Cultures Of Cardiac Fibroblasts Research Articles

Abstract Or114: Inhibiting IL-1 Signaling to Cardiac Fibroblasts Protects Against Acute Viral Myocarditis

Background: Understanding what factors perpetuate cardiac inflammation in patients with unremitting inflammatory dilated cardiomyopathy (iDCM) is critical for developing curative therapies. We have previously demonstrated that inflammatory fibroblasts (IFs), a subset of cardiac fibroblasts (CFs) that promote inflammation, depend on IL-17A signaling to drive iDCM progression in experimental autoimmune myocarditis. Here, we demonstrate that IL-1 signaling more potently activates IFs than IL-17A. IL-1 signaling has been implicated in the pathogenesis of viral myocarditis, the most common etiology of myocarditis, though the mechanism is unclear. Hypothesis: We hypothesize that IL-1 signaling to CFs induces their differentiation into IFs, which drive pathogenic inflammation during viral myocarditis. Methods: Primary murine CF cultures were used to characterize IF activation by various cytokines. Next, we both performed qPCR on sorted CFs and used a CCL2-mCherry reporter mouse line to phenotype IF activation during Coxsackievirus B3 (CVB3) myocarditis. Finally, in-vivo fibroblast-specific IL-1 signaling was genetically ablated using PDGFRα cre IL1r1 fl/fl mice. We infected PDGFRα cre and PDGFRα cre IL1r1 fl/fl mice with CVB3 and assessed myocarditis severity during the peak of inflammation using histological scoring and flow cytometry. Results: Innate, Th1, Th2, and Th17 related cytokines such as IL-1β, IFNγ, IL-13, and IL-17A induced unique IF gene expression signatures. IL-1β most potently activated IFs with a pro-myeloid cytokine inflammatory profile. During CVB3 myocarditis, IF activation peaked on day 3 post infection and was sustained until day 10. Ablating IL-1 signaling to CFs reduced the magnitude of cardiac inflammation by 45% ± 14% (p=0.002) during the peak of CVB3 myocarditis with a reduction in monocyte, CD4+ T cells, CD8+ T cells, and NK cell recruitment. Gene expression analysis of sorted CFs from mutant and control mice revealed reduced expression of pro-myeloid chemokines such as CXCL1 and CCL2 on day 3 of CVB3 myocarditis. Conclusions: Cardiac fibroblasts exhibit remarkable plasticity allowing them to respond to a changing micro-environment. Blocking IL-1 signaling to IFs during CVB3 myocarditis inhibited production of pro-inflammatory chemokines resulting in attenuation of myocardial inflammation. Therefore, early IF activity acts as a rheostat to modulate the magnitude of cardiac inflammation during myocarditis.

Glycopolymer Inhibitors of Galectin-3 Suppress the Markers of Tissue Remodeling in Pulmonary Hypertension.

Pulmonary hypertension is a cardiovascular disease with a low survival rate. The protein galectin-3 (Gal-3) binding β-galactosides of cellular glycoproteins plays an important role in the onset and development of this disease. Carbohydrate-based drugs that target Gal-3 represent a new therapeutic strategy in the treatment of pulmonary hypertension. Here, we present the synthesis of novel hydrophilic glycopolymer inhibitors of Gal-3 based on a polyoxazoline chain decorated with carbohydrate ligands. Biolayer interferometry revealed a high binding affinity of these glycopolymers to Gal-3 in the subnanomolar range. In the cell cultures of cardiac fibroblasts and pulmonary artery smooth muscle cells, the most potent glycopolymer 18 (Lac-high) caused a decrease in the expression of markers of tissue remodeling in pulmonary hypertension. The glycopolymers were shown to penetrate into the cells. In a biodistribution and pharmacokinetics study in rats, the glycopolymers accumulated in heart and lung tissues, which are most affected by pulmonary hypertension.

A transcriptomic analysis of correlation between mitochondrial function and energy metabolism remodeling in mice with myocardial fibrosis following myocardial infarction

