Cardiac autophagy dramatically increases in heart failure induced by sustained pressure overload. However, it has not yet been addressed if enhanced autophagy plays a role in protecting myocardium or mediating progression from compensative hypertrophy to heart failure. The aim of the present study was to detect autophagic flux of cardiomyocytes from 20-week transverse abdominal aortic constriction (TAC) rats. Fasting rats were used as the positive control for detecting cardiac autophagy. Echocardiography was applied to find the changes of cardiac structure and function. Immunofluorescent histochemistry and Western blot were used to analyze the related biomolecular indexes reflecting cardiac autophagic flux. After the previous methods for detecting cardiac autophagy were confirmed, the autophagic flux in cardiomyocytes of rats subjected to 20-week TAC was examined. The results showed that fasting had no obvious influence on parameters of cardiac structure in rats, including interventricular septal wall thickness and left ventricle posterior wall thickness, but heart rate, diastolic left ventricle internal dimension, fractional shortening of left ventricle dimension, ejection fraction and mitral inflow velocity decreased in rats after fasting for 3 d. Meanwhile, positively stained particles of LC3 and cathepsin D, but not ubiquitin and complement 9, distributed within cardiomyocytes of 3-day fasting rats, indicating augmented autophagic flux. Compared with sham rats, 20-week TAC rats did not show any changes of LC3, cathepsin D, ubiquitin and complement 9 in myocardium detected by immunofluorescent histochemistry. In addition, protein levels of LC3, cathepsin D and p62 in myocardium of TAC rats did not changed. These results reveal the unchanged autophagic flux in cardiomyocytes at middle or late phase of cardiac hypertrophy in TAC rats, implying a balance between inhibition of hypertrophy and activation of pressure load stress on autophagy.
Animals ; Aorta ; pathology ; Autophagy ; Cardiomegaly ; physiopathology ; Constriction ; Heart ; physiopathology ; Myocardium ; pathology ; Myocytes, Cardiac ; cytology ; Rats

Sarcoplasmic reticulum is a principal subcellular organelle which regulates calcium homeostasis, protein synthesis, and apoptosis of cardiomyocytes. Endoplasmic reticulum (ER) stress is defined as the perturbation of ER function which is caused by the alterations in the ER environment, such as the perturbation of Ca(2+) homeostasis, elevated protein synthesis, the deprivation of glucose, altered glycosylation, and the accumulation of misfolded proteins. Moderate ER stress is able to restore cellular homeostasis, i.e., to exert a compensatory effect on cardiomyocytes. However, intense or persistent ER stress may cause ER stress-induced apoptosis, which shifts the hypertrophied myocardium to failure, and affects the pathogenesis and development of myocardial hypertrophy. The article reviewed the role of ER stress response in the pathogenesis and development of myocardial hypertrophy.
Animals ; Apoptosis ; Endoplasmic Reticulum Stress ; Homeostasis ; Hypertrophy ; pathology ; Myocardium ; pathology ; Myocytes, Cardiac ; pathology ; Protein Biosynthesis ; Sarcoplasmic Reticulum ; pathology

Animals ; Apoptosis ; Cardiomegaly ; metabolism ; pathology ; Glycogen Synthase Kinase 3 ; metabolism ; Mice ; Mice, Transgenic ; Myocytes, Cardiac ; cytology

Animals ; Apoptosis ; drug effects ; Ginsenosides ; pharmacology ; Myocardial Reperfusion Injury ; pathology ; Myocytes, Cardiac ; cytology ; Rats ; Rats, Wistar

OBJECTIVETo study the effects of skeletal muscle satellite cells implanted into infarcted myocardium on the volume of remnant myocytes.

METHODSThirty-six adult mongrel canines were divided randomly into implantation group and control group. In the implantation group, skeletal muscle satellite cells taken from the gluteus maximus muscles of the dogs were cultured, proliferated and labeled with 4',6-diamidino-2-phenylindone (DAPI) in vitro. In both groups, a model of acute myocardial infarction was established in every dog. In the implantation group, each dog was injected with M199 solution containing autologous skeletal muscle satellite cells. The dogs in the control group received M199 solution without skeletal muscle satellite cells. The dogs of both groups were killed 2, 4 and 8 weeks after implantation (six dogs in a separate group each time). Both infarcted myocardium and normal myocytes distal from the infracted regions isolated were observed under optical and fluorescent microscope. Their volumes were determined using a confocal microscopy image analysis system and analyzed using SAS. A P < 0.05 was considered significant.

