Adult Human Cardiac Fibroblasts Research Articles

Dual Blockade of TGF-β Receptor and Endothelin Receptor Synergistically Inhibits Angiotensin II-Induced Myofibroblast Differentiation: Role of AT1R/Gαq-Mediated TGF-β1 and ET-1 Signaling.

Angiotensin II (Ang II) upregulates transforming growth factor-beta1 (TGF-β1) and endothelin-1 (ET-1) in various types of cells, and all of them act as profibrotic mediators. However, the signal transduction of angiotensin II receptor (ATR) for upregulation of TGF-β1 and ET-1, and their effectors that play an essential role in myofibroblast differentiation, are not fully understood. Therefore, we investigated the ATR networking with TGF-β1 and ET-1 and identified the signal transduction of these mediators by measuring the mRNA expression of alpha-smooth muscle actin (α-SMA) and collagen I using qRT-PCR. Myofibroblast phenotypes were monitored by α-SMA and stress fiber formation with fluorescence microscopy. Our findings suggested that Ang II induced collagen I and α-SMA synthesis and stress fiber formation through the AT1R/Gαq axis in adult human cardiac fibroblasts (HCFs). Following AT1R stimulation, Gαq protein, not Gβγ subunit, was required for upregulation of TGF-β1 and ET-1. Moreover, dual inhibition of TGF-β and ET-1 signaling completely inhibited Ang II-induced myofibroblast differentiation. The AT1R/Gαq cascade transduced signals to TGF-β1, which in turn upregulated ET-1 via the Smad- and ERK1/2-dependent pathways. ET-1 consecutively bound to and activated endothelin receptor type A (ETAR), leading to increases in collagen I and α-SMA synthesis and stress fiber formation. Remarkably, dual blockade of TGF-β receptor and ETR exhibited the restorative effects to reverse the myofibroblast phenotype induced by Ang II. Collectively, TGF-β1 and ET-1 are major effectors of AT1R/Gαq cascade, and therefore, negative regulation of TGF-β and ET-1 signaling represents a targeted therapeutic strategy for the prevention and restoration of cardiac fibrosis.

Abstract 12710: Adipocyte-Derived Exosomal Lncrna Sbf2-as1 Promotes Diabetic Myocardial Fibrosis Through Regulating Hnrnpa1/nrf2 Pathway via Sumoylation

Introduction: The inhibition of Nrf2 pathway is regarded as the dominant process that correlates with the pathogenesis of diabetic cardiomyopathy (DCM). Recently, accumulating evidence reveals that lncRNAs play key roles in regulating Nrf2 pathway. However, the underlying mechanisms remain unclear. Here, we found that adipocyte lncRNA SBF2-AS1 (SBF2-AS1) enhanced the SUMOylation of hnRNPA1, which subsequently facilitated the package of SBF2-AS1 into exosomes under high glucose conditions. Hypothesis: We hypothesized that AdEXO-SBF2-AS1 promotes diabetic myocardial fibrosis through regulating the hnRNPA1/Nrf2 pathway via SUMOylation. Methods: We examined the effect of exosomes from diabetic (db/db) mice-derived adipocytes on ANG-II-induced cardiac fibrosis and function in non-diabetic mice. In the invitro study, HG (33mmol/L)-induced AdEXO were cultured with adult human cardiac fibroblasts (aHCFs). Differentially expressed lncRNAs in AdEXO were screened using lncRNA sequencing. Results: Intramyocardial injection of diabetic AdEXO in the non-diabetic heart exacerbated myocardial fibrosis. Whereas administration of an exosomes biogenesis inhibitor attenuated cardiac fibrosis in diabetic mice. We identified SBF2-AS1 is a common molecule significantly increased in diabetic AdEXO and HG-stimulated non-diabetic AdEXO. After four weeks of ANG II infusion, EXO-db/dbWT-injected mice displayed significant fibrosis in the heart. However, interestingly, mice receiving SBF2-AS1-deficient db/db-EXO showed a decrease in cardiac fibrosis. Similarly, AdEXO-SBF2-AS1 promoted aHCFs proliferation and transformation capabilities in vitro. Mechanistically, SBF2-AS1 induced UBC9 overexpression to catalyze the SUMOylation of hnRNPA1, which facilitated its packaging into exosomes. Subsequently, exosomal SBF2-AS1 was specifically transmitted into aHCFs and epigenetically downregulated Nrf2 expression by decreasing H3K9 acetylation level in the Nrf2 promoter. Conclusions: Our findings highlight a novel mechanism whereby the AdEXO-mediated SBF2-AS1/hnRNPA1/Nrf2 regulatory axis promotes diabetic myocardial fibrosis in a SUMOylation-dependent manner and implicate SBF2-AS1 as an attractive therapeutic target for DCM.