To investigate the changes of mitochondrial respiratory function during myocardial fibrosis in mice with myocardial infarction (MI) and its correlation with the increase of glycolytic flux. Forty C57BL/6N mice were randomized into two equal groups to receive sham operation or ligation of the left anterior descending coronary artery to induce acute MI. At 28 days after the operation, 5 mice from each group were euthanized and left ventricular tissue samples were collected for transcriptomic sequencing. FPKM method was used to calculate gene expression levels to identify the differentially expressed genes (DEGs) in MI mice, which were analyzed using GO and KEGG databases to determine the pathways affecting the disease process. Heat maps were drawn to show the differential expressions of the pathways and the related genes in the enrichment analysis. In primary cultures of neonatal mouse cardiac fibroblasts (CFs), the changes in mitochondrial respiration and glycolysis levels in response to treatment with the pro-fibrotic agonist TGF-β1 were analyzed using Seahorse experiment. The mouse models of MI showed significantly increased diastolic and systolic left ventricular diameter (P < 0.05) and decreased left ventricular ejection fraction (P < 0.0001). A total of 124 up-regulated and 106 down-regulated DEGs were identified in the myocardial tissues of MI mice, and GO and KEGG enrichment analysis showed that these DEGs were significantly enriched in fatty acid metabolism, organelles and other metabolic pathways and in the mitochondria. Heat maps revealed fatty acid beta oxidation, mitochondrial dysfunction and increased glycolysis levels in MI mice. In the primary culture of CFs, treatment with TGF-β1 significantly reduced the basal and maximum respiratory levels and increased the basal and maximum glycolysis levels (P < 0.0001). During myocardial fibrosis, energy metabolism remodeling occurs in the CFs, manifested by lowered mitochondrial function and increased energy generation through glycolysis.

Bioresorbable molybdenum temporary epicardial pacing wires

Cardiac pacing with temporary epicardial pacing wires (TEPW) is used to treat rhythm disturbances after cardiac surgery. Occasionally, TEPW cannot be mechanically extracted and remain in the thorax, where they may rarely cause serious complications like migration and infection. We aim to develop bioresorbable TEPW that will dissolve over time even if postoperative removal is unsuccessful. In the present study, we demonstrate a completely bioresorbable design using molybdenum (Mo) as electric conductor and the resorbable polymers poly(D, L-lactic-co-glycolic acid) (PLGA) and polycaprolactone (PCL) for electrically insulating double-coating. We compared the pacing properties of these Mo TEPW demonstrators to conventional steel TEPW in Langendorff-perfused rat hearts and observed similar functionality. In vitro, static immersion tests in simulated body fluid for up to 28 days elucidated the degradation behaviour of uncoated Mo strands and the influence of polymer coating thereon. Degradation was considerably reduced in double-coated Mo TEPW compared to the uncoated and the PLGA-coated condition. Furthermore, we confirmed good biocompatibility of Mo degradation products in the form of low cytotoxicity in cell cultures of human cardiomyocytes and cardiac fibroblasts. Statement of significanceTemporary pacing wires are routinely implanted on the heart surface to treat rhythm disturbances in the days following cardiac surgery. Subsequently, these wires are to be removed. When removal attempts are unsuccessful, wires are cut at skin level and the remainders are left inside the chest. Retained fragments may migrate within the body or become a centre of infection. These complications may be prevented using resorbable pacing wires. We manufactured completely resorbable temporary pacing wires using molybdenum as electrical conductor and assessed their function, degradation and biological compatibility. Our study represents an important step in the development of a safer approach to the treatment of rhythm disturbances after cardiac surgery.

Three-dimensional co-culturing of stem cell-derived cardiomyocytes and cardiac fibroblasts reveals a role for both cell types in Marfan-related cardiomyopathy

Pathogenic variants in the FBN1 gene, which encodes the extracellular matrix protein fibrillin-1, cause Marfan syndrome (MFS), which affects multiple organ systems, including the cardiovascular system. Myocardial dysfunction has been observed in a subset of patients with MFS and in several MFS mouse models. However, there is limited understanding of the intrinsic consequences of FBN1 variants on cardiomyocytes (CMs). To elucidate the CM-specific contribution in Marfan's cardiomyopathy, cardiosphere cultures of CMs and cardiac fibroblasts (CFs) are used. CMs and CFs were derived by human induced pluripotent stem cell (iPSC) differentiation from MFS iPSCs with a pathogenic variant in FBN1 (c.3725G>A; p.Cys1242Tyr) and the corresponding CRISPR-corrected iPSC line (Cor).Cardiospheres containing MFS CMs show decreased FBN1, COL1A2 and GJA1 expression. MFS CMs cultured in cardiospheres have fewer binucleated CMs in comparison with Cor CMs. 13% of MFS CMs in cardiospheres are binucleated and 15% and 16% in cardiospheres that contain co-cultures with respectively MFS CFs and Cor CFs, compared to Cor CMs, that revealed up to 23% binucleation when co-cultured with CFs. The sarcomere length of CMs, as a marker of development, is significantly increased in MFS CMs interacting with Cor CF or MFS CF, as compared to monocultured MFS CMs. Nuclear blebbing was significantly more frequent in MFS CFs, which correlated with increased stiffness of the nuclear area compared to Cor CFs.Our cardiosphere model for Marfan-related cardiomyopathy identified a contribution of CFs in Marfan-related cardiomyopathy and suggests that abnormal early development of CMs may play a role in the disease mechanism.

