). However, whether TSF alleviates diabetes-associated myocardial fibrosis is still unknown. In the present research, we studied the effect and mechanism of TSF in the treatment of myocardial fibrosis in vivo and in vitro. We found that TSF treatment significantly downregulates myocardial fibrosis-related markers, including collagens I and III, and α-SMA. TSF also protects primary mouse cardiac fibroblast (CF) from transforming growth factor-β1- (TGF-β1-) induced damage. Moreover, TSF decreased the expression levels of TGF-β/Smad-related genes (α-SMA, collagens I and III, TGF-β1, and pSmad2/3), and increased Smad7 gene expression. Finally, TSF decreased the expressions of wnt1, active-β-catenin, FN, and MMP7 to regulate the Wnt/β-catenin pathway. Taken together, TSF seems to attenuate myocardial fibrosis in KKAy mice by inhibiting TGF-β/Smad2/3 and Wnt/β-catenin signaling pathways.

Hydrogen sulfide therapy: a narrative overview of current research and possible therapeutic implications in future

Diabetic nephropathy is one of the most important comorbidities in the diabetic population. In China, more and more young patients are showing an increasing prevalence of diabetes. As a gas molecule, hydrogen sulfide (H₂S) has some unique chemical and physiological functions. In recent years, it has been studied in various fields. These effects are manifested in the induction of renal vasodilation and anti-renal vascular fibrosis. The ball clearing function is improved. Therefore, increasing prospective studies have focused on how H₂S protects diabetic nephropathy and how to obtain H₂S by modern means to treat diabetic nephropathy.

Communication Between Cardiomyocytes and Fibroblasts During Cardiac Ischemia/Reperfusion and Remodeling: Roles of TGF-β, CTGF, the Renin Angiotensin Axis, and Non-coding RNA Molecules

Communication between cells is a foundational concept for understanding the physiology and pathology of biological systems. Paracrine/autocrine signaling, direct cell-to-cell interplay, and extracellular matrix interactions are three types of cell communication that regulate responses to different stimuli. In the heart, cardiomyocytes, fibroblasts, and endothelial cells interact to form the cardiac tissue. Under pathological conditions, such as myocardial infarction, humoral factors released by these cells may induce tissue damage or protection, depending on the type and concentration of molecules secreted. Cardiac remodeling is also mediated by the factors secreted by cardiomyocytes and fibroblasts that are involved in the extensive reciprocal interactions between these cells. Identifying the molecules and cellular signal pathways implicated in these processes will be crucial for creating effective tissue-preserving treatments during or after reperfusion. Numerous therapies to protect cardiac tissue from reperfusion-induced injury have been explored, and ample pre-clinical research has attempted to identify drugs or techniques to mitigate cardiac damage. However, despite great success in animal models, it has not been possible to completely translate these cardioprotective effects to human applications. This review provides a current summary of the principal molecules, pathways, and mechanisms underlying cardiomyocyte and cardiac fibroblast crosstalk during ischemia/reperfusion injury. We also discuss pre-clinical molecules proposed as treatments for myocardial infarction and provide a clinical perspective on these potential therapeutic agents.

miR-770-5p inhibits the activation of pulmonary fibroblasts and silica-induced pulmonary fibrosis through targeting TGFBR1

Silicosis is a devastating interstitial lung disease arising from long-term exposure to inhalable silica. Regrettably, no therapy currently can effectively reverse the silica-induced fibrotic lesion. Emerging evidence has indicated that the dysregulation of microRNAs is involved in silica-induced pulmonary fibrosis. The aim of this study is to explore the expression pattern and underlying mechanisms of miR-770-5p in silica-induced pulmonary fibrosis. Consistent with our previous miRNA microarray analysis, the results of qRT-PCR showed that miR-770-5p expression was downregulated in silica-induced pulmonary fibrosis in humans and animal models. Administration of miR-770-5p agomir significantly reduced the fibrotic lesions in the lungs of mice exposed to silica dust. MiR-770-5p also exhibited a dramatic reduction in TGF-β1-activated human pulmonary fibroblasts (MRC-5). Transfection of miR-770-5p mimics significantly decreased the viability, migration ability, and S/G0 phase distribution, as well as the expression of fibronectin, collagen I, and α-SMA in TGF-β1-treated MRC-5 cells. Transforming growth factor-β receptor 1 (TGFBR1) was confirmed as a direct target of regulation by miR-770-5p. The expression of TGFBR1 was significantly increased in pulmonary fibrosis. Knockdown of TGFBR1 blocked the transduction of the TGF-β1 signaling pathway and attenuated the activation of MRC-5 cells, while overexpression of TGFBR1 effectively restored the activation of MRC-5 cells inhibited by miR-770-5p. Together, our results demonstrated that miR-770-5p exerted an anti-fibrotic effect in silica-induced pulmonary fibrosis by targeting TGFBR1. Targeting miR-770-5p might provide a new therapeutic strategy to prevent the abnormal activation of pulmonary fibroblasts in silicosis.

[Platelet-rich plasma alleviates myocardial ischemia-reperfusion injury in rats]

OBJECTIVE

To investigate the protective effect of platelet-rich plasma (PRP) against acute myocardial ischemiareperfusion (IR) injury and the possible mechanism.

OBJECTIVE

Aortic blood samples were collected from 10 SD rats to prepare PRP, in which the concentrations of platelet-derived growth factor-BB (PDGF-BB) and transforming growth factor-β1 (TGF-β1) were measured. Cell models of IR injury were established in primary cultures of neonatal SD rat cardiomyocytes by exposing the cells to 3 h of hypoxia. The cells were then reoxygenated and co-cultured with 1%, 5%, 10%, and 20% volume of PRP for 12 h, and the changes in cell viability was assessed. Immunofluorescence staining of the cardiomyocytes was performed, and the cellular expression of AMPK and its phosphorylation level were detected. The effects of PRP on the proliferation and migration of rat aortic endothelial cells (RAOECs) were examined. In a SD rat model of myocardial IR injury, 100 μL of PRP (n= 20) or normal saline (n=20) was injected at 4 sites around the ligation site immediately after cardiac reperfusion. One day after the injection, 6 rats were selected from each group for TTC staining of the myocardial tissues and measurement of troponin Ⅰ content. One week later, the cardiac function of the remaining rats was assessed by echocardiography, and HE staining of the myocardial tissues was performed. The effect of PRP treatment for 24 h on polarization of M1 and M2 macrophages was also examined by flow cytometry in RAW264.7 cells after hypoxic exposure for 3 h.

