Permanent Coronary Artery Occlusion Research Articles

Glutaredoxin-1 Overexpression Enhances Neovascularization and Diminishes Ventricular Remodeling in Chronic Myocardial Infarction

Oxidative stress plays a critical role in the pathophysiology of cardiac failure, including the modulation of neovascularization following myocardial infarction (MI). Redox molecules thioredoxin (Trx) and glutaredoxin (Grx) superfamilies actively maintain intracellular thiol-redox homeostasis by scavenging reactive oxygen species. Among these two superfamilies, the pro-angiogenic function of Trx-1 has been reported in chronic MI model whereas similar role of Grx-1 remains uncertain. The present study attempts to establish the role of Grx-1 in neovascularization and ventricular remodeling following MI. Wild-type (WT) and Grx-1 transgenic (Grx-1Tg/+) mice were randomized into wild-type sham (WTS), Grx-1Tg/+ Sham (Grx-1Tg/+S), WTMI, Grx-1Tg/+MI. MI was induced by permanent occlusion of the LAD coronary artery. Sham groups underwent identical time-matched surgical procedures without LAD ligation. Significant increase in arteriolar density was observed 7 days (d) after surgical intervention in the Grx-1Tg/+MI group as compared to the WTMI animals. Further, improvement in myocardial functional parameters 30 d after MI was observed including decreased LVIDs, LVIDd, increased ejection fraction and, fractional shortening was also observed in the Grx-1Tg/+MI group as compared to the WTMI animals. Moreover, attenuation of oxidative stress and apoptotic cardiomyocytes was observed in the Grx-1Tg/+MI group as compared to the WTMI animals. Increased expression of p-Akt, VEGF, Ang-1, Bcl-2, survivin and DNA binding activity of NF-κB were observed in the Grx-1Tg/+MI group when compared to WTMI animals as revealed by Western blot analysis and Gel-shift analysis, respectively. These results are the first to demonstrate that Grx-1 induces angiogenesis and diminishes ventricular remodeling apparently through neovascularization mediated by Akt, VEGF, Ang-1 and NF-κB as well as Bcl-2 and survivin-mediated anti-apoptotic pathway in the infarcted myocardium.

Prevention of heart failure in mice by an antiviral agent that inhibits type 5 cardiac adenylyl cyclase

Despite numerous discoveries from genetically engineered mice, relatively few have been translated to the bedside, mainly because it is difficult to translate from genes to drugs. This investigation examines an antiviral drug, which also has an action to selectively inhibit type 5 adenylyl cyclase (AC5), a pharmaceutical correlate of the AC5 knockout (KO) model, which exhibits longevity and stress resistance. Our objective was to examine the extent to which pretreatment with this drug, adenine 9-β-d-arabinofuranoside (Ara-A), favorably ameliorates the development of heart failure (HF). Ara-A exhibited selective inhibition for AC5 compared with the other major cardiac AC isoform, AC6, i.e., it reduced AC activity significantly in AC5 transgenic (Tg) mice, but not in AC5KO mice and had little effect in either wild-type or AC6Tg mice. Permanent coronary artery occlusion for 3 wk in C57Bl/6 mice increased mortality and induced HF in survivors, as reflected by reduced cardiac function, while increasing cardiac fibrosis. The AC5 inhibitor Ara-A significantly improved all of these end points and also ameliorated chronic isoproterenol-induced cardiomyopathy. As with the AC5KO mice, Ara-A increased mitogen/extracellular signal-regulated kinase (MEK)/extracellular signal-regulated kinase (ERK) phosphorylation. A MEK inhibitor abolished the beneficial effects of the AC5 inhibitor in the HF model, indicating the involvement of the downstream MEK-ERK pathway of AC5. Our data suggest that pharmacological AC5 inhibition may serve as a new therapeutic approach for HF.

