Proteins In Cardiomyocytes Research Articles

Zinc Dyshomeostasis in Cardiomyocytes after Acute Hypoxia/Reoxygenation.

Zinc dyshomeostasis may play a role in the pathogenesis of myocardial ischemia/reperfusion injury. The objective of this study was to investigate the expression profile of zinc regulated transporter like- and iron-regulated transporter-like proteins (ZIPs) and zinc transporter proteins (ZnTs) in cardiomyocytes and their modulation in response to hypoxia and reoxygenation. Adult rat ventricular myocytes (ARVMs) were subjected to 6h of hypoxia, followed by 18h of reoxygenation. Intracellular and extracellular zinc concentrations were determined using Fluozin-3 and Newport Green fluorescence, respectively. Expression of ZnTs 1, 2, 5, and 9 along with ZIPs 1, 2, 3, 6, 7, 9, 10, 11, 13, and 14 was detectable in the cardiomyocytes by real-time reverse transcriptase polymerase chain reaction. Hypoxia elicited accumulation of intracellular free zinc, but subsequent reoxygenation resulted in striking loss of intracellular free zinc and decreased the cardiomyocyte viability. Concomitantly, extracellular zinc levels dropped rapidly during hypoxia, but increased after reoxygenation. Immunoblotting analysis revealed that hypoxia increased the expression of ZnT1, but reoxygenation significantly increased the expression of ZnTs 2 and 5. Neither hypoxia nor reoxygenation altered the levels of ZnT9. Increased intracellular zinc at the end of hypoxia is related to enhanced expression of ZIPs, whereas decreased intracellular zinc during reoxygenation appears to be due to lowered expression of all ZIPs, in addition to elevated levels of ZnTs 2 and 5. These results thus suggest that there is impaired accumulation of intracellular zinc during reoxygenation, due to overexpression of specific ZnTs and downregulation of ZIP expression.

Combination of Morroniside and Diosgenin Prevents High Glucose-Induced Cardiomyocytes Apoptosis.

Cornus officinalis and Dioscorea opposita are two traditional Chinese medicines widely used in China for treating diabetes mellitus and its complications, such as diabetic cardiomyopathy. Morroniside (Mor) of Cornus officinalis and diosgenin (Dio) of Dioscorea opposita formed an innovative formula named M + D. The aims of the present study were to investigate myocardial protective effect of M + D on diabetic cardiomyopathy (DCM) through the inhibition of expression levels of caspase-3 protein, and identify the advantage of M + D compared with Mor, Dio, and the positive drug metformin (Met). We detected cell viability, cell apoptosis, intracellular reactive oxygen species (ROS) levels, and the expression levels of Bcl-2, Bax, and caspase-3 protein in rat cardiomyocytes. In result, Mor, Dio, and M + D increased cell viability, inhibited cell apoptosis and decreased ROS levels. Additionally, the expression of Bax and Bcl-2 protein was modulated and the expression levels of caspase-3 protein were markedly decreased. Among the treatment groups, M + D produced the most prominent effects. In conclusion, our data showed for the first time that Mor, Dio, and M + D prevented high glucose (HG)-induced myocardial injury by reducing oxidative stress and apoptosis in rat cardiomyocytes. Among all the groups, M + D produced the strongest effect, while Mor and Dio produced weaker effects.

Connexin 43 and Mitochondria in Cardiovascular Health and Disease.

Connexin 43 (Cx43) is the major connexin protein in ventricular cardiomyocytes. Six Cx43 proteins assemble into so-called hemichannels at the sarcolemma and opposing hemichannels form gap junctions, which allow the passage of small molecules and electrical current flow between adjacent cells. Apart from its localization at the plasma membrane, Cx43 is also present in cardiomyocyte mitochondria, where it is important for mitochondrial function in terms of oxygen consumption and potassium fluxes. The expression of gap junctional and mitochondrial Cx43 is altered under several pathophysiological conditions among them are hypertension, hypertrophy, hypercholesterolemia, ischemia/reperfusion injury, post-infarction remodeling, and heart failure. The present review will focus on the role of Cx43 in cardiovascular diseases and will highlight the importance of mitochondrial Cx43 in cardioprotection.