OBJECTIVE

The concentrations of PDGF-BB and TGF-β1 were significantly higher in PRP than in whole blood. Addition of 1% volume of PRP significantly reduced death of the cardiomyocytes following reoxygenation, and this effect was closely related with the activation of AMPK. Treatment with PRP obviously promoted the proliferation and migration of RAOECs. In rat models of acute myocardial IR injury, injections of PRP significantly reduced the infarct size and troponin Ⅰ concentration as compared with saline injection (P < 0.001). One week after PRP injection, the rats showed significantly improved cardiac function with a lowered level of inflammatory response in comparison with the rats with saline injection. In RAW264.7 cells with hypoxic exposure, treatment with PRP obviously decreased the number of M1 macrophages and increase the number of M2 macrophages.

OBJECTIVE

PRP can improve acute myocardial IR injury in rats by phosphorylating AMPK and regulating macrophage polarization, which produces a protective immunomodulatory effect on the ischemic myocardial tissues.

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

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

TGF-β1 decreases CHOP expression and prevents cardiac fibroblast apoptosis induced by endoplasmic reticulum stress

Transforming growth factor-beta 1 (TGF-β1) is a cytokine with marked pro-fibrotic action on cardiac fibroblasts (CF). TGF-β1 induces CF-to-cardiac myofibroblast (CMF) differentiation, defined by an increase in α-smooth muscle cells (α-SMA), collagen secretion and it has a cytoprotective effect against stimuli that induce apoptosis. In the Endoplasmic Reticulum (ER) lumen, misfolded protein accumulation triggers ER stress and induces apoptosis, and this process plays a critical role in cell death mediated by Ischemia/Reperfusion (I/R) injury and by ER stress inducers, such as Tunicamycin (Tn). Here, we studied the regulation of CHOP, a proapoptotic ER-stress-related transcription factor in CF under simulated I/R (sI/R) or exposed to Tn. Even though TGF-β1 has been shown to participate in ER stress, its regulatory effect on CF apoptosis and ER stress-induced by sI/R or TN has not been evaluated yet. CF from neonatal rats were exposed to sI/R, and cell death was evaluated by cell count and apoptosis by flow cytometry. ER stress was assessed by western blot against CHOP. Our results evidenced that sI/R (8/24) h or Tn triggers CF apoptosis and an increase in CHOP protein levels. TGF-β1 pre-treatment partially prevented apoptosis induced by sI/R or Tn. Furthermore, TGF-β1 pre-treatment completely prevented CHOP increase by sI/R or Tn. Additionally, we found a decrease in α-SMA expression induced by sI/R and in collagen secretion induced by Tn, which were not prevented by TGF-β1 treatment. In conclusion, TGF-β1 partially protects CF apoptosis induced by sI/R or Tn, through a mechanism that would involve ER stress.

The role of Smad signaling cascades in cardiac fibrosis

Most myocardial pathologic conditions are associated with cardiac fibrosis, the expansion of the cardiac interstitium through deposition of extracellular matrix (ECM) proteins. Although replacement fibrosis plays a reparative role after myocardial infarction, excessive, unrestrained or dysregulated myocardial ECM deposition is associated with ventricular dysfunction, dysrhythmias and adverse prognosis in patients with heart failure. The members of the Transforming Growth Factor (TGF)-β superfamily are critical regulators of cardiac repair, remodeling and fibrosis. TGF-βs are released and activated in injured tissues, bind to their receptors and transduce signals in part through activation of cascades involving a family of intracellular effectors the receptor-activated Smads (R-Smads). This review manuscript summarizes our knowledge on the role of Smad signaling cascades in cardiac fibrosis. Smad3, the best-characterized member of the family plays a critical role in activation of a myofibroblast phenotype, stimulation of ECM synthesis, integrin expression and secretion of proteases and anti-proteases. In vivo, fibroblast Smad3 signaling is critically involved in scar organization and exerts matrix-preserving actions. Although Smad2 also regulates fibroblast function in vitro, its in vivo role in rodent models of cardiac fibrosis seems more limited. Very limited information is available on the potential involvement of the Smad1/5/8 cascade in cardiac fibrosis. Dissection of the cellular actions of Smads in cardiac fibrosis, and identification of patient subsets with overactive or dysregulated myocardial Smad-dependent fibrogenic responses are critical for design of successful therapeutic strategies in patients with fibrosis-associated heart failure.

Single-Cell RNA Sequencing Analysis Reveals a Crucial Role for CTHRC1 (Collagen Triple Helix Repeat Containing 1) Cardiac Fibroblasts After Myocardial Infarction

BACKGROUND

Cardiac fibroblasts (CFs) have a central role in the ventricular remodeling process associated with different types of fibrosis. Recent studies have shown that fibroblasts do not respond homogeneously to heart injury. Because of the limited set of bona fide fibroblast markers, a proper characterization of fibroblast population heterogeneity in response to cardiac damage is lacking. The purpose of this study was to define CF heterogeneity during ventricular remodeling and the underlying mechanisms that regulate CF function.

METHODS

Collagen1α1-GFP (green fluorescent protein)-positive CFs were characterized after myocardial infarction (MI) by single-cell and bulk RNA sequencing, assay for transposase-accessible chromatin sequencing, and functional assays. Swine and patient samples were studied using bulk RNA sequencing.

RESULTS

We identified and characterized a unique CF subpopulation that emerges after MI in mice. These activated fibroblasts exhibit a clear profibrotic signature, express high levels of Cthrc1 (collagen triple helix repeat containing 1), and localize into the scar. Noncanonical transforming growth factor-β signaling and different transcription factors including SOX9 are important regulators mediating their response to cardiac injury. Absence of CTHRC1 results in pronounced lethality attributable to ventricular rupture. A population of CFs with a similar transcriptome was identified in a swine model of MI and in heart tissue from patients with MI and dilated cardiomyopathy.