Regulation of phosphatase and tensin homolog on chromosome 10 in response to hypoxia

Phosphatase and tensin homolog on chromosome 10 (PTEN) is downregulated during hypertrophic and cancerous cell growth, leading to activation of the prosurvival Akt pathway. However, PTEN regulation in cardiac myocytes upon exposure to hypoxia remains unclear. We explored the role of PTEN in response to hypoxia/ischemia in the myocardium. We validated that PTEN is a transcriptional target of activating transcription factor 2 (ATF-2) and is positively regulated via a p38/ATF-2 signaling pathway. Accordingly, hypoxia-induced upregulation of phosphorylation of ATF-2 and PTEN were reversed by a dominant negative mutant p38. Inhibition of PTEN in cardiomyocytes attenuated hypoxia-induced cell death and apoptosis. Cardiac-specific knockout of PTEN resulted in increased phosphorylation of Akt and forkhead box O 1 (forkhead transcription factors), limited infarct size in animals exposed to ischemia-reperfusion injury, and ameliorated deterioration of left ventricular function and remodeling following permanent coronary artery occlusion. In addition, the activation of Bim, FASL, and caspase was coupled with PTEN activation, all of which were attenuated by PTEN inhibition. In conclusion, cardiomyocyte-specific conditional PTEN deletion limited myocardial infarct size in an in vivo model of ischemia-reperfusion injury and attenuated adverse remodeling in a model of chronic permanent coronary artery ligation.

Structure–Activity Relationship and Preclinical Evaluation of Carbon-11-Labeled Ammonium Salts as PET–Myocardial Perfusion Imaging Agents

Due to the limited availability of suitable positron emission tomography (PET) tracers, the majority of myocardial perfusion imaging (MPI) scans is performed using SPECT rather than PET. The aim of this study is to design and synthesize carbon-11-labeled ammonium salt derivatives and explore their structure–activity relationship (SAR) and their potential as PET–MPI agents. Three carbon-11-labeled ammonium salts were developed. SAR of the labeled compounds were explored vis-à-vis the effects of charge density and lipophilicity on the distribution kinetics in mice. These studies pointed at [11C]4 as the lead compound. Comparative microPET/CT scans in healthy rats, using both [11C]4 and [13 N]–NH3, substantiated the potential of [11C]4 ([11C]-DMDPA). A proof of concept for the potential of radiolabeled ammonium salts as MPI agents has been demonstrated in a newly developed swine model of permanent partial coronary artery occlusion. SAR studies of 11C-labeled ammonium salts suggest that both lipophilicity and charge density affect the performance of these compounds as MPI probes. In a swine model, the labeled lead successfully visualized the defect regions in the myocardium. The data presented call for the development of fluorine-18 analogues, to increase clinical impact.

Acute arrhythmogenesis after myocardial infarction in normotensive rats: Influence of high salt intake

A high salt diet is a known risk factor for cardiovascular diseases that leads to cardiac hypertrophy and creates a substrate for arrhythmias and sudden death. However, acute arrhythmogenesis after infarction has not been studied. Male Wistar rats (21days) received drinking water (MI) or 1% NaCl solution (MI-Salt-C) for 4weeks. Water was given to another group for 4weeks, and on the day before surgery, animals received a 1% NaCl solution (MI-Salt-A). Non-invasive systolic blood pressure (SBP) was obtained before surgery. Myocardial infarction (MI) was produced by permanent occlusion of the left coronary artery. Electrocardiogram was monitored during the first 30min post-occlusion to evaluate arrhythmias. Although SBP was not altered by salt intake (SHAM: 114±2, MI: 112±2, MI-Salt-C: 115±2, MI-Salt-A: 116±4mm Hg), ventricular hypertrophy was observed in the animals receiving chronic salt diet (SHAM: 0.22±0.008, MI: 0.23±0.007, MI-Salt-C: 0.28±0.01; MI-Salt-A: 0.23±0.01g/cm; P<0.05). Ventricular premature beats increased in both salt-loaded groups compared to MI group (MI: 805±81, MI-Salt-C: 1145±98; MI-Salt-A: 1023±77; P<0.05). Atrioventricular blockade was only observed in animals subjected to high salt intake (MI-Salt-C: 38.9%; MI-Salt-A: 42.1%). High salt intake was associated with increased post-infarct arrhythmias; however, this effect was unrelated to ventricular hypertrophy.