NEDD4-1 protects against ischaemia/reperfusion-induced cardiomyocyte apoptosis via the PI3K/Akt pathway.

Activation of the Akt pathway has been shown to protect the heart from ischaemia/reperfusion (I/R) injury. NEDD4-1 has been shown to positively regulate nuclear trafficking of the activated form of Akt. However, the role of NEDD4-1 in cardiac I/R injury remains to be elucidated. In the present study, Lentiviral vectors were constructed to overexpress or knockdown NEDD4-1 in H9c2 cardiomyocytes subjected to I/R injury or ischemic preconditioning (IPC). The results indicated that NEDD4-1 levels were decreased after I/R and increased after IPC in rat heart tissue and in H9c2 cardiomyocytes. Overexpression of NEDD4-1 activated the Akt pathway and regulated apoptosis-related proteins in H9c2 cardiomyocytes, attenuating SI/R-induced cell apoptosis and caspase 3/7 activities. Furthermore, in vivo overexpression of NEDD4-1 attenuated myocardial apoptosis following myocardial I/R. Our results demonstrated that NEDD4-1 protects the myocardium from I/R induced apoptosis by activating PI3K/Akt signaling.

The poly(ADP-ribosyl)ation of FoxO3 mediated by PARP1 participates in isoproterenol-induced cardiac hypertrophy

The Forkhead box-containing protein, O subfamily 3 (FoxO3) transcription factor negatively regulates myocardial hypertrophy, and its transcriptional activity is finely conditioned by diverse posttranslational modifications, such as phosphorylation, acetylation, ubiquitination, methylation and glycosylation. Here, we introduce a novel modification of the FoxO3 protein in cardiomyocytes: poly(ADP-ribosyl)ation (PARylation) mediated by poly(ADP-ribose) polymerase-1 (PARP1). This process catalyzes the NAD+-dependent synthesis of polymers of ADP-ribose (PAR) and their subsequent attachment to target proteins by PARPs. Primary-cultured neonatal rat cardiomyocytes were incubated with isoproterenol (ISO) to induce hypertrophy, or were infected with recombinant adenovirus vectors harboring PARP1 cDNA (Ad-PARP1). Sprague-Dawley (SD) rats were treated with ISO to induce cardiac hypertrophy, or were injected with Ad-PARP1 into the anterior and posterior left ventricular walls. Cardiomyocyte surface area, the mRNA expression of hypertrophic biomarkers, echocardiography, morphometry of the hearts were measured. The PARP1 activity was tested by cellular PAR levels. Interactions of PARP1 and FoxO3 were investigated by co-immunoprecipitation and immunofluorescence technique. PARylation of FoxO3 mediated by PARP1 facilitated its phosphorylation at the T32, S252 and S314 sites, triggered its nucleus export and suppressed its transcriptional activity and target genes expression, ultimately inducing cardiac hypertrophy. Additionally, PARP1 silencing or specific inhibition by 3-Aminobenzamide (3AB) and veliparib (ABT-888) alleviated the inhibition of FoxO3 activity by ISO, thus suppressing ISO-induced cardiac hypertrophy. Our data provide the first evidence that PARP1 exacerbates cardiac hypertrophy by PARylation of FoxO3.

Expression of connexin 43, ion channels and Ca2+-handling proteins in rat pulmonary vein cardiomyocytes.

Atrial fibrillation (AF) is the most common cardiac arrhythmia. AF is thought to be triggered by ectopic beats, originating primarily in the myocardial sleeves surrounding the pulmonary veins (PVs). The mechanisms underlying these cardiac arrhythmias remain unclear. To investigate this, frozen sections of heart and lung tissue from adult rats without arrhythmia were obtained in different planes, stained with Masson's trichrome, and immunolabeled for connexin 43 (Cx43), caveolin-3 (Cav3), hyperpolarization-activated cyclic nucleotide-gated channel 4 (HCN4), Nav1.5, Kir2.1, and the calcium handling proteins sarcoplasmic/endoplasmic reticulum calcium-ATPase 2a (SERCA2a) and ryanodine receptor 2 (RyR2). Transverse sections offered the best view of the majority of the PVs in the tissue samples. Cx43 was observed to be expressed throughout the atria, excluding the sinoatrial and atrioventricular nodes, and in the myocardial sleeves of the PVs. In contrast, HCN4 was only expressed in the sinoatrial and atrioventricular nodes. The immunodensity of Cav3, Nav1.5, Kir2.1, SERCA2a and RyR2 in the PVs imaged was similar to that in atria. The results suggest that in the absence of arrhythmia, the investigated molecular properties of the ion channels of rat PV cardiomyocytes resemble those of the working myocardium. This indicates that ectopic beats originating in the myocardial sleeves of the PVs occur only under pathological conditions.

