Cardiac-specific Gene Expression Research Articles

Trisomy 21 Alters Cell Proliferation and Migration of iPSC-Derived Cardiomyocytes on Type VI Collagen.

Individuals with Down syndrome (DS) are 2000 times more likely to develop a congenital heart defect (CHD) than the typical population Freeman et al. in Am J Med Genet 80:213-217 (1998). The majority of CHDs in individuals with DS characteristically involve the atrioventricular (AV) canal, including the valves and the atrial or ventricular septum. Type VI collagen (COLVI) is the primary structural component in the developing septa and endocardial cushions, with two of the three genes encoding for COLVI located on human chromosome 21 and upregulated in Down syndrome (von Kaisenberg et al. in Obstet Gynecol 91:319-323, 1998; Gittenberger-De Groot et al. in Anatom Rec Part A 275:1109-1116, 2023). To investigate the effect of COLVI dosage on cardiomyocytes with trisomy 21, induced pluripotent stem cells (iPSC) from individuals with DS and age- and sex-matched controls were differentiated into cardiomyocytes (iPSC-CM) and plated on varying concentrations of COLVI. Real time quantitative PCR showed decreased expression of cardiac-specific genes of DS iPSC-CM lines compared to control iPSC-CM. As expected, DS iPSC-CM had increased expression of genes on chromosome 21, including COL6A1, COL6A2, as well as genes not located on chromosome 21, namely COL6A3, HAS2 and HYAL2. We found that higher concentrations of COLVI result in decreased proliferation and migration of DS iPSC-CM, but not control iPSC-CM. These results suggest that the increased expression of COLVI in DS may result in lower migration-driven elongation of endocardial cushions stemming from lower cell proliferation and migration, possibly contributing to the high incidence of CHD in the DS population. The online version contains supplementary material available at 10.1007/s12195-023-00791-x.

Implications of deltamethrin on hematology, cardiac pathology, and gene expression in Nile tilapia (Oreochromis niloticus) and its possible amelioration with Shatavari (Asparagus racemosus).

Deltamethrin (DM) is one of the extensively used pyrethroids for controlling ectoparasites. Unfortunately, DM is highly toxic to fish as it primarily targets the sodium channels of the plasma membrane thereby affecting their cardiac and nervous systems. The present study investigated the protective efficacy of Shatavari (Asparagus racemosus) against DM-induced cardiotoxicity in Nile tilapia (Oreochromis niloticus). The fish were segregated into nine groups having 36 fish/group maintained in triplicates exposed to DM (1µg/L) and fed with a diet containing three different concentrations (10g, 20g, and 30g/kg feed) of aqueous extract of A. racemosus (ARE) for 21 days. DM caused significant alterations in the blood and serum parameters, and expression of cardiac and apoptotic genes compared to the control group. The ARE cotreatment significantly reduced the increase in serum transaminases, creatine kinase, and lactate dehydrogenase levels induced by DM. ARE facilitated the regain of electrolyte (sodium, potassium, chloride) homeostasis and antioxidants such as catalase, superoxide dismutase, glutathione peroxidase, and glutathione in DM-exposed fish. The cardiac histology exhibited loose separation of the cardiomyocytes and myofibrillar loss in the DM group which was ameliorated in the DM-ARE cotreatment group. Significant modulations were observed in the expression of cardiac-specific genes (gata4, myh6, tnT, cox1) and apoptosis signaling genes and proteins (HSP70, bax, bcl-2, caspase3), in the cotreatment group compared to the DM-exposed group. The current study suggests that ARE possesses potential cardioprotective properties that are effective in mitigating the toxic effects induced by DM via ameliorating oxidative stress, electrolyte imbalance, and apoptosis in tilapia.

Expression of human cardiac-specific genes: a novel method for post-mortem interval estimation.

In legal medicine, the determination of post-mortem interval (PMI) is not only an important but also one of the most difficult aspects. Several methods are used to estimate PMI such as physicochemical, entomological, biochemical, metabolic, autolytic, and physical methods. These methods provide a wide range of PMI as they are affected by different factors. The approach behind the present study is to calculate an accurate PMI by using mRNA degradation and fold change expression (FCE) of cardiac-specific genes viz. N-terminal pro-B-type natriuretic peptide (NPPB) and cardiac troponin I (TNNI3). Seventeen cadaver heart tissues were analysed within a time frame of up to 12 hours from the time since death, at different time intervals at room temperature. Gene expression was determined and the data were analysed using the value of average delta Ct (ΔCt) value of the assessed gene and housekeeping gene. Delta delta Ct (ΔΔCt) method was used to calculate the FCE at the different 7-time groups. The FCE of TNNI3 was almost stable till 15 hours of PMI and then after 15 hours, expression shows a decrease up to 24 hours after death; whereas, NPPB shows that FCE was stable till 12 hours of PMI and then after 12 hours, expression shows a decrease up to 24 hours after death. The FCE of NPPB and TNNI3 was almost stable till 12 hours. Thus, the estimation of PMI by analysis of the FCE of cardiac-specific genes can be a new promising method in forensic medicine.

