A calcium sensor in the sodium channel modulates cardiac excitability.

Sodium channels are principal molecular determinants responsible for myocardial conduction and maintenance of the cardiac rhythm. Calcium ions (Ca2+) have a fundamental role in the coupling of cardiac myocyte excitation and contraction, yet mechanisms whereby intracellular Ca2+ may directly modulate Na channel function have yet to be identified. Here we show that calmodulin (CaM), a ubiquitous Ca2+-sensing protein, binds to the carboxy-terminal 'IQ' domain of the human cardiac Na channel (hH1) in a Ca2+-dependent manner. This binding interaction significantly enhances slow inactivation-a channel-gating process linked to life-threatening idiopathic ventricular arrhythmias. Mutations targeted to the IQ domain disrupted CaM binding and eliminated Ca2+/CaM-dependent slow inactivation, whereas the gating effects of Ca2+/CaM were restored by intracellular application of a peptide modelled after the IQ domain. A naturally occurring mutation (A1924T) in the IQ domain altered hH1 function in a manner characteristic of the Brugada arrhythmia syndrome, but at the same time inhibited slow inactivation induced by Ca2+/CaM, yielding a clinically benign (arrhythmia free) phenotype.     

Human ES-cell-derived cardiomyocytes electrically couple and suppress arrhythmias in injured hearts

Transplantation studies in mice and rats have shown that human embryonic-stem-cell-derived cardiomyocytes (hESC-CMs) can improve the function of infarcted hearts, but two critical issues related to their electrophysiological behaviour in vivo remain unresolved. First, the risk of arrhythmias following hESC-CM transplantation in injured hearts has not been determined. Second, the electromechanical integration of hESC-CMs in injured hearts has not been demonstrated, so it is unclear whether these cells improve contractile function directly through addition of new force-generating units. Here we use a guinea-pig model to show that hESC-CM grafts in injured hearts protect against arrhythmias and can contract synchronously with host muscle. Injured hearts with hESC-CM grafts show improved mechanical function and a significantly reduced incidence of both spontaneous and induced ventricular tachycardia. To assess the activity of hESC-CM grafts in vivo, we transplanted hESC-CMs expressing the genetically encoded calcium sensor, GCaMP3 (refs 4, 5). By correlating the GCaMP3 fluorescent signal with the host ECG, we found that grafts in uninjured hearts have consistent 1:1 host–graft coupling. Grafts in injured hearts are more heterogeneous and typically include both coupled and uncoupled regions. Thus, human myocardial grafts meet physiological criteria for true heart regeneration, providing support for the continued development of hESC-based cardiac therapies for both mechanical and electrical repair.     

头孢曲松通过抑制Cx43磷酸化参与治疗创伤性颅脑损伤的机制

目的观察头孢曲松(CFX)通过调控与缝隙连接蛋白43(Cx43)表达在治疗创伤性颅脑损伤(TBI)的相关性机制。方法选取100只体重350～450g的4月龄的SD雄性大鼠,采用液压打击仪建立脑损伤模型,具体分组为:①假手术(sham)组、②治疗(TBI+CFX)治疗组、③甘珀酸(CBX)阻断(TBI+CFX+CBX)组、④溶媒(TBI+生理盐水)组及⑤损伤(TBI)组,每组20只。实验时间均设定为TBI后48 h。每组取10只大鼠进行行为学检测和脑组织含水量测定,另10只则获取海马区胶质组织通过蛋白免疫印记法(WB)法测定神经元缝隙连接蛋白40(Cx40)及磷酸化Cx43蛋白(p-Cx43)的变化、采用酶联免疫荧光(ELFA)检测神经元氧化应激因子NADPH氧化酶活性的变化。结果实验结果显示,采用CFX干预组神经损伤严重度评分(NSS)、脑水肿程度、腺嘌呤二核苷酸磷酸(NADPH)氧化酶活性及海马胶质细胞Cx40、p-Cx43表达均溶媒组及损伤组明显下降(P 0.05)。而CBX可明显抑制上述CFX对Cx40、p-Cx43蛋白表达下调及降低NADPH氧化酶的活性的作用(P0.05)。结论 CFX可能通过抑制Cx43蛋白磷酸化和Cx40蛋白异常增多,从而抑制氧化应激反应以达到脑损伤缓解作用。     