Endogenous CGRP protects retinal cells against stress induced apoptosis in rats

Acute stress can provoke apoptosis of the retina cells, and up-regulation of calcitonin gene related peptide (CGRP) in retina. However the role of CGRP in the pathology of the stress induced apoptosis of the retina cells is still elusive. The aim of this study was to investigate the endogenous of CGRP on retinal cell apoptosis induced by the stress of acute myocardial infarction induced by permanent coronary artery occlusion (CAO) in rats. The acute myocardial infarction model was established by ligating the left anterior descending branch of coronary artery in male Sprague-Dawley rats. The rats were randomized into two groups, the CGRP8-37 group and a control group, pretreated with CGRP8-37 (10−7mol/L, 1μL/g, intravenously injected), a specific antagonist of CGRP receptor, and 0.9% saline respectively, at 15min prior to the CAO. The samples of the retina were collected at 3h of CAO for the assays of TUNEL and caspase-3 activity respectively. The total apoptosis ratio of retinal cells in CGRP8-37 group was significantly higher than that in the control group (P<0.05). The capase-3 activity was significantly greater in the CGRP8-37 group, compared with the control group (P<0.05) at 3h of CAO. The vacuolar degeneration of retinal ganglion cells was observed in the CAO animals. The results suggest that the endogenous CGRP may play a protective role in the retinal cell apoptosis induced by the stress of acute myocardial infarction.

Coronary Artery Ligation and Intramyocardial Injection in a Murine Model of Infarction

Mouse models are a valuable tool for studying acute injury and chronic remodeling of the myocardium in vivo. With the advent of genetic modifications to the whole organism or the myocardium and an array of biological and/or synthetic materials, there is great potential for any combination of these to assuage the extent of acute ischemic injury and impede the onset of heart failure pursuant to myocardial remodeling. Here we present the methods and materials used to reliably perform this microsurgery and the modifications involved for temporary (with reperfusion) or permanent coronary artery occlusion studies as well as intramyocardial injections. The effects on the heart that can be seen during the procedure and at the termination of the experiment in addition to histological evaluation will verify efficacy. Briefly, surgical preparation involves anesthetizing the mice, removing the fur on the chest, and then disinfecting the surgical area. Intratracheal intubation is achieved by transesophageal illumination using a fiber optic light. The tubing is then connected to a ventilator. An incision made on the chest exposes the pectoral muscles which will be cut to view the ribs. For ischemia/reperfusion studies, a 1 cm piece of PE tubing placed over the heart is used to tie the ligature to so that occlusion/reperfusion can be customized. For intramyocardial injections, a Hamilton syringe with sterile 30gauge beveled needle is used. When the myocardial manipulations are complete, the rib cage, the pectoral muscles, and the skin are closed sequentially. Line block analgesia is effected by 0.25% marcaine in sterile saline which is applied to muscle layer prior to closure of the skin. The mice are given a subcutaneous injection of saline and placed in a warming chamber until they are sternally recumbent. They are then returned to the vivarium and housed under standard conditions until the time of tissue collection. At the time of sacrifice, the mice are anesthetized, the heart is arrested in diastole with KCl or BDM, rinsed with saline, and immersed in fixative. Subsequently, routine procedures for processing, embedding, sectioning, and histological staining are performed. Nonsurgical intubation of a mouse and the microsurgical manipulations described make this a technically challenging model to learn and achieve reproducibility. These procedures, combined with the difficulty in performing consistent manipulations of the ligature for timed occlusion(s) and reperfusion or intramyocardial injections, can also affect the survival rate so optimization and consistency are critical.

Coronary Artery Ligation and Intramyocardial Injection in a Murine Model of Infarction

Mouse models are a valuable tool for studying acute injury and chronic remodeling of the myocardium in vivo. With the advent of genetic modifications to the whole organism or the myocardium and an array of biological and/or synthetic materials, there is great potential for any combination of these to assuage the extent of acute ischemic injury and impede the onset of heart failure pursuant to myocardial remodeling. Here we present the methods and materials used to reliably perform this microsurgery and the modifications involved for temporary (with reperfusion) or permanent coronary artery occlusion studies as well as intramyocardial injections. The effects on the heart that can be seen during the procedure and at the termination of the experiment in addition to histological evaluation will verify efficacy. Briefly, surgical preparation involves anesthetizing the mice, removing the fur on the chest, and then disinfecting the surgical area. Intratracheal intubation is achieved by transesophageal illumination using a fiber optic light. The tubing is then connected to a ventilator. An incision made on the chest exposes the pectoral muscles which will be cut to view the ribs. For ischemia/reperfusion studies, a 1 cm piece of PE tubing placed over the heart is used to tie the ligature to so that occlusion/reperfusion can be customized. For intramyocardial injections, a Hamilton syringe with sterile 30gauge beveled needle is used. When the myocardial manipulations are complete, the rib cage, the pectoral muscles, and the skin are closed sequentially. Line block analgesia is effected by 0.25% marcaine in sterile saline which is applied to muscle layer prior to closure of the skin. The mice are given a subcutaneous injection of saline and placed in a warming chamber until they are sternally recumbent. They are then returned to the vivarium and housed under standard conditions until the time of tissue collection. At the time of sacrifice, the mice are anesthetized, the heart is arrested in diastole with KCl or BDM, rinsed with saline, and immersed in fixative. Subsequently, routine procedures for processing, embedding, sectioning, and histological staining are performed. Nonsurgical intubation of a mouse and the microsurgical manipulations described make this a technically challenging model to learn and achieve reproducibility. These procedures, combined with the difficulty in performing consistent manipulations of the ligature for timed occlusion(s) and reperfusion or intramyocardial injections, can also affect the survival rate so optimization and consistency are critical.