Understanding cardiomyocyte proliferation: an insight into cell cycle activity.

Cardiomyocyte proliferation and regeneration are key to the functional recovery of myocardial tissue from injury. In the recent years, studies on cardiomyocyte proliferation overturned the traditional belief that adult cardiomyocytes permanently withdraw from the cell cycle activity. Hence, targeting cardiomyocyte proliferation is one of the potential therapeutic strategies for myocardial regeneration and repair. To achieve this, a deep understanding of the fundamental mechanisms involved in cardiomyocyte cell cycle as well as differences between neonatal and adult cardiomyocytes' cell cycle activity is required. This review focuses on the recent progress in understanding of cardiomyocyte cell cycle activity at different life stages viz., gestation, birth, and adulthood. The temporal expression/activities of major cell cycle activators (cyclins and CDKs), inhibitors (p21, p27, p57, p16, and p18), and cell-cycle-associated proteins (Rb, p107, and p130) in cardiomyocytes during gestation and postnatal life are described in this review. The influence of different transcription factors and microRNAs on the expression of cell cycle proteins is demonstrated. This review also deals major pathways (PI3K/AKT, Wnt/β-catenin, and Hippo-YAP) associated with cardiomyocyte cell cycle progression. Furthermore, the postnatal alterations in structure and cellular events responsible for the loss of cell cycle activity are also illustrated.

A new monoclonal antibody (Cox mAB 31A2) detects VP1 protein of coxsackievirus B3 with high sensitivity and specificity.

Human enteroviruses, e.g. coxsackieviruses, induce a variety of severe acute and chronic forms of disease, including myocarditis, meningitis and diabetes mellitus type 1. To visualize enterovirus infection with a diagnostic intent, many studies have applied a commercially available antibody (anti-CVB5 VP1, clone 5-D8/1, Dako, Hamburg, Germany) that identifies VP1 of different enteroviral serotypes. Many antibodies, however, have been found to bind non-specifically to proteins of cardiomyocytes and in the interstitial space, resulting in non-specific staining in immunohistochemistry. In this paper we show that the anti-CVB5 VP1 antibody, recognizing VP1 of coxsackieviruses and widely used in diagnostics and research, shows strong cross-reactivity with cellular proteins in the heart (and pancreas) of humans and mice, which calls for a more specific antibody to be used for diagnostic purposes. We observed by Western blot analyses of lysates from human heart tissue samples and HeLa cells two cross-reactive bands when using clone 5-D8/1. Peptide mass fingerprinting (MALDI-TOF) identified these proteins as creatine kinase (B-type) and tubulin, confirming that this mAb detects cellular proteins in addition to viral VP1. In order to overcome the problems of false positive VP1 staining we generated a new highly specific and sensitive monoclonal antibody (Cox mAB 31A2) that recognizes VP1 from CVB3. The new antibody was characterized and was found to function well in immunohistochemistry, immunofluorescence staining, Western blotting, ELISA and FACS analyses.