CONCLUSIONS

We report CF heterogeneity and their dynamics during the course of MI and redefine the CFs that respond to cardiac injury and participate in myocardial remodeling. Our study identifies CTHRC1 as a novel regulator of the healing scar process and a target for future translational studies.

Cardiac fibroblast diversity in health and disease

The cardiac stroma plays essential roles in health and following cardiac damage. The major player of the stroma with respect to extracellular matrix deposition, maintenance and remodeling is the poorly defined fibroblast. It has long been recognized that there is considerable variability to the fibroblast phenotype. With the advent of new, high throughput analytical methods our understanding and appreciation of this heterogeneity has grown dramatically. This review aims to explore the diversity of cardiac fibroblasts and highlights new insights into the diverse nature of these cells and their progenitors as revealed by single cell sequencing and fate mapping studies. We propose that at least in part the observed heterogeneity is related to the existence of a differentiation cascade within stromal cells. Beyond in-organ heterogeneity, we also discuss how the stromal response to damage differs between non-regenerating organs such as the heart and regenerating organs such as skeletal muscle. In exploring possible causes for these differences, we outline that although fibrogenic cells from different organs overlap in many properties, they still possess organ-specific transcriptional signatures and differentiation biases that make them functionally distinct.

Biomarkers for the identification of cardiac fibroblast and myofibroblast cells

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

Pro-fibrotic effect of oxidized LDL in cardiac myofibroblasts

Inflammatory signals associated with cardiac diseases trigger trans-differentiation of cardiac fibroblasts to cardiac myofibroblasts. Cardiac myofibroblasts are the main cell type involved in the development of cardiac fibrosis, a diffuse and disproportionate accumulation of collagen in the myocardium. Although the role of the scavenger like-lectin receptor LOX-1 was previously investigated in cardiac fibroblasts and fibrosis, the involvement of the LOX-1 ligand -oxidized low-density lipoprotein (oxLDL)- on cardiac myofibroblast function still remains unexplored. In the present work, we investigated the effect of oxLDL/LOX-1 on fibrotic markers and cardiac myofibroblast function. Our in vitro results showed that oxLDL increased cardiac myofibroblast proliferation, triggered an increase in the synthesis of collagen type I and fibronectin containing extra domain A, and stimulated collagen type I secretion. oxLDL also decreased cardiac myofibroblast migration, collagen gel contraction and cell area, without modifying α-smooth muscle actin protein levels. These effects were dependent on LOX-1, because LOX-1 knockdown abolished oxLDL effects. Collectively these data showed that oxLDL has important modulatory effects on cardiac myofibroblast function.

The Association of Ascorbic Acid, Deferoxamine and N-Acetylcysteine Improves Cardiac Fibroblast Viability and Cellular Function Associated with Tissue Repair Damaged by Simulated Ischemia/Reperfusion

Acute myocardial infarction is one of the leading causes of death worldwide and thus, an extensively studied disease. Nonetheless, the effects of ischemia/reperfusion injury elicited by oxidative stress on cardiac fibroblast function associated with tissue repair are not completely understood. Ascorbic acid, deferoxamine, and N-acetylcysteine (A/D/N) are antioxidants with known cardioprotective effects, but the potential beneficial effects of combining these antioxidants in the tissue repair properties of cardiac fibroblasts remain unknown. Thus, the aim of this study was to evaluate whether the pharmacological association of these antioxidants, at low concentrations, could confer protection to cardiac fibroblasts against simulated ischemia/reperfusion injury. To test this, neonatal rat cardiac fibroblasts were subjected to simulated ischemia/reperfusion in the presence or absence of A/D/N treatment added at the beginning of simulated reperfusion. Cell viability was assessed using trypan blue staining, and intracellular reactive oxygen species (ROS) production was assessed using a 2′,7′-dichlorofluorescin diacetate probe. Cell death was measured by flow cytometry using propidium iodide. Cell signaling mechanisms, differentiation into myofibroblasts and pro-collagen I production were determined by Western blot, whereas migration was evaluated using the wound healing assay. Our results show that A/D/N association using a low concentration of each antioxidant increased cardiac fibroblast viability, but that their separate administration did not provide protection. In addition, A/D/N association attenuated oxidative stress triggered by simulated ischemia/reperfusion, induced phosphorylation of pro-survival extracellular-signal-regulated kinases 1/2 (ERK1/2) and PKB (protein kinase B)/Akt, and decreased phosphorylation of the pro-apoptotic proteins p38- mitogen-activated protein kinase (p38-MAPK) and c-Jun-N-terminal kinase (JNK). Moreover, treatment with A/D/N also reduced reperfusion-induced apoptosis, evidenced by a decrease in the sub-G1 population, lower fragmentation of pro-caspases 9 and 3, as well as increased B-cell lymphoma-extra large protein (Bcl-xL)/Bcl-2-associated X protein (Bax) ratio. Furthermore, simulated ischemia/reperfusion abolished serum-induced migration, TGF-β1 (transforming growth factor beta 1)-mediated cardiac fibroblast-to-cardiac myofibroblast differentiation, and angiotensin II-induced pro-collagen I synthesis, but these effects were prevented by treatment with A/D/N. In conclusion, this is the first study where a pharmacological combination of A/D/N, at low concentrations, protected cardiac fibroblast viability and function after simulated ischemia/reperfusion, and thereby represents a novel therapeutic approach for cardioprotection.

