大鼠心肌梗死后心肌NADPH氧化酶亚单位p22phox的表达

目的：探讨心肌梗死大鼠心室重塑与还原型烟酰胺腺嘌呤二核苷酸磷酸（NADPH）氧化酶亚单位p22phox和超氧阴离子的关系。 方法： Sprague-Dawley大鼠冠脉左前降支结扎复制心肌梗死模型，8周后，心脏超声、血流动力学、心脏形态学方法检测分析心室重塑，检测血浆和非梗死心肌脂质过氧化物的浓度。用RT-PCR和免疫组化方法检测p22phox mRNA水平和蛋白水平的分布。用激光共聚焦方法检测心肌超氧阴离子分布。 结果： 心肌梗死后大鼠心室重塑过程显著，与正常对照组比较，左室舒张末压、左室舒张末径［(3.09±1.52 vs 18.24±6.58)mmHg，(0.67±0.06 vs 0.90±0.15)mm, P<0.01］和脂质过氧化物水平在血浆和非梗死心肌均显著大于正常对照组(P<0.05)。p22phox mRNA和蛋白表达以及超氧阴离子分布在梗死和非梗死心肌亦均显著增加。 结论： 大鼠心肌梗死后，NADPH氧化酶表达增高，其来源的超氧阴离子可能通过氧化应激参加心室重塑过程。     

梗死灶周围心肌C3G蛋白表达增加参与了异丙肾上腺素诱导的梗死后心脏重塑恶化的发病机制

 目的 通过观察梗死灶周围心肌C3G蛋白的表达及异丙肾上腺素(ISO)对其的影响,探讨梗死灶周围心肌C3G蛋白是否参与了异丙肾上腺素诱导的梗死后心脏重塑恶化的发病机制。方法 按Litwin方法建立心肌梗死(心梗)及假手术模型。 术后7天仍存活的雄性SD大鼠分为心梗组,假手术组,心梗ISO组,假手术ISO组。其中,心梗组及假手术组给予生理盐水5ml/kg每三天一次, 腹腔注射,至干预后12周;心梗ISO组及假手术ISO组给予ISO 5mg/kg每三天一次, 腹腔注射,余方法同上。免疫印迹检测梗死灶周围心肌C3G 蛋白的表达。结果 干预后12周, 梗死灶周围心肌C3G蛋白表达积分光密度标化值分别为：心梗组（1.14±0.29, n=8）, 假手术组（0.90±0.10,n=6）, 心梗ISO组（1.51±0.18,n=10 ）, 假手术ISO组（0.97±0.26, n=8）。心梗组较假手术组、 心梗ISO组较假手术ISO组、及心梗ISO组较心梗组梗死灶周围心肌C3G蛋白的表达均显著增高（P＜0.05）。 结论 梗死灶周围心肌C3G蛋白表达显著增加, 而ISO可使C3G蛋白表达更显著增加; C3G蛋白表达增加参与了梗死后心室重塑,缺血性心肌病及心力衰竭的发病机制,且C3G蛋白表达进一步增加参与了ISO诱导的梗死后心室重塑,缺血性心肌病及心力衰竭恶化的发病机制。     

心肌梗塞不同时期心肌Ⅰ、Ⅲ型胶原重建的研究

目的:对心肌梗塞不同时期心脏各部位胶原重建进行定性、定位、定量研究。方法:应用免疫组化技术结合自动图象分析方法观察Ⅰ、Ⅲ型胶原分布及含量的变化。结果:心肌梗塞后坏死区Ⅰ、Ⅲ型胶原含量及Ⅰ/Ⅲ比值均增加,以Ⅰ型胶原为主,急性期胶原仍交织成网状,至恢复期坏死心肌全部被胶原取代,呈致密束状与心腔表面平行排列。室间隔(未梗塞区)两型胶原含量及比值均增加,急性期以Ⅲ型胶原增加明显,恢复期以Ⅰ型胶原增加为主。右室在急性期胶原含量无明显改变,恢复期变化同室间隔,也以Ⅰ型胶原为主。结论:心肌梗塞后胶原重建,梗塞区呈修复性纤维化,非梗塞区呈反应性纤维化,右室纤维化较左室晚。     

Intramyocardial transplantation of circulating CD34+ cells: source of stem cells for myocardial regeneration