Substrate stiffness modulates cardiac fibroblast activation, senescence, and proinflammatory secretory phenotype.

In vitro cultures of primary cardiac fibroblasts (CFs), the major extracellular matrix (ECM)-producing cells of the heart, are used to determine molecular mechanisms of cardiac fibrosis. However, the supraphysiologic stiffness of tissue culture polystyrene (TCPS) triggers the conversion of CFs into an activated myofibroblast-like state, and serial passage of the cells results in the induction of replicative senescence. These phenotypic switches confound the interpretation of experimental data obtained with cultured CFs. In an attempt to circumvent TCPS-induced activation and senescence of CFs, we used poly(ethylene glycol) (PEG) hydrogels as cell culture platforms with low and high stiffness formulations to mimic healthy and fibrotic hearts, respectively. Low hydrogel stiffness converted activated CFs into a quiescent state with a reduced abundance of α-smooth muscle actin (α-SMA)-containing stress fibers. Unexpectedly, lower substrate stiffness concomitantly augmented CF senescence, marked by elevated senescence-associated β-galactosidase (SA-β-Gal) activity and increased expression of p16 and p21, which are antiproliferative markers of senescence. Using dynamically stiffening hydrogels with phototunable cross-linking capabilities, we demonstrate that premature, substrate-induced CF senescence is partially reversible. RNA-sequencing analysis revealed widespread transcriptional reprogramming of CFs cultured on low-stiffness hydrogels, with a reduction in the expression of profibrotic genes encoding ECM proteins, and an attendant increase in expression of NF-κB-responsive inflammatory genes that typify the senescence-associated secretory phenotype (SASP). Our findings demonstrate that alterations in matrix stiffness profoundly impact CF cell state transitions, and suggest mechanisms by which CFs change phenotype in vivo depending on the stiffness of the myocardial microenvironment in which they reside.NEW & NOTEWORTHY Our findings highlight the advantages and pitfalls associated with culturing cardiac fibroblasts on hydrogels of varying stiffness. The findings also define stiffness-dependent signaling and transcriptional networks in cardiac fibroblasts.

MiR-214 could promote myocardial fibrosis and cardiac mesenchymal transition in VMC mice through regulation of the p53 or PTEN-PI3K-Akt signali pathway, promoting CF proliferation and inhibiting its ng pathway

IntroductionThis study aimed to investigate the role of miR-214 in the bidirectional regulation of p53 and PTEN and its influence on myocardial fibrosis and cardiac mesenchymal transformation in mice with viral myocarditis (VMC). MethodsThe study established a VMC model in BALB/c mice by injecting them with the CVB3 virus intraperitoneally. Techniques such as ELISA, H&E staining, Masson staining, immunohistochemical staining, RT-qPCR, western blot, and dual-luciferase reporter gene assay were used to detect the expression levels of relevant factors in tissues and cells. Isolation and culture of cardiac fibroblasts (CFs) were also conducted. ResultsThe study found that miR-214 bidirectional regulation of p53 and PTEN promotes myocardial fibrosis and cardiac mesenchymal transformation in mice with VMC. The expression levels of collagen-related peptides, inflammatory-related factors, miR-214, mesenchymal transformation-related factors, and fibrosis-related factors were significantly increased, while the expression levels of p53, PTEN, and epithelial/endothelial cell phenotype marker factors were significantly decreased. Downregulation of miR-214 or upregulation of p53 and PTEN expression inhibited inflammatory cell and fibroblast infiltration in VMC mouse myocardial tissue. It reduced the proliferation ability while increasing the apoptosis of cardiac fibroblasts. ConclusionmiR-214 plays a significant role in the bidirectional inhibition of p53 and PTEN, which leads to myocardial fibrosis and cardiac mesenchymal transformation in mice with VMC. Downregulation of miR-214 or upregulation of p53 and PTEN expression may provide potential therapeutic targets for treating VMC-induced cardiac fibrosis and mesenchymal transformation.