MiR-20a regulates proliferation, differentiation and apoptosis in P19 cell model of cardiac differentiation by targeting Smoothened

ABSTRACTMicroRNA (miR)-20a, a member of the miR-17-92 cluster related to cardiac development, was obviously downregulated in myocardially differentiated P19 cells compared with normal P19 cells. Smoothened (SMO) is a member of the Hh pathway. Hh signaling induces cardiac differentiation in P19 cells, and SMO mediates the Hh pathway during embryonic development. Using bioinformatic prediction software Targetscan (http://www.targetscan.org/), PicTar (http://pictar.bio.nyu.edu), and miRBase (http://microrna.sanger.ac.uk/), miR-20a and the 3′-untranslated region (3′-UTR) of SMO mRNA were predicted to have complementary binding regions. Accordingly, we inferred that miR-20a might act as a regulator of SMO, and regulate proliferation, differentiation and apoptosis in P19 cells. We determined the expression of miR-20a, SMO and marker proteins of cardiomyocytes (cTnT, GATA4 and desmin) by quantitative real-time PCR (qRT-PCR) and western blot assays, and found that P19 cells had differentiated into cardiomyocytes successfully at differentiation day 10, and downregulation of miR-20a and upregulation of SMO existed in myocardially differentiated P19 cells. Cell proliferation, differentiation and apoptosis detection showed that miR-20a upregulation inhibited proliferation and differentiation and enhanced apoptosis in P19 cells. Moreover, we verified that miR-20a directly targeted SMO and knockdown of SMO and miR-20a overexpression had similar effects on P19 cell proliferation, differentiation and apoptosis, which verified the speculation that miR-20a inhibits proliferation and differentiation and enhances apoptosis in P19 cells by directly targeting SMO. Our results suggest that miR-20a may be a potential target against congenital heart diseases.

Abstract 131: PDE1 Inhibition Improves Cardiac Protein Quality Control

Protein quality control (PQC) functions to minimize the level and toxicity of misfolded proteins in the cell. PQC relies on molecular chaperones and the targeted degradation of misfolded proteins. The latter is currently known to require the ubiquitin-proteasome system (UPS) and the autophagic-lysosomal pathway (ALP). Virtually all cardiovascular diseases end up heart failure (HF), the leading cause of death of our society. UPS function insufficiency is implicated in the genesis of a large subset of HF, making cardiac PQC enhancement via promoting UPS and ALP function a promising therapeutic strategy to treat HF. Previously, we have demonstrated that stimulating protein kinase G (PKG) genetically or via inhibition of the type 5 phosphodiesterase (PDE5) improves UPS performance, facilitates the removal of misfolded proteins in cardiomyocytes and slows down the progression of cardiac proteinopathy in a transgenic mouse model (CryAB R120G ). PKA has also been shown to enhance proteasomal function. Our preliminary studies reveal that myocardial protein levels of PDE1A, which suppresses both PKG and PKA, are remarkably elevated in the CryAB R120G mice. Hence we hypothesize that PDE1 inhibition (PDE1I) stimulates cardiac proteasomes via PKG and PKA activation and thereby protects against cardiac proteotoxicity. To test our hypothesis, we took advantage of a proven surrogate UPS substrate (GFPu or GFPdgn) as well as a bona fide misfolded protein (CryAB R120G ) that is known to induce cardiac proteinopathy in human and mice. In cultured cardiomyocytes, PDE1 inhibitor LSN2790158 dose- and time-dependently decreased GFPu. Cycloheximide (CHX) chase assays further confirmed that PDE1I shortened the half-life of GFPu, indicative of improved UPS performance. Furthermore, PDE1I promoted the degradation of CryAB R120G . Our in vivo findings revealed that GFPdgn mice treated with LSN2790158 (3mg/kg, i.p.) displayed a significant reduction of myocardial GFPdgn protein but not mRNA levels. Taken together, our data strongly indicate that PDE1I improves cardiac UPS performance and PDE1 represents a potential target to treat cardiac diseases with elevated proteotoxicity.