RESULTSA portion of the implanted cells differentiated into muscle fiber with striations and were connected with intercalated discs. Cross-sectional area and cell volume were increased in normal myocardium. Hypertrophy of remnant myocytes in the infarcted site after skeletal muscle cell implantation was much more evident than in the control group. Cross-sectional area, cell area and cell volume differed significantly from those of the control group (P < 0.05). Hypertrophy of the cells occurred predominantly in terms of width and thickness, whereas cell length remained unchanged.

CONCLUSIONSkeletal muscle satellite cells implanted into infarct myocardium, could induce the hypertrophy of remnant myocyte cells in the infarcted site and could also aid in the recovery of the contractile force of the infarcted myocardium.

Animals ; Cell Size ; Dogs ; Myocardial Infarction ; pathology ; Myocardium ; pathology ; Myocytes, Cardiac ; cytology ; Random Allocation ; Satellite Cells, Skeletal Muscle ; cytology ; physiology

OBJECTIVETo investigate the degree of injury to microtubule of myocardium at early post-hypoxia stage.

METHODSCardiomyocytes from Wistar rats were isolated and cultured, and they were then divided into normal control and hypoxia groups. The distribution and morphological changes in microtubules were observed with laser confocal microscopy and scanning electron microscope at 10, 20, 30 post-hypoxia minutes (PHM) and 1 post-hypoxia hour (PHH). Then the fluorescence intensity of alpha-microtubule was detected with RT-PCR, the morphology of microtubule was observed, and the expression of dissociative alpha-microtubule was determined by Western blot.

RESULTSCompared with normal control group, the bead-like structure of the microtubule in hypoxia group disappeared at 10 PHM, but no obvious change was observed in the distribution and number of microtubules. Despite the disappearance of bead-like structure of the microtubule, the microtubule derangement and loss of microtubule at the edge of cell were observed at 20 PHM. The fragmentation, derangement of texture, and loss of regularity in cardiomyocytes were observed at 30 PHM and 1 PHH. The fluorescence intensity of alpha-microtubule in hypoxia group was evidently decreased than that in normal group in a time-dependent manner. The expression of dissociative alpha-microtubule in hypoxia group at 10 PHM (46,644 +/- 145) was obviously higher than that in normal group (13,357 +/- 98, P < 0.01), and its increase was maintained with elapse of time.

CONCLUSIONMicrotubule injury to cardiomyocytes occurs at early stage of post-hypoxia, with destruction of its structure and distribution.

Animals ; Cell Hypoxia ; Cells, Cultured ; Microtubule-Associated Proteins ; biosynthesis ; Microtubules ; metabolism ; pathology ; Myocytes, Cardiac ; metabolism ; pathology ; Rats ; Rats, Wistar

OBJECTIVETo investigate the influence of hypoxia induced microtubule damage on the opening of mitochondrial permeable transition pore (MPTP)of cardiac myocytes and on the decrease of respiratory function in rat.

METHODSPrimary cultured myocardial cells from 30 neonatal rats were randomized as normoxic group (A), hypoxia group (B), normoxia with microtubule destabilizing agent group (C, with treatment of 8 micromol/L colchicines for 30 minutes before normoxia), and hypoxia with microtubule stabilizing agent group (D, with treatment of 10 micromol/L taxol for 30 minutes before hypoxia). beta-tubulin immunofluorescence ,the opening of mitochondria permeability transition pore, and the mitochondrial inner membrane potential were detected at 0.5, 1, 3, 6 and 12 post-treatment hours (PTH), and the mitochondrial respiratory function was determined by MTT method. The changes in these indices were also determined in A group at the corresponding time-points.

RESULTSObvious damage of polymerized microtubule, opening of MPTP, mitochondrial inner membrane potential loss and decrease of myocardial respiratory activity were observed in both group B and C at 0.5 PTH, and they became more and more serious afterwards. However, the changes in the above indices in D group were much better than those in B group (P < 0.05 or 0.01), and no difference was found between D (92.8 +/- 4.0)% and C [(100.0 +/- 0.0) %, P > 0.05] groups.