Abstract P2104: Branched-chain Amino Acids Are Required For Acquisition Of The Cardiac Myofibroblast Phenotype

Introduction: Branched-chain amino acids (BCAAs) are critical mediators of anabolic signaling and are essential for cell growth. Findings in both animals and humans indicate that intra-cardiac BCAA levels are markedly elevated in the myocardium after infarction. Nevertheless, it remains unclear how BCAAs contribute to processes involved in post-infarction cardiac remodeling, such as fibrosis. The goals of these studies were to evaluate whether BCAAs can regulate collagen production and facilitate myofibroblast transdifferentiation. Methods and Results: To determine how profibrogenic stimuli influence genes critical for BCAA uptake and catabolism, we performed bulk RNA sequencing on fibroblasts isolated from sham and post-infarcted hearts as well as from naïve fibroblasts treated with TGFβ. Compared with fibroblasts from sham hearts, fibroblasts from post-infarcted hearts had higher expression of BCAA transporters ( Slc7a8 , Slc3a2 , Slc38a1 , Slc1a5 ), lower levels of the inhibitory kinase Bckdk , and higher levels of Bckdh complex constituents ( Dbt, Dld ; n=3–6/group;,q&lt;0.05). Similarly, TGFβ elevated Slc3a and Slc38a1 as well as the BCAA catabolic gene, Bcat1 (n=3/group; q&lt;0.05). Culture of cardiac fibroblasts in BCAA-free medium completely prevented TGFβ-induced Col1a1 and periostin upregulation and markedly diminished α-smooth muscle actin abundance (n=3/group; p&lt;0.05). Conclusion: In cardiac fibroblasts, profibrogenic stimuli increase the expression of genes involved in BCAA uptake and catabolism. BCAA availability significantly impacts fibroblast activation by regulating collagen synthesis and myofibroblast transdifferentiation. Ongoing studies will elucidate whether BCAA catabolism contributes to myofibroblast activation and whether lower dietary BCAA levels influence cardiac remodeling after myocardial infarction.

Melatonin increases collagen content accumulation and Fibroblast Growth Factor-2 secretion in cultured human cardiac fibroblasts

BackgroundThe extracellular matrix serves as a scaffold for cardiomyocytes, allowing them to work in accord. In rats, collagen metabolism within a myocardial infarction scar is regulated by melatonin. The present study determines whether melatonin influences matrix metabolism within human cardiac fibroblast cultures and examines the underlying mechanism.MethodsThe experiments were performed on cultures of cardiac fibroblasts. The Woessner method, 1,9-dimethylmethylene blue assay, enzyme-linked immunosorbent assay and quantitative PCR were used in the study.ResultsMelatonin treatment lowered the total cell count within the culture, elevated necrotic and apoptotic cell count as well as augmented cardiac fibroblast proliferation, and increased total, intracellular, and extracellular collagen within the fibroblast culture; it also elevated type III procollagen α1 chain expression, without increasing procollagen type I mRNA production. The pineal hormone did not influence matrix metalloproteinase-2 (MMP-2) release or glycosaminoglycan accumulation by cardiac fibroblasts. Melatonin increased the release of Fibroblast Growth Factor-2 (FGF-2) by human cardiac fibroblasts, but cardiotrophin release was not influenced.ConclusionWithin human cardiac fibroblast culture, collagen metabolism is regulated by melatonin. The profibrotic effect of melatonin depends on the elevation of procollagen type III gene expression, and this could be modified by FGF-2. Two parallel processes, viz., cell elimination and proliferation, induced by melatonin, lead to excessive replacement of cardiac fibroblasts.

Isolation and Culture of Primary Fibroblasts from Neonatal Murine Hearts to Study Cardiac Fibrosis.

Cardiac fibroblasts are one of the major constituents of a healthy heart. Cultured cardiac fibroblasts are a crucial resource for conducting studies on cardiac fibrosis. The existing methods for culturing cardiac fibroblasts involve complicated steps and require special reagents and instruments. The major problems faced with primary cardiac fibroblast culture are the low yield and viability of the cultured cells and contamination with other heart cell types, including cardiomyocytes, endothelial cells, and immune cells. Numerous parameters, including the quality of the reagents used for the culture, conditions maintained during digestion of the cardiac tissue, composition of the digestion mixture used, and age of the pups used for culture determine the yield and purity of the cultured cardiac fibroblasts. The present study describes a detailed and simplified protocol to isolate and culture primary cardiac fibroblasts from neonatal murine pups. We demonstrate the transdifferentiation of fibroblasts into myofibroblasts through transforming growth factor (TGF)-β1 treatment, representing the changes in fibroblasts during cardiac fibrosis. These cells can be used to study the various aspects of cardiac fibrosis, inflammation, fibroblast proliferation, and growth.

Biomimetic design of bioartificial scaffolds for the in vitro modelling of human cardiac fibrosis.