Wnt signaling pathway inhibitor promotes mesenchymal stem cells differentiation into cardiac progenitor cells in vitro and improves cardiomyopathy in vivo.

Cardiovascular diseases particularly myocardial infarction (MI) are the leading cause of mortality and morbidity around the globe. As cardiac tissue possesses very limited regeneration potential, therefore use of a potent small molecule, inhibitor Wnt production-4 (IWP-4) for stem cell differentiation into cardiomyocytes could be a promising approach for cardiac regeneration. Wnt pathway inhibitors may help stem cells in their fate determination towards cardiomyogenic lineage and provide better homing and survival of cells in vivo. Mesenchymal stem cells (MSCs) derived from the human umbilical cord have the potential to regenerate cardiac tissue, as they are easy to isolate and possess multilineage differentiation capability. IWP-4 may promote the differentiation of MSCs into the cardiac lineage. To evaluate the cardiac differentiation ability of IWP-4 and its subsequent in vivo effects. Umbilical cord tissue of human origin was utilized to isolate the MSCs which were characterized by their morphology, immunophenotyping of surface markers specific to MSCs, as well as by tri-lineage differentiation capability. Cytotoxicity analysis was performed to identify the optimal concentration of IWP-4. MSCs were treated with 5 μM IWP-4 at two different time intervals. Differentiation of MSCs into cardiomyocytes was evaluated at DNA and protein levels. The MI rat model was developed. IWP-4 treated as well as untreated MSCs were implanted in the MI model, then the cardiac function was analyzed via echocardiography. MSCs were labeled with 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate (DiI) dye for tracking, while the regeneration of infarcted myocardium was examined by histology and immunohistochemistry. MSCs were isolated and characterized. Cytotoxicity analysis showed that IWP-4 was non-cytotoxic at 5 μM concentration. Cardiac specific gene and protein expression analyses exhibited more remarkable results in fourteen days treated group that was eventually selected for in vivo transplantation. Cardiac function was restored in the IWP-4 treated group in comparison to the MI group. Immunohistochemical analysis confirmed the homing of pre-differentiated MSCs that were labeled with DiI cell labeling dye. Histological analysis confirmed the significant reduction in fibrotic area, and improved left ventricular wall thickness in IWP-4 treated MSC group. Treatment of MSCs with IWP-4 inhibits Wnt pathway and promotes cardiac differentiation. These pre-conditioned MSCs transplanted in vivo improved cardiac function by cell homing, survival, and differentiation at the infarcted region, increased left ventricular wall thickness, and reduced infarct size.

An efficient human stem cells derived cardiotoxicity testing platform for testing oncotherapeutic analogues of quercetin and cinnamic acid.

Oncotherapeutics research is progressing at a rapid pace, however, not many drugs complete the successful clinical trial because of severe off-target toxicity to cardiomyocytes which ultimately leads to cardiac dysfunction. It is thus important to emphasize the need for early testing for possible cardiotoxicity of emerging oncotherapeutics. In this study, we assessed a novel stem cell-derived cardiac model for testing for cardiotoxicity of novel oncotherapeutics. We evaluated the cardiotoxic effect of synthesized derivatives of oncotherapeutics, quercetin (QMJ-2, -5, and -6) and cinnamic acid (NMJ-1, -2, and -3) using human Wharton's jelly mesenchymal stem cells-derived cardiomyocytes (WJCM) against known cardiotoxic oncologic drugs, doxorubicin, 5-fluorouracil, cisplatin. QMJ-6, NMJ-2, and NMJ-3 were not cardiotoxic and had minimum cardiac side effects. They did not show any effect on cardiomyocyte viability, caused low LDH release, and intracellular ROS production kept the calcium flux minimal and protected the active mitochondrial status in cardiomyocytes. They persevered cardiac-specific gene expression as well. However, compounds QMJ-2, QMJ-5, and NMJ-1 were cardiotoxic and the concentration needs to be reduced to prevent toxic effects on cardiomyocytes. Significantly, we were able to demonstrate that WJCM is an efficient cardiac testing model to analyze the cardiotoxicity of drugs in a human context.

