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Diabetic cardiomyopathy, clinically diagnosed as ventricular dysfunction in the absence of coronary atherosclerosis or hypertension in diabetic patients, is a cardiac muscle-specific disease that increases the risk of heart failure and mortality. Its clinical course is characterized initially by diastolic dysfunction, later by systolic dysfunction, and eventually by clinical heart failure from an uncertain mechanism. Light microscopic features such as interstitial fibrosis, inflammation, and cardiomyocyte hypertrophy are observed in diabetic cardiomyopathy, but are common to failing hearts generally and are not specific to diabetic cardiomyopathy. Electron microscopic studies of biopsy samples from diabetic patients with heart failure have revealed that the essential mechanism underlying diabetic cardiomyopathy involves thickening of the capillary basement membrane, accumulation of lipid droplets, and glycogen as well as increased numbers of autophagic vacuoles within cardiomyocytes. Autophagy is a conserved mechanism that contributes to maintaining intracellular homeostasis by degrading long-lived proteins and damaged organelles and is observed more often in cardiomyocytes within failing hearts. Diabetes mellitus (DM) impairs cardiac metabolism and leads to dysregulation of energy substrates that contribute to cardiac autophagy. However, a "snapshot" showing greater numbers of autophagic vacuoles within cardiomyocytes may indicate that autophagy is activated into phagophore formation or is suppressed due to impairment of the lysosomal degradation step. Recent in vivo studies have shed light on the underlying molecular mechanism governing autophagy and its essential meaning in the diabetic heart. Autophagic responses to diabetic cardiomyopathy differ between diabetic types: they are enhanced in type 1 DM, but are suppressed in type 2 DM. This difference provides important insight into the pathophysiology of diabetic cardiomyopathy. Here, we review recent advances in our understanding of the pathophysiology of diabetic cardiomyopathy, paying particular attention to autophagy in the heart, and discuss the therapeutic potential of interventions modulating autophagy in diabetic cardiomyopathy., (Copyright © 2020. Published by Elsevier Ltd.)

Aims: Glucagon-like peptide-1 (GLP-1) is a neuroendocrine hormone secreted by the intestine. Its receptor (GLP-1R) is expressed in various organs, including the heart. However, the dynamics and function of the GLP-1 signal in heart failure remains unclear. We investigated the impact of the cardio-intestinal association on hypertensive heart failure using miglitol, an α-glucosidase inhibitor known to stimulate intestinal GLP-1 production., Methods and Results: Dahl salt-sensitive (DS) rats fed a high-salt diet were assigned to miglitol, exendin (9-39) (GLP-1R blocker) and untreated control groups and treated for 11 weeks. Control DS rats showed marked hypertension and cardiac dysfunction with left ventricular dilatation accompanied by elevated plasma GLP-1 levels and increased cardiac GLP-1R expression as compared with age-matched Dahl salt-resistant (DR) rats. Miglitol further increased plasma GLP-1 levels, suppressed adverse cardiac remodelling, and mitigated cardiac dysfunction. In cardiomyocytes from miglitol-treated DS hearts, mitochondrial size was significantly larger with denser cristae than in cardiomyocytes from control DS hearts. The change in mitochondrial morphology reflected enhanced mitochondrial fusion mediated by protein kinase A activation leading to phosphorylation of dynamin-related protein 1, expression of mitofusin-1 and OPA-1, and increased myocardial adenosine triphosphate (ATP) content. GLP-1R blockade with exendin (9-39) exacerbated cardiac dysfunction and led to fragmented mitochondria with disarrayed cristae in cardiomyocytes and reduction of myocardial ATP content. In cultured cardiomyocytes, GLP-1 increased expression of mitochondrial fusion-related proteins and ATP content. When GLP-1 and exendin (9-39) were administered together, their effects cancelled out., Conclusions: Increased intestinal GLP-1 secretion is an adaptive response to heart failure that is enhanced by miglitol. This could be an effective strategy for treating heart failure through regulation of mitochondrial dynamics., (Published on behalf of the European Society of Cardiology. All rights reserved. © The Author(s) 2019. For permissions, please email: journals.permissions@oup.com.)