Abstract 390: Dysregulation of ATF2 in Dilated Cardiomyopathy Caused by FBXO32 Mutation

Background: Dilated cardiomyopathy (DCM) is a common form of cardiomyopathy causing systolic dysfunction and heart failure. Rare variants in more than 30 genes mostly encoding sarcomeric proteins and proteins of the extracellular matrix have been implicated in familial DCM to date. We recently identified a novel mutation (Gly243Arg) in FBXO32 causing familial DCM through abnormal SKP1/CUL/F-BOX (SCF) complex formation and defects in proteins regulating the autophagy/lysosome machinery (Al-Yacoub, Genome Biology, 2016). Objective: To explore in more details the mechanisms by which the defective SCF FBXO32 complex leads to the development of DCM. Methodology: Using a PCR-based microarray, we screened for mRNAs significantly dysregulated in the heart of the patient carrying the FBXO32 mutation compared to control and idiopathic human hearts. Subsequently, we validated dysregulation of a candidate gene using immunoblot analysis and tested the effect of the mutant or wild-type FBXO32 on the novel candidate identified in primary neonatal rat cardiomyocytes. Results: We found a robust up-regulation in mRNA expression of the Activating transcription Factor 2 (ATF2), a member of the leucine zipper family of DNA binding proteins, which plays a critical role in cardiac development. ATF2 protein level was also strongly increased in the heart with the FBXO32 mutation compared to control hearts and to hearts of idiopathic origin. Expression of the mutant FBXO32 protein in primary cardiomyocytes enhanced ATF2 protein expression compared to cells expressing the wild-type FBXO32 protein. Since FBXO32 is member of the SCF complex and has ubiquitin ligase activity, experiments are now investigating whether FBXO32 directly regulates ATF2 protein stability and the role of ATF2 in autophagy flux regulation in dilated cardiomyopathy. Conclusion: Our results indicate that abnormal SCF activity due to the FBXO32 mutation stabilizes the AFT2 transcription factor and suggest a new mechanism by aberrant SCF activity causes DCM in human.

Abstract 29: Porcine Decellularized Heart Tissue Enhance the Expression of Contractile Proteins in Human Cardiomyocytes and Differentiated Cardiac Progenitor Cells

Tissue engineering is an evolving tool for repair of cardiovascular damage, in particular after myocardial infarction. Currently, most studies are focused on providing gel or thin synthetic matrices to provide structural support for injured valves, or ventricle. But little is known about how cardiac cells (eg, endothelial cells [ECs], cardiomyocytes [CMs] and cardiac progenitor cells [CPCs]) are modified by an exposure to a scaffold much less how a xenogeneic scaffold may affect cell physiology or function. Our study was designed to examine the effect of rat or pig collagen matrix and decellularized left ventricle extracellular matrix (dECM) tissues on the phenotype of human cardiac cells. Human ECs, CMs and CPCs derived from IPs cells (Cellular Dynamics International) were cultured singly or together on rat or pig collagen matrices or on dECM. Protein and gene expression was investigated by immunohistochemistry, histology and real time PCR. All 3 cell types survived on both types of support when delivered singly or together. Endothelial cell PECAM-1 expression was enhanced on decellularized tissues particularly on rat matrix. Cardiomyocyte contractile protein expression did not differ with support type, whereas CPC contractile protein gene expression increased on both decellularized tissues more so on pig matrix. Additionally, when the cells were co-cultured, single cell type gene expression was modified. Our study showed that human cardiac cells are influenced by the structural support on which they are cultivated. Cardiac ECM enhanced the expression of contractile proteins and endothelial markers but matrix species had minimal influence on this effect. Furthermore, cell co-culture altered gene expression suggesting cell communication is intact on the matrix. This study shows that cell phenotype and behavior is impacted by the tissue matrix to a greater degree than occurs with a simple one protein support and suggests complex decellularized matrix may be superior to successfully engineer cardiac constructs with intact physiology. Additionally, the successful differentiation of IPs cells into cardiomyocytes on decellularized matrix opens avenue to build tissue engineer constructs from patients with heart disease as a screening tool.