This study was designed to investigate the increase in the number of circulating CD34+ cells after acute myocardial infarction (MI) and the differentiation of these cells to cardiomyocytes after transplantation into infarcted myocardium. The study involved five donor groups: MI (n=27), sham (n=26), granulocyte-colony stimulating factor (GCSF) (n=26), MI+GCSF (n=25), and control (n=25). Acute MI was induced by ligating the left anterior descending coronary arteries (LAD) of donor rats, and LAD of recipient rats were ligated on the same day. Seven days after ligation, CD34+ cells in donor rats were counted and then were directly injected into the infarcted myocardium of recipient rats. Eight weeks after the transplantation, significant differences (p<0.001) were observed in the CD34+cell counts among the 5 donor groups with the greatest increase in the MI+GCSF donor group. In rats receiving CD34+ cells, the size of the scar area smaller (p<0.001) and the thickness of the scar was greater (p=0.001) than in CD34- and saline-transplanted rats. The transplanted CD34+ cells differentiated into cardiomyocytes in the scar. This study suggests that CD34+ cells may be a potential source of stem cells and that they may be useful in strategies aimed at the regeneration of infarcted myocardium.     

睾酮对心肌梗塞大鼠肥大心肌肌球蛋白ATP酶活性及其同工酶分布的影响

本文观察了肌注睾酮对心肌梗塞(MI)雄鼠左室非梗塞区心肌肥大以及肥大心肌肌球蛋白ATP酶活性和同工酶分布的影响。术后第21日,经睾酮处理的MI组不仅心肌细胞直径明显大于对照MI组,且肌球蛋白ATP酶活性也比对照MI组明显提高(P<0.05)。电泳分析进一步表明,这种提高与同工酶V_1的含量增加有关(80% vs 74%,P<0.05)。提示MI后肌注睾酮在促进非梗塞心肌肥大的同时还能提高心肌的收缩性能,从而有助于左室功能的改善。     

Reactive oxygen species promote angiogenesis in the infarcted rat heart

The purpose of this study was to determine whether reactive oxygen species (ROS) promote cardiac angiogenesis following myocardial infarction (MI) and contribute to cardiac repair. Rats with MI were treated with or without antioxidants, tempol and apocynin. Hearts of these rats were collected at days 2, 4, 7 and 14 post‐MI. We examined the spatial and temporal relationship between oxidative stress and angiogenesis as well as the potential regulation of ROS in cardiac angiogenesis. We found: (i) following MI, gp91^phox, a subunit of NADPH oxidase, a key enzyme for ROS production, was significantly increased in the border zone at day 2, followed by the infarcted myocardium at day 4, peaked at day 7 and declined at day 14, while superoxide dismutase was significantly reduced; (ii) malondialdehyde, a marker of oxidative stress, was significantly increased in the infarcted myocardium at day 7; (iii) pre‐existing blood vessels in the infarcted myocardium underwent necrosis post‐MI, whereas newly formed vessels appeared at the border zone at day 4, and then extended into the infarcted myocardium, where microvascular density peaked at day 7 and (iv) antioxidant treatment significantly reduced microvascular density in the infarcted myocardium at day 7. These observations suggest that following MI, angiogenesis is mostly active in the infarcted myocardium in the first week, which is temporally and spatially coincident with enhanced ROS. Suppression of angiogenesis by antioxidants indicates that ROS promote angiogenesis in the infarcted myocardium and contribute to cardiac repair. Further studies are required to determine the mechanisms responsible for ROS‐mediated cardiac angiogenesis.     

血小板源生长因子对大鼠肝层星状细胞增殖和胶原及血小板源 …

目的 证实血小板源生长因子（ＰＤＧＦ）对体外培养大鼠肝星状细胞增殖和胶原基因表达及ＰＤＧＦ自分泌的作用。方法 ⑴采用完全无血清培养,用＾３Ｈ－ＴｄＲ掺入检测了ＰＤＧＦ、转化生长因子β１（ＴＧＦ－β１）和表皮生长因子（ＥＧＦ）对肝星状细胞的ＤＮＡ合成作用;⑵应用Ｎｏｒｔｈｅｒｎ分子杂交检测了ＰＤＧＦ对肝星状细胞的Ⅰ、Ⅲ型前胶原及ＰＤＧＦ－Ｂ等ｍＲＮＡ表达水平的影响。结果 ＰＤＧＦ、ＥＧＦ均可剂量依赖     

Experimental myocardial infarction in the rat: qualitative and quantitative changes during pathologic evolution.