Embryonic cardio-respiratory impairments in rainbow trout (Oncorhynchus mykiss) following exposure to hydraulic fracturing flowback and produced water

During hydraulic fracturing, wastewaters - termed flowback and produced water (FPW) - are created as a by-product during hydrocarbon extraction. Given the large volumes of FPW that a single well can produce, and the history of FPW release to surface water bodies, it is imperative to understand the hazards that hydraulic fracturing and FPW pose to aquatic biota. Using rainbow trout embryos as model organisms, we investigated impacts to cardio-respiratory system development and function following acute (48 h) and sub-chronic (28-day) FPW exposure by examining occurrences of developmental deformities, rates of embryonic respiration (MO2), and changes in expression of critical cardiac-specific genes. FPW-exposed embryos had significantly increased rates of pericardial edema, yolk-sac edema, and tail/trunk curvatures at hatch. Furthermore, when exposed at three days post-fertilization (dpf), acute 5% FPW exposures significantly increased embryonic MO2 through development until 15 dpf, where a switch to significantly reduced MO2 rates was subsequently recorded. A similar trend was observed during sub-chronic 1% FPW exposures. Interestingly, at certain specific developmental timepoints, previous salinity exposure seemed to affect embryonic MO2; a result not previously observed. Following acute FPW exposures, embryonic genes for cardiac development and function were significantly altered, although at termination of sub-chronic exposures, significant changes to these same genes were not found. Together, our evidence of induced developmental deformities, modified embryonic MO2, and altered cardiac transcript expression suggest that cardio-respiratory tissues are toxicologically targeted following FPW exposure in developing rainbow trout. These results may be helpful to regulatory bodies when developing hazard identification and risk management protocols concerning hydraulic fracturing activities.

Effects of macrophages on the proliferation and cardiac differentiation of human induced pluripotent stem cells

BackgroundMacrophage phenotypes switch from proinflammatory (M1) to anti-inflammatory (M2) following myocardial injury. Implanted stem cells (e.g., induced pluripotent stem cells (iPSCs)) for cardiomyogenesis will inevitably contact the inflammatory environment at the myocardial infarction site. To understand how the macrophages affect the behavior of iPSCs, therefore, improve the therapeutic efficacy, we generated three macrophage subtypes and assessed their effects on the proliferation, cardiac differentiation, and maturation of iPSCs.MethodsM0, M1, and M2 macrophages were polarized using cytokines, and their properties were confirmed by the expression of specific markers using reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and immunofluorescence. The effects of macrophages on iPSCs were studied using Transwell co-culture models. The proliferative ability of iPSCs was investigated by cell counting and CCK-8 assays. The cardiac differentiation ability of iPSCs was determined by the cardiomyocyte (CM) yield. The maturation of CM was analyzed by the expression of cardiac-specific genes using RT-qPCR, the sarcomere organization using immunofluorescence, and the mitochondrial function using oxidative respiration analysis.ResultsThe data showed that the co-culture of iPSCs with M0, M1, or M2 macrophages significantly decreased iPSCs’ proliferative ability. M2 macrophages did not affect the CM yield during the cardiac differentiation of iPSCs. Still, they promoted the maturation of CM by improving sarcomeric structures, increasing contractile- and ion transport-associated gene expression, and enhancing mitochondrial respiration. M0 macrophages did not significantly affect the cardiomyogenesis ability of iPSCs during co-culture. In contrast, co-culture with M1 macrophages significantly reduced the cardiac differentiation and maturation of iPSCs.ConclusionsM1- or M2-polarized macrophages play critical roles in the proliferation, cardiac differentiation, and maturation of iPSCs, providing knowledge to improve the outcomes of stem cell regeneration therapy.Ek74ekwDSfp11RpYeRrwHZVideo abstract

Three-dimensional cardiac organoid formation accelerates the functional maturation of human induced pluripotent stem cell-derived cardiomyocytes

Human induced pluripotent stem cell (hiPSC)-derived cardiomyocytes (CMs) offer a promising source for heart regeneration, disease modeling, and drug screening. Recent developments in organoid technology have made it possible to study how hiPSC-derived CMs interact together, and this culture system mimics the tissue environment and behavior of the cardiac cells in our body. However, the similarities and differences between conventional 2-dimensional (2D) culture and 3-dimensional (3D) organoid culture systems for CM differentiation have been incompletely elucidated. To study how the individual microenvironment formed by each culture system affects the properties of CMs differentiated from hiPSCs, we conducted a comparative study between 2D monolayer and direct 3D cardiac organoid (hiCO) differentiation from hiPSCs throughout the sequential differentiation stages. Although identical differentiation cues were applied to hiPSCs, the 3D differentiation system strongly exhibited higher mesoderm commitment and cardiac induction than 2D monolayer differentiation. In the late stage of differentiation, the 3D hiCOs showed a higher frequency of a mature myofibrillar isoform switching in sarcomere structure of differentiated CMs than was observed in monolayer culture, although over 94% of cardiac troponin T-positive cells resulted at the end point of differentiation in both systems. Furthermore, the accelerated structural maturation in 3D hiCOs resulted in increased expression of cardiac-specific ion channel genes and Ca2+ transient properties, with a high signal amplitude and rapid contractility. The present study provides details surrounding the 2D and 3D culture methods for CM differentiation from iPSCs, and focuses on 3D cell culture as an improved strategy for approaching and applying cardiac maturation.