Autoimmunity and Prognosis of Patients With Morphologically Documented Myocarditis

to assess clinical and prognostic value of circulating cardiospecific autoantibodies (AAB) and CD4+ T-regulatory cells in patients with myocarditis. We included into this study 47 patients with lymphocytic myocarditis verified by analysis of histological and immunohistochemical data. Comparison group consisted of 30 practically healthy persons. Content of marker cardiotropic AAT were measured with the help of standardized immune enzyme test-systems. Number of circulating CD4+CD25+ and CD4+CD25+FoxP3+ T-lymphocytes were evaluated by flow cytometry. Among factors determining prognosis of patients with lymphocytic myocarditis factors of key significance were the presence of clinically overt heart failure at the disease debut, and degree of reduction of left ventricular ejection fraction. Distinctive feature of active myocarditis was elevation of titer of AABs to sarcomeric, cytoskeleton, and cytoplasmic proteins of cardiomyocytes, as well as elevated level of AABs to various epitopes of adenine nucleotide translocator. Elevated level of AAB to 1-adrenoreceptors was an independent predictor of unfavorable outcome in patients with lymphocytic myocarditis. Increased population of circulating CD4+CD25+ T-regulatory cells was as sociated with elevated concentration of of natriuretic peptide. Abnormalities in the system of autoimmunity play key role not only in pathogenesis but also in prognosis of inflammatory myocardial diseases. Changes of profile of circulating cardiospecific AABs and T-regulatory cells can bear a protective function.

Downregulation of GSTK1 Is a Common Mechanism Underlying Hypertrophic Cardiomyopathy.

Hypertrophic cardiomyopathy (HCM) is characterized by left ventricular hypertrophy and is associated with a number of potential outcomes, including impaired diastolic function, heart failure, and sudden cardiac death. Various etiologies have been described for HCM, including pressure overload and mutations in sarcomeric and non-sarcomeric genes. However, the molecular pathogenesis of HCM remains incompletely understood. In this study, we performed comparative transcriptome analysis to identify dysregulated genes common to five mouse HCM models of differing etiology: (i) mutation of myosin heavy chain 6, (ii) mutation of tropomyosin 1, (iii) expressing human phospholamban on a null background, (iv) knockout of frataxin, and (v) transverse aortic constriction. Gene-by-gene comparison identified five genes dysregulated in all five HCM models. Glutathione S-transferase kappa 1 (Gstk1) was significantly downregulated in the five models, whereas myosin heavy chain 7 (Myh7), connective tissue growth factor (Ctgf), periostin (Postn), and reticulon 4 (Rtn4) were significantly upregulated. Gene ontology comparison revealed that 51 cellular processes were significantly enriched in genes dysregulated in each transcriptome dataset. Among them, six processes (oxidative stress, aging, contraction, developmental process, cell differentiation, and cell proliferation) were related to four of the five genes dysregulated in all HCM models. GSTK1 was related to oxidative stress only, whereas the other four genes were related to all six cell processes except MYH7 for oxidative stress. Gene–gene functional interaction network analysis suggested correlative expression of GSTK1, MYH7, and actin alpha 2 (ACTA2). To investigate the implications of Gstk1 downregulation for cardiac function, we knocked out gstk1 in zebrafish using the clustered regularly interspaced short palindromic repeats/Cas9 system. We found that expression of the zebrafish homologs of MYH7, ACTA2, and actin alpha 1 were increased in the gstk1-knockout zebrafish. In vivo imaging of zebrafish expressing a fluorescent protein in cardiomyocytes showed that gstk1 deletion significantly decreased the end diastolic volume and, to a lesser extent, end systolic volume. These results suggest that downregulation of GSTK1 may be a common mechanism underlying HCM of various etiologies, possibly through increasing oxidative stress and the expression of sarcomere genes.

735. Functional Restoration of Dystrophin Protein in HiPSC-Derived Skeletal Myotubes and Cardiomyocytes After CRISPR/Cas9-Mediated Deletion of 530-725kb of DMD