TGF-β1 induced up-regulation of B1 kinin receptor promotes antifibrotic activity in rat cardiac myofibroblasts

Cardiac myofibroblast (CMF) are non-muscle cardiac cells that play a crucial role in wound healing and in pathological remodeling. These cells are mainly derived of cardiac fibroblast (CF) differentiation mediated by TGF-β1. Evidence suggests that bradykinin (BK) regulates cardiac fibroblast function in the heart. Both B1 and B2 kinin receptors (B1R and B2R, respectively) mediate the biological effects of kinins. We recently showed that both receptors are expressed in CMF and its stimulation decreases collagen secretion. Whether TGF-β1 regulates B1R and B2R expression, and how these receptors control antifibrotic activity in CMF remains poorly understood. In this work, we sought to study, the regulation of B1R expression in cultured CMF mediated by TGF-β1, and the molecular mechanisms involved in B1R activation on CMF intracellular collagen type-I levels. Cardiac fibroblast-primary culture was obtained from neonatal rats. Hearts were digested and CFs were attached to dishes and separated from cardiomyoctes. CMF were obtained from CF differentiation with TGF-β1 5 ng/mL. CF and CMF were treated with B1R and B2R agonists and with TGF-β1 at different times and concentrations, in the presence or absence of chemical inhibitors, to evaluate signaling pathways involved in B1R expression, collagen type-I and prostacyclin levels. B1R and collagen type-I levels were evaluated by western blot. Prostacyclin levels were quantified by an ELISA kit. TGF-β1 increased B1R expression via TGFβ type I receptor kinase (ALK5) activation and its subsequent signaling pathways involving Smad2, p38, JNK and ERK1/2 activation. Moreover, in CMF, the activation of B1R and B2R by their respective agonists, reduced collagen synthesis. This effect was mediated by the canonical signaling pathway; phospholipase C (PLC), protein kinase C (PKC), phospholipase A₂ (PLA₂), COX-2 activation and PGI₂ secretion and its autocrine effect. TGF-β1 through ALK5, Smad2, p38, JNK and ERK1/2 increases B1R expression; whereas in CMF, B1R and B2R activation share common signaling pathways for reducing collagen synthesis.

miR‑216a exacerbates TGF‑β‑induced myofibroblast transdifferentiation via PTEN/AKT signaling

Myofibroblast transdifferentiation is an important feature of cardiac fibrosis. Previous studies have indicated that microRNA‑216a (miR‑216a) is upregulated in response to transforming growth factor‑β (TGF‑β) in kidney cells and can activate Smad3; however, its role in myofibroblast transdifferentiation remains unclear. The present study aimed to investigate the role of miR‑216a in TGF‑β‑induced myofibroblast transdifferentiation, and to determine the underlying mechanisms. Adult mouse cardiac fibroblasts were treated with TGF‑β to induce myofibroblast transdifferentiation. An antagomir and agomir of miR‑216a were used to inhibit or overexpress miR‑216a in cardiac fibroblasts, respectively. Myofibroblast transdifferentiation was evaluated based on the levels of fibrotic markers and α‑smooth muscle actin expression. The miR‑216a antagomir attenuated, whereas the miR‑216a agomir promoted TGF‑β‑induced myofibroblast transdifferentiation. Mechanistically, miR‑216a accelerated myofibroblast transdifferentiation via the AKT/glycogen synthase kinase 3β signaling pathway, independent of the canonical Smad3 pathway. In addition, it was observed that miR‑216a activated AKT via the downregulation of PTEN. In conclusion, miR‑216a was involved in the regulation of TGF‑β‑induced myofibroblast transdifferentiation, suggesting that targeting miR‑216a may aid in developing effective interventions for the treatment of cardiac fibrosis.

Protective transcriptional mechanisms in cardiomyocytes and cardiac fibroblasts

Heart failure is the leading cause of morbidity and mortality worldwide. Several lines of evidence suggest that physical activity and exercise can pre-condition the heart to improve the response to acute cardiac injury such as myocardial infarction or ischemia/reperfusion injury, preventing the progression to heart failure. It is becoming more apparent that cardioprotection is a concerted effort between multiple cell types and converging signaling pathways. However, the molecular mechanisms of cardioprotection are not completely understood. What is clear is that the mechanisms underlying this protection involve acute activation of transcriptional activators and their corresponding gene expression programs. Here, we review the known stress-dependent transcriptional programs that are activated in cardiomyocytes and cardiac fibroblasts to preserve function in the adult heart after injury. Focus is given to prominent transcriptional pathways such as mechanical stress or reactive oxygen species (ROS)-dependent activation of myocardin-related transcription factors (MRTFs) and transforming growth factor beta (TGFβ), and gene expression that positively regulates protective PI3K/Akt signaling. Together, these pathways modulate both beneficial and pathological responses to cardiac injury in a cell-specific manner.

Cardiovascular disease models: A game changing paradigm in drug discovery and screening

Cardiovascular disease is the leading cause of death worldwide. Although investment in drug discovery and development has been sky-rocketing, the number of approved drugs has been declining. Cardiovascular toxicity due to therapeutic drug use claims the highest incidence and severity of adverse drug reactions in late-stage clinical development. Therefore, to address this issue, new, additional, replacement and combinatorial approaches are needed to fill the gap in effective drug discovery and screening. The motivation for developing accurate, predictive models is twofold: first, to study and discover new treatments for cardiac pathologies which are leading in worldwide morbidity and mortality rates; and second, to screen for adverse drug reactions on the heart, a primary risk in drug development. In addition to in vivo animal models, in vitro and in silico models have been recently proposed to mimic the physiological conditions of heart and vasculature. Here, we describe current in vitro, in vivo, and in silico platforms for modelling healthy and pathological cardiac tissues and their advantages and disadvantages for drug screening and discovery applications. We review the pathophysiology and the underlying pathways of different cardiac diseases, as well as the new tools being developed to facilitate their study. We finally suggest a roadmap for employing these non-animal platforms in assessing drug cardiotoxicity and safety.