In vitro Assessment of Cardiac Reprogramming by Measuring Cardiac Specific Calcium Flux with a GCaMP3 Reporter.

Cardiac reprogramming has become a potentially promising therapy to repair a damaged heart. By introducing multiple transcription factors, including Mef2c, Gata4, Tbx5 (MGT), fibroblasts can be reprogrammed into induced cardiomyocytes (iCMs). These iCMs, when generated in situ in an infarcted heart, integrate electrically and mechanically with the surrounding myocardium, leading to a reduction in scar size and an improvement in heart function. Because of the relatively low reprogramming efficiency, purity, and quality of the iCMs, characterization of iCMs remains a challenge. The currently used methods in this field, including flow cytometry, immunocytochemistry, and qPCR, mainly focus on cardiac-specific gene and protein expression but not on the functional maturation of iCMs. Triggered by action potentials, the opening of voltage-gated calcium channels in cardiomyocytes leads to a rapid influx of calcium into the cell. Therefore, quantifying the rate of calcium influx is a promising method to evaluate cardiomyocyte function. Here, the protocol introduces a method to evaluate iCM function by calcium (Ca2+) flux. An αMHC-Cre/Rosa26A-Flox-Stop-Flox-GCaMP3 mouse strain was established by crossing Tg(Myh6-cre)1Jmk/J (referred to as Myh6-Cre below) with Gt(ROSA)26Sortm38(CAG-GCaMP3)Hze/J (referred to as Rosa26A-Flox-Stop-Flox-GCaMP3 below) mice. Neonatal cardiac fibroblasts (NCFs) from P0-P2 neonatal mice were isolated and cultured in vitro, and a polycistronic construction of MGT was introduced to NCFs, which led to their reprogramming to iCMs. Because only successfully reprogrammed iCMs will express GCaMP3 reporter, the functional maturation of iCMs can be visually assessed by Ca2+ flux with fluorescence microscopy. Compared with un-reprogrammed NCFs, NCF-iCMs showed significant calcium transient flux and spontaneous contraction, similar to CMs. This protocol describes in detail the mouse strain establishment, isolation and selection of neonatal mice hearts, NCF isolation, production of retrovirus for cardiac reprogramming, iCM induction, the evaluation of iCM Ca2+ flux using our reporter line, and related statistical analysis and data presentation. It is expected that the methods described here will provide a valuable platform to assess the functional maturation of iCMs for cardiac reprogramming studies.

In Vivo Cardiac-specific Expression of Adenylyl Cyclase 4 Gene Protects against Klotho Deficiency-induced Heart Failure

Klotho is an aging-suppressor gene. Klotho gene deficiency causes heart failure in Klotho-hypomorphic mutant (KL (-/-)) mice. RNA-seq and western blot analysis showed that adenylyl cyclase type IV (AC4) mRNA and protein expression was largely decreased in cardiomyocytes of KL (-/-) mice. The objective of this study was to investigate whether in vivo cardiac-specific expression of AC4 gene protects against Klotho deficiency-induced heart failure. Interestingly, in vivo AAV-based cardiac-specific AC4 gene expression increased left ventricular fractional shortening, ejection fraction, stroke volume, and left ventricular end-diastolic volume in KL (-/-) mice, suggesting that cardiac-specific AC4 gene expression improves Klotho deficiency-induced heart dysfunction. Cardiac-specific AC4 gene expression also decreased Klotho deficiency-induced cardiac hypertrophy. Cardiac-specific AC4 gene expression alleviated Klotho deficiency-induced cardiac fibrosis and calcification. Furthermore, cardiac-specific AC4 gene expression attenuated mitochondrial dysfunction, superoxide accumulation and cardiomyocyte apoptotic cell death. Thus, downregulation of AC4 may contribute to Klotho deficiency-induced heart failure. Mechanistically, AAV2/9-αMHC-AC4 increased cardiomyocytic cAMP levels and thus regulated the PKA-PLN-SERCA2 signal pathway, which is critical in modulating calcium flux and mitochondrial function. In conclusion, cardiac-specific AC4 gene expression protects against Klotho deficiency-induced heart failure through increasing cardiomyocytic cAMP levels, which alleviates cAMP-dependent mitochondrial dysfunction, superoxide accumulation and apoptotic cell death. AC4 regulates superoxide levels via the cAMP-PKA pathway. AC4 could be a potential therapeutic target for heart failure associated with Klotho deficiency. Heart failure is the major cause of mortality in patients with chronic kidney disease (CKD). A decrease in Klotho levels is linked to CKD.