We investigated whether microRNA-145 (miR-145) has a cardioprotective effect in a rabbit model of myocardial infarction (MI) and in H9c2 rat cardiomyoblasts. Rabbits underwent 30 min of coronary occlusion, followed by 2 days or 2 wk of reperfusion. Control microRNA (control group; 2.5 nmol/kg, n = 10) or miR-145 (miR-145 group, 2.5 nmol/kg, n = 10) encapsulated in liposomes was intravenously administered immediately after the start of reperfusion. H9c2 rat cardiomyoblasts were transfected with miR-145. The MI size was significantly smaller in the miR-145 group than in the control group at 2 days and 2 wk post-MI. miR-145 had improved the cardiac function and remodeling at 2 wk post-MI. These effects were reversed by chloroquine. Western blot analysis showed that miR-145 accelerated the transition of LC3B I to II and downregulated p62/SQSTM1 at 2 days or 2 wk after MI, but not at 4 wk, and activated Akt in the ischemic area at 2 days after MI. miR-145 inhibited the growth of H9c2 cells, accelerated the transition of LC3B I to II, and increased phosphorylated Akt in the H9c2 cells at 2 days after miR-145 transfection. Antagomir-145 significantly abolished the morphological change, the transition of LC3B I to II, and the increased phosphorylated Akt induced by miR-145 in H9c2 cells. We determined fibroblast growth factor receptor substrate 2 mRNA to be a target of miR-145, both in an in vivo model and in H9c2 cells. In conclusion, post-MI treatment with miR-145 protected the heart through the induction of cardiomyocyte autophagy by targeting fibroblast growth factor receptor substrate 2., (Copyright © 2015 the American Physiological Society.)

We investigated the effect of restriction of food intake, a potent inducer of autophagy, on postinfarction cardiac remodeling and dysfunction. Myocardial infarction was induced in mice by left coronary artery ligation. At 1 week after infarction, mice were randomly divided into four groups: the control group was fed ad libitum (100%); the food restriction (FR) groups were fed 80%, 60%, or 40% of the mean amount of food consumed by the control mice. After 2 weeks on the respective diets, left ventricular dilatation and hypofunction were apparent in the control group, but both parameters were significantly mitigated in the FR groups, with the 60% FR group showing the strongest therapeutic effect. Cardiomyocyte autophagy was strongly activated in the FR groups, as indicated by up-regulation of microtubule-associated protein 1 light chain 3-II, autophagosome formation, and myocardial ATP content. Chloroquine, an autophagy inhibitor, completely canceled the therapeutic effect of FR. This negative effect was associated with reduced activation of AMP-activated protein kinase and of ULK1 (a homolog of yeast Atg1), both of which were enhanced in hearts from the FR group. In vitro, the AMP-activated protein kinase inhibitor compound C suppressed glucose depletion-induced autophagy in cardiomyocytes, but did not influence activity of chloroquine. Our findings imply that a dietary protocol with FR could be a preventive strategy against postinfarction heart failure., (Copyright © 2014 American Society for Investigative Pathology. Published by Elsevier Inc. All rights reserved.)

It has been suggested that apoptosis may be responsible for a significant amount of the cardiomyocyte death that contributes to the development and progression of heart failure. However, studies of actual heart disease and in vivo experimental models have provided little or no direct morphological evidence that cardiomyocyte apoptosis occurs at any stage of heart failure, despite the availability of much indirect evidence that includes detection of DNA fragmentation and apoptosis-related factors. The Nomenclature Committee on Cell Death (NCCD), an international organization consulting on cell death, proposed an international standard for the definition and classification of cell death, in which cell death was defined based purely on morphological criteria. This is because there is no clear-cut equivalence between ultrastructural alterations and biochemical cell death characteristics. This review will first introduce the NCCD definition and classification of cell death and, based on this classification, survey the available data from both animals and humans to critically assess the impact of cardiomyocyte apoptosis during the progression of heart failure of various etiologies. Particularly noteworthy is the wide variation in the reported rates of apoptosis--e.g., the difference was >1000-fold in one heart failure model--but even more importantly, no morphological (ultrastructural) data has ever been shown definitively demonstrating apoptosis of a cardiomyocyte. We conclude from our survey that even the existence of cardiomyocyte apoptosis in heart failure remains controversial., (Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.)