Duchenne muscular dystrophy (DMD) is typically due to frameshifting mutations in the DMD gene encoding dystrophin. Loss of dystrophin protein results in progressive muscle degeneration and premature death. Approximately 60% of DMD patients have frameshifting mutations in a hotspot region within exons 45-55 in the rod domain of dystrophin. Genotype/phenotype assessments have revealed that in-frame deletion of exons 45-55 leads to the milder, allelic disease, Becker muscular dystrophy. This finding suggests that restoration of the reading frame by targeting exons 45-55 could treat ~60% of DMD patients to greatly reduce disease severity. We have developed a platform using clustered regularly interspaced short palindromic repeats (CRISPR) and- associated protein (Cas9) gene editing to achieve this purpose. We have utilized CRISPR/Cas9-mediated deletion and rejoining of up to 725kb to restore the reading frame in DMD human induced pluripotent stem cells (hiPSCs). This is the largest deletion shown to date in DMD. Clonal hiPSC lines containing the exon 45-55 deletion were differentiated to disease relevant types, such as cardiomyocytes and skeletal muscle myotubes, which had restored dystrophin protein. We demonstrated, for the first time, that the internally deleted dystrophin generated by CRISPR/Cas9 was functional and improved membrane integrity, reduced miR31 expression, and restored the dystrophin glycoprotein complex in vitro and after engraftment of skeletal muscle cells in vivo. This gene editing platform restores the reading frame for the majority of DMD patients and offers potential as an ex vivo correction for stem cell therapy or for use in vivo.

AAV9-mediated gene transfer of desmin ameliorates cardiomyopathy in desmin-deficient mice.

Mutations of the human desmin (DES) gene cause autosomal dominant and recessive myopathies affecting skeletal and cardiac muscle tissue. Desmin knockout mice (DES-KO), which develop progressive myopathy and cardiomyopathy, mirror rare human recessive desminopathies in which mutations on both DES alleles lead to a complete ablation of desmin protein expression. Here, we investigated whether an adeno-associated virus-mediated gene transfer of wild-type desmin cDNA (AAV-DES) attenuates cardiomyopathy in these mice. Our approach leads to a partial reconstitution of desmin protein expression and the de novo formation of the extrasarcomeric desmin–syncoilin network in cardiomyocytes of treated animals. This finding was accompanied by reduced fibrosis and heart weights and improved systolic left-ventricular function when compared with control vector-treated DES-KO mice. Since the re-expression of desmin protein in cardiomyocytes of DES-KO mice restores the extrasarcomeric desmin–syncoilin cytoskeleton, attenuates the degree of cardiac hypertrophy and fibrosis, and improves contractile function, AAV-mediated desmin gene transfer may be a novel and promising therapeutic approach for patients with cardiomyopathy due to the complete lack of desmin protein expression.

Assessment of developmental cardiotoxic effects of some commonly used phytochemicals in mouse embryonic D3 stem cell differentiation and chick embryonic cardiomyocyte micromass culture models.

Pregnant women often use herbal medicines to alleviate symptoms of pregnancy. The active phytochemicals eugenol (from holy basil) and α-bisabolol (from chamomile) are recommended to promote calmness and reduce stress. There is evidence that both eugenol and α-bisabolol possess pro-apoptotic and anti-proliferative effects and induce reactive oxygen species. The potential effect was examined by monitoring cardiomyocyte contractile activity (differentiation), cell activity, protein content and ROS production for mouse D3 embryonic stem cell and ‎chick embryonic micromass culture. The results showed that eugenol (0.01-80μM) demonstrated effects on cell activity (both systems) and ROS production (stem cell system only), as well as decreasing the contractile activity and protein content at high concentrations in both systems. Additionally, α-bisabolol (0.01-80μM) at high concentrations decreased the contractile activity and cell activity and in the stem cell system induced ROS production and decreased protein content. The results suggest only low concentrations should be ingested in pregnancy.‎.

The cardiomyocyte protein αT-catenin contributes to asthma through regulating pulmonary vein inflammation

Recent genome-wide association studies have identified single nucleotide polymorphisms in the gene encoding the protein αT-catenin (CTNNA3) that correlate with both steroid-resistant atopic asthma and asthmatic exacerbations. α-Catenins are important mediators of cell-cell adhesion, and αT-catenin is predominantly expressed in cardiomyocytes. In the lung αT-catenin appears to be exclusively expressed in cardiomyocytes surrounding the pulmonary veins (PVs), but its contribution to atopic asthma remains unknown. We sought to understand the role of αT-catenin in asthma pathogenesis. We used αT-catenin knockout mice and a house dust mite (HDM) extract model of atopic asthma, with assessment by means of forced oscillation, bronchoalveolar lavage, and histologic analysis. We found that the genetic loss of αT-catenin in mice largely attenuated HDM-induced airway inflammation and airway hyperresponsiveness to methacholine. Mice lacking αT-catenin that were exposed to HDM extract had reduced PV inflammation, specifically near the large veins surrounded by cardiac cells. The proximity of the airways to PVs correlated with the severity of airway goblet cell metaplasia, suggesting that PVs can influence the inflammatory milieu of adjacent airways. Loss of αT-catenin led to compensatory upregulation of αE-catenin, which itself has a defined anti-inflammatory function. These data mechanistically support previous clinical and genetic associations between αT-catenin and the development of atopic asthma and suggest that PVs might have an underappreciated role in allergic airway inflammation.