Abstract 10183: Augmentation of Cardiac Micrornas Enhanced Cardiac Mesenchymal Cell Differentiation Into Cardiomyocyte Like Cells

Introduction: Infusion of cardiac mesenchymal cells (CMCs) showed improved cardiac function in myocardial infarction models. Cell based therapy to treat cardiac injuries have shown modest success due to limitations, including poor retention and differentiation. Current studies are focused to improve engraftment and differentiation potential of the therapeutic cells. Here, we used cardiac miRNAs in CMCs to increase their differentiation potential towards cardiac lineage. Hypothesis: Increased expression of cardiac miRNAs in CMCs could allow them to differentiate into cardiomyocyte like cells. Methods: Mouse CMCs were isolated from the adult mouse heart and analyzed for the expression of cardiac miRNAs. The CMCs were transiently transfected with cardiac miRNAs cocktail (miR-1, miR-133, miR-208 and miR-499) and cultured for 48h. (n=3) The potential miRNAs targets such as HDAC4 (miR-1), Snail-1 (miR-133), myostatin (miR-208) and Sox6 (miR-499) were analyzed using western blot and immunostaining. The miRNAs cocktail transfected CMCs were cultured for 7 days and analyzed for the expression of cardiac specific genes with RT-PCR. (n=3) Results: Quantitative PCR analysis showed that the cardiac miRNAs were either less or not expressed in CMCs, whereas transient transfection significantly elevated them. Western blot analysis showed significant downregulation of cardiac miRNAs targets HDAC4 (0.62±0.06), Snail1 (0.61±0.03), Sox6 (0.75±0.01) and Myostatin (0.3±0.04). Immunostaining confirmed significant reduction of these target proteins. Cardiac miRNAs cocktail transfected CMCs showed significantly increased expression of cardiac specific genes such as mef2c (3.87±1.54), Gata4 (3.73±1.07), Tnni3 (3.31±1.01), Nkx2.5 (3.89±0.37) Actc1 (4.27±1.57), Tnnt2 (2.49±1.12) and Cx40 (2.37±0.61). The expression of fibroblast markers such as Col1a and Thy1 were reduced upon enriching the cardiac miRNAs in the CMCs. Conclusions: Our results demonstrate that enrichment of cardiac miRNAs in CMCs increase their differentiation into cardiomyocyte lineage, which could improve their therapeutic efficacy. Further in vivo experiments would reveal functional benefits from these improved CMCs for clinical use.

Nitro-Oleic Acid Inhibits Stemness Maintenance and Enhances Neural Differentiation of Mouse Embryonic Stem Cells via STAT3 Signaling.

Nitro-oleic acid (NO2-OA), pluripotent cell-signaling mediator, was recently described as a modulator of the signal transducer and activator of transcription 3 (STAT3) activity. In our study, we discovered new aspects of NO2-OA involvement in the regulation of stem cell pluripotency and differentiation. Murine embryonic stem cells (mESC) or mESC-derived embryoid bodies (EBs) were exposed to NO2-OA or oleic acid (OA) for selected time periods. Our results showed that NO2-OA but not OA caused the loss of pluripotency of mESC cultivated in leukemia inhibitory factor (LIF) rich medium via the decrease of pluripotency markers (NANOG, sex-determining region Y-box 1 transcription factor (SOX2), and octamer-binding transcription factor 4 (OCT4)). The effects of NO2-OA on mESC correlated with reduced phosphorylation of STAT3. Subsequent differentiation led to an increase of the ectodermal marker orthodenticle homolog 2 (Otx2). Similarly, treatment of mESC-derived EBs by NO2-OA resulted in the up-regulation of both neural markers Nestin and β-Tubulin class III (Tubb3). Interestingly, the expression of cardiac-specific genes and beating of EBs were significantly decreased. In conclusion, NO2-OA is able to modulate pluripotency of mESC via the regulation of STAT3 phosphorylation. Further, it attenuates cardiac differentiation on the one hand, and on the other hand, it directs mESC into neural fate.

Ectopic expression of Id1 or Id3 inhibits transcription of the GATA-4 gene in P19CL6 cells under differentiation condition.

Inhibitor of DNA binding (Id) is a dominant negative form of the E-box binding basic-helix-loop-helix (bHLH) transcription factor since it is devoid of the basic region required for DNA binding and forms an inactive hetero dimer with bHLH proteins. The E-box sequence located in the promoter region of the GATA-binding protein 4 (GATA-4) gene is essential for transcriptional activation in P19CL6 cells. These cells differentiate into cardiomyocytes and start to express GATA-4, which further triggers cardiac-specific gene expression. In this study, expression plasmids for Ids tagged with human influenza hemagglutinin (HA)-FLAG were constructed and introduced into P19CL6 cells. The stable clones expressing the recombinant Id proteins (Id1 or Id3) were isolated. The GATA-4 gene expression in these clones under differentiation condition in the presence of 1% dimethyl sulfoxide (DMSO) was repressed, with concomitant abolishment of the transcription of α-myosin heavy chain (α-MHC), which is a component of cardiac myofibrils. Thus, the increased expression of Id protein could affect GATA-4 gene expression and negatively regulate the differentiation of P19CL6 cells.