Surgical occlusion of the left coronary artery of the rat is a relatively simple, economical technique for producing experimental myocardial infarction (MI). Histologic study of 1- to 21-day-old MI in rats showed that following a mild and brief acute inflammatory response at the margins of the necrotic myocardium, there is chronic inflammation, vascular and collagenous proliferation, and resorption of necrostic tissue which progresses until scar formation is complete, usually by 21 days. From Day 1 to Day 21 the volume of infarcted myocardium decreases from 45.9 +/- 5.9% (mean +/- SEM) to 26.1 +/- 3.2% of the left ventricle and infarct thickness decreases from 1.30 +/- 0.06 mm to 0.47 +/- 0.02 mm. Concomitantly, the percent of the surface area of the left ventricle which is infarcted decreases insignificantly from 55.7 +/- 7.2% to 48.3 +/- 4.2%, indicating that the decrease in volume of the infarcted tissue occurs primarily as a result of thinning of the MI. This study provides qualitative and quantitative information on the natural history of MI in rats, which should be useful as a baseline for future studies.     

Characterization of excessive collagen production during development of pulmonary fibrosis induced by chronic silica inhalation in rats.

The activation of collagen synthesis during development of silicotic fibrosis was studied in rats exposed, in dusting chambers, to respirable SiO2 for periods of 2, 4, 6 or 12 months. Control animals were exposed similarly to clean air or TiO2. Development of fibrosis was followed by histological examination, measurement of lung weight and determination of lung collagen content (as hydroxyproline). A steady increase in lung weight and collagen content together with changes in cellularity and metabolic activity of the lungs, as ascertained by chemical determination of DNA and RNA, were measured in the lungs of the SiO2-exposed animals. Hybridization of total lung RNA, extracted at each time point, with cDNA probes specific for type I and type III procollagen mRNA levels showed that the development of fibrosis was associated with increased levels, as compared to age matched controls, of pulmonary procollagen mRNAs. Interestingly, the highest levels of procollagen mRNAs were observed in young (pretreatment control) animals, suggesting that during pulmonary development collagen metabolism in lungs is even greater than during development of fibrosis. In rats exposed to SiO2 the increase in type III procollagen mRNA occurred earlier than the increase in type I procollagen mRNAs. These observations demonstrate both age-dependent and silicosis-related changes in pulmonary procollagen mRNA levels. The results suggest that development of silicosis is associated with an altered capacity of the lungs to regulate collagen accumulation.     

Characterization of excessive collagen production during development of pulmonary fibrosis induced by chronic silica inhalation in rats

The activation of collagen synthesis during development of silicotic fibrosis was studied in rats exposed, in dusting chambers, to respirable SiO2 for periods of 2, 4, 6 or 12 months. Control animals were exposed similarly to clean air or TiO2. Development of fibrosis was followed by histological examination, measurement of lung weight and determination of lung collagen content (as hydroxyproline). A steady increase in lung weight and collagen content together with changes in cellularity and metabolic activity of the lungs, as ascertained by chemical determination of DNA and RNA, were measured in the lungs of the SiO2-exposed animals. Hybridization of total lung RNA, extracted at each time point, with cDNA probes specific for type I and type III procollagen mRNA levels showed that the development of fibrosis was associated with increased levels, as compared to age matched controls, of pulmonary procollagen mRNAs. Interestingly, the highest levels of procollagen mRNAs were observed in young (pretreatment control) animals, suggesting that during pulmonary development collagen metabolism in lungs is even greater than during development of fibrosis. In rats exposed to SiO2 the increase in type III procollagen mRNA occurred earlier than the increase in type I procollagen mRNAs. These observations demonstrate both age-dependent and silicosis-related changes in pulmonary procollagen mRNA levels. The results suggest that development of silicosis is associated with an altered capacity of the lungs to regulate collagen accumulation.     