Aims: Active autophagy has recently been reported in doxorubicin-induced cardiotoxicity; here we investigated its pathophysiological role., Methods and Results: Acute cardiotoxicity was induced in green fluorescent protein-microtubule-associated protein 1 light chain 3 (GFP-LC3) transgenic mice by administering two intraperitoneal injections of 10 mg/kg doxorubicin with a 3 day interval. A starvation group was deprived of food for 48 h before each injection to induce autophagy in advance. Doxorubicin treatment caused left ventricular dilatation and dysfunction within 6 days. Cardiomyocyte autophagy appeared to be activated in the doxorubicin group, based on LC3, p62, and cathepsin D expression, while it seemed somewhat diminished by starvation prior to doxorubicin treatment. Unexpectedly, however, myocardial ATP levels were reduced in the doxorubicin group, and this reduction was prevented by earlier starvation. Electron microscopy revealed that the autophagic process was indeed initiated in the doxorubicin group, as shown by the increased lysosomes, but was not completed, i.e. autophagolysosome formation was rare. Starvation prior to doxorubicin treatment partly restored autophagosome formation towards control levels. Autophagic flux assays in both in vivo and in vitro models confirmed that doxorubicin impairs completion of the autophagic process in cardiomyocytes. The activities of both AMP-activated protein kinase and the autophagy-initiating kinase unc-51-like kinase 1 (ULK1) were found to be decreased by doxorubicin, and these were restored by prior starvation., Conclusion: Prior starvation mitigates acute doxorubicin cardiotoxicity; the underlying mechanism may be, at least in part, restoration and further augmentation of myocardial autophagy, which is impaired by doxorubicin, probably through inactivation of AMP-activated protein kinase and ULK1.

Aims: Autophagy is activated in cardiomyocytes in ischaemic heart disease, but its dynamics and functional roles remain unclear after myocardial infarction. We observed the dynamics of cardiomyocyte autophagy and examined its role during postinfarction cardiac remodelling., Methods and Results: Myocardial infarction was induced in mice by ligating the left coronary artery. During both the subacute and chronic stages (1 and 3 weeks postinfarction, respectively), autophagy was found to be activated in surviving cardiomyocytes, as demonstrated by the up-regulated expression of microtubule-associated protein-1 light chain 3-II (LC3-II), p62 and cathepsin D, and by electron microscopic findings. Activation of autophagy, specifically the digestion step, was prominent in cardiomyocytes 1 week postinfarction, especially in those bordering the infarct area, while the formation of autophagosomes was prominent 3 weeks postinfarction. Bafilomycin A1 (an autophagy inhibitor) significantly aggravated postinfarction cardiac dysfunction and remodelling. Cardiac hypertrophy was exacerbated in this group and was accompanied by augmented ventricular expression of atrial natriuretic peptide. In these hearts, autophagic findings (i.e. expression of LC3-II and the presence of autophagosomes) were diminished, and activation of AMP-activated protein kinase was enhanced. Treatment with rapamycin (an autophagy enhancer) brought about opposite outcomes, including mitigation of cardiac dysfunction and adverse remodelling. A combined treatment with bafilomycin A1 and rapamycin offset each effect on cardiomyocyte autophagy and cardiac remodelling in the postinfarction heart., Conclusion: These findings suggest that cardiomyocyte autophagy is an innate mechanism that protects against progression of postinfarction cardiac remodelling, implying that augmenting autophagy could be a therapeutic strategy.