In vitro models of pathological cardiac tissue have attracted interest as predictive platforms for preclinical validation of therapies. However, models reproducing specific pathological features, such as cardiac fibrosis size (i.e., thickness and width) and stage of development are missing. This research was aimed at engineering 2D and 3D models of early-stage post-infarct fibrotic tissue (i.e., characterized by non-aligned tissue organization) on bioartificial scaffolds with biomimetic composition, design, and surface stiffness. 2D scaffolds with random nanofibrous structure and 3D scaffolds with 150µm square-meshed architecture were fabricated from polycaprolactone, surface-grafted with gelatin by mussel-inspired approach and coated with cardiac extracellular matrix (ECM) by 3weeks culture of human cardiac fibroblasts. Scaffold physicochemical properties were thoroughly investigated. AFM analysis of scaffolds in wet state, before cell culture, confirmed their close surface stiffness to human cardiac fibrotic tissue. Following 3weeks culture, biomimetic biophysical and biochemical scaffold properties triggered the activation of myofibroblast phenotype. Upon decellularization, immunostaining, SEM and two-photon excitation fluorescence microscopy showed homogeneous decoration of both 2D and 3D scaffolds with cardiac ECM. The versatility of the approach was demonstrated by culturing ventricular or atrial cardiac fibroblasts on scaffolds, thus suggesting the possibility to use the same scaffold platforms to model both ventricular and atrial cardiac fibrosis. In the future, herein developed in vitro models of cardiac fibrotic tissue, reproducing specific pathological features, will be exploited for a fine preclinical tuning of therapies.

Formation of human cardiomyocytes is impaired by fibroblastic paracrine signalling: breaking down the mechanisms involved in rebuilding the heart

Abstract To date (pre-)clinical effects of inducing cardiac regeneration by cardiac cell therapy have been disappointing. This lack of success may result from the fact that it remains largely unclear how the receiving pathological microenvironment affects this process of cardiac differentiation of implanted cells, and thereby may (negatively) influence the therapeutic outcome. We have recently generated lines of conditionally immortalized human CMCs (ciCMCs) through doxycycline-dependent expression of SV40 large T antigen. In these cells, proliferation and differentiation can be tightly controlled. The aim of this study is to improve our understanding of cardiac differentiation of transplanted cells in the context of the receiving microenvironment from a paracrine perspective. To investigate the role of fibroblastic paracrine signalling on cardiomyogenic differentiation, transwell experiments were conducted. Cardiac differentiation was induced in human ciCMCs while cardiac fibroblasts were cultured in the top inserts in different ratios (human ciCMCs:cardiac fibroblasts 1:1, 2:1 and 3:1). Cardiomyogenic differentiation was determined by immunostaining for cardiac specific markers, quantitative RT-PCR, and electrophysiological analysis. After 12 days of differentiation, under the influence of the fibroblastic paracrine signaling, the amount of ciCMCs that expressed the sarcomeric protein α-actinin and myosin light chain 2a was significantly and increasingly reduced (P&amp;lt;0.01) in the groups cultured under the influence of the cardiac fibroblasts (4.8±0.6, 8.1±1.9, 22.4±4.2 for 1:1, 2:1 and 3:1 human ciCMCs:cardiac fibrolasts respectively [%, mean±SD]) while in absence of the cardiac fibroblasts (control group) 41% (±9.8) human ciCMCs were formed. In corroboration with these results, quantitative RT-PCR showed significant reduction (P&amp;lt;0.05) of all cardiac specific markers on a mRNA level in 1:1 human ciCMC: cardiac fibroblasts cultures compared to the control group. Electrophysiological analysis showed a significantly reduced (P&amp;lt;0.01) conduction velocity in the group cultured under the influence of the highest amount of cardiac fibroblasts compared to the control group (13.1±1.0 vs 10.6±0.9 control group vs 1:1 human ciCMCs:cardiac fibroblasts [cm/s, mean±SD]). Additionally, action potential duration was significantly prolonged (P&amp;lt;0.05) in the 1:1 human ciCMC:cardiac fibroblast cultures compared to the control group (93.6±4.8 vs 129.9±3.5 control group vs 1:1 human ciCMCs:cardiac fibroblasts [ms, mean±SD]). In conclusion, fibroblastic paracrine signalling has a negative effect on the structural and electrical differentiation of human cardiomyocytes. This not only emphasizes the need to consider the interaction between the transplanted cells and the receiving microenvironment in cardiac regenerative medicine, but also offers new leads to increase the therapeutic potential of this strategy. Funding Acknowledgement Type of funding sources: Foundation. Main funding source(s): Leiden University Fund