Increased mRNAs for procollagens and key regulating enzymes in rat skeletal muscle following downhill running

 The purpose of the study was to investigate pre-translational regulation of collagen expression after a single bout of exercise. We analysed steady-state messenger ribonucleic acid (mRNA) levels for collagen types I, III and IV, α- and β-subunits of prolyl 4-hydroxylase and lysyl oxidase (enzymes modifying procollagen chains), and enzyme activity of prolyl 4-hydroxylase from rat soleus muscle (MS) and the red parts of quadriceps femoris muscle (MQF) after 12 h and after 1, 2, 4, 7 and 14 days of downhill (–13.5°) treadmill running at a speed of 17 m·min^–1 for 130 min. Histological and biochemical assays revealed exercise-induced muscle damage in MQF but not MS. Steady-state mRNA levels for the α- and β-subunits of prolyl 4-hydroxylase in MQF, lysyl oxidase in MS and MQF were increased 12 h after running, whereas prolyl 4-hydroxylase activity did not increase until 2 days after exercise. The mRNA levels for the fibrillar collagens (I and III) and basement membrane type IV collagen significantly increased 1 day and 12 h after exertion, respectively. Peak mRNA levels were observed 2–4 days after running, the increases being more pronounced in MQF than in MS. No significant changes were observed in types I or III collagen at the protein level. Strenuous downhill running thus causes an increase in gene expression for collagen types I and III and their post-translational modifying enzymes in skeletal muscle in a co-ordinated manner. These changes, together with the increased gene expression of type IV collagen, may represent the regenerative response of muscle extracellular matrix to exercise-induced injury and an adaptive response to running exertion. Received: 20 July 1998 / Received after revision: 30 November 1998 / Accepted: 26 January 1999     

Effects of ascorbic acid on collagen mRNA levels in short term chondrocyte cultures

Chondrocytes isolated from 16 day chicken embryo sterna and adult (18 month) bovine metacarpalphalangeal joint cartilage were grown in monolayer culture for up to 5 days in the presence and absence of ascorbate (50 micrograms/ml). RNA was isolated from these cultures and the steady-state levels of alpha 1(I), alpha 2(I) and alpha 1(II) mRNAs were assayed using cloned DNA probes encoding the respective procollagen mRNAs. Both ascorbate-treated and control chicken chondrocytes maintained the characteristic morphology and phenotype synthesizing the same levels of type II procollagen mRNA observed for sternal chondrocytes. The chicken chondrocytes, with or without ascorbate, did not synthesize increased levels of alpha 1(I) or alpha 2(I) mRNA. In contrast, when bovine articular chondrocytes were cultured with ascorbate, an increase in type II procollagen mRNA and, more interestingly, an increase in type I procollagen mRNA was observed during the 5 day culture period. Low levels of type I procollagen mRNA were detected in untreated chicken and bovine cultured chondrocytes and chicken chondrocytes isolated from sterna. These experiments suggest that when cultured in the presence of ascorbate under the conditions examined, chicken embryo chondrocytes retain the differentiated phenotype unaffected by ascorbic acid while bovine articular chondrocytes begin to undergo a phenotypic change.     

激活PPARδ对梗死心肌MMP-9及纤连蛋白表达的影响

目的: 研究过氧化物酶体增殖物激活受体δ(PPARδ)激动剂GW610742X对梗死心肌重塑过程中基质金属蛋白酶9(MMP-9)及细胞间基质纤连蛋白(FN)表达的影响。方法: 雄性Wistar大鼠,分为对照组、假手术组、心肌梗死(MI)组和MI+GW610742X(GW)组。结扎大鼠左冠状动脉建立MI模型,GW组予以GW610742X(100 mg·kg^-1·d^-1)喂养。术后3个月检测各组大鼠左心室游离壁(LVFW)中PPARδ、MMP-9及FN的mRNA及蛋白表达;免疫荧光法检测LVFW中FN的分布。结果: MI组术后3个月LVFW心肌有不同程度的坏死及纤维化。MI组PPARδ表达高于对照组、假手术组及GW组(P＜0.01),GW组PPARδ表达低于对照组及假手术组(P＜0.05);MI组及GW组MMP-9表达高于对照组及假手术组,FN表达低于对照组及假手术组(P＜0.01或P＜0.05)。GW组MMP-9表达低于MI组(P＜0.05),FN表达高于MI组(P＜0.01)。假手术组与对照组MMP-9及FN的表达无显著差异(P＞0.05)。结论: 梗死心肌重构过程中,MMP-9表达上调,FN被降解;激活PPARδ 可能通过抑制MMP-9的表达,减轻FN的降解,从而改善心肌重塑。     

