OBJECTIVETo investigate the myocardial proliferation/regeneration capacities at different time points and at different parts of the heart post acute myocardial infarction (AMI) in rats.

METHODSA total of 64 adult Sprague-Dawley (SD) rats were randomly divided into AMI group (left anterior descending coronary ligation, n = 44) and sham-operated group (n = 20). Rats were sacrificed on day 3, 5, 7, 14 and 60 respectively post operation (n = 5-9 at each time point) and ventricular tissues were harvested. 5-Bromo-2-deoxyUridine (Brdu, 50 mg/kg) was injected intraperitoneally at 12 and 24 hours before sacrifice. Morphological and pathological changes of the myocardium were observed after HE staining. Brdu-positive and c-kit and Brdu double-positive cardiomyocytes were analyzed post immunohistochemistry and immunofluorescence staining. Striated structure of new cells was detected by PTAH staining. Alpha-sarcomeric actin antibody was used to identify new cardiomyocytes.

RESULTBrdu-positive cardiomyocytes at border zone and non-ischemic zone were significantly increased at 5 days post AMI and peaked at 7th day post operation (Border zone, AMI: 1.26% ± 0.15% vs.Sham: 0.22% ± 0.06%, P < 0.01; right ventricle, AMI: 0.75% ± 0.12% vs.Sham: 0.18% ± 0.07%, P < 0.01). There was no significant difference between the two groups on the 60th post-operation day. Brdu-positive cells were 1.7-fold higher in infarct border zone than in the right ventricular area of AMI rats on the 7th post operation day (1.26% ± 0.15%, vs.0.75% ± 0.12%, P < 0.01) and was 1.4-fold higher on the 14th post operation day (0.77% ± 0.09%, vs.0.54% ± 0.11%, P < 0.01). PTAH staining evidenced myocardial striated structure inside the new cells. Immunofluorescent assay showed that parts of Brdu positive cells were myocardial actin positive, and the c-kit and Brdu double-positive myocardial cells were also observed. Most nuclei of tehse new cardiomyocytes were small and round-shaped.

CONCLUSIONSMyocardial proliferation/regeneration increased significantly after AMI in rats, especially around the infarct border zone. The myocardial proliferation/regeneration was time-dependent. Parts of the new cardiomyocytes had some characteristics of cardiac stem cells. This study suggests that myocardial proliferation/regeneration may be activated after acute myocardial injury.

Animals ; Cell Proliferation ; Male ; Myocardial Infarction ; pathology ; Myocytes, Cardiac ; pathology ; Rats ; Rats, Sprague-Dawley ; Regeneration

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

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

OBJECTIVETo investigate the histopathological features of primary restrictive cardiomyopathy (PRCM).

METHODSNine extransplanted hearts from heart transplantation recipients were examined. Gross and histopathological findings were observed, photographed and final pathological diagnosis was compared to clinical diagnosis. The myocardial ultrastructure changes were determined using transmission electron microscopy.

RESULTSThe hallmark pathologic feature of PRCM was distinguished by myocardial cell degeneration and hyperplastic collagen fibrils around the myocardial cells.Fibrosis was severer in left ventricle free wall than in ventricular septum and right ventricle. The degree of myocardial cell degeneration and poloidal disorder were severer in patients with reduced ejection fraction (EF) than in patients with preserved EF. Transmission electron microscope evidenced severe interstitial fibrosis, myofibrillar changes of sarcomere structure, abnormalities both on intercalated disc number and distribution.

CONCLUSIONSPRCM is characterized by hyperplastic collagen fibrils around the cardiomyocytes. Fibrosis is severer in left ventricle than in right ventricle. Sarcomere dysplasia is the main cause of PRCM, and ultrastructural examination is helpful for PRCM diagnosis.

Cardiomyopathy, Restrictive ; surgery ; Fibrosis ; Heart Transplantation ; Heart Ventricles ; Humans ; Myocardium ; pathology ; Myocytes, Cardiac ; Sarcomeres

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 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 dynamic changes of cardiomyocyte apoptosis and the role of death receptor apoptotic pathway in a rat model of coronary microembolization (CME).

METHODSAdult rats were randomized to coronary microembolization (CME group, n = 63) or sham-operated group (S group, n = 55). CME model was established by aortic injection of 0.1 ml microspheres (42 microm, 3 x 10(4)/ml) into the left ventricle when the ascending aorta was temporarily clamped.S group received 0.1 ml saline injection and survived rats were randomly examined at 0, 3, 6, 12 and 24 hour post CME (n = 10 each). Heart function was evaluated by echocardiography. Myocardium sample was stained with hematoxylin-eosin and hematoxylin-basic fuchsin-picric acid to detect infarct areas. Cardiomyocyte apoptosis was detected with TUNEL staining. The expression of caspase-3 and caspase-8 was measured by Western blot analysis.

RESULTSCompared with S group, the left ventricular ejection fraction was significantly decreased and left ventricular end-diastolic diameter was significantly increased in CME group (all P < 0.05) except 0 hour CME group. The infarct sizes were similar in 3 hour, 6 hour, 12 hour, and 24 hour CME groups (P > 0.05). The apoptosis index (AI) in CME group were significantly higher at each time point compared to S group (P < 0.05) except 0 hour CME group and peaked at 6 hours. Apoptotic cardiomyocytes were found mainly in the myocardial microinfarcted area and border zones. The relative expression of caspase-3 and caspase-8 in CME group were both significantly increased at 3 hours and peaked at 6 hour post CME (P < 0.05).

CONCLUSIONCardiomyocytes apoptosis was significantly increased after coronary microembolization via activating death receptor apoptotic pathway in this coronary microembolization model.

Animals ; Apoptosis ; Coronary Vessels ; pathology ; Male ; Myocytes, Cardiac ; metabolism ; Rats ; Rats, Sprague-Dawley ; Receptors, Death Domain ; metabolism ; Thromboembolism ; metabolism ; pathology

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