美洲大蠊提取物CⅡ-3对大鼠心律失常的保护作用

目的:研究美洲大蠊提取物CⅡ-3对乌头碱致大鼠心律失常的保护作用,并初步探讨其作用机制。方法:采用股静脉注射乌头碱诱发大鼠心律失常,观察CⅡ-3对乌头碱致VP、VT、VF、CA用量和VP、VT、VF、CA发生率及心律失常评分的影响,测定大鼠血清中CK和LDH的活性。结果:一定剂量的CⅡ-3可以提高乌头碱所致大鼠VP、VT、VF、CA的用量(P<0.05,0.01),能降低大鼠VT、VF、CA的发生率及大鼠心律失常评分,降低血清中CK的活性(P<0.05,0.01),但对LDH的活性影响甚小(P>0.05)。结论:CⅡ-3对乌头碱诱导的大鼠心律失常具有一定的保护作用。     

DBP介导Cx43对大鼠睾丸Leydig细胞睾酮合成的影响

目的观察邻苯二甲酸二丁酯(DBP)对成年大鼠睾丸Leydig细胞连接蛋白43(Cx43)及其引起睾酮分泌变化的影响,探讨DBP对睾酮(T)的调节是否与Cx43有关.方法将原代培养纯化的leydig细胞分为3组:50μg/mL DBP处理组,50μg/mL DBP+10μmol/L前列腺素E2(PGE2)组及DMSO处理组,分别同时处理细胞24h;采用细胞免疫荧光法检测细胞膜Cx43表达变化,Western印记法观察Cx43总蛋白量的变化,应用睾酮试剂盒测定睾酮值.结果与对照组相比,DBP处理24h后,Cx43表达与睾酮值均降低,差异具有统计学意义(P0.05);但加入Cx43增强剂(PGE2)组与DBP组相比,CX43表达明显恢复,但T值变化不明显(P0.05).结论DBP对睾酮及Cx43均有影响,但对Leydig细胞睾酮合成抑制作用并不一定是通过调节Cx43的表达来实现.     

补充白藜芦醇对大强度运动大鼠心肌损伤的保护作用

目的:探讨RES对大强度运动心肌过氧化损伤的保护作用.方法:在活动跑台上建立大强度运动模型,测试心肌各项过氧化损伤指标.结果:大强度运动可造成大鼠心肌MDA,TNOS,iNOS,NO显著升高,TSOD,CuZn-SOD,GSH-Px,cNOS,Na+,K+-ATPase,Ca2+-ATPase显著下降.补充RES可使大鼠运动后心肌MDA,TNOS,iNOS,NO下降,TSOD,CuZn-SOD,Mn-SOD,GSH-Px,cNOS,Na+,K+-ATPase,Ca2+-ATPase升高.结论:RES可增强心肌的抗氧化能力,保持心肌酶活性.提示RES对大强度运动后心肌过氧化损伤具有保护作用.     

Oestrogen protects FKBP12.6 null mice from cardiac hypertrophy

FK506 binding proteins 12 and 12.6 (FKBP12 and FKBP12.6) are intracellular receptors for the immunosuppressant drug FK506 (ref. 1). The skeletal muscle ryanodine receptor (RyR1) is isolated as a hetero-oligomer with FKBP12 (ref. 2), whereas the cardiac ryanodine receptor (RyR2) more selectively associates with FKBP12.6 (refs 3, 4, 5). FKBP12 modulates Ca2+ release from the sarcoplasmic reticulum in skeletal muscle and developmental cardiac defects have been reported in FKBP12-deficient mice, but the role of FKBP12.6 in cardiac excitation-contraction coupling remains unclear. Here we show that disruption of the FKBP12.6 gene in mice results in cardiac hypertrophy in male mice, but not in females. Female hearts are normal, despite the fact that male and female knockout mice display similar dysregulation of Ca2+ release, seen as increases in the amplitude and duration of Ca2+ sparks and calcium-induced calcium release gain. Female FKBP12.6-null mice treated with tamoxifen, an oestrogen receptor antagonist, develop cardiac hypertrophy similar to that of male mice. We conclude that FKBP12.6 modulates cardiac excitation-contraction coupling and that oestrogen plays a protective role in the hypertrophic response of the heart to Ca2+ dysregulation.     