Sirt6 activation blocks LPS induced expression of inflammatory cytokines in cardiac cells

Sepsis induced myocardial dysfunction is a common complication that has been linked to an increased mortality. The activation of NFkB pathway and excessive production of pro‐inflammatory cytokines is considered to be one of the most important signaling pathway involved in the pathogenesis of sepsis. Earlier studies have shown that Sirt6, a member of class III of histone deacetylases, attenuates hyper‐activation of NFkB signaling that contributes to inflammation and the aging process. In the present study we tested the hypothesis whether pharmacological activation of Sirt6 can prevent LPS induced myocardial inflammation. Primary cultures of adult rat cardiac fibroblasts were treated with UBCS039, an allosteric activator of Sirt6, for 48 hours. The results showed a dose‐dependent increase in steady‐state levels of Sirt6 as well as deacetylation of its target H3K9 by Western analysis. A similar effect of UBCS039 treatment was observed in H9C2 cardiac myocytes. We also tested effects of UBCS039 on LPS induced NFkB activation and cytokine production in these cells. Our data showed that pretreatment of cardiac fibroblasts with UBCS039 for 48 hrs significantly reduced LPS (100ng/ml)‐induced phosphorylated levels of NFkB (pNFkB). By real‐time PCR analysis we found that LPS led to increased expression (4‐9 fold) of mRNA of IL‐6, IL‐1b, TLR4 and CD‐38 in cardiac fibroblasts within 6h of treatment. This effect of LPS in cardiac fibroblasts was completely blocked when cells were pretreated with UBCS039. These data thus indicated that pharmacological activation of Sirt6 is capable of blocking LPS induced inflammatory response in cardiac cells, and has the potential to alleviate sepsis induced myocardial dysfunction and related health consequences.

Insulin Therapy is Associated With Increased Myocardial Interstitial Fibrosis and Cardiomyocyte Apoptosis in a Rodent Model of Experimental Diabetes.

The incidence of diabetes mellitus (DM) is rising. DM is a risk factor for developing left ventricular (LV) dysfunction and adverse cardiovascular outcomes. Insulin, commonly used to treat DM, is associated with further worsening of such outcomes. Yet, the pathophysiology of the adverse properties of insulin on the heart remains poorly defined. Therefore, the objective of this study was to determine the biological effects of insulin on the heart in DM, which we tested in vivo in a diabetic rat model and in vitro on human cardiomyocytes and fibroblasts. Male Wistar rats were divided into 3 groups: controls (n = 17), untreated diabetics (UDM, n = 15), and insulin-treated diabetics (IDM, n = 9). Diabetes was induced with Streptozotocin. Insulin pumps in IDM and saline pumps in UDM and controls were implanted for 4 weeks before tissue collection. Separately, cultures of human cardiomyocytes (AC16) and human cardiac fibroblasts (HCF) were treated with insulin to assess apoptosis and fibrosis, respectively. In rats, insulin partially rescued the DM-associated weight loss while fully restoring euglycemia. However, IDM had 2 × the rate of LV fibrosis (p < 0.0001) compared to UDM, and triple the rate of cardiomyocyte apoptosis compared to controls (p < 0.05). Similarly, in vitro, insulin triggered apoptosis in a dose-dependent fashion in AC16 cells, and it increased fibrosis and upregulated SMAD2 in HCF to levels comparable to Transforming Growth Factor Beta 1. Therefore, we conclude that insulin therapy is associated with increased cardiomyocyte apoptosis and myocardial interstitial fibrosis. Longer studies are needed to explore the long-term effects of insulin on cardiac structure and function.

Isolation methods of large and small extracellular vesicles derived from cardiovascular progenitors: A comparative study

Since the discovery of the beneficial therapeutical effects of extracellular vesicles (EVs), these agents have been attracting great interest as next-generation therapies. EVs are nanosized membrane bodies secreted by all types of cells that mediate cell–cell communication. Although the classification of different subpopulations of EVs can be complex, they are broadly divided into microvesicles and exosomes based on their biogenesis and in large and small EVs based on their size. As this is an emerging field, current investigations are focused on basic aspects such as the more convenient method for EV isolation. In the present paper, we used cardiac progenitor cells (CPCs) to study and compare different cell culture conditions for EV isolation as well as two of the most commonly employed purification methods: ultracentrifugation (UC) and size-exclusion chromatography (SEC). Large and small EVs were separately analysed. We found that serum starvation of cells during the EV collecting period led to a dramatic decrease in EV secretion and major cell death. Regarding the isolation method, our findings suggest that UC and SEC gave similar EV recovery rates. Separation of large and small EV-enriched subpopulations was efficiently achieved with both purification protocols although certain difference in sample heterogeneity was observed. Noteworthy, while calnexin was abundant in large EVs, ALIX and CD63 were mainly found in small EVs. Finally, when the functionality of EVs was assessed on primary culture of adult murine cardiac fibroblasts, we found that EVs were taken up by these cells, which resulted in a pronounced reduction in the proliferative and migratory capacity of the cells. Specifically, a tendency towards a larger effect of SEC-related EVs was observed. No differences could be found between large and small EVs. Altogether, these results contribute to establish the basis for the use of EVs as therapeutic platforms, in particular in regenerative fields.