Autophagy limits acute myocardial infarction induced by permanent coronary artery occlusion

Ischemia is known to potently stimulate autophagy in the heart, which may contribute to cardiomyocyte survival. In vitro, transfection with small interfering RNAs targeting Atg5 or Lamp-2 (an autophagy-related gene necessary, respectively, for the initiation and digestion step of autophagy), which specifically inhibited autophagy, diminished survival among cultured cardiomyocytes subjected to anoxia and significantly reduced their ATP content, confirming an autophagy-mediated protective effect against anoxia. We next examined the dynamics of cardiomyocyte autophagy and the effects of manipulating autophagy during acute myocardial infarction in vivo. Myocardial infarction was induced by permanent ligation of the left coronary artery in green fluorescent protein-microtubule-associated protein 1 light chain 3 (GFP-LC3) transgenic mice in which GFP-LC3 aggregates to be visible in the cytoplasm when autophagy is activated. Autophagy was rapidly (within 30 min after coronary ligation) activated in cardiomyocytes, and autophagic activity was particularly strong in salvaged cardiomyocytes bordering the infarcted area. Treatment with bafilomycin A1, an autophagy inhibitor, significantly increased infarct size (31% expansion) 24 h postinfarction. Interestingly, acute infarct size was significantly reduced (23% reduction) in starved mice showing prominent autophagy before infarction. Treatment with bafilomycin A1 reduced postinfarction myocardial ATP content, whereas starvation increased myocardial levels of amino acids and ATP, and the combined effects of bafilomycin A1 and starvation on acute infarct size offset one another. The present findings suggest that autophagy is an innate and potent process that protects cardiomyocytes from ischemic death during acute myocardial infarction.

The Combined Administration of Multiple Soluble Factors in the Repair of Chronically Infarcted Rat Myocardium

The purpose of this study was to investigate a potential benefit of simultaneous administration of multiple soluble factors (SFs) in the repair of chronically infarcted rat myocardium. Rats subjected to a permanent coronary artery occlusion (myocardial infarction) received a cocktail of SF or a phosphate buffer. Four SFs, fibroblast growth factor-2 (2 μg), insulin-like growth factor-1 (1 μg), hepatocyte growth factor (2 μg), and stromal cell-derived factor-1α (0.6 μg) were injected directly into the ischemic myocardium at the onset of occlusion and subsequently at 3, 7, 14, and 21 days of surgery (intraperitoneally). Cardiac contractile function, infarct size and remodeling, and blood vessel density were studied at 4 weeks postsurgery. Infarct size, left ventricular circumference and cavity volume, thinning ratio, and expansion index were not statistically different between groups. Treatment of SF did not alter ejection fraction, compared with control. No statistical difference in total blood vessel density in the infarct zone was observed in SF versus control. In conclusion, our results that there were no enhancements in cardiac function, reductions in infarct size, improvements in remodeling, or increases in vasculature density in SF versus control do not support the study hypothesis that the combined use of multiple SF benefits the hearts with myocardial infarct.