Early association of electrocardiogram alteration with infarct size and cardiac function after myocardial infarction

OBJECTIVE: Myocardial infarction (MI) is the main cause of heart failure, but the relationship between the extent of MI and cardiac function has not been clearly determined. The present study was undertaken to investigate early changes in the electrocardiogram associated with infarct size and cardiac function after MI. METHODS: MI was induced by ligating the left anterior descending coronary artery in rats. Electrocardiograms, echocardiographs and hemodynamic parameters were assessed and myocardial infarct size was measured from mid-transverse sections stained with Masson's trichrome. RESULTS: The sum of pathological Q wave amplitudes was strongly correlated with myocardial infarct size (r = 0.920, P < 0.0001), left ventricular ejection fraction (r = -0.868, P < 0.0001) and left ventricular end diastolic pressure (r = 0.835, P < 0.0004). Furthermore, there was close relationship between MI size and cardiac function as assessed by left ventricular ejection fraction (r = -0.913, P < 0.0001) and left ventricular end diastolic pressure (r = 0.893, P < 0.0001). CONCLUSION: The sum of pathological Q wave amplitudes after MI can be used to estimate the extent of MI as well as cardiac function.     

Study on the effect of doxorubicin on expressions of genes encoding myocardial sarcoplasmic reticulum Ca^2＋ transport proteins and the effect of taurine on myocardial protection in rabbits

To investigate the effect of doxorubicin(DOX) on gene expression of the myocardial sarcoplasmic reticulum (SR)Ca^2 transport proteins and the mechanism of taurine(Tau) protecting cardiac muscle cells, 9 rabbits were injected with DOX , 8 rabbits with DOX and Tau, and 9 rabbits with normal saline. Cardiac function , concentration of calcium in cardiomyocytes ( Myo [ Ca^2 ]i ), activity of SR Ca^2 -ATPase (SERCA2a) , level of SERCA2a mRNA and Ca^2 released channels(RYR2) mRNA were detected. The left ventricle tissues were observed by electron microscopy. The results showed that cardiac index, left ventricular systolic pressure, activity of SR Ca^2 -ATPase and level of SERCA2a mRNA decreased , while Myo[ Ca^2 ]i increased in DOX-treated rabbits. DOX could not affect the level of RYR2 mRNA. Tau intervention could alleviate the increase of left ventricular diastolic pressure, Myo[ Ca^2 ] i and the decrease of SERCA2a mRNA induced by doxorubicin. Tile results suggested that downregulation of SERCA2a gene expression was an important mechanism of DOX-induced cardiomyopathy and that Tau could partially improve the heart function by reducing calcium overload and alleviating downregulation of SERCA2a mRNA.     

大鼠心肌缺血模型在环境毒理学中应用的探讨

结扎大鼠左冠状动脉的左室支,造成局部心肌缺血,大体标本活性体染色与光镜检查的结果相符合,均显示缺血中心区大部分心肌梗塞,变性;缺血损伤在导致心电图紊乱的同时,还使心肌组织的脂质过氧化产物丙二醛大量生成和自由基清除剂超氧化物歧化酶的活性显著下降;     

极化液对大鼠不同血糖浓度下心肌缺血再灌注的影响

目的:探讨不同血糖浓度下大鼠心肌缺血再灌注(MI/R)心肌损伤的程度及明确极化液(GIK)对高血糖心肌MI/R的保护作用.方法:将12只健康SD大鼠,随机分为4组,每组3只,即对照组、GIK组、高血糖组、GIK+高血糖组.每组大鼠结扎左冠状动脉前降支30 min,再灌注120 min.采用氯化三苯基四氮唑(TTC)染色法检测大鼠缺血再灌注心肌的心肌梗死面积.动态观察Ⅱ导联心电图QRS波、T波、ST段和心率变化.结果:TTC染色显示每组大鼠心肌都有梗死,心肌梗死面积高血糖组>GIK+高血糖组>对照组>GIK组;心电图显示高血糖大鼠心肌缺血期ST段明显抬高,再灌注后实验动物出现心律失常.GIK对正常血糖大鼠MI/R具有明显保护作用.结论:GIK对高血糖大鼠心肌缺血再灌注损伤保护作用有限,而对正常血糖大鼠MI/R损伤有较好的保护作用.     

Synaptic function modulated by changes in the ratio of synaptotagmin I and IV.