Lipoplexes for effective in vitro delivery of microRNAs to adult human cardiac fibroblasts for perspective direct cardiac cell reprogramming

Design of nanocarriers for efficient miRNA delivery can significantly improve miRNA-based therapies. Lipoplexes based on helper lipid, dioleoyl phosphatidylethanolamine (DOPE) and cationic lipid [2-(2,3-didodecyloxypropyl)-hydroxyethyl] ammonium bromide (DE) were formulated to efficiently deliver miR-1 or a combination of four microRNAs (miRcombo) to adult human cardiac fibroblasts (AHCFs). Lipoplexes with amino-to-phosphate groups ratio of 3 (N/P 3) showed nanometric hydrodynamic size (372 nm), positive Z-potential (40 mV) and high stability under storage conditions. Compared to commercial DharmaFECT1 (DF), DE-DOPE/miRNA lipoplexes showed superior miRNA loading efficiency (99 % vs. 64 %), and faster miRNA release (99 % vs. 82 % at 48 h). DE-DOPE/miR-1 lipoplexes showed superior viability (80–100 % vs. 50 %) in AHCFs, a 2-fold higher miR-1 expression and Twinfilin-1 (TWF-1) mRNA downregulation. DE-DOPE/miRcombo lipoplexes significantly enhanced AHCFs reprogramming into induced cardiomyocytes (iCMs), as shown by increased expression of CM markers compared to DF/miRcombo.

Contractility analysis of human engineered 3D heart tissues by an automatic tracking technique using a standalone application.

The use of Engineered Heart Tissues (EHT) as in vitro model for disease modeling and drug screening has increased, as they provide important insight into the genetic mechanisms, cardiac toxicity or drug responses. Consequently, this has highlighted the need for a standardized, unbiased, robust and automatic way to analyze hallmark physiological features of EHTs. In this study we described and validated a standalone application to analyze physiological features of EHTs in an automatic, robust, and unbiased way, using low computational time. The standalone application “EHT Analysis” contains two analysis modes (automatic and manual) to analyzes the contractile properties and the contraction kinetics of EHTs from high speed bright field videos. As output data, the graphs of displacement, contraction force and contraction kinetics per file will be generated together with the raw data. Additionally, it also generates a summary file containing all the data from the analyzed files, which facilitates and speeds up the post analysis. From our study we highlight the importance of analyzing the axial stress which is the force per surface area (μN/mm2). This allows to have a readout overtime of tissue compaction, axial stress and leave the option to calculate at the end point of an experiment the physiological cross-section area (PSCA). We demonstrated the utility of this tool by analyzing contractile properties and compaction over time of EHTs made out of a double reporter human pluripotent stem cell (hPSC) line (NKX2.5EGFP/+-COUP-TFIImCherry/+) and different ratios of human adult cardiac fibroblasts (HCF). Our standalone application “EHT Analysis” can be applied for different studies where the physiological features of EHTs needs to be analyzed under the effect of a drug compound or in a disease model.

Cardiac Tissue-like 3D Microenvironment Enhances Route towards Human Fibroblast Direct Reprogramming into Induced Cardiomyocytes by microRNAs.

The restoration of cardiac functionality after myocardial infarction represents a major clinical challenge. Recently, we found that transient transfection with microRNA combination (miRcombo: miR-1, miR-133, miR-208 and 499) is able to trigger direct reprogramming of adult human cardiac fibroblasts (AHCFs) into induced cardiomyocytes (iCMs) in vitro. However, achieving efficient direct reprogramming still remains a challenge. The aim of this study was to investigate the influence of cardiac tissue-like biochemical and biophysical stimuli on direct reprogramming efficiency. Biomatrix (BM), a cardiac-like extracellular matrix (ECM), was produced by in vitro culture of AHCFs for 21 days, followed by decellularization. In a set of experiments, AHCFs were transfected with miRcombo and then cultured for 2 weeks on the surface of uncoated and BM-coated polystyrene (PS) dishes and fibrin hydrogels (2D hydrogel) or embedded into 3D fibrin hydrogels (3D hydrogel). Cell culturing on BM-coated PS dishes and in 3D hydrogels significantly improved direct reprogramming outcomes. Biochemical and biophysical cues were then combined in 3D fibrin hydrogels containing BM (3D BM hydrogel), resulting in a synergistic effect, triggering increased CM gene and cardiac troponin T expression in miRcombo-transfected AHCFs. Hence, biomimetic 3D culture environments may improve direct reprogramming of miRcombo-transfected AHCFs into iCMs, deserving further study.