The small leucine-rich proteoglycan decorin is a natural inhibitor of transforming growth factor-beta (TGF-beta) and exerts antifibrotic effects in heart and to stimulate skeletal muscle regeneration. We investigated decorin's chronic effects on postinfarction cardiac remodeling and dysfunction. Myocardial infarction (MI) was induced in mice by left coronary artery ligation. An adenoviral vector encoding human decorin (Ad. CAG-decorin) was then injected into the hindlimbs on day 3 post-MI (control, Ad.CAG-LacZ). Four weeks post-MI, the decorin-treated mice showed significant mitigation of the left ventricular dilatation and dysfunction seen in control mice. Although infarct size did not differ between the two groups, the infarcted wall thickness was greater and the segmental length of the infarct was smaller in decorin-treated mice. In addition, cellular components, including myofibroblasts and blood vessels, were more abundant within the infarcted area in decorin-treated mice, and fibrosis was significantly reduced in both the infarcted and noninfarcted areas of the left ventricular wall. Ten days post-MI, there was greater cell proliferation and less apoptosis among granulation tissue cells in the infarcted areas of decorin-treated mice. The treatment, however, did not affect proliferation and apoptosis of salvaged cardiomyocytes. Although decorin gene therapy did not affect TGF-beta1 expression in the infarcted heart, it inhibited Smad2/3 activation (downstream mediators of TGF-beta signaling). In summary, postinfarction decorin gene therapy mitigated cardiac remodeling and dysfunction by altering infarct tissue noncardiomyocyte dynamics and preventing cardiac fibrosis, accompanying inhibition of Smad2/3 activation.

To address whether adult rat ventricular cardiomyocytes (ARVCs) exposed to oxidant stress die via apoptosis (secondarily by necrosis) or primarily by necrosis, we exposed ARVCs to hydrogen peroxide (H2O2; 0.1-100 microM) for up to 24 h and then compared them with isoproterenol-induced apoptotic and Triton X-induced necrotic controls. Cellular shrinkage preceded plasma membrane disruption, reflected by trypan blue uptake in ARVCs exposed to lower concentrations of H2O2 (<1 microM; an apoptotic pattern), but the order was reversed in cells exposed to higher concentrations of H2O2 (>1 microM; a necrotic pattern). DNA fragmentation, caspase-3 activation, mitochondrial membrane potential preservation, and ATP preservation were all apparent in ARVCs treated with low H2O2 (0.5 microM), but not in those treated with high H2O2 (10 microM). In addition, electron microscopy revealed unique morphology in H2O2-treated ARVCs; i.e., the nuclei had a homogeneous ground glass-like appearance that was never accompanied by chromatin condensation. Apparently, high concentrations of H2O2 caused primary necrosis in ARVCs, whereas low concentrations induced biochemically comparable apoptosis, although the latter did not satisfy the morphological criteria of apoptosis. These findings caution against the use of oxidant stress, H2O2 in particular, as an inducer of apoptosis in ARVCs.

To examine the functional significance and morphological characteristics of starvation-induced autophagy in the adult heart, we made green fluorescent protein-microtubule-associated protein 1-light chain 3 (LC3) transgenic mice starve for up to 3 days. Electron microscopy revealed round, homogenous, electron-dense lipid droplet-like vacuoles that initially appeared in cardiomyocytes as early as 12 hours after starvation; these vacuoles were identified as lysosomes based on cathepsin D-immunopositive reactivity and acid phosphatase activity. The increase in the number of lysosomes depended on the starvation interval; typical autophagolysosomes with intracellular organelles also appeared, and their numbers increased at the later phases of starvation. Myocardial expression of autophagy-related proteins, LC3-II, cathepsin D, and ubiquitin, increased, whereas both myocardial ATP content and starvation integral decreased. Treatment with bafilomycin A1, an autophagy inhibitor, did not affect cardiac function in normally fed mice but significantly depressed cardiac function and caused significant left ventricular dilatation in mice starved for 3 days. The cardiomyocytes were occupied with markedly accumulated lysosomes in starved mice treated with bafilomycin A1, and both the myocardial amino acid content, which was increased during starvation, and the myocardial ATP content were severely decreased, potentially contributing to cardiac dysfunction. The present findings suggest a critical role of autophagy in the maintenance of cardiac function during starvation in the adult.

