Survival of engineered myocardium constructed by bone marrow mesenchymal stem cells in vitro / 中国组织工程研究

BACKGROUND:So far, engineered myocardium is stil facing many problems. Research has demonstrated that bone marrow mesenchymal stem cells can be differentiated into myocardial cells. Polyglycolide and polycaprolactone are commonly used artificial polymers, which have good biocompatibility. OBJECTIVE:To observe the growth of the poly(glycolic acid)/poly(e-caprolactone) copolymer patch in vitro in normal myocardium and infarcted myocardium. METHODS:Bone marrow mesenchymal stem cells in Sprague-Dawley rats were separated using adherent separation and selection method, cultured in vitro. The third passage was labeled with DAPI. The bone marrow mesenchymal stem cellsuspensions (2×106/cm2) were produced and planted on poly(glycolic acid)/poly(e-caprolactone) copolymer scaffolds to form poly(glycolic acid)/poly(e-caprolactone) copolymer patch. After culturing for 48 hours, the specimens were observed under electron microscope, stained with hematoxylin and eosin, and then observed under light microscope. Rat models of myocardial infarction were established by ligating left anterior descending coronary artery. Poly(glycolic acid)/poly(e-caprolactone) copolymer patch was implanted into the normal and infarcted myocardium for 5 weeks. The survival of bone marrow mesenchymal stem cells was determined by the detection of pathology. RESULTS AND CONCLUSION:Results of light microscope and electron microscope demonstrated that bone marrow mesenchymal stem cells grew three-dimensional y on poly(glycolic acid)/poly(e-caprolactone) copolymer patch. cells and patch were adhesive wel . Under laser confocal microscopy, compared with the first week, bone marrow mesenchymal stem cells were marked by DAPI in the myocardium at the fifth week. There were bone marrow mesenchymal stem cells marked by DAPI in the infracted area. Results of hematoxylin-eosin staining exhibited that bone marrow mesenchymal stem cells were detected in the infarct area. These results suggested that bone marrow mesenchymal stem cells adhered to the poly(glycolic acid)/poly(e-caprolactone) copolymer stent wel . The complexes of poly(glycolic acid)/poly(e-caprolactone) copolymer and bone marrow mesenchymal stem cells can be used for reparation of myocardium.

Role of Angiotensin II Type 1A Receptor-Mediated Signaling in the Development of Pressure Overload-Induced Left Ventricular Hypertrophy and Fibrosis

BACKGROUND AND OBJECTIVES: The roles of angiotensin II (Ang II) in the regulation of heart function under normal and pathological conditions have been well documented, with its biological actions mainly mediated via the Ang II type 1A receptor (AT(1A)R). Since the inhibition of the renin-angiotensin system can prevent or regress left ventricular hypertrophy (LVH) with hypertension, AT(1A)R-mediated signaling is considered one of the important transcriptional pathways in the development of cardiac hypertrophy. SUBJECTS AND METHODS: To address whether AT(1A)R-mediated signaling plays an important role in the development of pressure overload-induced LVH and fibrosis, the physiological, biochemical, hemodynamic and histopathological parameters were evaluated before and after transverse aortic constriction (TAC) in wild-type (WT) and AT(1A)R knockout (KO) mice. RESULTS: Although the LV systolic pressure (83.2+/-10.0 mmHg, n=5) of the KO mice was lower than that (90.0+/-5.0 mmHg, n=7) of the WT mice, there was no difference in the increase in the LV systolic pressure between the WT and KO mice (WT, 42.0 mmHg; KO, 41.8 mmHg). Also, there was no difference between the baseline LV-to-body weight (LVW/BW) ratio between the two groups (WT, 3.10+/-0.21 mg/g; KO 3.04+/-0.21 mg/g). Two weeks after TAC, the degree of increase in the LVW/BW ratio was markedly increased in both the WT (4.17+/-0.28 mg/g, n=9) and KO mice (4.16+/-0.43 mg/g, n=8), which were almost identical (WT, 34.5%; KO, 36.8%). There were no significant differences in the LV end-diastolic pressure, LV+dP/dt(max), and heart rate between the two groups. The ERK44/42 and p38-MAPK activities in the LV were markedly increased by TAC in both groups, but that of JNK was not. Interstitial and perivascular fibrosis developed in both groups following TAC. However, the degree of increased fibrosis was significantly attenuated in the KO mice. CONCLUSION: These results suggest AT(1A)R-mediated signaling is not indispensable for the development of pressure overload-induced LVH, and provides new insights into the development of novel therapeutic strategies for cardiac hypertrophy.