Communication within the nervous system is mediated by Ca2+-triggered fusion of synaptic vesicles with the presynaptic plasma membrane. Genetic and biochemical evidence indicates that synaptotagmin I may function as a Ca2+ sensor in neuronal exocytosis because it can bind Ca2+ and penetrate into lipid bilayers. Chronic depolarization or seizure activity results in the upregulation of a distinct and unusual isoform of the synaptotagmin family, synaptotagmin IV. We have identified a Drosophila homologue of synaptotagmin IV that is enriched on synaptic vesicles and contains an evolutionarily conserved substitution of aspartate to serine that abolishes its ability to bind membranes in response to Ca2+ influx. Synaptotagmin IV forms hetero-oligomers with synaptotagmin I, resulting in synaptotagmin clusters that cannot effectively penetrate lipid bilayers and are less efficient at coupling Ca2+ to secretion in vivo: upregulation of synaptotagmin IV, but not synaptotagmin I, decreases evoked neurotransmission. These findings indicate that modulating the expression of synaptotagmins with different Ca2+-binding affinities can lead to heteromultimers that can regulate the efficiency of excitation-secretion coupling in vivo and represent a new molecular mechanism for synaptic plasticity.     

SUMO1-dependent modulation of SERCA2a in heart failure

The calcium-transporting ATPase ATP2A2, also known as SERCA2a, is a critical ATPase responsible for Ca(2+) re-uptake during excitation-contraction coupling. Impaired Ca(2+) uptake resulting from decreased expression and reduced activity of SERCA2a is a hallmark of heart failure. Accordingly, restoration of SERCA2a expression by gene transfer has proved to be effective in improving cardiac function in heart-failure patients, as well as in animal models. The small ubiquitin-related modifier (SUMO) can be conjugated to lysine residues of target proteins, and is involved in many cellular processes. Here we show that SERCA2a is SUMOylated at lysines 480 and 585 and that this SUMOylation is essential for preserving SERCA2a ATPase activity and stability in mouse and human cells. The levels of SUMO1 and the SUMOylation of SERCA2a itself were greatly reduced in failing hearts. SUMO1 restitution by adeno-associated-virus-mediated gene delivery maintained the protein abundance of SERCA2a and markedly improved cardiac function in mice with heart failure. This effect was comparable to SERCA2A gene delivery. Moreover, SUMO1 overexpression in isolated cardiomyocytes augmented contractility and accelerated Ca(2+) decay. Transgene-mediated SUMO1 overexpression rescued cardiac dysfunction induced by pressure overload concomitantly with increased SERCA2a function. By contrast, downregulation of SUMO1 using small hairpin RNA (shRNA) accelerated pressure-overload-induced deterioration of cardiac function and was accompanied by decreased SERCA2a function. However, knockdown of SERCA2a resulted in severe contractile dysfunction both in vitro and in vivo, which was not rescued by overexpression of SUMO1. Taken together, our data show that SUMOylation is a critical post-translational modification that regulates SERCA2a function, and provide a platform for the design of novel therapeutic strategies for heart failure.     

A sodium-channel mutation causes isolated cardiac conduction disease

Cardiac conduction disorders slow the heart rhythm and cause disability in millions of people worldwide. Inherited mutations in SCN5A, the gene encoding the human cardiac sodium (Na+) channel, have been associated with rapid heart rhythms that occur suddenly and are life-threatening; however, a chief function of the Na+ channel is to initiate cardiac impulse conduction. Here we provide the first functional characterization of an SCN5A mutation that causes a sustained, isolated conduction defect with pathological slowing of the cardiac rhythm. By analysing the SCN5A coding region, we have identified a single mutation in five affected family members; this mutation results in the substitution of cysteine 514 for glycine (G514C) in the channel protein. Biophysical characterization of the mutant channel shows that there are abnormalities in voltage-dependent 'gating' behaviour that can be partially corrected by dexamethasone, consistent with the salutary effects of glucocorticoids on the clinical phenotype. Computational analysis predicts that the gating defects of G514C selectively slow myocardial conduction, but do not provoke the rapid cardiac arrhythmias associated previously with SCN5A mutations.     