CONCLUSIONHypoxia played a role in the myocardial microtubule damage as well as in the opening of MPTP. Moreover, hypoxia could also impair the mitochondrial respiratory function. Microtubule destabilizing agent could reproduce well the process of hypoxia induced microtubule damage, while the stabilizing agent exerted protective effect by improving the transition of mitochondrial permeability and the mitochondria respiratory function.

Animals ; Cell Hypoxia ; Cells, Cultured ; Hypoxia ; metabolism ; pathology ; Membrane Potential, Mitochondrial ; Microtubules ; pathology ; Mitochondria, Heart ; metabolism ; pathology ; Myocytes, Cardiac ; metabolism ; pathology ; Rats ; Rats, Sprague-Dawley

OBJECTIVETo investigate the mechanism of miR-133a in reversing neonatal rat cardiomyocyte hypertrophy induced by phenylephrine.

METHODSA miR-133a precursor cDNA was used to construct an adenovirus vector, which was transfected into 293 cells to harvest miR-133a-containing virus. Neonatal rat cardiac myocytes treated by phenylephrine were exposed to miR-133a adenovirus, and the changes in cell area was measured; the expression levels of miR-133a and Acta1, Actc1, Actb, Myh6, Myh7, and BNP mRNAs were detected by quantitative RT-PCR.

RESULTSPhenylephrine treatment increased the area of cardiomyocytes by more than 3 folds and significantly enhanced the expression levels of Acta1, Actc1, Actb, Myh6, Myh7 and BNP mRNAs. All these changes were obviously reverse by miR-133a treatment.

CONCLUSIONmiR-133a is an important regulator of phenylephrine-induced cardiomyocyte hypertrophy and negatively regulates this process.

Adenoviridae ; Animals ; Cells, Cultured ; Genetic Vectors ; Hypertrophy ; MicroRNAs ; genetics ; Myocytes, Cardiac ; cytology ; pathology ; Phenylephrine ; adverse effects ; RNA, Messenger ; Rats ; Transfection

AIMThe observation of the relationship between the level of NO detected by ESR in the blood and the myocardial apoptosis and function caused by the recurrent, reversible myocardial ischemia/reperfusion injury.

METHODSFifteen New Zealand white rabbits were randomly divided into three groups (n = 5): (1) control group, (2) L-Arg group, (3) L-NNA group. The rabbits were anesthetized with intravenous pentobarbital. A suture ligature was passed around the left anterior descending coronary artery (LAD), so it could be snare occluded and reperfused. The LAD was occluded for 10 min three times, the first and second occlusions were followed by 10 min of reflow, after the third occlusion, the reperfusion was 120 min.

RESULTSIn all groups dp/dt(max) began to decrease at 5 min after the first ischemia. But compared with control group at 5 min after first reperfusion: in L-Arg group NO and apoptosis level were elevated but dp/dt(max) decreased significantly. In L-NNA group NO and apoptosis decreased significantly, dp/dt(max) improved significantly.

CONCLUSIONThe fact that the level of NO and apoptosis elevated suggested that they had taken part in the process of myocardial stunning.

Animals ; Apoptosis ; Female ; Male ; Myocardial Reperfusion Injury ; metabolism ; pathology ; physiopathology ; Myocytes, Cardiac ; metabolism ; Nitric Oxide ; metabolism ; Rabbits

The purpose of this study was to observe whether human peripheral dervied monouncleas cells (hMNCs) could participate in the regeneration process of the ischemic hearts in the way of differentiating into cardiomyocytes, vascular endothelial cells and smooth muscle cells. hMNCs were transplanted into the bodies of the mice with myocardial infarction through the tail vein injection. Hearts were harvested 2-12 weeks after injection then sliced up into frozen sections of 5 micron thickness. Double immunofluorescence staining was used to test the differentiation of the grafted cells into cardiomyocytes, smooth muscle cells and vascular endothelial cells which revealed that cells expressing both HLA and TNT, HLA and alpha-SMA, HLA and vWF existed in the hearts of the mice. According to the study, it is probable that hMNCs could participate in the regeneration process of the infarcted hearts in the way of differentiation.
Animals ; Cell Differentiation ; physiology ; Humans ; Leukocytes, Mononuclear ; transplantation ; Mice ; Mice, Nude ; Myocardial Infarction ; pathology ; therapy ; Myocytes, Cardiac ; cytology ; Transplantation, Heterologous