MiR-150 Attenuates Maladaptive Cardiac Remodeling Mediated by Long Noncoding RNA MIAT and Directly Represses Profibrotic Hoxa4.

MicroRNA-150 (miR-150) plays a protective role in heart failure (HF). Long noncoding RNA, myocardial infarction-associated transcript (MIAT) regulates miR-150 function in vitro by direct interaction. Concurrent with miR-150 downregulation, MIAT is upregulated in failing hearts, and gain-of-function single-nucleotide polymorphisms in MIAT are associated with increased risk of myocardial infarction (MI) in humans. Despite the correlative relationship between MIAT and miR-150 in HF, their in vivo functional relationship has never been established, and molecular mechanisms by which these 2 noncoding RNAs regulate cardiac protection remain elusive. We use MIAT KO (knockout), Hoxa4 (homeobox a4) KO, MIAT TG (transgenic), and miR-150 TG mice. We also develop DTG (double TG) mice overexpressing MIAT and miR-150. We then use a mouse model of MI followed by cardiac functional, structural, and mechanistic studies by echocardiography, immunohistochemistry, transcriptome profiling, Western blotting, and quantitative real-time reverse transcription-polymerase chain reaction. Moreover, we perform expression analyses in hearts from patients with HF. Lastly, we investigate cardiac fibroblast activation using primary adult human cardiac fibroblasts and in vitro assays to define the conserved MIAT/miR-150/HOXA4 axis. Using novel mouse models, we demonstrate that genetic overexpression of MIAT worsens cardiac remodeling, while genetic deletion of MIAT protects hearts against MI. Importantly, miR-150 overexpression attenuates the detrimental post-MI effects caused by MIAT. Genome-wide transcriptomic analysis of MIAT null mouse hearts identifies Hoxa4 as a novel downstream target of the MIAT/miR-150 axis. Hoxa4 is upregulated in cardiac fibroblasts isolated from ischemic myocardium and subjected to hypoxia/reoxygenation. HOXA4 is also upregulated in patients with HF. Moreover, Hoxa4 deficiency in mice protects the heart from MI. Lastly, protective actions of cardiac fibroblast miR-150 are partially attributed to the direct and functional repression of profibrotic Hoxa4. Our findings delineate a pivotal functional interaction among MIAT, miR-150, and Hoxa4 as a novel regulatory mechanism pertinent to ischemic HF.

Direct Reprogramming of Adult Human Cardiac Fibroblasts into Induced Cardiomyocytes Using miRcombo.

Direct reprogramming of fibroblasts into induced cardiomyocytes (iCMs) through microRNAs (miRNAs) is a new emerging strategy for myocardial regeneration after ischemic heart disease. Previous studies have reported that murine fibroblasts can be directly reprogrammed into iCMs by transient transfection with four miRNAs (miRs-1, 133, 208 and 499 - termed "miRcombo"). While advancement in the knowledge of direct cell reprogramming molecular mechanism is in progress, it is important to investigate if this strategy may be translated to humans. Recently, we demonstrated that miRcombo transfection is able to induce direct reprogramming of adult human cardiac fibroblasts (AHCFs) into iCMs. Although additional studies are needed to achieve iCM maturation, our early findings pave the way toward new therapeutic strategies for cardiac regeneration in humans. This chapter describes methods for inducing direct reprogramming of AHCFs into iCMs through miRcombo transient transfection, showing experiments to perform for assessing iCM generation.

Cortical bone stem cell-derived exosomes' therapeutic effect on myocardial ischemia-reperfusion and cardiac remodeling.