Cellular Cardiomyoplasty Using Bone Marrow Derived Mesenchymal Stem Cells Transplantation in Post Myocardial Infarction Heart Failure

BACKGROUND AND OBJECTIVES: Cellular cardiomyoplasty (CCM) is considered to be a novel therapeutic approach for post-myocardial infarction (MI) heart failure. In this study, the functional effects of cultured mesenchymal stem cells (MSCs) transplantation and the associated histopathologic changes were evaluated in a rat model of MI. MATERIALS AND METHODS: Rats were subjected to 5 hours of coronary ligation followed by reperfusion, and 10 days after MI, animals were randomized into either the MSCs transplantation (MI-MSC, n=8) group or the control (n=8) group. Allogeneic MSCs (3x10(6) cells) or media were epicardially injected into the center and the border area of the infarct scar. RESULTS: Four weeks after the MSCs transplantation, the echocardiogram showed preserved anterior regional wall motion and increases in fractional shortening in the MI-MSC heart relative to the control heart. Left ventricular (LV) end diastolic pressure was smaller in the MI-MSC than in the control group. Implanted MSCs formed islands of cell clusters on the border of the infarct scar, and the cells were positively immunostained by sarcomeric alpha-actinin and cardiac troponin T. In addition, the number of microvessels on the border area of the infarct scar was greater in the MI-MSC than in the control group. CONCLUSION: Allogeneic MSCs transplanted into the MI scar formed clusters of cell grafts on the border of the infarct, expressed cardiac muscle proteins, increased microvessel formation, and improved regional and global LV function. Our data indicate that CCM using MSCs may have a significant role in the treatment of post-MI heart failure.

Establishment and Magnetocardiographic Changes of Pressure Overload Left Ventricular Hypertrophy and Its Regression in Rats

BACKGROUND AND OBJECTIVES: Regression of left ventricular hypertrophy (LVH) is important because development of myocardial ischemia, heart failure or arrhythmias may be reduced. However, an animal model for LVH regression is not well established and there are no useful parameters to predict LVH regression. Magnetocardiogram (MCG), magnetic signal generated from the heart, has recently been investigated for the detection of electrical current changes of the heart. This study was undertaken to establish rat models of LVH-regression and to assess MCG changes during LVH induction and regression. MATERIALS AND METHODS: Rat models of pressure overload LVH were established by transverse aortic constriction (TAC) and LVH regression was generated by untying 2 weeks after TAC. Hemodynamic, echocardiographic and biochemical evaluation were performed in order to confirm this model. Magnetic fields were recorded with a SQUID gradiometer before and after TAC, and also recorded at 1, 3, 7, and 14 days after untying, respectively. RESULTS: Rat models of LVH-regression were established successfully by TAC and untying. The pressure gradient across TAC disappeared within 10 minutes after untying. LV weight, LV weight/body weight ratio, LV mass and expression level of atrial natriuretic factor were significantly increased following TAC and decreased to baseline value after pressure unloading. Deeper S waves and strain patterns were observed after LVH induction and gradually returned to basal levels over the 2 weeks after untying. CONCLUSION: MCG changes in the rat models of LVH-regression indicate that MCG can be a helpful modality for the diagnosis and evaluation of LVH as well as follow-up after treatment of LVH.