Overexpression of microRNA-202-3p protects against myocardial ischemia-reperfusion injury through activation of TGF-β1/Smads signaling pathway by targeting TRPM6

MicroRNAs (miRNAs) have been found to act as key regulators in the pathogenesis of myocardial ischemic-reperfusion (I/R) injury. In this study, we explore the role and mechanism of microRNA-202-3p (miR-202-3p) in regulating cardiomyocyte apoptosis, in respective of the TGF-β1/Smads signaling pathway by targeting the transient receptor potential cation channel, subfamily M, member 6 (TRPM6). The targeting relationship between miR-202-3p and TRPM6 was verified by a dual-luciferase reporter gene assay. Sprague-Dawley rat models of myocardial I/R injury were initially established and treated with different mimics, inhibitors and siRNAs to test the effects of miR-202-3p and TRPM6 on myocardial I/R injury. The levels of inflammatory factors; IL-1β, IL-6, TNF-α as well as the degree of myocardial fibrosis and cardiomyocyte apoptosis were determined in rats transfected with different plasmids. TRPM6 was found to be the target of miR-202-3p. Up-regulated miR-202-3p or knockdown of TRPM-6 alleviated oxidative stress and inflammatory response, reduced ventricular mass, altered cardiac hemodynamics, suppressed myocardial infarction, attenuated cell apoptosis, and inhibited myocardial fibrosis. MiR-202-3p overexpression activates the TGF-β1/Smads signaling pathway by negatively regulating TRPM6 expression. Taken together, these findings suggest that miR-202-3p offers protection against ventricular remodeling after myocardial I/R injury via activation of the TGF-β1/Smads signaling pathway.

Expression, purification, and evaluation of in vivo anti-fibrotic activity for soluble truncated TGF-β receptor II as a cleavable His-SUMO fusion protein

Excessive production of transforming growth factor-β1 (TGF-β1) and its binding to transforming growth factor-β receptor type II (TGF-βRII) promotes fibrosis by activation of the TGF-β1-mediated signaling pathway. Thus, the truncated extracellular domain of TGF-βRII (tTβRII) is a promising anti-fibrotic candidate, as it lacks the signal transduction domain. In this work, the native N-terminal tTβRII was prepared as a His-SUMO fusion protein (termed His-SUMO-tTβRII) in Escherichia coli strain BL21 (DE3). His-SUMO-tTβRII was expressed as a soluble protein under optimal conditions (6 h of induction with 0.5 mM IPTG at 37 °C). His-SUMO-tTβRII was purified by Ni-NTA resin chromatography, and then cleaved with SUMO protease to release native tTβRII, which was re-purified using a Ni-NTA column. Approximately 12 mg of native tTβRII was obtained from a one liter fermentation culture with no less than 95% purity. In vivo studies demonstrated that tTβRII prevented CCl₄-induced liver fibrosis, as evidenced by the inhibition of fibrosis-related Col I and α-SMA protein expression in C57BL/6 mice. In addition, tTβRII downregulated phosphorylation of SMAD2/3, which partly repressed TGF-β1-mediated signaling. These data indicate that the His-SUMO expression system is an efficient approach for preparing native tTβRII that possesses anti-liver fibrotic activity, allowing for the large-scale production of tTβRII, which potentially could serve as an anti-fibrotic candidate for treatment of TGF-β1-related diseases.

TGF-β/Smad3 pathway enhances the cardio-protection of S1R/SIPR1 in in vitro ischemia-reperfusion myocardial cell model

Ischemia-reperfusion (IR) injury is usually associated with a high risk of cardiomyocyte death in patients with acute myocardial infarction. Sphingosine 1-phosphate (S1P) and transforming growth factor (TGF)-β are thought to be involved in the protection of cardiomyocyte and heart function following IR-induced injury. However, the possible association of S1P and S1P receptor 1 (S1PR1) with the TGF-β/Smad3 pathway as the potential protective mechanism has remained to be investigated. In the present study, an in vitro ischemia/reperfusion injury model was established and evaluated by analysis of apoptosis, lactate dehydrogenase (LDH) release and caspase3 activity. The mRNA and protein levels of S1PR1, TGF-β and Smad3 after treatment with 1 µM S1P alone or combined with 0.4 µM W146 (a specific S1PR1 antagonist) were assessed. The mRNA expression of five S1PRs (S1PR1-5) and the protein levels of S1PR1 were also assayed following treatment with 1 ng/ml TGF-β for 0, 4 or 24 h. The mRNA expression of S1PR1 and the levels of S1P were further assessed following exposure to 10 µM SB4 (TGFβR1 inhibitor) plus 1 ng/ml TGF-β and 2 µM SIS3 (Smad3 inhibitor) plus 1 ng/ml TGF-β. The results indicated that apoptosis, LDH release and caspase3 activity were all increased in the established IR model. Exogenous S1P increased the mRNA and protein levels of S1PR1, TGF-β and Smad3, which was abolished by addition of W146. Extraneous TGF-β resulted in the stimulation of several S1PRs, most prominently of S1PR1, while supplementation with SB4 and SIS3 offset the stimulation by TGF-β. These results suggested that the TGF-β/Smad3 pathway was closely associated with S1P/S1PR1 in the protection of myocardial cells from IR injury.

The TGFβ superfamily in cardiac dysfunction

TGFβ superfamily includes the transforming growth factor βs (TGFβs), bone morphogenetic proteins (BMPs), growth and differentiation factors (GDFs) and Activin/Inhibin families of ligands. Among the 33 members of TGFβ superfamily ligands, many act on multiple types of cells within the heart, including cardiomyocytes, cardiac fibroblasts/myofibroblasts, coronary endothelial cells, smooth muscle cells, and immune cells (e.g. monocytes/macrophages and neutrophils). In this review, we highlight recent discoveries on TGFβs, BMPs, and GDFs in different cardiac residential cellular components, in association with functional impacts in heart development, injury repair, and dysfunction. Specifically, we will review the roles of TGFβs, BMPs, and GDFs in cardiac hypertrophy, fibrosis, contractility, metabolism, angiogenesis, and regeneration.

Acute CD47 Blockade During Ischemic Myocardial Reperfusion Enhances Phagocytosis-Associated Cardiac Repair

Our data suggest that, after a myocardial infarction, integrin-associated protein CD47 on cardiac myocytes is elevated. In culture, increased CD47 on the surface of dying cardiomyocytes impairs phagocytic removal by immune cell macrophages. After myocardial ischemia and reperfusion, acute CD47 inhibition with blocking antibodies enhanced dead myocyte clearance by cardiac phagocytes and also improved the resolution of cardiac inflammation, reduced infarct size, and preserved cardiac contractile function. Early targeting of CD47 in the myocardium after reperfusion may be a new strategy to enhance wound repair in the ischemic heart.