Heart failure is the one of the leading causes of death in the United States. Heart failure is a complex syndrome caused by numerous diseases, including severe myocardial infarction (MI). MI occurs after an occlusion of a cardiac artery causing downstream ischemia. MI is followed by cardiac remodeling involving extensive remodeling and fibrosis, which, if the original insult is severe or prolonged, can ultimately progress into heart failure. There is no "cure" for heart failure because therapies to regenerate dead tissue are not yet available. Previous studies have shown that in both post-MI and post-ischemia-reperfusion (I/R) models of heart failure, administration of cortical bone stem cell (CBSC) treatment leads to a reduction in scar size and improved cardiac function. Our first study investigated the ability of mouse CBSC-derived exosomes (mCBSC-dEXO) to recapitulate mouse CBSCs (mCBSC) therapeutic effects in a 24-h post-I/R model. This study showed that injection of mCBSCs and mCBSC-dEXOs into the ischemic region of an infarct had a protective effect against I/R injury. mCBSC-dEXOs recapitulated the effects of CBSC treatment post-I/R, indicating exosomes are partly responsible for CBSC's beneficial effects. To examine if exosomes decrease fibrotic activation, adult rat ventricular fibroblasts (ARVFs) and adult human cardiac fibroblasts (NHCFs) were treated with transforming growth factor β (TGFβ) to activate fibrotic signaling before treatment with mCBSC- and human CBSC (hCBSC)-dEXOs. hCBSC-dEXOs caused a 100-fold decrease in human fibroblast activation. To further understand the signaling mechanisms regulating the protective decrease in fibrosis, we performed RNA sequencing on the NHCFs after hCBSC-dEXO treatment. The group treated with both TGFβ and exosomes showed a decrease in small nucleolar RNA (snoRNA), known to be involved with ribosome stability.NEW & NOTEWORTHY Our work is noteworthy due to the identification of factors within stem cell-derived exosomes (dEXOs) that alter fibroblast activation through the hereto-unknown mechanism of decreasing small nucleolar RNA (snoRNA) signaling within cardiac fibroblasts. The study also shows that the injection of stem cells or a stem-cell-derived exosome therapy at the onset of reperfusion elicits cardioprotection, emphasizing the importance of early treatment in the post-ischemia-reperfusion (I/R) wounded heart.

Scaffold mediated delivery of dual miRNAs to transdifferentiate cardiac fibroblasts

The standard scaffold-mediated delivery of drugs/biomolecules has been successful due to the unique attributes of scaffolds, specifically the electrospun polymeric scaffolds that mimic ECM are well suited for advanced regenerative applications. Cardiac tissue engineering includes the interpretation of cellular and molecular mechanisms concerning heart regeneration and identifying an efficient reprogramming strategy to overcome the limitation of delivery systems and enhance the reprogramming efficiency. This study is a step towards developing a functional scaffold through a parallel interpretation of electrospun PLLA scaffolds with two distinct topologies to achieve sustained delivery of two muscle-specific microRNAs (miR-1 and miR-133a) to directly reprogram the adult human cardiac fibroblasts into cardiomyocyte-like cells. Polyethyleneimine was used to form stable PEI-miRNA complexes through electrostatic interactions. These complexes were immobilized on the electrospun smooth and porous scaffolds, where a loading efficiency of ~96% for the fibronectin modified and ~38% for unmodified surfaces was observed, regardless of their surface topology. The in-vitro release experiment exhibited a biphasic release pattern of PEI-miRNA polyplexes from the scaffolds. These dual miRNA scaffold systems proved to be an excellent formulation since their combinatorial effect involving the topographic cues of electrospun fibers, and dual miRNAs helped control the cardiac fibroblast cell fate precisely.

Engineering aligned human cardiac muscle using developmentally inspired fibronectin micropatterns

Cardiac two-dimensional tissues were engineered using biomimetic micropatterns based on the fibronectin-rich extracellular matrix (ECM) of the embryonic heart. The goal of this developmentally-inspired, in vitro approach was to identify cell–cell and cell-ECM interactions in the microenvironment of the early 4-chambered vertebrate heart that drive cardiomyocyte organization and alignment. To test this, biomimetic micropatterns based on confocal imaging of fibronectin in embryonic chick myocardium were created and compared to control micropatterns designed with 2 or 20 µm wide fibronectin lines. Results show that embryonic chick cardiomyocytes have a unique density-dependent alignment on the biomimetic micropattern that is mediated in part by N-cadherin, suggesting that both cell–cell and cell-ECM interactions play an important role in the formation of aligned myocardium. Human induced pluripotent stem cell-derived cardiomyocytes also showed density-dependent alignment on the biomimetic micropattern but were overall less well organized. Interestingly, the addition of human adult cardiac fibroblasts and conditioning with T3 hormone were both shown to increase human cardiomyocyte alignment. In total, these results show that cardiomyocyte maturation state, cardiomyocyte-cardiomyocyte and cardiomyocyte-fibroblast interactions, and cardiomyocyte-ECM interactions can all play a role when engineering anisotropic cardiac tissues in vitro and provides insight as to how these factors may influence cardiogenesis in vivo.