Effects of bisphenol A exposure during cardiac cell differentiation

Heart development requires a precise temporal regulation of gene expression in cardiomyoblasts. Therefore, the transcriptional changes in differentiating cells can lead to congenital heart diseases. Although the genetic mutations underlie most of these alterations, exposure to environmental contaminants, such as bisphenol A (BPA), has been recently considered as a risk factor as well. In this study we investigated the genotoxic and epigenotoxic effects of BPA throughout cardiomyocyte differentiation. H9c2 cells (rat myoblasts) were exposed to 10 and 30 μM BPA before and during the last two days of cardiac-driven differentiation. Then, we have analysed the phenotypic and molecular modifications (at transcriptional, genetic and epigenetic level). The results showed that treated myoblasts developed a skeletal muscle cell-like phenotype. The transcriptional changes induced by BPA in genes codifying proteins involved in heart differentiation and function depend on the window of exposure to BPA. The exposure before differentiation repressed the expression of heart transcription factors (Hand2 and Gata4), whereas exposure during differentiation reduced the expression of cardiac-specific genes (Tnnt2, Myom2, Sln, and Atp2a1). Additionally, significant effects were observed regarding DNA damage and histone acetylation levels after the two periods of BPA exposure: in cells exposed to the toxicant the percentage of DNA repair foci (formed by the co-localization of γH2AX and 53BP1) increased in a dose-dependent manner, whereas the treatment with the toxicant triggered a decrease in the epigenetic marks H3K9ac and H3K27ac. Our in vitro results reveal that BPA seriously interferes with the process of cardiomyocyte differentiation, which could be related to the reported in vivo effects of this toxicant on cardiogenesis.

In Vivo Cardiac‐specific Adenylyl Cyclase 4 gene delivery protects against Klotho deficiency‐induced heart failure

Background and Objective Heart failure is the leading cause of death in the world. Adenylyl cyclase, that catalyzes the formation of cAMP from ATP, regulates many aspects of cardiac physiology and pathology. Klotho deficiency causes heart failure in Kotho-hypomorphic mutant (KL (-/-)) mice. The objective of this study was to investigate whether in vivo cardiac-specific adenylyl cyclase type 4 (AC4) gene expression protects against Klotho deficiency- induced heart failure. Methods and Results We found that Klotho deficiency-induced heart failure was accompanied by AC4 reduction. Next, we constructed a rAAV vector in which the truncated αMHC promoter drives the expression of AC4 (AAV2/9-αMHC-AC4). The AAV viral particles were then administered intravenously via the tail vein and the mice were sacrificed at 7 weeks after gene delivery. Interestingly, cardiac-specific AC4 gene delivery increased left ventricular fractional shortening, ejection fraction, stroke volume, and left ventricular end-diastolic volume, suggesting that cardiac-specific AC4 gene delivery protected against Klotho deficiency-induced heart dysfunction. Meanwhile, cardiac-specific AC4 gene delivery also decreased heart weight to body weight ratio and cardiomyocyte cross-section area, suggesting that cardiac-specific AC4 gene expression protected against Klotho deficiency-induced cardiac hypertrophy. Cardiac-specific AC4 gene delivery also alleviated Klotho deficiency-induced cardiac fibrosis and calcification. Furthermore, cardiac-specific AC4 gene delivery attenuated cardiomyocyte apoptotic cell death and mitochondrial dysfunction. Mechanistically, AAV2/9-αMHC-AC4 increased cardiomyocytic cAMP levels and so regulated PKA-PLN-SERCA2 signal pathway, which are critical in modulating calcium flux, mitochondrial function. Conclusion Cardiac-specific AC4 gene delivery protected against Klotho deficiency-induced heart failure through increasing cardiomyocytic cAMP levels, which alleviated PKA-dependent mitochondrial dysfunction and apoptotic cell death. AC4 could be a potential therapeutic target for heart failure associated with Klotho deficiency in aging or chronic kidney disease.