Augmentation of cardiac calcium current by flash photolysis of intracellular caged-Ca2+ molecules

The entry of calcium ions into cells through voltage-activated Ca2+ channels in the plasma membrane triggers many important cellular processes. The activity of these channels is regulated by several hormones and neurotransmitters, as well as intracellular messengers such as Ca2+ itself (for examples, see refs 1-9). In cardiac muscle, myoplasmic Ca2+ has been proposed to potentiate Ca2+ influx, although a direct effect of Ca2+ on these channels has not yet been demonstrated. Photosensitive 'caged-Ca2+' molecules such as nitr-5, however, provide powerful tools for investigating possible regulatory roles of Ca2+ on the functioning of Ca2+ channels. Because its affinity for Ca2+ is reduced by irradiation, nitr-5 can be loaded into cells and induced to release Ca2+ with a flash of light. By using this technique we found that the elevation of intracellular Ca2+ concentration directly augmented Ca2+-channel currents in isolated cardiac muscle cells from both frog and guinea pig. The time course of the current potentiation was similar to that seen with beta-adrenergic stimulation. Thus Ca2+ may work through a similar pathway, involving phosphorylation of a regulatory Ca2+-channel protein. This mechanism is probably important for the accumulation of Ca2+ and the amplification of the contractile response in cardiac muscle, and may have a role in other excitable cells.     

黄芪丹参配伍提取物对心肌缺血大鼠的心脏保护作用

为证实黄芪丹参配伍提取物对心肌缺血模型大鼠的心脏具有保护作用,通过左前降支结扎诱导心肌梗死（MI）大鼠模型的方法,研究培哚普利组（PB组）、黄芪组（HQ组）、丹参组（DS组）、黄芪丹参配伍提取物组（HQ+DS组）等药物干预后对心功能的影响。采用Notch信号抑制剂RO4929097探讨Notch信号在HQ+DS组诱导心肌梗死边缘区（infarcted border zone,IBZ）血管生成中的作用。用动物超声和Masson染色评价左室射血分数（left ventricular ejection fraction,LVEF）和心肌梗死面积百分比。用免疫荧光法测定心肌IBZ中CD31和vWF的平均光密度（average optical densities,AODs）。Western blot法检测低氧诱导因子1-??（hypoxia inducible factor 1-alpha,HIF-1??）、成纤维细胞生长因子受体1（fibroblast growth factor receptor 1,FGFR-1）、Notch1和Notch胞内结构域（Notch intracellular domain,NICD）等血管生成相关蛋白和干细胞动员相关蛋白,例如基质细胞衍生因子1（stromal cell-derived factor 1,SDF-1）、C-X-C趋化因子受体4型（C-X-C chemokine receptor type 4,CXCR-4）和心肌营养素1（cardiotrophin 1,CT-1）。结果表明：与模型组相比,治疗3周后HQ+DS和PB组的LVEF均明显改善、心肌梗死面积降低,尽管与模型组相比HQ组和DS组LVEF增加、心肌梗死面积减少,但差异不显著;模型组和HQ+DS-I组IBZ中CD31的AODs均明显低于假手术组,与模型组相比,HQ+DS显著增加IBZ中CD31的 AODs,降低梗死区CD31和vWF的AODs;模型组和各治疗组HIF-1的表达均高于假手术组;与模型组相比,HQ+DS组的FGFR-1、SDF-1、CT-1、Notch1和NICD表达增加;与HQ+DS组相比,HQ+DS-I组的Notch1和NICD表达降低。可见黄芪丹参配伍对IBZ心肌细胞的保护作用优于黄芪或丹参单独应用,黄芪丹参配伍保护MI大鼠的的机制可能通过Notch信号传导和动员干细胞向IBZ移动而发挥促血管新生作用。     

Postnatal isl1+ cardioblasts enter fully differentiated cardiomyocyte lineages

The purification, renewal and differentiation of native cardiac progenitors would form a mechanistic underpinning for unravelling steps for cardiac cell lineage formation, and their links to forms of congenital and adult cardiac diseases. Until now there has been little evidence for native cardiac precursor cells in the postnatal heart. Herein, we report the identification of isl1+ cardiac progenitors in postnatal rat, mouse and human myocardium. A cardiac mesenchymal feeder layer allows renewal of the isolated progenitor cells with maintenance of their capability to adopt a fully differentiated cardiomyocyte phenotype. Tamoxifen-inducible Cre/lox technology enables selective marking of this progenitor cell population including its progeny, at a defined time, and purification to relative homogeneity. Co-culture studies with neonatal myocytes indicate that isl1+ cells represent authentic, endogenous cardiac progenitors (cardioblasts) that display highly efficient conversion to a mature cardiac phenotype with stable expression of myocytic markers (25%) in the absence of cell fusion, intact Ca2+-cycling, and the generation of action potentials. The discovery of native cardioblasts represents a genetically based system to identify steps in cardiac cell lineage formation and maturation in development and disease.     