TRAF3 Interacting Protein 2 (TRAF3IP2) Expression is Increased in Failing Human Hearts of Ischemic Origin and Mediates the Pro‐fibrotic Responses of Transforming Growth Factor‐β (TGF‐β) in Adult Human Cardiac Fibroblasts

Heart failure (HF) is a leading cause of morbidity and mortality worldwide. Chronic inflammation contributes to HF development and progression. We have previously demonstrated the causal role and the therapeutic potential of targeting TRAF3IP2, a proinflammatory cytoplasmic adapter molecule, in ischemia/reperfusion-induced adverse myocardial remodeling and heart failure development in a mouse model. However, it is not known whether failing human hearts of ischemic origin express increased TRAF3IP2. Therefore, we hypothesized that TRAF3IP2 expression is increased during human HF of ischemic origin and investigated the molecular mechanisms underlying the induction and role of TRAF3IP2 in TGF-β-induced pro-fibrotic responses in cultured primary human cardiac fibroblasts (CF). The expression of TRAF3IP2 and its downstream signaling intermediates were analyzed in left ventricular (LV) tissue from explanted human hearts (failing human hearts of ischemic origin, HF-I) of both sexes, with LV tissue from non-failing (NF) human donor hearts deemed unsuitable for transplantation serving as controls. The data show that HF-I is characterized by myocardial hypertrophy, fibrosis (Picrosirius Red staining), contractile dysfunction (echocardiography), increased TRAF3IP2 expression (Western blotting and immunofluorescence), activation of Nuclear Factor Kappa B (NF-κB, phospho-p65), Activator Protein 1 (AP-1, phospho-c-Jun), and p38 Mitogen-Activated Protein Kinase (p38 MAPK, phospho-p38) (Western blotting using activation-specific antibodies), and enhanced expression of pro-inflammatory and pro-fibrotic mediators Interleukin-6 (IL-6), IL-17A, IL-18, Connective Tissue Growth Factor (CTGF) (RT-qPCR), collagens I and III, lysyl oxidase, Matrix Metalloproteinases (MMPs) (Western blotting), and TGF-β (functional assay). In cultured CF, TGF-β induced TRAF3IP2 expression in part via AP-1, and induced TRAF3IP2-dependent inflammatory cytokine expression, MMP2/9 activation, collagen expression, and migration (Boyden chamber assay) and proliferation (CyQuant assay). Moreover, forced expression of TRAF3IP2 by itself induced TGF-β expression. These data suggest that TRAF3IP2 plays a causal role in the development and progression of heart failure, and may be a therapeutic target.

3D Bioprinted Spheroidal Droplets for Engineering the Heterocellular Coupling between Cardiomyocytes and Cardiac Fibroblasts.

Since conventional human cardiac two-dimensional (2D) cell culture and multilayered three-dimensional (3D) models fail in recapitulating cellular complexity and possess inferior translational capacity, we designed and developed a high-throughput scalable 3D bioprinted cardiac spheroidal droplet-organoid model with cardiomyocytes and cardiac fibroblasts that can be used for drug screening or regenerative engineering applications. This study helped establish the parameters for bioprinting and cross-linking a gelatin-alginate-based bioink into 3D spheroidal droplets. A flattened disk-like structure developed in prior studies from our laboratory was used as a control. The microstructural and mechanical stability of the 3D spheroidal droplets was assessed and was found to be ideal for a cardiac scaffold. Adult human cardiac fibroblasts and AC16 cardiomyocytes were mixed in the bioink and bioprinted. Live-dead assay and flow cytometry analysis revealed robust biocompatibility of the 3D spheroidal droplets that supported the growth and proliferation of the cardiac cells in the long-term cultures. Moreover, the heterocellular gap junctional coupling between the cardiomyocytes and cardiac fibroblasts further validated the 3D cardiac spheroidal droplet model.

Abstract 15671: Adipocyte-derived Exosomal Lncrna Nbr2 Promotes Diabetic Myocardial Fibrosis Through Regulating the Ikba/nf-kb Pathway

Introduction: The activation of NF-κB is the dominant process that correlates with the pathogenesis of diabetic cardiomyopathy (DCM). Recently, accumulating evidence shows that long noncoding RNAs (lncRNAs) play crucial roles in sustaining the NF-κB pathway. However, the underlying mechanisms remain unclear. In this study, we identified the upregulated expressed lncRNA NBR2 in adipocyte-derived exosomes (AdEXO) and investigated its regulatory role in diabetic myocardial fibrosis. Hypothesis: We hypothesized that AdEXO-NBR2 promotes diabetic myocardial fibrosis through regulating the IκBα/NF-κB pathway. Methods: We examined the effect of exosomes from diabetic (db/db) mice-derived adipocytes on ANG-II-induced cardiac fibrosis and function in non-diabetic (C57BL/6J mice). In the invitro study, HG (33mmol/L)-stimulated AdEXO were cultured with adult human cardiac fibroblasts (aHCFs). Differentially expressed lncRNAs in AdEXO were screened using lncRNA sequencing. Results: Intramyocardial injection of diabetic AdEXO in the non-diabetic heart significantly exacerbated myocardial fibrosis, as evidenced by poorer cardiac function and enhancer collagen deposition. Whereas administration of a exosomes biogenesis inhibitor mitigated cardiac fibrosis in diabetic mice. We found lncRNA-NBR2 is a common molecule significantly increased in diabetic AdEXO and HG-stimulated non-diabetic AdEXO. After four weeks of ANG II infusion, EXO-db/dbWT-injected mice displayed fibrosis in the heart. However, interestingly, mice receiving NBR2-deficient db/db-EXO showed a decrease in cardiac fibrosis. Similarly, AdEXO-NBR2 promoted aHCFs proliferation and transformation capabilities in vitro. Mechanistically, NBR2 was loaded to AdEXO by directly interacting with heterogeneous nuclear ribonucleoprotein K (hnRNPK). Subsequently, AdEXO-NBR2 was internalized by aHCFs and epigenetically downregulated IκBα expression by recruitment of hnRNPK/SETDB1 and increasing the H3K9 trimethylation level in the IκBα promoter, ultimately activating the NF-κB pathway. Conclusions: Our findings highlight a novel epigenetic mechanism of AdEXO lncRNA-mediated diabetic cardiac fibrosis and identify NBR2 as a therapeutic target of DCM.