Expression of Nitric Oxide Synthase Isoforms after Endothelial Denudation of the Rat Carotid Artery

BACKGROUND AND OBJECTIVES: The nitric oxide synthase (NOS) system may be involved in the healing process following arterial injury. The expressions of eNOS or iNOS have been observed separately following endothelial denudation of rat carotid arteries. However, the expressions of nitric oxide synthase isoforms (eNOS, iNOS and nNOS) have not been observed simultaneously. MATERIALS AND METHODS: Using balloon catheter denudation of the rat carotid artery, as a model for arterial injury and restenosis, we have evaluated the time course of the expressions of eNOS, iNOS and nNOS simultaneously using immunohistochemistry and RT-PCR. RESULTS: From the immunohistochemistry, the iNOS protein was shown to be rapidly induced following injury (day 1) and was later seen to be relocalized to the neointima (day 5). Two weeks following injury the iNOS expression had declined. After 4 weeks the iNOS expression had disappeared completely. The eNOS protein was not detected until three days post injury. Two weeks following injury the eNOS expression was observed at the "pseudoendothelial" surface forming intimal smooth muscle cells. By week 4 the eNOS expression was detected on the morphological endothelium. The nNOS expression was detected at the media one day following injury and for the subsequent two weeks, but it was not detected at the neointima at all. RT-PCR demonstrated that iNOS mRNA was faintly expressed 1 day following endothelial denudation. The expression level of the iNOS mRNA was highest at 5 days, but gradually decreased until 2 weeks following injury. CONCLUSION: These results suggest that endothelial disruption may induce the expressions of iNOS and nNOS, and the re-expression of eNOS may reduce these expressions. The expressions of iNOS and nNOS could be a homeostatic mechanism that compensates for the loss of endothelium.

Molecular Cloning of Mouse FK-506 Binding Protein 12.6 Gene and Its Biological Function and Expression Patterns in the Various Models of Heart Disease

BACKGROUND AND OBJECTIVES: The FK-506 binding protein 12 (FKBP12) regulates intracellular Ca2+ release by stabilizing the Ca2+-induced Ca2+-release channel (ryanodine receptor) in skeletal muscle. It has been recently shown that a different FKBP, FKBP12.6, is specifically associated with cardiac ryanodine receptor. Since the role of FKBP12.6 in excitation-contraction coupling in the cardiac muscle has not been precisely determined, its biological function was assessed and expression patterns of FKBP12.6 were evaluated in the various models of heart disease. MATERIAL AND METHODS: The mouse (m) FKBP12.6 gene was cloned and characterized after screening a mouse genomic DNA library using a mFKBP12.6 cDNA obtained through reverse transcriptase-polymerase chain reaction. Expression levels of mFKBP12.6 was evaluated during cardiac development and in the models of cardiac hypertrophy and failure. RESULTS: Both mFKBP12.6 and mFKBP12 contain an open reading frame of 327 nucleotides encoding 108 amino acids. Comparison of mFKBP12.6 cDNA to rat FKBP12.6, human FKBP12.6 and mFKBP12 cDNA revealed 95%, 94% and 74% identity in nucleotide sequence and 98%, 97% and 80% identity in amino acid sequence, respectively. Purified recombinant mFKBP12.6 migrated slower than either mFKBP12 or human FKBP12 on an SDS-polyacrylamide gel, despite having the same number of amino acids and a slightly lower calculated molecular mass. Northern blot analysis showed that the expression of FKBP12 and FKBP12.6 to be highest in brain. While the expression of FKBP12 was much stronger in adult than in embryonic hearts, it was further increased following pressure overload hypertrophy. FKBP12.6 mRNA expression analyzed by RNase protection assay was upregulated after induction of cardiac hypertrophy like FKBP12, whereas it was decreased in the failing heart. The mFKBP12.6 gene contains 5 exons and the proteincoding region of the gene was divided into 4 exon modules. CONCLUSION: We report the molecular cloning and characterization of the mouse FKBP12.6 gene. According to these results, FKBP12 and FKBP12.6 may play a role in the development of cardiac hypertrophy and transition to heart failure. To precisely determine the role of FKBP12 and FKBP12.6 in the heart, a strategy using homologous recombination in embryonic stem cells to conditionally ablate exon 2 of mFKBP12.6 gene has been developed and initial characterization is now underway.

