心肌梗死局部注射壳聚糖水凝胶材料的存留和降解

背景：研究发现壳聚糖水凝胶可促进受损组织新生血管生成,修复损伤细胞和组织。 目的：观察心肌梗死部位局部注射壳聚糖水凝胶材料的存留和降解及其对心脏功能的保护作用。 方法：结扎Wistar大鼠冠状动脉左前降支致心肌梗死30 min 后,随机抽签法分为壳聚糖水凝胶注射组、心肌梗死模型组、PBS注射组。术后1,2,4 周使大鼠心脏停留在舒张期行心肌组织学检查,术后4周进行心电图、心脏超声检测,并进行大鼠颈动脉插管,检测心脏功能和心室内压。 结果与结论：壳聚糖水凝胶注射1,2 周后在心肌组织中有明显存留,4 周后已降解吸收,无明显残留。注射4周后心脏超声、心室血流动力学及心室内压检测结果表明,壳聚糖水凝胶注射组心脏功能明显好于心肌梗死模型组、PBS 注射组,而心肌梗死模型组和PBS 注射组之间没有明显的区别。说明以壳聚糖为支架材料,应用配制的可注射性液态支架进行心肌梗死局部注射治疗,注射4周后无明显残留,保护和改善了心脏功能,适宜作为可注射性组织工程化心肌的支架材料。     

胚胎干细胞移植治疗急性心肌梗死后心肌病理形态学及血流动力学变化

目的：探讨胚胎干细胞(ESC)移植治疗急性心肌梗死(AMI)后心肌组织形态学及血液动力学变化。 方法： Wistar大鼠40只随机分为正常对照组、梗死未治疗组(梗死组)、梗死中心移植组(中心组)、梗死周边移植组(周边组)共4组。结扎冠状动脉左前降支制成心肌梗死模型，梗死后1周移植体外分化并经标记的ESCs，移植后4周分别检测组织形态及血流动力学指标的改变。 结果： 移植后4周，周边组移植细胞稳定存活，而中心组移植细胞未能存活。心功能及组织学检测表明中心组与梗死组无显著差异(P＞0.05)；与梗死组比较，周边组梗死面积显著小于梗死组(P＜0.01)，(21.0±1.3)% vs (40.7±2.2)%；左室重量小于梗死组(P＜0.01)，(702.0±24.0)mg vs (882.2±32.6)mg；反映左室收缩功能的指标+dp/dtmax和LVSP均大于梗死组(P＜0.01)，分别为 (7.9±0.7)×103mmHg/s vs (5.9±0.5)×103 mmHg/s和(117.5±10.7) mmHg vs (89.2±8.1) mmHg；而LVEDP均明显小于梗死组(P＜0.01)，(8.5±0.3)mmHg vs (13.6±1.2)mmHg。 结论： 急性心肌梗死后于梗死周边区移植ESCs可以阻止心室重构、减少瘢痕面积、改善心功能。     

Complement localization in ischemic baboon myocardium

Complement localization was examined by direct immunoperoxidase procedures on frozen sections of baboon myocardium obtained 24 hours after ligation of the left anterior descending coronary artery. There was extensive localization of C3, C4, and C5 in most infarcted myocardial fibers; however, in these infarcted areas of myocardium, complement components were not found in myocytes immediately adjacent to either the endocardium or epicardium. Although C3, C4, and C5 were all present within the same myocardial fibers as assessed in adjacent serial sections, the light microscopic distribution of these components was dissimilar, i.e., C3 and C5 were present in both a granular and a diffuse pattern within myocytes, whereas C4 was always localized in a diffuse pattern. Complement components C3 and C5, but not C4, were also localized in the walls of small muscular arteries in infarcted myocardium. No complement was observed in myocardial fibers or blood vessels in normal baboon myocardium. Electron microscopic evaluation of C3 localization within infarcted myocardium indicated that C3 was associated with contractile elements of myocytes, as well as with membranes of myocyte nuclei, mitochondria, and sarcoplasmic reticulum. Within vascular smooth muscular cells, C3 was associated with myofilaments and mitochondrial membranes. Thus, the results of this study provide new information regarding the cellular and subcellular distribution of complement components in infarcted baboon myocardium. If this localization of C3, C4, and C5 is a result of their in situ activation within the ischemic myocardium, a variety of complement-derived phlogistic products would be expected to have been produced and to have effected, in part, the subsequent inflammatory response.     