Metformin improves cardiac function in rats via activation of AMP‐activated protein kinase

1. Metformin is one of the most commonly used drugs for the treatment of Type 2 diabetes. Accumulating evidence suggests that metformin also has cardioprotective effects. In the present study, we investigated the cardioprotective effects of metformin and the mechanisms involved. 2. A rat model of chronic heart failure was established by permanent left coronary artery occlusion. Heart failure rats were randomly divided into four groups: (i) a saline-treated group given 4 mL/kg day via intragastric gavage; (ii) a metformin-treated group, given 100 mg/kg metformin once daily via intragastric gavage; (iii) a group treated with 5 mg/kg 5'-aminoimidazole-4-carboxyamide-ribonucleoside (AICAR), an AMP-activated protein kinase (AMPK) agonist, every second day; and (iv) a group treated with 100 mg/kg per day metformin + 20 mg/kg, i.p., compound C (an AMPK antagonist). After 4 weeks treatment, echocardiography was used to assess left ventricular (LV) dimensions and function. Expression of AMPK, endothelial nitric oxide synthase (eNOS) and transforming growth factor (TGF)-β1 was determined by reverse transcription-polymerase chain reaction and western blot analysis. 3. Metformin administration significantly improved cardiac function and LV remodelling, as evidenced by increases in LV systolic pressure and LV ejection fraction and decreases in LV end-diastolic diameter and LV end-systolic diameter. These beneficial effects of metformin were associated with increased AMPK and eNOS phosphorylation, as well as reductions in insulin, TGF-β1, basic fibroblast growth factor and tumour necrosis factor-α levels in the circulation and/or myocardium. 4. The results indicate that chronic low-dose metformin confers significant cardioprotective effects against chronic heart failure by activating the AMPK-eNOS pathway.

Accelerating global left-ventricular function assessment in mice using reduced slice acquisition and three-dimensional guide-point modelling.

BackgroundTo investigate the utility of three-dimensional guide-point modeling (GPM) to reduce the time required for CMR evaluation of global cardiac function in mice, by reducing the number of image slices required for accurate quantification of left-ventricular (LV) mass and volumes.MethodsFive female C57Bl/6 mice 8 weeks post myocardial infarction induced by permanent occlusion of the left coronary artery, and six male control (un-operated) C57Bl/6 mice, were subject to CMR examination under isoflurane anaesthesia. Contiguous short axis (SAX) slices (1 mm thick 7-9 slices) were obtained together with two long axis (LAX) slices in two chamber and four chamber orientations. Using a mathematical model of the heart to interpolate information between the available slices, GPM LV mass and volumes were determined using full slice (all SAX and two LAX), six slice (four SAX and two LAX) and four slice (two SAX and two LAX) analysis protocols. All results were compared with standard manual volumetric analysis using all SAX slices.ResultsInfarct size was 39.1 ± 5.1% of LV myocardium. No significant differences were found in left ventricular mass and volumes between the standard and GPM full and six slice protocols in infarcted mice (113 ± 10, 116 ± 11, and 117 ± 11 mg respectively for mass), or between the standard and GPM full, six and four slice protocols in control mice, (105 ± 14, 106 ± 10, 104 ± 12, and 105 ± 7 mg respectively for mass). Significant differences were found in LV mass (135 ± 18 mg) and EF using the GPM four slice protocol in infarcted mice (p < 0.05).ConclusionGPM enables accurate analysis of LV function in mice with relatively large infarcts using a reduced six slice acquisition protocol, and in mice with normal/symmetrical left-ventricular topology using a four slice protocol.

Thioredoxin 1 enhances neovascularization and reduces ventricular remodeling during chronic myocardial infarction: A study using thioredoxin 1 transgenic mice

Oxidative stress plays a crucial role in disruption of neovascularization by alterations in thioredoxin 1 (Trx1) expression and its interaction with other proteins after myocardial infarction (MI). We previously showed that Trx1 has angiogenic properties, but the possible therapeutic significance of overexpressing Trx1 in chronic MI has not been elucidated. Therefore, we explored the angiogenic and cardioprotective potential of Trx1 in an in vivo MI model using transgenic mice overexpressing Trx1. Wild-type (W) and Trx1 transgenic (Trx1Tg/+) mice were randomized into W sham (WS), Trx1Tg/+ sham (TS), WMI, and TMI. MI was induced by permanent occlusion of LAD coronary artery. Hearts from mice overexpressing Trx1 exhibited reduced fibrosis and oxidative stress and attenuated cardiomyocyte apoptosis along with increased vessel formation compared to WMI. We found significant inhibition of Trx1 regulating proteins, TXNIP and AKAP 12, and increased p-Akt, p-eNOS, p-GSK-3β, HIF-1α, β-catenin, VEGF, Bcl-2, and survivin expression in TMI compared to WMI. Echocardiography performed 30days after MI revealed significant improvement in myocardial functions in TMI compared to WMI. Our study identifies a potential role for Trx1 overexpression and its association with its regulatory proteins TXNIP, AKAP12, and subsequent activation of Akt/GSK-3β/β-catenin/HIF-1α-mediated VEGF and eNOS expression in inducing angiogenesis and reduced ventricular remodeling. Hence, Trx1 and other proteins identified in our study may prove to be potential therapeutic targets in the treatment of ischemic heart disease.