A collagen α2(I) mutation impairs healing after experimental myocardial infarction

Collagen breakdown and de novo synthesis are important processes during early wound healing after myocardial infarction (MI). We tested the hypothesis that collagen I, the main constituent of the extracellular matrix, affects wound healing after MI. The osteogenesis imperfecta mouse (OIM), lacking procollagen-α2(I) expression, represents a model of the type III form of the disease in humans. Homozygous (OIM/OIM), heterozygous (OIM/WT), and wild-type (WT/WT) mice were subjected to a permanent myocardial infarction protocol or sham surgery. Baseline functional and geometrical parameters determined by echocardiography did not differ between genotypes. After MI but not after sham surgery, OIM/OIM animals exhibited significantly increased mortality, due to early ventricular rupture between day 3 and 7. Echocardiography at day 1 demonstrated increased left ventricular dilation in OIM/OIM animals. Less collagen I mRNA within the infarct area was found in OIM/OIM animals. At 2 days after MI, MMP-9 expression in the infarct border zone was higher in OIM/OIM than in WT/WT animals. Increased granulocyte infiltration into the infarct border zone occurred in OIM/OIM animals. Neither granulocyte depletion nor MMP inhibition reduced mortality in OIM/OIM animals. In this murine model, deficiency of collagen I leads to a myocardial wound-healing defect. Both structural alterations within pre-existing collagen matrix and impaired collagen de novo expression contribute to a high rate of early myocardial rupture after MI.     

Quantitative measurement of SC5b-9 and C5b-9(m) in infarcted areas of human myocardium.

Previous immunohistochemical work has indicated that terminal C5b-9 complement complexes are selectively deposited in infarcted areas of human myocardium. In the present study, we sought to quantify C5b-9 levels in myocardial tissue, and to differentiate between the membrane-bound C5b-9 (m) and the cytolytically inactive SC5b-9 complex. Paired tissue specimens from infarcted and non-infarcted myocardium were obtained from 36 autopsies. The homogenized and washed tissues were extracted with n-octyl-beta-D-glucopyranoside (octylglucoside) detergent, and the concentrations of C5b-9 in the extracts were determined by ELISA. Membrane-derived C5b-9 (m) and SC5b-9 were differentiated from each other on the basis of their characteristic sedimentation behaviour in sucrose density gradients. It was found that infarcted myocardial tissue contained on average an approximately three-fold higher concentration of C5b-9, compared with non-infarcted tissue. This increase was due in part to an increase in levels of C5b-9 (m). The results corroborate previous immunohistochemical data and show that complement activation occurs to completion with the generation of potentially cytotoxic C5b-9 complexes in infarcted myocardial tissues.     

Fibroblast migration after myocardial infarction is regulated by transient SPARC expression

Secreted protein, acidic, and rich in cysteine (SPARC) is thought to regulate cell matrix interaction during wound repair. We hypothesized that SPARC might promote migration via integrin-dependent mechanisms. The present study was designed to clarify the contribution of SPARC in the wound healing process after myocardial infarction (MI). Adult mice received a specific α_v integrin inhibitor or vehicle through osmotic mini pumps. Mice of each group were either sham-operated or MI was induced. SPARC expression was investigated 2 days, 7 days, and 1 month after the surgical procedure. For migration assays, a modified Boyden chamber assay was used. A transient increase of SPARC levels was observed, starting at day 2 (2.55±0.21), day 7 (3.72±0.28), and 1 month (1.9±0.16) after MI. After 2 months, SPARC expression dropped back to normal levels compared to sham-operated hearts. Immunofluorescence analysis showed an increase of SPARC in the infarcted area 2 days after MI, a strong increase in the scar area 7 days after MI, and only low levels in the scar area 2 months after MI. Integrin α_v inhibition abolished the up-regulation of SPARC. In vitro migration assays demonstrated that fibronectin-stimulated haptotaxis of fibroblasts was modulated by SPARC. This study provides evidence that SPARC is significantly up-regulated in the infarcted region after MI. This up-regulation is dependent on α_v integrins. As SPARC is found to regulate fibroblast migration, it appears to play an important role in the injured myocardium with regard to healing and scar formation. Electronic Supplementary Material Supplementary material is available for this article at .     