Role of Calcineurin-Dependent Signaling Pathway on the Left Ventricular Hypertrophy Induced by Pressure Overload

BACKGROUND AND OBJECTIVES: Calcineurin-dependent transcriptional pathway has recently been implicated in cardiac hypertrophy. Whether calcineurin inhibition can prevent the development of pressure-overload left ventricular hypertrophy (LVH) is still controversial. To elucidate this issue, the effects of calcineurin inhibitors on the prevention of pressure-overload LVH were examined in mice. MATERIALS AND METHODS: Pressure overload was induced by transverse aortic contriction (TAC) in 57 ICR mice. Three different doses of CsA (TAC/CsA group, n=21) and FK506 (TAC/FK group, n=20) were administered subcutaneously from -2 to 14 days after surgery and 16 mice were treated with vehicle (TAC group). Another 60 mice were sham-operated and treated with CsA (CsA group, n=19), FK506 (FK group, n=18) or vehicle (Control group, n=23). RESULTS: Two weeks after TAC, the LV weight-to-body weight (LVW/BW) ratio was not significantly different among the Control, CsA and FK groups although it was greater in the TAC group (4.55+/-0.69 mg/g) than in the Control(2.78+/-0.70 mg/g) and other sham-operated groups (p<0.00005). Low-dose CsA (5 mg/kg/day) or FK506 (0.6 mg/kg/day) injection following TAC did not decrease the LVW/BW ratio. However, intermediate-dose and high-dose CsA (25 and 50 mg/kg/day) or FK506 (2 and 6 mg/kg/day) treatment prevented pressure-overload induced LVH and the degree of LVH inhibition was dose-dependent. Interstitial and/or perivascular fibrosis was remarkably decreased by the administration of intermediate and high doses of calcineurin inhibitors for 2 weeks following TAC. CONCLUSION: Taken together, calcineurin inhibitors, CsA and FK506, attenuated pressure-overload LVH response in a dose-dependent fashion. This data indicates that a calcineurin-dependent signaling pathway is crucial in the development of pressure-overload LVH.

Mode of Onset of Paroxysmal Atrial Fibrillation during 24 hour Holter Monitoring

BACKGROUND: Paroxysmal atrial fibrillation (PAF) causes not only severe symptoms and hemodynamic changes, but may progress to chronic atrial fibrillation. Autonomic nervous system or atrial premature beat (APB) has been suggested to contribute to the spontaneous initiation of PAF, but the exact mechanism has been largely unknown. METHODS: One hundred and twenty nine episodes of PAF lasting longer than 5 sec were analyzed in 18 patients (M:F=11:?). Two minutes of normal sinus rhythm before the onset of PAF, and the initial one minute of PAF were printed and analyzed. RESULTS: Most of PAFs were initiated by APBs (38%) or rapid atrial tachycardias (AT, 59%). The frequency of APBs tended to increase immediately before PAF onset (p=0.08). The coupling intervals and coupling indices were not significantly different between PAF-producing APBs and benign APBs. More than half of PAF episodes were initiated by rapid ATs (rate, 357+/-50 bpm). After the onset, they accelerated over several seconds and then degenerated into AF. In some cases, transition from AF to atrial flutter and vice versa were observed. Heart rate, measured at 60-second intervals during 2 minutes before PAF onset, did not change significantly (p=0.44). CONCLUSION: Most of PAFs were initiated by APBs or rapid ATs. Heart rate did not change significantly but the frequency of APBs tended to increase immediately before PAF onset. Rapid ATs frequently accelerated and degenerated into AF. In this regard, Holter monitoring could be useful in identifying patients with PAF triggered by rapid ATs.