Abstract 428: Cortical Bone Stem Cell-derived Exosomes Reduce Myofibroblast Activation in Rat and Human Cardiac Fibroblasts

Rationale: Heart failure is the one of the leading causes of death in the United States. Post-myocardial infarction is followed by cardiac remodeling that involves extensive fibrosis and ultimately progresses into heart failure. We have seen improvements in scar size and cardiac function as a result of administration of cortical bone stem cell-derived (CBSC) exosomes. Objectives: We investigated the mechanism through which CBSC-derived exosomes altered wound healing and reduced scar formation through in vitro experimentation. We continue to broaden our understanding of how CBSCs exert their anti-fibrotic effects. Methods and Results: We cultured adult rat ventricular fibroblasts and adult human cardiac fibroblasts and treated them +/- TGF β with mouse and human CBSC-derived exosomes, respectively. We saw a dose-dependent decrease in myofibroblast activation with increasing concentrations of mCBSC and hCBSC exosomes, with 100 fold decrease compared to baseline fibroblast activation in hCBSC treated cardiac fibroblasts (9.5 x 10 5 of 1.6 x 10 7 intensity), and by 40% in mCBSC treated cardiac fibroblasts (2.4 x 10 5 of 1.0 x 10 6 intensity). In the presence of TGFβ and 2.0 x 10 6 exosome particles/cell treated, the αSMA levels were still reduced by nearly 50% vs TGFβ alone (1.2 x 10 6 of 2.2 x 10 7 intensity). We performed RNA sequencing on both the rat and human cardiac fibroblasts in order to discover which fibrosis-related genes were being altered by CBSC exosomes treatment. Conclusions: Our findings show that the wound healing induced by CBSC exosome treatment post-MI involves the reduction of myofibroblast activation and decreasing the production of pro-fibrotic mRNA in cardiac fibroblasts and cardiac endothelial cells.

Beneficial Effects of Mineralocorticoid Receptor Antagonism on Myocardial Fibrosis in an Experimental Model of the Myxomatous Degeneration of the Mitral Valve.

Mitral valve prolapse (MVP) patients develop myocardial fibrosis that is not solely explained by volume overload, but the pathophysiology has not been defined. Mineralocorticoid receptor antagonists (MRAs) improve cardiac function by decreasing cardiac fibrosis in other heart diseases. We examined the role of MRA in myocardial fibrosis associated with myxomatous degeneration of the mitral valve. Myocardial fibrosis has been analyzed in a mouse model of mitral valve myxomatous degeneration generated by pharmacological treatment with Nordexfenfluramine (NDF) in the presence of the MRA spironolactone. In vitro, adult human cardiac fibroblasts were treated with NDF and spironolactone. In an experimental mouse, MRA treatment reduced interstitial/perivascular fibrosis and collagen type I deposition. MRA administration blunted NDF-induced cardiac expression of vimentin and the profibrotic molecules galectin-3/cardiotrophin-1. In parallel, MRA blocked the increase in cardiac non-fibrillar proteins such as fibronectin, aggrecan, decorin, lumican and syndecan-4. The following effects are blocked by MRA: in vitro, in adult human cardiac fibroblasts, NDF-treatment-induced myofibroblast activation, collagen type I and proteoglycans secretion. Our findings demonstrate, for the first time, the contribution of the mineralocorticoid receptor (MR) to the development of myocardial fibrosis associated with mitral valve myxomatous degeneration. MRA could be a therapeutic approach to reduce myocardial fibrosis associated with MVP.