Mouse myocardial first‐pass perfusion MR imaging

A first-pass myocardial perfusion sequence for mouse cardiac MRI is presented. A segmented ECG-triggered acquisition combined with parallel imaging acceleration was used to capture the first pass of a Gd-DTPA bolus through the mouse heart with a temporal resolution of 300-400 msec. The method was applied in healthy mice (N = 5) and in mice with permanent occlusion of the left coronary artery (N = 6). Baseline semiquantitative perfusion values of healthy myocardium showed excellent reproducibility. Infarct regions revealed a significant decrease in the semiquantitative myocardial perfusion values (0.05 ± 0.02) compared to remote myocardium (0.20 ± 0.04). Myocardial areas of decreased perfusion correlated well to infarct areas identified on the delayed-enhancement scans. This protocol is a valuable addition to the mouse cardiac MRI toolbox for preclinical studies of ischemic heart disease.

Autophagy Reduces the Size of Acute Myocardial Infarction Induced by Permanent Coronary Artery Occlusion

Autophagy Reduces the Size of Acute Myocardial Infarction Induced by Permanent Coronary Artery Occlusion

Response to the Letter by Seropian et al

In response to the letter by Seropian et al, we wish to briefly emphasize some important points addressed in our original article. Our study specifically focused on reparative angiogenesis in a mouse model of myocardial infarction (MI) by permanent coronary artery occlusion.1 We found that MI induces a marked upregulation of phosphoinositide-3 kinase (PI3K)γ in cardiomyocytes and endothelial cells of the periinfarct zone, associated with activation of Akt kinase activity and increased phosphorylation of glycogen synthase kinase-3β and endothelial nitric oxide synthase (eNOS). To ascertain the functional importance of PI3Kγ/Akt induction, we used AS605240, the most potent member of a new class of PI3Kγ-selective inhibitors recently introduced as powerful antiinflammatory agents. AS605240 was given before MI induction to simulate the condition of patients who experience an ischemic accident while under medication with such an agent. AS605240 strongly …

Adenoviral transfer of PKGIα; attenuates apoptosis and necrosis in adipose derived stem cells

Adenoviral transfer of protein kinase G-Iα (PKGIα) protects myocytes from ischemia but the effect of PKGIα on adipose derived stem cells (ASCs) remains unknown. We hypothesize that PKGIα will attenuate necrosis and apoptosis of ASCs in an ischemic environment. ASCs were infected with adenoviral vectors containing PKGIα or a mutant then subjected to simulated ischemia (SI) and reoxygenation (RO) for necrosis or apoptosis studies. To determine the role of PKG overexpression in vivo, adult male ICR mice underwent permanent left coronary artery occlusion before receiving treatment of 2x10^5 cells overexpressing PKGIα or mutant. 2 weeks after surgery, transthoracic echocardiography (TTE) was performed to assess left ventricular (LV) function. PKGIα overexpression reduced necrosis as seen by a decrease in trypan blue positive cells and LDH release when compared to SI/RO control (Fig 1 A, B). TUNEL revealed that apoptosis was also significantly reduced in cells overexpressing PKGIα (5.1± 0.47%) as compared to SI/RO control (12.8±1.07%). ASCs infected with the inactive PKGIαK390A mutant lacked protection. TTE results showed reduced LV dilatation and preservation of ejection fraction with PKG overexpression (Fig 1 C, D). Therefore, adenoviral gene transfer of PKGIα may provide a novel strategy for protecting ASCs against ischemia which could translate to a favorable function in hearts following ischemia. Figure 1Open in figure viewerPowerPoint

The combined administration of multiple soluble factors in the repair of chronically infarcted rat myocardium