The role of ZFP580, a novel zinc finger protein, in TGF-mediated cytoprotection against chemical hypoxia‑induced apoptosis in H9c2 cardiac myocytes

Zing finger protein 580 (ZFP580) is a novel Cys2-His2 zinc-finger transcription factor that has an anti-apoptotic role in myocardial cells. It is involved in the endothelial transforming growth factor-β1 (TGF-β1) signal transduction pathway as a mothers against decapentaplegic homolog (Smad)2 binding partner. The aim of the present study was to determine the involvement of ZFP580 in TGF-β1-mediated cytoprotection against chemical hypoxia-induced apoptosis, using H9c2 cardiac myocytes. Hypoxia was chemically induced in H9c2 myocardial cells by exposure to cobalt chloride (CoCl₂). In response to hypoxia, cell viability was decreased, whereas the expression levels of hypoxia inducible factor-1α and ZFP580 were increased. Pretreatment with TGF-β1 attenuated CoCl₂-induced cell apoptosis and upregulated ZFP580 protein expression; however, these effects could be suppressed by SB431542, an inhibitor of TGF-β type I receptor and Smad2/3 phosphorylation. Furthermore, suppression of ZFP580 expression by RNA interference reduced the anti-apoptotic effects of TGF-β1 and thus increased CoCl₂-induced apoptosis. B-cell lymphoma (Bcl)-2-associated X protein/Bcl-2 ratio, reactive oxygen species generation and caspase-3 activation were also increased following ZFP580 inactivation. In conclusion, these results indicate that ZFP580 is a component of the TGF-β1/Smad signaling pathway, and is involved in the protective effects of TGF-β1 against chemical hypoxia-induced cell apoptosis, through inhibition of the mitochondrial apoptotic pathway.

Notch3 Ameliorates Cardiac Fibrosis After Myocardial Infarction by Inhibiting the TGF-β1/Smad3 Pathway

Notch3 and TGF-β1 signaling play a key role in the pathogenesis and progression of chronic cardiovascular disease. However, whether Notch3 protects against myocardial infarction (MI) and the underlying mechanisms remains unknown. C57BL/6 mice were randomized to be treated with Notch3 siRNA (siNotch3) or lentivirus carrying Notch3 cDNA (Notch3) before coronary artery ligation. Four weeks after constructing MI model, cardiac function and fibrosis were compared between groups. The cardiac fibroblast cells (CFs) were isolated from newborn C57BL/6 mice (1-3 days old) and transfected with lentivirus carrying Notch3 cDNA. TGF-β1 (5 ng/ml), a well-known pro-fibrotic factor, was administered 72 h after Notch3 cDNA administration in CFs. The related proteins of fibrosis such as a-smooth muscle actin (a-SMA), Type I collagen, metalloprotease (MMP)-9 and the tissue inhibitor of metalloproteinases (TIMP)-2 were examined by western blot analysis. Notch3 cDNA treatment attenuated cardiac damage and inhibited fibrosis in mice with MI. Meanwhile, Notch3 siRNA administration aggravated cardiac function damage and markedly enhanced cardiac fibrosis in mice with MI. Overexpression of Notch3 inhibited TGF-β1-induced fibroblast-myofibroblast transition of mouse cardiac fibroblast cells, as evidenced by down-regulating a-SMA and Type I collagen expression. Notch3 cDNA treatment also increased MMP-9 expression and decreased TIMP-2 expression in the TGF-β1-stimulated cells. This study indicates that Notch3 is an important protective factor for cardiac fibrosis in a MI model, and the protective effect of Notch3 is attributable to its action on TGF-β1/Smad3 signaling.

Protective effects of intercalated disk protein afadin on chronic pressure overload-induced myocardial damage

Adhesive intercellular connections at cardiomyocyte intercalated disks (IDs) support contractile force and maintain structural integrity of the heart muscle. Disturbances of the proteins at IDs deteriorate cardiac function and morphology. An adaptor protein afadin, one of the components of adherens junctions, is expressed ubiquitously including IDs. At present, the precise role of afadin in cardiac physiology or disease is unknown. To explore this, we generated conditional knockout (cKO) mice with cardiomyocyte-targeted deletion of afadin. Afadin cKO mice were born according to the expected Mendelian ratio and have no detectable changes in cardiac phenotype. On the other hand, chronic pressure overload induced by transverse aortic constriction (TAC) caused systolic dysfunction, enhanced fibrogenesis and apoptosis in afadin cKO mice. Afadin deletion increased macrophage infiltration and monocyte chemoattractant protein-1 expression, and suppressed transforming growth factor (TGF) β receptor signaling early after TAC procedure. Afadin also associated with TGFβ receptor I at IDs. Pharmacological antagonist of TGFβ receptor I (SB431542) augmented mononuclear infiltration and fibrosis in the hearts of TAC-operated control mice. In conclusion, afadin is a critical molecule for cardiac protection against chronic pressure overload. The beneficial effects are likely to be a result from modulation of TGFβ receptor signaling pathways by afadin.

H2S improves renal fibrosis in STZ-induced diabetic rats by ameliorating TGF-β1 expression

Nephropathy develops in many patients with type 1 diabetes mellitus (T1DM). However, the specific mechanisms and therapies remain unclear. For this purpose we investigated the effects of hydrogen sulfide (H₂S) on renal fibrosis in streptozotocin (STZ) induced diabetic rats and its underlying mechanisms.