Nitric oxide regulates the heart by spatial confinement of nitric oxide synthase isoforms

Subcellular localization of nitric oxide (NO) synthases with effector molecules is an important regulatory mechanism for NO signalling. In the heart, NO inhibits L-type Ca2+ channels but stimulates sarcoplasmic reticulum (SR) Ca2+ release, leading to variable effects on myocardial contractility. Here we show that spatial confinement of specific NO synthase isoforms regulates this process. Endothelial NO synthase (NOS3) localizes to caveolae, where compartmentalization with beta-adrenergic receptors and L-type Ca2+ channels allows NO to inhibit beta-adrenergic-induced inotropy. Neuronal NO synthase (NOS1), however, is targeted to cardiac SR. NO stimulation of SR Ca2+ release via the ryanodine receptor (RyR) in vitro, suggests that NOS1 has an opposite, facilitative effect on contractility. We demonstrate that NOS1-deficient mice have suppressed inotropic response, whereas NOS3-deficient mice have enhanced contractility, owing to corresponding changes in SR Ca2+ release. Both NOS1-/- and NOS3-/- mice develop age-related hypertrophy, although only NOS3-/- mice are hypertensive. NOS1/3-/- double knockout mice have suppressed beta-adrenergic responses and an additive phenotype of marked ventricular remodelling. Thus, NOS1 and NOS3 mediate independent, and in some cases opposite, effects on cardiac structure and function.     

Caffeine induces a transient inward current in cultured cardiac cells

Electrical excitation of cardiac muscle may sometimes be due to initiation of inward current by the presence of Ca2+ ions at the inner surface of the cell membrane. During digitalis toxicity and other conditions that abnormally augment cellular Ca2+ stores, premature release of Ca2+ from the sarcoplasmic reticulum leads to a transient inward current, which is large enough to initiate premature beats and is accompanied by a transient contractile response. This inward current may be mediated either by electrogenic sodium-calcium exchange or by specific Ca2+-activated cation channels that have recently been characterized in tissue cultures of cardiac myocytes. An obvious question raised by these observations is whether release of the sequestered Ca2+ stores during each normal beat exerts a similar influence on membrane potential. To explore this, chick embryonic myocardial cell aggregates were voltage-clamped during abrupt exposure to caffeine, which is known to release Ca2+ from the sarcoplasmic reticulum. The speed of the perfusion system and the relative absence of diffusion barriers in the tissue-cultured cells allowed the effects of caffeine-induced Ca2+ release to be studied on a time scale comparable to that of a single normal beat. We report here that abrupt exposure of the cells to caffeine produced a transient inward current having similar features to that of digitalis toxicity, and which was both large enough and rapid enough to potentially contribute to the action potential.     

In vivo reprogramming of murine cardiac fibroblasts into induced cardiomyocytes

The reprogramming of adult cells into pluripotent cells or directly into alternative adult cell types holds great promise for regenerative medicine. We reported previously that cardiac fibroblasts,which represent 50%of the cells in the mammalian heart, can be directly reprogrammed to adult cardiomyocyte-like cells in vitro by the addition of Gata4, Mef2c and Tbx5 (GMT). Here we use genetic lineage tracing to show that resident non-myocytes in the murine heart can be reprogrammed into cardiomyocyte-like cells in vivo by local delivery of GMT after coronary ligation. Induced cardiomyocytes became binucleate, assembled sarcomeres and had cardiomyocyte-like gene expression. Analysis of single cells revealed ventricular cardiomyocyte-like action potentials, beating upon electrical stimulation, and evidence of electrical coupling. In vivo delivery of GMT decreased infarct size and modestly attenuated cardiac dysfunction up to 3 months after coronary ligation. Delivery of the pro-angiogenic and fibroblast-activating peptide, thymosin b4, along with GMT, resulted in further improvements in scar area and cardiac function. These findings demonstrate that cardiac fibroblasts can be reprogrammed into cardiomyocyte-like cells in their native environment for potential regenerative purposes.