We induced autophagy in isolated adult rat ventricular cardiomyocytes by incubating them in glucose-free medium supplemented with mannitol for up to 4 days. The upregulation of LC3 and vacuoles containing partially degraded subcellular organelles were readily apparent in glucose-starved cells. Most dead cells in both groups showed features of necrosis, although the survival rate was significantly lower among glucose-starved cells than among the controls. In contrast, the rate of apoptosis was about the same in both groups. Two inhibitors of autophagy, 3-methyladenine (3-MA) and leupeptin, significantly reduced the viability of both control and glucose-starved cells in a dose-dependent manner and caused specific morphological alterations: 3-MA reduced the number of autophagic vacuoles, whereas leupeptin greatly increased their number and size. Conversely, rapamycin, an enhancer of autophagy, improved the survival of glucose-starved cells. The reduction in cellular ATP caused by glucose depletion was exacerbated by the inhibitors but mitigated by rapamycin, suggesting that inhibition of autophagy may accelerate energy depletion, leading to necrosis. Our findings suggest that in cardiomyocytes, autophagy is a compensatory, prosurvival response to stress, and that autophagic death is an unsuccessful outcome brought on by necrosis.

Autophagy is simultaneously a mode of programmed cell death and an important physiological process for cell survival, but its pathophysiological significance in cardiac myocytes remains largely unknown. We induced autophagy in isolated adult rat ventricular cardiomyocytes (ARVCs) by incubating them in glucose-free, mannitol-supplemented medium for up to 4 days. Ultrastructurally, intracellular vacuoles containing degenerated subcellular organelles (e.g., mitochondria) were markedly apparent in the glucose-starved cells. Microtubule-associated protein-1 light chain 3 was significantly upregulated among the glucose-starved ARVCs than among the controls. After 4 days, glucose-starved ARVCs showed a significantly worse survival rate (19+/-5.2%) than the controls (55+/-8.3%, P<0.005). Most dead ARVCs in both groups showed features of necrosis, and the rate of apoptosis did not differ between the groups. Two inhibitors of autophagy, 3-methyladenine (3-MA) and leupeptin, significantly and dose-dependently reduced the viability of both control and glucose-starved ARVCs and caused specific morphological alterations; 3-MA reduced autophagic findings, whereas leupeptin greatly increased the numbers and the sizes of vacuoles that contained incompletely digested organelles. The knockdown of the autophagy-related genes with small interfering RNA also reduced the glucose-starved ARVCs viability, but rapamycin, an autophagy enhancer, improved it. Reductions in the ATP content of ARVCs caused by glucose depletion were exacerbated by the inhibitors while attenuated by rapamycin, suggesting that autophagy inhibition might accelerate energy depletion, leading to necrosis. Taken together, our findings suggest that autophagy in cardiomyocytes reflects a prosurvival, compensatory response to stress and that autophagic cardiomyocyte death represents an unsuccessful outcome due to necrosis.

Although recanalization of the infarct-related artery late after myocardial infarction (MI) is known to reduce both cardiac remodeling and mortality, the mechanisms responsible are not yet fully understood. We compared infarcted rat hearts in which the infarct-related coronary artery was opened 24 hours after infarction (late reperfusion [LR] group) with those having a permanently occluded artery. Left ventricular dilatation and dysfunction were significantly mitigated in the LR group 1, 2, and 4 weeks post-MI. Attributable, in large part, to the greater number of cells present, the infarcted wall was significantly thicker in the LR group, which likely reduced wall stress and mitigated cardiac dysfunction. Granulation tissue cell proliferation was increased to a greater degree in the LR group 4 days post-MI, whereas the incidence of apoptosis was significantly lower throughout the subacute stage (4 days, 1 week, and 2 weeks post-MI), further suggesting preservation of granulation tissue cells contributes to the thick, cell-rich scar. Functionally, myocardial debris was more rapidly removed from the infarcted areas in the LR group during subacute stages, and stouter collagen was more rapidly synthesized in those areas. Direct acceleration of Fas-mediated apoptosis by hypoxia was confirmed in vitro using infarct tissue-derived myofibroblasts. In salvaged cardiomyocytes, degenerative changes, but not apoptosis, were mitigated in the LR group, accompanied by restoration of GATA-4 and sarcomeric protein expression. Along with various mechanisms proposed earlier, the present findings appear to provide an additional pathophysiological basis for the benefits of late reperfusion.