Abstract MP258: The Cell Surface Receptors Ror1/2 Control Cardiac Myofibroblast Differentiation

Background: A hallmark of heart failure is cardiac fibrosis, which results from the injury-induced differentiation response of resident fibroblasts to myofibroblasts that deposit extracellular matrix. During myofibroblast differentiation, fibroblasts progress through polarization stages of early pro-inflammation, intermediate proliferation, and late maturation, but the regulators of this progression are poorly understood. Planar cell polarity receptors, receptor tyrosine kinase like orphan receptor 1 and 2 (Ror1/2), can function to promote cell differentiation and transformation. In this study, we investigated the role of the Ror1/2 in a model of heart failure with emphasis on myofibroblast differentiation. Methods and Results: The role of Ror1/2 during cardiac myofibroblast differentiation was studied in cell culture models of primary murine cardiac fibroblast activation and in knockout mouse models that underwent transverse aortic constriction (TAC) surgery to induce cardiac injury by pressure overload. Expression of Ror1 and Ror2 were robustly and exclusively induced in fibroblasts in hearts after TAC surgery, and both were rapidly upregulated after early activation of primary murine cardiac fibroblasts in culture. Cultured fibroblasts isolated from Ror1/2-KO mice displayed a pro-inflammatory phenotype indicative of impaired myofibroblast differentiation. Although the combined ablation of Ror1/2 in mice did not result in a detectable baseline phenotype, TAC surgery led to the death of all mice by day 6 that was associated with myocardial hyper-inflammation and vascular leakage. Conclusions: Together, these results show that Ror1/2 are essential for the progression of myofibroblast differentiation and for the adaptive remodeling of the heart in response to pressure overload.

The Cell Surface Receptors Ror1/2 Control Cardiac Myofibroblast Differentiation.

BackgroundA hallmark of heart failure is cardiac fibrosis, which results from the injury‐induced differentiation response of resident fibroblasts to myofibroblasts that deposit extracellular matrix. During myofibroblast differentiation, fibroblasts progress through polarization stages of early proinflammation, intermediate proliferation, and late maturation, but the regulators of this progression are poorly understood. Planar cell polarity receptors, receptor tyrosine kinase–like orphan receptor 1 and 2 (Ror1/2), can function to promote cell differentiation and transformation. In this study, we investigated the role of the Ror1/2 in a model of heart failure with emphasis on myofibroblast differentiation.Methods and ResultsThe role of Ror1/2 during cardiac myofibroblast differentiation was studied in cell culture models of primary murine cardiac fibroblast activation and in knockout mouse models that underwent transverse aortic constriction surgery to induce cardiac injury by pressure overload. Expression of Ror1 and Ror2 were robustly and exclusively induced in fibroblasts in hearts after transverse aortic constriction surgery, and both were rapidly upregulated after early activation of primary murine cardiac fibroblasts in culture. Cultured fibroblasts isolated from Ror1/2 knockout mice displayed a proinflammatory phenotype indicative of impaired myofibroblast differentiation. Although the combined ablation of Ror1/2 in mice did not result in a detectable baseline phenotype, transverse aortic constriction surgery led to the death of all mice by day 6 that was associated with myocardial hyperinflammation and vascular leakage.ConclusionsTogether, these results show that Ror1/2 are essential for the progression of myofibroblast differentiation and for the adaptive remodeling of the heart in response to pressure overload.