The fibrosis-cell death axis in heart failure

Cardiac stress can induce morphological, structural and functional changes of the heart, referred to as cardiac remodeling. Myocardial infarction or sustained overload as a result of pathological causes such as hypertension or valve insufficiency may result in progressive remodeling and finally lead to heart failure (HF). Whereas pathological and physiological (exercise, pregnancy) overload both stimulate cardiomyocyte growth (hypertrophy), only pathological remodeling is characterized by increased deposition of extracellular matrix proteins, termed fibrosis, and loss of cardiomyocytes by necrosis, apoptosis and/or phagocytosis. HF is strongly associated with age, and cardiomyocyte loss and fibrosis are typical signs of the aging heart. Fibrosis results in stiffening of the heart, conductivity problems and reduced oxygen diffusion, and is associated with diminished ventricular function and arrhythmias. As a consequence, the workload of cardiomyocytes in the fibrotic heart is further augmented, whereas the physiological environment is becoming less favorable. This causes additional cardiomyocyte death and replacement of lost cardiomyocytes by fibrotic material, generating a vicious cycle of further decline of cardiac function. Breaking this fibrosis-cell death axis could halt further pathological and age-related cardiac regression and potentially reverse remodeling. In this review, we will describe the interaction between cardiac fibrosis, cardiomyocyte hypertrophy and cell death, and discuss potential strategies for tackling progressive cardiac remodeling and HF.

Maturation Towards Pure β-Myosin Protein Expression and Corresponding Functional Properties of Individual hESC-Cardiomyocytes

Human embryonic stem cell derived cardiomyocytes (hESC-CMs) represent a powerful tool for analyzing pathogenesis of cardiac diseases such as hypertrophic or dilative cardiomyopathies. Several studies revealed an immature state of CMs after differentiation from pluripotent stem cells. This immature state is indicated, for example, by the high expression level of the fast atrial cardiac myosin heavy chain (α-MyHC). In human ventricular cardiomyocytes, however, the slow β-MyHC predominates.Here we show maturation of hESC-CMs towards exclusive expression of β-MyHC protein in individual cardiomyocytes and their functional characterization.After growing hESC-CMs in cardiac bodies vs. plated on laminin-coated coverslips, myosin heavy chain isoform was determined using a specific antibody against ventricular β-MyHC and a newly generated anti-atrial α-MyHC-specific antibody. A single-cell mapping technique was established to relate functional characteristics of individual cardiomyocytes to their expression of α- vs. β-MyHC-protein isoforms.Cardiomyocytes grown in cardiac bodies for a maximum of 110 days mostly contained a mixture of α- and β-MyHC. Only a minority of about 10% of cardiomyocytes expressed β-MyHC exclusively. However, cardiomyocytes plated on laminin-coated coverslips shifted MyHC-expression towards 66% and 87% of all cardiomyocytes expressing exclusively β-MyHC after 35 and 75 days, respectively. This isoform switch was accompanied by morphological changes towards more elongated cardiomyocytes with highly organized sarcomeres. Surprisingly, twitch kinetics and calcium transients were found unaffected by the MyHC-isoform in the sarcomeres while cardiomyocytes grown on laminin-coated coverslips in general displayed faster twitch kinetics and calcium transients.We conclude that cultivating conditions of hESC-CMs during maturation severely affect sarcomeric protein isoform expression in individual cardiomyocytes up to pure β-MyHC expression, thus changing the functional phenotype of the CMs, which is crucial for tissue engineering and cardiac disease models with functional assessment up to single cell level.