Background: The nucleus of the myocytes in human hypertrophic hearts is characterized by its bizarre shape and widespread clumping of chromatin. The functional significance has not been determined., Methods and Results: Left ventricular (LV) endomyocardial biopsies obtained from patients with dilated cardiomyopathy (DCM, n=23), postmyocarditis (n=13), hypertrophic cardiomyopathy (HCM, n=21), apical hypertrophic cardiomyopathy (APH, n=11) and hypertensive heart disease (HHD, n=11), and from nonhypertrophic hearts (controls, n=14) were examined. Myocyte size and LV mass index were similar among the hypertrophic hearts, but the nuclear hypertrophy score (grade 0-3) was highest in hearts with systolic failure (DCM and postmyocarditis) and higher in those without it (HCM, APH, and HHD), compared with controls. So were biosynthetic activities such as DNA repair/synthesis, immunohistochemically assessed by proliferating cell nuclear antigen, transcription activity by spliceosome component of 35 kDa, and translation efficiency by 70 kDa S6 protein kinase. There were significant correlations between nuclear hypertrophy and each biosynthetic activity. Additionally, most of the proliferating cell nuclear antigen-positive nuclei co-expressed oxidative DNA damage markers., Conclusion: A link is suggested between structural alteration and molecular biological events in the nuclei of myocytes from human hypertrophic hearts; the nuclear hypertrophy reflects increased biosynthetic activities of DNA repair/synthesis, transcription, and translation efficiency.

During early apoptosis, adult cardiomyocytes show unusual beating, suggesting possible participation of abnormal Ca(2+) transients in initiation of apoptotic processes in this cell type. Simultaneously with the beating, these cells show dynamic structural alteration resulting from cytoskeletal disintegration that is quite rapid. Because of the specialized structure and extensive cytoskeleton of cardiomyocytes, we hypothesized that its degradation in so short a time would require a particularly efficient mechanism. To better understand this mechanism, we used serial video microscopy to observe beta-adrenergic stimulation-induced apoptosis in isolated adult rat cardiomyocytes while simultaneously recording intracellular Ca(2+) concentration and cell length. Trains of Ca(2+) transients and corresponding rhythmic contractions and relaxations (beating) were observed in apoptotic cells. Frequencies of Ca(2+) transients and beating gradually increased with time and were accompanied by cellular shrinkage. As the cells shrank, amplitudes of Ca(2+) transients declined and diastolic intracellular Ca(2+) concentration increased until the transients were lost. Beating and progression of apoptosis were significantly inhibited by antagonists against the L-type Ca(2+) channel (nifedipine), ryanodine receptor (ryanodine), inositol 1,4,5-trisphosphate receptor (heparin), sarco(endo)plasmic Ca(2+)-ATPase (thapsigargin), and Na(+)/Ca(2+) exchanger (KB-R7943). Electron-microscopic examination of beating cardiomyocytes revealed progressive breakdown of Z disks. Immunohistochemical analysis and Western blot confirmed that disappearance of Z disk constituent proteins (alpha-actinin, desmin, and tropomyosin) preceded degradation of other cytoskeletal proteins. It thus appears that, in adult cardiomyocyte apoptosis, Ca(2+) transients mediate apoptotic beating and efficient sarcomere destruction initiated by Z disk breakdown.