Effect of Paclitaxel Local Delivery on Neointimal Formation after Endothelial Denudation of the Rat Carotid Artery

BACKGROUND AND OBJECTIVES: Mechanisms of restenosis following successful coronary angioplasty (PTCA) are knownasvascularsmoothmuscle cells(VSMCs)proliferationandmigration, elastic recoil or vascular wall remodeling. Paclitaxel whose effect on the stabilization of microtubles leads to cell death is highly lipophilic, permitting easy pass through cell membrane, and has a long-term antiproliferative effect. This study was performed to evaluate effect of paclitaxel on VSMCs proliferation and whether locally delivered paclitaxel can prevent stenosis and neointimal formation in rat carotid artery injury model. MATERIALS AND METHODS: Cultured VSMCs were exposed to sequential concentrations of paclitaxel in vitro, and proliferation inhibition was analyzed with 3H-thymidine incorporation. Paclitaxel of a suitable concentration was applied to the endothelium-denuded carotid artery of Fisher 344 inbred rats for 20 minutes. Angiogram and morphometric analysis of carotid artery was performed after 2 weeks. RESULTS: 3H-thymidine incorporation in cultured VSMCs was decreased dose-dependently from the concentration of 0.1 micromol/L (2,454+/-149cpm/ microgram protein) to 100 micromol/L (1,323+/-69cpm/ microgram protein) of paclitaxel by single and 20-minute exposure in the presence of platelet-derived growth factor (p<0.005). In the absence of platelet-derived growth factor, the decrement of 3H-thymidine incorporation was evident above the concentration of 5 micromol/L of paclitaxel. To evaluate in vivo effect, paclitaxel (0.1 or 1 micromol/L) was administered into the endothelium-denuded carotid artery by balloon injury and incubated for 20 minutes. Percent stenoses (32.2+/-9.8%) of paclitaxel-treated group was less than those (46.3+/-7.5%) of control group on histologic analysis (p<0.01). Paclitaxel-treated group also had wider lumen on carotid angiogram and less neointimal thickening than control on histologic examination (p<0.005). CONCLUSION: Proliferation of VSMCs was effectively inhibited and neointimal formation and luminal stenosis was prevented in rat carotid artery injury model by single, brief and local delivery of low-dose paclitaxel. This strategy could be applied to clinical settings for the prevention of restenosis after PTCA.

Evidence for a major role of Mg~(2+) in bFGF-mediated angiogenesis / 中国药理学通报

Aim The mechanism of basic fibroblast growth factor(bFGF)in mediating increase of intracellular free magnesium ([Mg2+]i) in human umbilical vein endothelial cells (HUVECs), and the relationship between Mg2+and angiogenesis were investigated in this study.Methods The change of[Mg2+]i in HUVECs were quantitatively detected in intracellular cation measurement system via loaded with the fluorescent magnesium indicator mag-fura-2. Endothelial cells were primarily acquired by infusion of collagen enzyme solutioninto the lumens of human umbilical veins and cultured in M199 with 0.2 fetal bovine serum. The role of bFGF in angiogenesis was observed in presence of 0,1 mmol?L-1 or 2 mmol?L-1 of extracellular Mg2+.Results bFGF dose-dependently increased [Mg2+]i, and there was not any significant difference among the groups of 0,1 mmol?L-1and 2 mmol?L-1 of extracellular Mg2+;similar results were obtained in groups done with Na+ and Ca2+. Pretreatment with bFGF receptor-2 (KDR) inhibitor (SU1498) blocked the increase of [Mg2+]i induced by bFGF.Unlike in the group of 0 mmol?L-1extracellular Mg2+,the apparent angiogeneses were observed in the groups of 1 mmol?L-1 and 2 mmol?L-1 extracellular Mg2+ in the presence of bFGF.bFGF-induced angiogenesis was significantly blocked with SU1498 in the presence of 1 mmol?L-1 extracelluar Mg2+.Conclusions These results suggest that the increase of [Mg2+]i by bFGF come from intracellular Mg2+ pools mediated by KDR-dependent signaling pathways,thereby resulting in the bFGF-induced angiogenesis.