Mechanical stretch promotes antioxidant responses and cardiomyogenic differentiation in P19 cells

Accumulating evidence has suggested that mechanical stimuli play a crucial role in regulating the lineage-specific differentiation of stem cells through fine-tuning redox balance. We aimed to investigate the effects of cyclic tensile strain (CTS) on the expression of antioxidant enzymes and cardiac-specific genes in P19 cells, a widely characterized tool for cardiac differentiation research. A stretching device was applied to generate different magnitude and duration of cyclic strains on P19 cells. The messenger RNA and protein levels of targeted genes were determined by real-time polymerase chain reaction and Western blot assays, respectively. Proper magnitude and duration of cognitivestimulationtherapy (CST) stimulation substantially enhanced the expression of both antioxidant enzymes and cardiac-specific genes in P19 cells. Sirtuin 1 (SIRT1) played an essential role in the CTS-induced cardiomyogenic differentiation of P19, as evidenced by changes in the expression of antioxidant enzymes and cardiac-specific genes. Mechanical loading promoted the cardiomyogenic differentiation of P19 cells. SIRT1 was involved in CST-mediated P19 differentiation, implying that SIRT1 might serve as an important target for developing methods to promote cardiomyogenic differentiation of stem cells.

Effects of miR-155 on High Glucose Induced-Cardiac Developmental Defects of Zebrafish Embryos

Background: Gestational diabetes mellitus (GDM) is known to have a teratogenic effect on heart development. Former studies determined that miR-155 is elevated in GDM patients. In the present study, we explored the potential role of miR-155 on high glucose-induced cardiac developmental defects. Methods: Serum miR-155 of GDM patients was determined by using ELISA. Fetal cardiac characteristics were collected by echocardiography. Zebrafish embryos were exposed to 2% D-Glucose in a fluctuating manner. The expression levels of miR-155, Ets1 and cardiac specific genes were evaluated by real-time PCR or western blot. Reactive oxygen species (ROS) were detected by DCFH-DA. Findings: High glucose exposure in zebrafish embryos altered the morphology of the heart, increased the expression of miR-155 and cardiac specific genes. Upregulation of miR-155 activated Igf1-Akt-Gsk3β pathway by targeting Ets1 and increased the production of ROS and may thereby exert teratogenic effect on cardiac development. Knockdown of miR-155 could rescue high glucose-induced zebrafish heart developmental defects. Besides, miR-155 levels are increased in serum from GDM patients and are correlated with fetal cardiac structural changes. Moreover, loss of miR-155 blocked Igf1 survival pathway and induced apoptosis and may thus cause zebrafish cardiac developmental defects. Interpretation: miR-155 is a key molecule for heart development and is involved in high glucose-induced cardiac malformation and it might be a novel biomarker as well as a potential drug target of high glucose-induced cardiac defects. Funding：This work was supported by grants from: (1) the Youth Program of National Natural Science Foundation (NSF)of China (81200125) to LY; (2) the Priority Academic Program Development (PAPD) and the Key Project of Natural Science Foundation of the Higher Education Institutions (17KJA310001) to LY; (3) the Six Talent Peaks Project (STPP) of Jiangsu Province (2015-WSN-032) to ZXT. Declaration of Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. Ethics Approval Statement: The studies involving human participants were reviewed and approved by Ethical Committee, Jiangsu province Hospital. The patients/participants provided their written informed consent to participate in this study. Zebrafish maintenance and procedures were conducted in accordance with the medical ethics committee of Nanjing Medical University. All experiments were approved by the medical ethics committee of Nanjing Medical University.

Abstract 15916: Role of Small-cajal Body Associated RNAs (scaRNAs) in Regulation of Cardiomyogenesis

Introduction: The requirement of non-coding RNAs particularly scaRNAs are playing a critical role in alternative splicing and maturation of mRNAs. Dysregulated splicing of mRNAs has been shown to cause heart defects. In this study, we are comparing the role of scaRNAs during differentiation of induced pluripotent stem cells (iPSCs) into cardiomyocytes (iCMCs) from normal individual and Noonan syndrome (NS) patient. We have selected NS patient cells because it is an autosomal dominant genetic disorder which leads to cardiomyopathy and congenital heart defects in humans. Hypothesis: We hypothesize that scaRNA1 and scaRNA20 have a significant role in the development of cardiomyocytes, and these scaRNAs are dysfunctional in iCMCs derived from NS. Methods and Results: We have compared the normal skin fibroblast-derived iPSCs (N-iPSCs) and N-iCMCs with NS patient-derived NS-iPSCs and NS-iCMCs using quantitative RT-PCR, Western blot and immunofluorescence analyses. We also used the knockdown and overexpression of scaRNA1 and scaRNA20 approaches to delineate the importance of these scaRNAs during cardiomyogenesis. Our qRT-PCR data showed a significantly lower expression of scaRNA1 and scaRNA20 (Fig. A) as well as the cardiac-specific genes CTT and GATA4 (Fig. B) in NS-iCMCs when compared to the normal iCMCs. Furthermore, the qRT-PCR data from the scaRNA20 overexpressed N-iCMC showed an increased expression of cardiac-specific genes (Fig. C) when compared to the N-iCMCs. These studies clearly indicate that scaRNA1 and scaRNA20 plays an important role in cardiomyogenesis. Further studies are underway to explore the mechanisms of these scaRNAs in regulation of cardiac genes. Conclusions: Our findings indicate that scaRNA1 and scaRNA20 are involved in mRNA splicing and maturation of cardiac genes. Moreover, these scaRNAs are dysfunctional in NS patient’s iCMCs and targeting these molecules will have a therapeutic potential for a patient with NS.