厄贝沙坦对大鼠梗死心肌组织中HGF mRNA和蛋白水平的影响

目的:通过观察厄贝沙坦对大鼠心肌梗死模型中缺血心肌肝细胞生长因子(HGF)mRNA和蛋白水平的影响,探讨厄贝沙坦减轻心肌纤维化的可能机制。方法:采用雄性Wistar大鼠建立心肌梗死模型,术后24 h将存活大鼠随机分为模型组和厄贝沙坦组,另设假手术组,每组9只大鼠。厄贝沙坦组予以厄贝沙坦50 mg·kg-1·d-1灌胃,模型组及假手术组给予等体积生理盐水灌胃,每天1次。4周后心脏取材,测量各组大鼠体重及左室重量,HE染色法观察缺血心肌病理改变,RT-q PCR和Western blot法检测各组大鼠心肌组织中HGF mRNA及蛋白水平的表达。结果:HE染色可见假手术组心肌细胞排列整齐,模型组及厄贝沙坦组心肌结构紊乱,药物组病理改变较模型组减轻;4周后各组大鼠体重无显著差异,各组间左心室重量差异有统计学意义(P0.01),厄贝沙坦组及模型组左室重量高于假手术组(P0.05),同时厄贝沙坦组低于模型组(P0.05);各组大鼠心肌组织中均检测到HGF的mRNA及蛋白水平,厄贝沙坦组及模型组HGF的mRNA与蛋白含量均高于假手术组(P0.05),厄贝沙坦组HGF的mRNA与蛋白水平低于模型组(P0.05)。结论:心肌梗死模型大鼠应用厄贝沙坦治疗4周时左室重量明显减轻,心肌组织病理变化得到改善,心肌组织中HGF的mRNA与蛋白水平降低。     

Previous exercise training increases levels of PPAR-α in long-term post-myocardial infarction in rats,which is correlated with better inflammatory response

OBJECTIVE:

Exercise is a protective factor for cardiovascular morbidity and mortality, with unclear mechanisms. Changing the myocardial metabolism causes harmful consequences for heart function and exercise contributes to metabolic adjustment modulation. Peroxisome proliferator-activated receptors (PPARs) are also myocardium metabolism regulators capable of decreasing the inflammatory response. We hypothesized that PPAR-α is involved in the beneficial effects of previous exercise on myocardial infarction (MI) and cardiac function, changing the expression of metabolic and inflammatory response regulators and reducing myocardial apoptosis, which partially explains the better outcome.

METHODS AND RESULTS:

Exercised rats engaged in swimming sessions for 60 min/day, 5 days/week, for 8 weeks. Both the exercised rats and sedentary rats were randomized to MI surgery and followed for 1 week (EI1 or SI1) or 4 weeks (EI4 or SI4) of healing or to sham groups. Echocardiography was employed to detect left ventricular function and the infarct size. Additionally, the TUNEL technique was used to assess apoptosis and immunohistochemistry was used to quantitatively analyze the PPAR-α, TNF-α and NF-κB antigens in the infarcted and non-infarcted myocardium. MI-related mortality was higher in SI4 than in EI4 (25% vs 12%), without a difference in MI size. SI4 exhibited a lower shortening fraction than EI4 did (24% vs 35%) and a higher apoptosis/area rate (3.97±0.61 vs 1.90±1.82) in infarcted areas (both p=0.001). Immunohistochemistry also revealed higher TNF-α levels in SI1 than in EI1 (9.59 vs 4.09, p<0.001) in infarcted areas. In non-infarcted areas, EI4 showed higher levels of TNF-α and positive correlations between PPAR-α and NF-κB (r=0.75, p=0.02), in contrast to SI4 (r=0.05, p=0.87).

CONCLUSION:

Previously exercised animals had better long-term ventricular function post-MI, in addition to lower levels of local inflammatory markers and less myocardial apoptosis, which seemed to be related to the presence of PPAR-α.