Human Cardiac Fibroblast Number and Activation State Modulate Electromechanical Function of hiPSC-Cardiomyocytes in Engineered Myocardium.

Cardiac tissue engineering using hiPSC-derived cardiomyocytes is a promising avenue for cardiovascular regeneration, pharmaceutical drug development, cardiotoxicity evaluation, and disease modeling. Limitations to these applications still exist due in part to the need for more robust structural support, organization, and electromechanical function of engineered cardiac tissues. It is well accepted that heterotypic cellular interactions impact the phenotype of cardiomyocytes. The current study evaluates the functional effects of coculturing adult human cardiac fibroblasts (hCFs) in 3D engineered tissues on excitation and contraction with the goal of recapitulating healthy, nonarrhythmogenic myocardium in vitro. A small population (5% of total cell number) of hCFs in tissues improves tissue formation, material properties, and contractile function. However, two perturbations to the hCF population create disease-like phenotypes in engineered cardiac tissues. First, increasing the percentage of hCFs to 15% resulted in tissues with increased ectopic activity and spontaneous excitation rate. Second, hCFs undergo myofibroblast activation in traditional two-dimensional culture, and this altered phenotype ablated the functional benefits of hCFs when incorporated into engineered cardiac tissues. Taken together, the results of this study demonstrate that human cardiac fibroblast number and activation state modulate electromechanical function of hiPSC-cardiomyocytes and that a low percentage of quiescent hCFs are a valuable cell source to advance a healthy electromechanical response of engineered cardiac tissue for regenerative medicine applications.

MicroRNA-Mediated Direct Reprogramming of Human Adult Fibroblasts Toward Cardiac Phenotype.

Modulation of microRNA expression holds the promise to achieve direct reprogramming of fibroblasts into cardiomyocyte-like cells as a new strategy for myocardial regeneration after ischemic heart disease. Previous reports have shown that murine fibroblasts can be directly reprogrammed into induced cardiomyocytes (iCMs) by transient transfection with four microRNA mimics (miR-1, 133, 208, and 499, termed “miRcombo”). Hence, study on the effect of miRcombo transfection on adult human cardiac fibroblasts (AHCFs) deserves attention in the perspective of a future clinical translation of the approach. In this brief report, we studied for the first time whether miRcombo transient transfection of AHCFs by non-viral vectors might trigger direct reprogramming of AHCFs into cardiomyocyte-like cells. Initially, efficient miRNA delivery to cells was demonstrated through the use of a commercially available transfection agent (DharmaFECT1). Transient transfection of AHCFs with miRcombo was found to upregulate early cardiac transcription factors after 7 days post-transfection and cardiomyocyte specific marker cTnT after 15 days post-transfection, and to downregulate the expression of fibroblast markers at 15 days post-transfection. The percentage of cTnT-positive cells after 15 days from miRcombo transfection was ∼11%, as evaluated by flow cytometry. Furthermore, a relevant percentage of miRcombo-transfected AHCFs (∼38%) displayed spontaneous calcium transients at 30 days post-transfection. Results evidenced the role of miRcombo transfection on triggering the trans differentiation of AHCFs into iCMs. Although further investigations are needed to achieve iCM maturation, early findings from this study pave the way toward new advanced therapies for human cardiac regeneration.

ECM Mimetic Electrospun Porous Poly (L-lactic acid) (PLLA) Scaffolds as Potential Substrates for Cardiac Tissue Engineering.

Cardiac tissue engineering (CTE) aims to generate potential scaffolds to mimic extracellular matrix (ECM) for recreating the injured myocardium. Highly porous scaffolds with properties that aid cell adhesion, migration and proliferation are critical in CTE. In this study, electrospun porous poly (l-lactic acid) (PLLA) porous scaffolds were fabricated and modified with different ECM derived proteins such as collagen, gelatin, fibronectin and poly-L-lysine. Subsequently, adult human cardiac fibroblasts (AHCF) were cultured on the protein modified and unmodified fibers to study the cell behavior and guidance. Further, the cytotoxicity and reactive oxygen species (ROS) assessments of the respective fibers were performed to determine their biocompatibility. Excellent cell adhesion and proliferation of the cardiac fibroblasts was observed on the PLLA porous fibers regardless of the surface modifications. The metabolic rate of cells was on par with the conventional cell culture ware while the proliferation rate surpassed the latter by nearly two-folds. Proteome profiling revealed that apart from being an anchorage platform for cells, the surface topography has modulated significant expression of the cellular proteome with many crucial proteins responsible for cardiac fibroblast growth and proliferation.