Effect of a dianthin G analogue in the differentiation of rat bone marrow mesenchymal stem cells into cardiomyocytes.

Loss of cardiomyocytes due to myocardial infarction results in ventricular remodeling which includes non-contractile scar formation, which can lead to heart failure. Stem cell therapy aims to replace the scar tissue with the functional myocardium. Mesenchymal stem cells (MSCs) are undifferentiated cells capable of self-renewal as well as differentiation into multiple lineages. MSCs can be differentiated into cardiomyocytes by treating them with small molecules and peptides. Here, we report for the first time, the role of a cyclic peptide, an analogue of dianthin G, [Glu2]-dianthin G (1) in the in vitro cardiac differentiation of rat bone marrow MSCs. In this study, [Glu2]-dianthin G (1) was synthesized using solid-phase total synthesis and characterized by NMR spectroscopy. MSCs were treated with two different concentrations (0.025 and 0.05mM) of the peptide separately for 72h and then incubated for 15days to allow the cells to differentiate into cardiomyocytes. Treated cells were analyzed for the expression of cardiac-specific genes and proteins. Results showed significant upregulation of cardiac-specific genes GATA4, cardiac troponin T (cTnT), cardiac troponin I (cTnI), cardiac myosin heavy chain, and connexin 43 in the treated MSCs compared to the untreated control. For cardiac-specific proteins, GATA4, cTnT, and Nkx2.5 were analyzed in the treated cells and were shown to have significant upregulation as compared to the untreated control. In conclusion, this study has demonstrated the cardiac differentiation potential of [Glu2]-dianthin G (1)-treated rat bone marrow MSCs in vitro both at the gene and at the protein levels. Transplantation of pre-differentiated MSCs into the infarcted myocardium may result in the efficient regeneration of cardiac cells and restoration of normal cardiac function.

Small molecule 2'-deoxycytidine differentiates human umbilical cord-derived MSCs into cardiac progenitors in vitro and their in vivo xeno-transplantation improves cardiac function.

Small molecules are widely used to induce stem cell differentiation. 2'-deoxycytidine (2-DC) belongs to the cytidine family. It stimulates the expression of cardiac-specific genes and proteins, and directs mesenchymal stem cells towards cardiomyogenic differentiation. We aim to investigate the role of 2-DC-treated human umbilical cord mesenchymal stem cells (UC-MSCs) into myogenic lineage and explore their application in regeneration of infarcted myocardium. UC-MSCs were treated with 5, 10, 20, and 40µM 2-DC following optimization by cytotoxicity analysis. Rat model of myocardial infarction (MI) was induced by ligating left anterior descending coronary artery. Normal, and 2-DC treated UC-MSCs were transplanted in the left ventricular wall immediately after ligation. Echocardiographic measurements were performed to assess cardiac function. Tissue architecture of the myocardium was examined by histological analysis to determine fate of the transplanted cells. MSCs were successfully isolated from human umbilical cord tissue. 2-DC treatment did not produce any significant cytotoxic effect in UC-MSCs at all concentrations. qPCR analysis of treated UC-MSCs showed induction of myogenic differentiation, which is more pronounced at 20μM concentration. Fluorescently labeled 2-DC-treated UC-MSCs showed significant (**P < 0.01) homing in the infarcted myocardium as compared to normal UC-MSCs. Hearts transplanted with 2-DC-treated UC-MSCs significantly (***P < 0.001) improved the cardiac systolic and diastolic functions and pumping ability as compared to normal UC-MSCs and MI groups. Fibrotic area and left ventricular wall thickness were significantly improved (***P < 0.001) in 2-DC-treated group as compared to normal UC-MSCs. Immunohistochemical staining showed co-localization of fluorescently labeled cells and patches of differentiated myocytes which were stained for cardiac proteins in the infarct zone implying that the treated UC-MSCs regenerated cardiomyocytes. We report for the first time that 2-DC induces cardiac differentiation in UC-MSCs. Transplanted cells differentiated into functional cardiomyocytes and significantly improved cardiac performance. These pre-differentiated cardiac progenitors showed better survival, homing, and distribution in the infarcted zone. 2-DC treated cells not only improved cardiac function, but also restored tissue homeostasis, suggesting a better therapeutic option for the regeneration of cardiac tissue in the clinical setup.