Excitation-contraction coupling in hypothermic ischemic myocardium

The excitation-contraction coupling system of the global ischemic hypothermic myocardium was studied by evaluating the functional integrity of the isolated sarcoplasmic reticulum (SR) and myofibrils and determining glycogen decay 30 and 60 min after the onset of surgically induced global ischemia. Calcium uptake by the SR from both the 30- and 60-min groups was depressed (control 0.940 +/- 0.05, 30 min 0.430 +/- 0.033, 60 min 0.535 +/- 0.033 mumol Ca2+ . mg-1 . min-1; P less than 0.001). In contrast SR Ca2+-ATPase activity was not different in the three groups (control 1.150 +/- 0.080, 30 min 1.468 +/- 0.025, 60 min 1.338 +/- 0.199 mumol Pi . mg-1 . min-1; P greater than 0.2). Glycogen decay in the hypothermic group was depressed compared to control (control 7.52 +/- 2.01, 30 min 6.152 +/- 1.16, 60 min 5.814 +/- 1.76 mumol glycogen/mg myocardium; P less than 0.05). Myofibrillar pCa-ATPase curves in both hypothermic ischemic groups were depressed (maximal ATPase activity; control 0.160 +/- 0.028, 30 min 0.1130 +/- 0.01, 60 min 0.127 +/- 0.008 mumol Pi . mg-1 . min-1; P less than 0.01). Kinetic analysis of the myofibrillar pCa-ATPase data, utilizing double-reciprocal plots, demonstrated an increase in Km for the hypothermic ischemic groups. It is concluded that the excitation-contraction coupling system of the hypothermic ischemic myocardium at 1 h is characterized by a defect in the calcium transport system of the sarcoplasmic reticulum with preservation of the Ca2+-ATPase, a depression of the myofibrillar ATPase activity, a decrease in affinity, and the preservation of adequate glycogen stores. It is hypothesized that these defects may explain an observed depression in myocardial function following reperfusion.     

镁对缺血心肌的保护作用

本工作在大鼠离体等容收缩心脏模型上首次观察单纯在缺血期灌注高镁溶液对低血流缺血及缺血后再灌注心肌的作用。结果表明，高镁溶液能减轻缺血期左心室末期压力升高的幅度，减少缺血再灌注心肌乳酸脱氢酶的漏出，维持谷胱甘肽过氧化物酶的活性，脂质过氧化反应终末产物丙二醛生成减少，心功能得到较好的恢复，综合评价各项指标，１５ｍｍｏｌＭｇ＾２＋可能为最佳浓度。     

山莨菪碱对缺血心肌的保护作用

本文观察山莨菪碱(654-2)对大鼠缺血心肌的保护作用。发现大鼠左冠状动脉主干结扎后早期腹腔注射654-2,可使结扎后6小时及21天时的梗塞范围显著缩小,并使21天时的左室心肌收缩性恢复得更好,而结扎后3小时缺血区心肌的超微结构改变得到显著改善。654-2对冠脉结扎与非冠脉结扎大鼠的直接血液动力学作用表现为平均动脉压、心输出量和左室心肌收缩性显著降低,提示654-2可以减少心肌氧耗量,从而对缺血心肌发生有利影响。     

Cell transplantation into ischemic myocardium using mesenchymal stem cells transfected by vascular endothelial growth factor

Aims: To investigate the effects of mesenchymal stem cells (MSCs) transplantation combining with vascular endothelial growth factor (VEGF) gene therapy on myocardium rebuilding, angiogenesis, and heart function improvement in rats with myocardial infarction. Methods: SD rat MSCs were isolated, cultured in vitro, labeled with BrdU and transfected by Ad.VEGF gene. Four weeks after left anterior descending artery was ligated to create rat myocardial infarction, cardiac function was examined with echocardiography. Rats were randomly divided into four groups (n = 10 in each group): Group I: MSCs/Ad.VEGF implantation; Group II: MSCs implantation; Group III: Ad.VEGF injection; Group IV: Control. MSCs differentiation was observed 4 weeks after transplantation. Immunohistochemistry and angiogenesis were observed. Echocardiography was performed to detect the effects on heart function. Results: MSCs labeled with BrdU could be identified in host hearts in group I and II, most of them positively stained with cTnT antibody. Echocardiography indicated that the improvement of the LVEF value in group I was more significant than that in the other three groups (P < 0.01, respectively). Some cells were incorporated into the coronary capillaries in the infarcted region. The capillary density in group I was higher than that in the other three groups (P < 0.01, respectively). Conclusion: MSCs implantation combining with VEGF gene therapy can obviously repair damaged myocardium and enhance the angiogenesis in ischemic heart tissue.     