Experimental rats were randomly divided into four groups: Control group (normal rats), DM group (diabetes rats), DM + NaHS group [diabetes rats treated with sodium hydrosulfide (NaHS)], and NaHS group (normal rats treated with NaHS). The diabetic models were established by intraperitoneal injection of STZ. The NaHS-treated rats were injected with NaHS as an exogenous donor of H₂S. At the same time, control group and DM group were administrated with equal doses of normal saline (NS). After eight weeks, the rats’ urine samples were collected to measure the renal hydroxyproline content by basic hydrolysis method with a hydroxyproline detection kit. Collagen I and III content was detected by immunohistochemical method, and the pathology morphology of kidney was analyzed by Masson staining. Protein expressions of transforming growth factor beta 1 (TGF-β1), ERK1/2, TIMP1, TIMP2, MMP-2, MMP-7, MMP-8, MMP-11, and MMP-14 were assessed by western blotting. The results showed that significant fibrosis occurred in the kidney of diabetes rats. NaHS treatment downregulated TGF-β1, ERK1/2, TIMP1, TIMP2, MMP-2, MMP-7, MMP-8, MMP-11, and MMP-14 expressions in the kidney of these diabetes rats (p<.01). This result suggests that NaHS treatment could attenuate renal fibrosis by TGF-β1 signaling, and its mechanisms may be correlated with ERK1/2 expression and modulation of MMPs/TIMPs expression. Therefore, H₂S may provide a promising option for defensing against diabetic renal fibrosis through TGF-β1 signaling, equilibrating the balance between profibrotic and antifibrotic mediators.

Does growth differentiation factor 11 protect against myocardial ischaemia/reperfusion injury? A hypothesis

The pathogenesis of myocardial ischaemia/reperfusion injury is multifactorial. Understanding the mechanisms of myocardial ischaemia/reperfusion will benefit patients with ischaemic heart disease. Growth differentiation factor 11 (GDF11), a member of the secreted transforming growth factor-β superfamily, has been found to reverse age-related hypertrophy, revealing the important role of GDF11 in cardiovascular disease. However, the functions of GDF11 in myocardial ischaemia/reperfusion have not been elucidated yet. A number of signalling molecules are known to occur downstream of GDF11, including mothers against decapentaplegic homolog 3 (SMAD3) and forkhead box O3a (FOXO3a). A hypothesis is presented that GDF11 has protective effects in acute myocardial ischaemia/reperfusion injury through suppression of oxidative stress, prevention of calcium ion overload and promotion of the elimination of abnormal mitochondria via both canonical (SMAD3) and non-canonical (FOXO3a) pathways. Since circulating GDF11 may mainly derive from the spleen, the lack of a spleen may make the myocardium susceptible to damaging insults. Administration of GDF11 may be an efficacious therapy to protect against cardiovascular diseases in splenectomized patients.

Cardioprotective effect of notoginsenoside R1 in a rabbit lung remote ischemic postconditioning model via activation of the TGF-β1/TAK1 signaling pathway

Pharmacological postconditioning using cardioprotective agents is able to reduce myocardial infarct size. Notoginsenoside R1 (NG-R1), a phytoestrogen isolated from Panax notoginseng saponins (PNS), is considered to have anti-oxidative and anti-apoptotic properties. However, its cardioprotective properties and underlying mechanisms remain largely unknown. The aim of the present study was to determine the cardioprotective and anti-apoptotic effects of NG-R1 in an ischemia-reperfusion (IR)-induced myocardial injury rabbit model. A total of 45 Japanese big-ear rabbits were equally randomized to three groups: Control group, remote ischemic postconditioning (RIP) group and NG-R1 intervention group. At the endpoint of the experiment, the animals were sacrificed to remove myocardial tissues for the detection of transforming growth factor (TGF)-β1-TGF-β activated kinase 1 (TAK1) pathway-related proteins by immunohistochemistry and western blot analysis, the activities of caspase-3, -8 and -9 in myocardial cells by fluorometric assay, and the apoptosis of myocardial cells by terminal deoxynucleotidyl-transferase-mediated dUTP nick end labeling. Right and left lung tissues were stained with hematoxylin and eosin (H&E) to observe the severity of injury. NG-R1 treatment reduced the activity of superoxide dismutase, increased the content of malondialdehyde, reduced the activities of caspase-3, -8 and -9, and inhibited the apoptosis of myocardial cells in rabbits undergoing RIP. In addition, the expression of TGF-β1-TAK1 signaling pathway-related proteins was downregulated following NG-R1 intervention. H&E staining of bilateral lung tissues showed that cell morphology was generally intact without significant alveolar congestion, and there was no significant difference among the three groups. These results indicate that NG-R1 protects the heart against IR injury, possibly by inhibiting the activation of the TGF-β1-TAK1 signaling pathway and attenuating apoptotic stress in the myocardium.

Cardiac Fibrosis: The Fibroblast Awakens

Myocardial fibrosis is a significant global health problem associated with nearly all forms of heart disease. Cardiac fibroblasts comprise an essential cell type in the heart that is responsible for the homeostasis of the extracellular matrix; however, upon injury, these cells transform to a myofibroblast phenotype and contribute to cardiac fibrosis. This remodeling involves pathological changes that include chamber dilation, cardiomyocyte hypertrophy and apoptosis, and ultimately leads to the progression to heart failure. Despite the critical importance of fibrosis in cardiovascular disease, our limited understanding of the cardiac fibroblast impedes the development of potential therapies that effectively target this cell type and its pathological contribution to disease progression. This review summarizes current knowledge regarding the origins and roles of fibroblasts, mediators and signaling pathways known to influence fibroblast function after myocardial injury, as well as novel therapeutic strategies under investigation to attenuate cardiac fibrosis.

Transcriptional control of cardiac fibroblast plasticity

Cardiac fibroblasts help maintain the normal architecture of the healthy heart and are responsible for scar formation and the healing response to pathological insults. Various genetic, biomechanical, or humoral factors stimulate fibroblasts to become contractile smooth muscle-like cells called myofibroblasts that secrete large amounts of extracellular matrix. Unfortunately, unchecked myofibroblast activation in heart disease leads to pathological fibrosis, which is a major risk factor for the development of cardiac arrhythmias and heart failure. A better understanding of the molecular mechanisms that control fibroblast plasticity and myofibroblast activation is essential to develop novel strategies to specifically target pathological cardiac fibrosis without disrupting the adaptive healing response. This review highlights the major transcriptional mediators of fibroblast origin and function in development and disease. The contribution of the fetal epicardial gene program will be discussed in the context of fibroblast origin in development and following injury, primarily focusing on Tcf21 and C/EBP. We will also highlight the major transcriptional regulatory axes that control fibroblast plasticity in the adult heart, including transforming growth factor β (TGFβ)/Smad signaling, the Rho/myocardin-related transcription factor (MRTF)/serum response factor (SRF) axis, and Calcineurin/transient receptor potential channel (TRP)/nuclear factor of activated T-Cell (NFAT) signaling. Finally, we will discuss recent strategies to divert the fibroblast transcriptional program in an effort to promote cardiomyocyte regeneration. This article is a part of a Special Issue entitled "Fibrosis and Myocardial Remodeling".