Interleukin-1α dependent survival of cardiac fibroblasts is associated with StAR/STARD1 expression and improved cardiac remodeling and function after myocardial infarction

AimsOne unaddressed aspect of healing after myocardial infarction (MI) is how non-myocyte cells that survived the ischemic injury, keep withstanding additional cellular damage by stress forms typically arising during the post-infarction inflammation. Here we aimed to determine if cell survival is conferred by expression of a mitochondrial protein novel to the cardiac proteome, known as steroidogenic acute regulatory protein, (StAR/STARD1). Further studies aimed to unravel the regulation and role of the non-steroidogenic cardiac StAR after MI. Methods and resultsFollowing permanent ligation of the left anterior descending coronary artery in mouse heart, timeline western blot analyses showed that StAR expression corresponds to the inflammatory response to MI. Following the identification of StAR in mitochondria of cardiac fibroblasts in culture, confocal microscopy immunohistochemistry (IHC) identified StAR expression in left ventricular (LV) activated interstitial fibroblasts, adventitial fibroblasts and endothelial cells. Further work with the primary fibroblasts model revealed that interleukin-1α (IL-1α) signaling via NF-κB and p38 MAPK pathways efficiently upregulates the expression of the Star gene products. At the functional level, IL-1α primed fibroblasts were protected against apoptosis when exposed to cisplatin mimicry of in vivo apoptotic stress; yet, the protective impact of IL-1α was lost upon siRNA mediated StAR downregulation. At the physiological level, StAR expression was nullified during post-MI inflammation in a mouse model with global IL-1α deficiency, concomitantly resulting in a 4-fold elevation of apoptotic fibroblasts. Serial echocardiography and IHC studies of mice examined 24 days after MI revealed aggravation of LV dysfunction, LV dilatation, anterior wall thinning and adverse tissue remodeling when compared with loxP control hearts. ConclusionsThis study calls attention to overlooked aspects of cellular responses evolved under the stress conditions associated with the default inflammatory response to MI. Our observations suggest that LV IL-1α is cardioprotective, and at least one mechanism of this action is mediated by induction of StAR expression in border zone fibroblasts, which renders them apoptosis resistant. This acquired survival feature also has long-term ramifications on the heart recovery by diminishing adverse remodeling and improving the heart function after MI.

The stiffness-controlled release of interleukin-6 by cardiac fibroblasts is dependent on integrin α2β1.

Cardiac fibroblasts are able to sense the rigidity of their environment. The present study examines whether the stiffness of the substrate in cardiac fibroblast culture can influence the release of interleukin‐6 (IL‐6), interleukin‐11 (IL‐11) and soluble receptor of IL‐6 (sIL‐6R). It also examines the roles of integrin α2β1 activation and intracellular signalling in these processes. Cardiac fibroblasts were cultured on polyacrylamide gels and grafted to collagen, with an elasticity of E = 2.23 ± 0.8 kPa (soft gel) and E = 8.28 ± 1.06 kPa (stiff gel, measured by Atomic Force Microscope). Flow cytometry and ELISA demonstrated that the fibroblasts cultured on the soft gel demonstrated higher expression of the α2 integrin subunit and increased α2β1 integrin count and released higher levels of IL‐6 and sIL‐6R than those on the stiff gel. Substrate elasticity did not modify fibroblast IL‐11 content. The silencing of the α2 integrin subunit decreased the release of IL‐6. Similar effects were induced by TC‐I 15 (an α2β1 integrin inhibitor). The IL‐6 levels in the serum and heart were markedly lower in α2 integrin‐deficient mice B6.Cg‐Itga2tm1.1Tkun/tm1.1Tkun than wild type. Inhibition of Src kinase by AZM 475271 modifies the IL‐6 level. sIL‐6R secretion is not dependent on α2β1 integrin. Conclusion: The elastic properties of the substrate influence the release of IL‐6 by cardiac fibroblasts, and this effect is dependent on α2β1 integrin and kinase Src activation.

Role of sialidase Neu3 and ganglioside GM3 in cardiac fibroblasts activation.

Cardiac fibrosis is a key physiological response to cardiac tissue injury to protect the heart from wall rupture. However, its progression increases heart stiffness, eventually causing a decrease in heart contractility. Unfortunately, to date, no efficient antifibrotic therapies are available to the clinic. This is primarily due to the complexity of the process, which involves several cell types and signaling pathways. For instance, the transforming growth factor beta (TGF-β) signaling pathway has been recognized to be vital for myofibroblasts activation and fibrosis progression. In this context, complex sphingolipids, such as ganglioside GM3, have been shown to be directly involved in TGF-β receptor 1 (TGF-R1) activation. In this work, we report that an induced up-regulation of sialidase Neu3, a glycohydrolytic enzyme involved in ganglioside cell homeostasis, can significantly reduce cardiac fibrosis in primary cultures of human cardiac fibroblasts by inhibiting the TGF-β signaling pathway, ultimately decreasing collagen I deposition. These results support the notion that modulating ganglioside GM3 cell content could represent a novel therapeutic approach for cardiac fibrosis, warranting for further investigations.