Retention of reference memory following ischemic hippocampal damage

Retention of reference memory was evaluated in an animal model of cerebral ischemia. Rats were trained for 70 daily trials on an 8-arm radial maze with 5 arms baited, subjected to 30 minutes of forebrain ischemia, allowed to recover for 30 days, and then tested for an additional 50 trials. Post ischemic (PI) rats demonstrated normal retention of reference memory (p less than 0.05). Working memory was significantly impaired postoperatively (p less than 0.05). Morphologic analysis showed that PI rats had primary loss of pyramidal neurons in the CA1 region of hippocampus.     

非创伤缺血预处理对大鼠缺血再灌注心肌的作用

目的:确定非创伤性缺血预处理对大鼠缺血/再灌注(I/R)心肌损伤是否具有对抗作用,以扩展缺血预处理的实际应用.方法:采用非创伤性下肢缺血预处理及经典缺血预处理的动物模型,比较两种处理方法对I/R心肌损伤的效应.实验动物分4组:正常对照组(NC,n=8),开胸旷置50 min;缺血/再灌注组(I/R,n=12),结扎冠脉30 min,再灌注20、180 min;经典缺血预处理组(C-IPC,n=12),按经典Murry法复制;非创伤性下肢缺血预处理组(N-WIPC,n=12),捆绑双下肢5 min,松开5 min,反复4次后,阻断冠脉30 min,再灌20、180 min.以左室功能,心肌梗塞范围,血清肌酸激酶(CK)及心肌组织丙二醛(MDA)含量、超氧化物歧化酶(SOD)活性为观察指标.结果:与I/R组相比,N-WIPC组与C-IPC组均显著缩小I/R后的心肌梗塞范围(P＜0.01);明显恢复I/R后的左室功能(P＜0.05,0.01);减轻自由基对心肌的损害:血清CK,心肌MDA含量显著降低(P＜0.01).N-WIPC组还使心肌SOD活性增高(P＜0.05).结论:非创伤性下肢缺血预处理与经典缺血预处理可诱发同等强度的心肌预处理效应.     

缺血心肌蛋白质组初步研究

目的：研究缺血心肌相关蛋白表达谱。方法： 通过腹腔注射垂体后叶素造成心肌缺血模型，取左心室肌进行二维凝胶电泳，利用PDQuest7.1.1软件分析实验结果。结果： 心肌组织可得512±52个蛋白点，心肌缺血后有10个蛋白表达发生了显著变化(pI/Mr: 4.72/46.16 kD, 5.60/32.35 kD, 7.17/53.14 kD, 7.93/12.78 kD,6.59/35.72 kD,8.56/12.47 kD,8.68/37.49 kD,6.31/13.19 kD, 6.51/60.29 kD, 5.86/13.07 kD)。其中表达增强的有6个蛋白(pI/Mr: 4.72/46.16 kD,5.60/32.35 kD,7.17/53.14 kD, 6.59/35.72 kD, 8.68/37.49 kD, 6.51/60.29 kD)，表达降低的有4个蛋白(pI/Mr: 7.93/12.78 kD, 8.56/12.47 kD, 6.31/13.19 kD, 5.86/13.07 kD)。结论： 这些差异表达的蛋白可能在心肌缺血后的保护与损伤中发挥作用。     