The purpose of this study was to investigate a potential benefit of simultaneous administration of multiple soluble factors (SF) in the repair of chronically infarcted rat myocardium. Rats subjected to a permanent coronary artery occlusion (MI) received a cocktail of SF or a phosphate buffer. Four soluble factors, fibroblast growth factor‐2 (2 μg), insulin‐like growth factor‐1 (1 μg), hepatocyte growth factor (2 μg), and stromal cell‐derived factor‐1α (0.6 μg) were injected directly into the ischemic myocardium at the onset of occlusion and subsequently at 3, 7, 14, and 21 days of surgery (ip). Cardiac contractile function, infarct size and remodeling, and blood vessel density were studied at 4 weeks post surgery. Infarct size, left ventricular circumference and cavity volume, thinning ratio, and expansion index were not statistically different between groups. Treatment of SF did not alter ejection fraction, compared to control. No statistical difference in total blood vessel density in the infarct zone was observed in SF vs. control. In conclusion, our results showed that there were no enhancements in cardiac function, reductions in infarct size, improvements in remodeling, nor increases in vasculature density in SF vs. control. These results do not support the study hypothesis that the combined use of SF benefits the hearts with myocardial infarct.

Human umbilical cord blood cells in infarcted rats

Therapy with bone marrow-derived cells has been used in ischemic patients with reported success. The aim of this study was to determine the therapeutic efficacy of fresh and frozen human umbilical cord blood cells (hUCB) in Wistar rats submitted to permanent occlusion of the left coronary artery. Three hours after myocardial infarction, 2 x 10(7) hUCB cells or vehicle were administered by intramyocardial injection. The animals were divided into five groups: control (N = 10), sham operated (N = 10), infarcted that received vehicle (N = 9), infarcted treated with cryopreserved hUCB (N = 7), and infarcted treated with fresh hUCB (N = 5). Cardiac function was evaluated by electrocardiogram (ECG) and echocardiogram (ECHO) before cell therapy, and by ECG, ECHO, cardiopulmonary test, and left ventricular pressure measurements 3 weeks later. After 3 weeks, both groups treated with hUCB still had Q wave present in L1, âQRS >90 degrees and reduced shortening fraction (less than 50%). In addition, cardiac indexes of left ventricular contractility and relaxation were 5484 +/- 875 and -4032 +/- 643 mmHg (cryopreserved hUCB) and 4585 +/- 955 and -2862 +/- 590 mmHg (fresh hUCB), respectively. These values were not statistically different from those of saline-treated animals. Cardiopulmonary exercise test profile was typical of infarcted hearts; exercise time was about 14 min and maximal VO2 was 24.77 +/- 5.00 mL.kg-1.min-1. These data show that hUCB therapy did not improve the cardiac function of infarcted animals or prevent cardiac remodeling.

Blockade of spinal nerves attenuates myocardial apoptosis in acute myocardial ischaemia/infarction in rats

Evidence showed involvement of neural activity in acute myocardial ischaemia but the knowledge about the role in the pathology is still limited. The objective of this study was to examine whether low cervical and upper thoracic epidural anaesthesia could reduce apoptosis of the myocardium induced by 3-h and 6-h permanent coronary artery occlusion (CAO) in rats. The left anterior descending branch of coronary artery was ligated in anaesthetized Sprague-Dawley rats with and without precondition of epidural anaesthesia at the level of upper thoracic segments. Apoptosis of the myocardium insulted by acute myocardial ischaemia and infarction was assessed using terminal deoxynucleotidyl transferase-mediated dUTP nick endlabelling and caspase assay. The apoptotic rates of the myocytes were 16.90 +/- 1.38 and 19.75 +/- 1.47% in the groups of CAO 3 h and CAO 6 h, respectively, whereas in the epidural groups, 10.25 +/- 1.07 and 13.05 +/- 1.19% of the apoptotic rates were detected at 3 and 6 h of CAO, significantly lower than that in the time-matched CAO animals without epidural anaesthesia (P < 0.01). Lower caspase-3 activity was observed in epidural anaesthesia group, 1.41 +/- 0.11 folds of the sham (versus 1.86 +/- 0.14 folds in CAO-3 h group) and 2.0 +/- 0.18 folds (versus 2.87 +/- 0.20 folds in CAO-6 h group) at 3 and 6 h of CAO, respectively, which were statistically significant (P < 0.05). The findings may indicate blockade of spinal nerves could reduce apoptosis of myocardium in acute myocardial ischaemia and infarction.