Abstract 525: In vitro Reverse Remodeling After Mechanical Unloading With Engineered Heart Tissue

LVADs serve as a bridge to transplantation for many dilated cardiomyopathy (DCM) patients with advanced heart failure. In rare cases, mechanical unloading can lead to reverse myocardial remodeling sufficient for the removal of LVAD. We recreated the first reverse remodeling process in vitro in order to examine the role of active actin-myosin contraction and fibroblasts in contributing to this recovery, and to test the efficacy of drugs commonly prescribed for concurrent use with LVAD implantation. Engineered heart tissue (EHT) were prepared from decellularized porcine ventricular scaffolds in a proof-of-concept animal model with neonatal rat cardiomyocytes and subsequently with human induced pluripotent stem cell-derived cardiomyocytes and adult human cardiac fibroblasts. Mechanical stretch and myosin inhibition were used to simulate the pathological remodeling of DCM. Preliminary animal data showed that our model was able to capture the key features of DCM and reverse remodeling process including improved slack length, tissue stiffness, and active kinetics following mechanical unloading. β-adrenergic receptor response, protein assay, immunohistochemistry, and genetic analysis are being carried out to comprehensively investigate reverse remodeling in this artificial human system. Additional drug studies aim to investigate how reverse remodeling is affected by concurrent administration of β 1 antagonists and β 2 agonists (typical drug regimen for heart failure) and may inform new potential treatment during mechanical unloading to promote beneficial reverse remodeling for patients.

Featured Article: TGF-β1 dominates extracellular matrix rigidity for inducing differentiation of human cardiac fibroblasts to myofibroblasts.

Cardiac fibroblasts and their activated derivatives, myofibroblasts, play a critical role in wound healing after myocardial injury and often contribute to long-term pathological outcomes, such as excessive fibrosis. Thus, defining the microenvironmental factors that regulate the phenotype of cardiac fibroblasts and myofibroblasts could lead to new therapeutic strategies. Both chemical and biomechanical cues have previously been shown to induce myofibroblast differentiation in many organs and species. For example, transforming growth factor beta 1, a cytokine secreted by neutrophils, and rigid extracellular matrix environments have both been shown to promote differentiation. However, the relative contributions of transforming growth factor beta 1 and extracellular matrix rigidity, two hallmark cues in many pathological myocardial microenvironments, to the phenotype of human cardiac fibroblasts are unclear. We hypothesized that transforming growth factor beta 1 and rigid extracellular matrix environments would potentially have a synergistic effect on the differentiation of human cardiac fibroblasts to myofibroblasts. To test this, we seeded primary human adult cardiac fibroblasts onto coverslips coated with polydimethylsiloxane of various elastic moduli, introduced transforming growth factor beta 1, and longitudinally quantified cell phenotype by measuring expression of α-smooth muscle actin, the most robust indicator of myofibroblasts. Our data indicate that, although extracellular matrix rigidity influenced differentiation after one day of transforming growth factor beta 1 treatment, ultimately transforming growth factor beta 1 superseded extracellular matrix rigidity as the primary regulator of myofibroblast differentiation. We also measured expression of POSTN, FAP, and FSP1, proposed secondary indicators of fibroblast/myofibroblast phenotypes. Although these genes partially trended with α-smooth muscle actin expression, they were relatively inconsistent. Finally, we demonstrated that activated myofibroblasts incompletely revert to a fibroblast phenotype after they are re-plated onto new surfaces without transforming growth factor beta 1, suggesting differentiation is partially reversible. Our results provide new insights into how microenvironmental cues affect human cardiac fibroblast differentiation in the context of myocardial pathology, which is important for identifying effective therapeutic targets and dictating supporting cell phenotypes for engineered human cardiac disease models. Impact statement Heart disease is the leading cause of death worldwide. Many forms of heart disease are associated with fibrosis, which increases extracellular matrix (ECM) rigidity and compromises cardiac output. Fibrotic tissue is synthesized primarily by myofibroblasts differentiated from fibroblasts. Thus, defining the cues that regulate myofibroblast differentiation is important for understanding the mechanisms of fibrosis. However, previous studies have focused on non-human cardiac fibroblasts and have not tested combinations of chemical and mechanical cues. We tested the effects of TGF-β1, a cytokine secreted by immune cells after injury, and ECM rigidity on the differentiation of human cardiac fibroblasts to myofibroblasts. Our results indicate that differentiation is initially influenced by ECM rigidity, but is ultimately superseded by TGF-β1. This suggests that targeting TGF-β signaling pathways in cardiac fibroblasts may have therapeutic potential for attenuating fibrosis, even in rigid microenvironments. Additionally, our approach can be leveraged to engineer more precise multi-cellular human cardiac tissue models.