Cardiac stem cells transplantation enhances the expression of connexin 43 via the ANG II/AT1R/TGF-beta1 signaling pathway in a rat model of myocardial infarction

BACKGROUND

In this study, we hypothesized that CSCs mediated the expression of Cx43 after transplantation post MI via the ANG II/AT1R/TGF-beta1 signaling pathway.

METHODS

Myocardial infarction (MI) was induced in twenty male Sprague-Dawley rats. The rats were randomized into two groups and were then received the injection of 5 × 10(6) CSCs labeled with PKH26 in phosphate buffer solution (PBS) or equal PBS alone into the infarct anterior ventricular free wall two weeks after MI. Six weeks later, relevant signaling molecules involved were all examined.

RESULTS

In the CSCs group, an increased expression of Cx43 could be observed in different zones of the left ventricle (P<0.01). There was a significant reduction of the angiotensin II (ANG II) level in plasma and different regions of the left ventricular cardiac tissues (P<0.05; P<0.01). The angiotensin II type I receptor (AT1R) was decreased accompanied with an enhanced expression of angiotensin II type II receptor (AT2R) (P<0.01). Transforming growth factor beta-1(TGF-beta1) was downregulated (P<0.01). The expression of mothers against decapentaplegic homolog (SMAD) proteins including SMAD2 and SMAD3 was attenuated whereas SMAD7 was elevated (P<0.01, P<0.01, P<0.05). In addition, the expression of mitogen-activated protein kinases (MAPKs) including extracellular kinases 1/2 (ERK1/2) and p38 was also found to be reduced (P<0.01).

CONCLUSION

CSCs transplantation could enhance the level of Cx43 after MI. They might function through intervening the ANGII/AT1R/TGF-beta1 signaling pathway to regulate the expression of Cx43.

Getting to the heart of the matter: new insights into cardiac fibrosis

Fibrotic diseases are a significant global burden for which there are limited treatment options. The effector cells of fibrosis are activated fibroblasts called myofibroblasts, a highly contractile cell type characterized by the appearance of α-smooth muscle actin stress fibers. The underlying mechanism behind myofibroblast differentiation and persistence has been under much investigation and is known to involve a complex signaling network involving transforming growth factor-β, endothelin-1, angiotensin II, CCN2 (connective tissue growth factor), and platelet-derived growth factor. This review addresses the contribution of these signaling molecules to cardiac fibrosis.

Beneficial effects of muscone on cardiac remodeling in a mouse model of myocardial infarction

Musk has been traditionally used in East Asia to alleviate the symptoms of angina pectoris. However, it remains unclear as to whether muscone, the main active ingredient of musk, has any beneficial effects on persistent myocardial ischemia in vivo. The aim of the present study was to investigate whether muscone can improve cardiac function and attenuate myocardial remodeling following myocardial infarction (MI) in mice. Mice were subjected to permanent ligation of the left anterior descending coronary artery to induce MI, and then randomly treated with muscone (2 mg/kg/day) or the vehicle (normal saline) for 3 weeks. Sham-operated mice were used as controls and were also administered the vehicle (normal saline). Treatment with muscone significantly improved cardiac function and exercise tolerance, as evidenced by the decrease in the left ventricular end-systolic diameter, left ventricular end-diastolic diameter, as well as an increase in the left ventricular ejection fraction, left ventricular fractional shortening and time to exhaustion during swimming. Pathological and morphological assessments indicated that treatment with muscone alleviated myocardial fibrosis, collagen deposition and improved the heart weight/body weight ratio. Muscone inhibited the inflammatory response by reducing the expression of transforming growth factor (TGF)‑β1, tumor necrosis factor (TNF)-α, interleukin (IL)-1β and nuclear factor (NF)-κB. Treatment with muscone also reduced myocardial apoptosis by enhancing Bcl-2 and suppressing Bax expression. Muscone also induced the phosphorylation of protein kinase B (Akt) and endothelial nitric oxide synthase (eNOS). Our results demonstrate that muscone ameliorates cardiac remodeling and dysfunction induced by MI by exerting anti-fibrotic, anti-inflammatory and anti-apoptotic effects in the ischemic myocardium.

Expression and mechanism of BRP-39 in bleomycin-induced pulmonary fibrosis in rat

The purpose of the study was to explore the effects of breast regression protein 39 (BRP-39) in bleomycin-induced pulmonary fibrosis and its mechanism in pulmonary fibrosis by studying change in BRP-39 to provide a novel direction for the treatment of idiopathic pulmonary fibrosis. SPF grade male C57BL/6 rats were randomly divided into three groups, including bleomycin group, bleomycin+ BRP-39 recombinant protein group and control group. HE and Masson staining were applied to test the change in lung tissue after being treated by BRP-39, ELISA was applied to test the expression of TGF-β1 in different groups, and Western blot was used to test the expression of BRP-39 in rat lung tissue. Expression of BRP-39 increased, the fibrosis was obvious, and lung tissue collagen increased in bleomycin-induced pulmonary fibrosis in rat lung tissue. Increasing BRP-39 protein level and intratracheal bleomycin medication to establish pulmonary fibrosis model can aggravate pulmonary fibrosis. Along with the increase in BRP-39 protein level, TGF-β1 expression level also increased in lung tissue. Western blot results showed the expression of BRP-39, and TGF-β1 had the same trend in different groups. BRP-39 has effects in bleomycin-induced rat pulmonary fibrosis. Change in BRP-39 can affect the process of bleomycin-induced pulmonary fibrosis. The mechanism of BRP-3 in pulmonary fibrosis may work by regulating TGF-β1.