Protection of ischemic rabbit myocardium by glutamic acid

Glutamic acid may protect the ischemic myocardium by increasing the flux through anaerobic pathways for ATP production. We tested this in isolated rabbit hearts that were treated with 0 or 2 mM glutamate. Hearts were stabilized for 30 min, subjected to ischemia for 30 min, and then reperfused for 30 min. Cardiac performance was defined by measuring peak left ventricular pressure (PLVDP) at the apex of a Starling curve and expressed as the %PLVDP attained during the preischemia period. Glutamate improved cardiac performance (%PLVDP, treated vs. untreated) after moderate ischemia (92 vs. 67), severe ischemia (79 vs. 65), and total ischemia (61 vs. 41). During severe ischemia, improved performance was associated with enhanced release (nmol X g wet wt -1 X min -1, treated vs. untreated) of alpha-ketoglutarate (2.3 vs. 1.3), succinate (21.7 vs. 12.3), and lactate (478 vs. 386). The ischemic myocardial content (nmol/mg myocardial protein, treated vs. untreated) of alpha-ketoglutarate (1.7 vs. 1.2) was increased by glutamate. The ischemic content of ATP (25.4 vs. 21.9) and succinate (15.7 vs. 12.1) showed a slight trend toward improvement under glutamate treatment. The study shows an association between improved postischemic cardiac performance and increased production of alpha-ketoglutarate and succinate during glutamate treatment.     

Changes in the microvasculature of ischemic and infarcted myocardium.

The fine structure of the small vessels in experimental myocardial infarcts of 10- to 360-minute duration was studied in 32 dogs and compared with the appearance of the small vessels in the corresponding normal myocardium. Following 10 to 60 minutes of coronary artery occlusion, increasing numbers of endothelial cells showed a marked swelling which was consistent with the presence of an intracellular edema and frequently resulted in various degrees of obstruction of the vessel lumen. After 120 minutes of ischemia, not all endothelial cells were obviously swollen, but all showed signs of degeneration, including changes in organelles similar to those in surrounding muscle cells. A progressive intensification of degenerative changes, particularly with respect to the continuity of the endothelial lining and the integrity of the membrane systems of individual endothelial cells, was observed at 3, 4, 5, and 6 hours after coronary artery ligation, and cell debris could be seen in the lumina of most small vessels.     

The relaxation of sarcomeres in ischemic injury of myocardium

Summary Polarization-microscopic and micrometric investigations of the myocardium during infarction at autopsy and in experimental ischemic conditions, has shown that one of the earliest and most typical morphological signs of ischemic myocardium is sarcomere relaxation. The latter is expressed by the loss of contractility of muscle cells in life time and in strongly frozen corpses, and due to the effects of fixatives. Increase of the percentage of relaxed sarcomeres parallels the duration of experimental ischemia and the time after myocardial infarction. This allows the indirect calculation of irreversible cell change.     

Impaired sarcolemmal membrane permeability in reperfused ischemic myocardium

Summary Sarcolemmal membrane permeability to intravenously injected horseradish peroxidase HRP (MW=40,000) was examined in 8 Wistar rats which had temporary ischaemia produced by left coronary artery ligation. HRP reaction product was identified following 6 min of circulation time by light and electron microscopy. Controls included 4 uninjected animals with coronary ligation, 2 uninjected animals without myocardial ischaemia and 2 injected non operated rats.In normal myocardium, the tracer permeated endothelial plasmalemmal vesicles, intercellular spaces and intracellular vesicles of the T-tubule system, but never permeated the cytoplasm of myocardium cells.As early as 15 min after coronary artery ligation followed by 6 min of reperfusion with circulation of the tracer, HRP product could be seen in the cytoplasm of muscle cells randomly distributed in the subendocardial area. The quantity of permeated cells increased when the ischaemic myocardium is reperfused during 10 min before injecting the tracer.These data indicate that sarcolemmal membrane alteration is an early event in myocardial ischaemic injury and precede the irreversible cellular degenerative changes.This work was supported by research grant from INSERM (ATP 78-95)     

The role of calcium in the ischemic myocardium.

Ischemia of the myocardium results in a loss of ultrastructure and function. Tension generation is diminished or abolished, electrolyte imbalance occurs, and the ATP-generating capacity of the mitochondria is reduced. An intracellular accumulation of Ca2+ appears to precipitate many of these changes, the intracellular accumulation of Ca2+ being caused, in turn, by a failure of the ATP-dependent mechanisms responsible for maintaining intracellular homeostasis with respect to Ca2+. This hypothesis has been tested by the use of hypothermia, pretreatment with verapamil and a reduced extracellular Ca2+ to modify the events precipitated by an ischemic episode.