In UM-X7.1 hamster model of human dilated cardiomyopathy, heart failure progressively develops and causes 50% mortality by 30 weeks of age. Through ultrastructural analysis, we found that many cardiomyocytes of this model contain typical autophagic vacuoles including degraded mitochondria, glycogen granules, and myelin-like figures. In addition, ubiquitin, cathepsin D, and Rab7 were overexpressed as determined by immunoassays. Importantly, most cardiomyocytes with leaky plasma membranes were positive for cathepsin D, suggesting a direct link between autophagic degeneration and cell death. Meanwhile, cardiomyocyte apoptosis appeared insignificant. Granulocyte colony-stimulating factor (10 microg/kg/day), injected 5 days/week from 15 to 30 weeks of age, improved survival among 30-week-old hamsters (100% versus 53% in the untreated hamsters, P < 0.0001); ventricular function and remodeling, increased cardiomyocyte size, and reduced myocardial fibrosis followed by a dramatic reduction in the autophagic findings were also seen. Granulocyte colony-stimulating factor also down-regulated tumor necrosis factor-alpha and increased activities of Akt signal transducer and activator of transcription-3, and matrix metalloproteinases. However, there was no clear evidence of transdifferentiation from bone marrow cells into cardiomyocytes. In conclusion, autophagic death is important for cardiomyocyte loss in the cardiomyopathic hamster, and the beneficial effect of granulocyte colony-stimulating factor acts mainly via an anti-autophagic mechanism rather than anti-apo-ptosis or regeneration.

Objective: Whether bone marrow cells injected following acute myocardial infarction (MI) transdifferentiate into cardiomyocytes remains controversial, and how these cells affect repair-related cytokines is not known., Methods: Autologous bone marrow-derived mononuclear cells (BM-MNCs) labeled with DiI, 1,1'-dioctadecyl-1 to 3,3,3',3'-tetramethylindocarbocyanine perchlorate, or saline were intravenously injected into rabbits 5 h following a 30-min ischemia and reperfusion protocol, and cardiac function and the general pathology of the infarcted heart were followed up 1 and 3 months post-MI. To search for regenerated myocardium, electron microscopy as well as confocal microscopy were performed in the infarcted myocardium 7 days post-MI. Expression levels of repair-related cytokines were evaluated by immunohistochemistry and Western blotting., Results: Improvements in cardiac function and reductions in infarct size were observed in the BM-MNC group 1 month and 3 months post-MI. Using electron microscopy 7 days after infarction, clusters of very immature (fetal) and relatively mature cardiomyocytes undergoing differentiation were identified in the infarcted anterior LV wall in the BM-MNC group, though their numbers were small. These cells contained many small and dense DiI particles (a BM-MNC marker), indicating that cardiomyocytes had regenerated from the injected BM-MNCs. The expression of both transforming growth factor-beta, which stimulates collagen synthesis and matrix metalloproteinase-1, a collagenase, were both down-regulated 7 days and 1 month post-MI in the BM-MNC group. Stromal cell-derived factor-1, which is known to recruit BM-MNCs into target tissues, was overexpressed in the infarcted areas of BM-MNC hearts 7 days post-MI., Conclusions: Intravenous transplantation of BM-MNCs leads to the development of BM-MNC-derived myocyte-like cells and regulates the expression of repair-related cytokines that facilitate repair following myocardial infarction.

Insulin-like growth factor (IGF), hepatocyte growth factor (HGF), and heparin-binding epidermal growth factor-like growth factor (HB-EGF) are cardiogenic and cardiohypertrophic growth factors. Although the therapeutic effects of IGF and HGF have been well demonstrated in injured hearts, it is uncertain whether natural upregulation of HB-EGF after myocardial infarction (MI) plays a beneficial or pathological role in the process of remodeling. To answer this question, we conducted adenoviral HB-EGF gene transduction in in vitro and in vivo injured heart models, allowing us to highlight and explore the HB-EGF-induced phenotypes. Overexpressed HB-EGF had no cytoprotective or additive death-inducible effect on Fas-induced apoptosis or oxidative stress injury in primary cultured mouse cardiomyocytes, although it significantly induced hypertrophy of cardiomyocytes and proliferation of cardiac fibroblasts. Locally overexpressed HB-EGF in the MI border area in rabbit hearts did not improve cardiac function or exhibit an angiogenic effect, and instead exacerbated remodeling at the subacute and chronic stages post-MI. Namely, it elevated the levels of apoptosis, fibrosis, and the accumulation of myofibroblasts and macrophages in the MI area, in addition to inducing left ventricular hypertrophy. Thus, upregulated HB-EGF plays a pathophysiological role in injured hearts in contrast to the therapeutic roles of IGF and HGF. These results imply that regulation of HB-EGF may be a therapeutic target for treating cardiac hypertrophy and fibrosis.