Swine Model Of Chronic Ischemia Research Articles

Extracellular Vesicle Injection Improves Myocardial Function and Increases Angiogenesis in a Swine Model of Chronic Ischemia.

BackgroundMesenchymal stem cell–derived extracellular vesicles (EVs) are believed to be cardioprotective in myocardial infarct. The objective of this study was to examine the effects of human mesenchymal cell–derived EV injection on cardiac function, myocardial blood flow, and vessel density in the setting of chronic myocardial ischemia.Methods and ResultsTwenty‐three Yorkshire swine underwent placement of an ameroid constrictor on their left circumflex artery. Two weeks later, the animals were split into 2 groups: the control group (CON; n=7) and the EV myocardial injection group (MVM; n=10). The MVM group underwent myocardial injection of 50 μg of EVs in 2 mL 0.9% saline into the ischemic myocardium. Five weeks later, the pigs underwent a harvest procedure, and the left ventricular myocardium was analyzed. Absolute blood flow and the ischemic/nonischemic myocardial perfusion ratio were increased in the ischemic myocardium in the MVM group compared with the CON group. Pigs in the MVM group had increased capillary and arteriolar density in the ischemic myocardial tissue compared with CON pigs. There was an increase in expression of the phospho–mitogen‐activated protein kinase/mitogen‐activated protein kinase ratio, the phospho–endothelial nitric oxide synthase/endothelial nitric oxide synthase ratio, and total protein kinase B in the MVM group compared with CON. There was an increase in cardiac output and stroke volume in the MVM group compared with CON.ConclusionsIn the setting of chronic myocardial ischemia, myocardial injection of human mesenchymal cell–derived EVs increases blood flow to ischemic myocardial tissue by induction of capillary and arteriolar growth via activation of the protein kinase B/endothelial nitric oxide synthase and mitogen‐activated protein kinase signaling pathways resulting in increased cardiac output and stroke volume.

Effects of Red Wine and Vodka on Collateral-Dependent Perfusion and Cardiovascular Function in Hypercholesterolemic Swine

Moderate consumption of alcohol, particularly red wine, has been shown to decrease cardiac risk. We used a hypercholesterolemic swine model of chronic ischemia to examine the effects of 2 alcoholic beverages on the heart. Yorkshire swine fed a high-cholesterol diet underwent left circumflex ameroid constrictor placement to induce chronic ischemia at 8 weeks of age. One group (HCC, n=9) continued on the diet alone, the second (HCW, n=8) was supplemented with red wine (pinot noir, 12.5% alcohol, 375 mL daily), and the third (HCV, n=9) was supplemented with vodka (40% alcohol, 112 mL daily). After 7 weeks, cardiac function was measured, and ischemic myocardium was harvested for analysis of perfusion, myocardial fibrosis, vessel function, protein expression, oxidative stress, and capillary density. Platelet function was measured by aggregometry. Perfusion to the ischemic territory as measured by microsphere injection was significantly increased in both HCW and HCV compared with HCC at rest, but in only the HCW group under ventricular pacing. Microvessel relaxation response to adenosine 5'-diphosphate was improved in the HCW group alone as was regional contractility in the ischemic territory, although myocardial fibrosis was decreased in both HCW and HCV. Expression of proangiogenic proteins phospho-endothelial nitric oxide synthase and vascular endothelial growth factor was increased in both HCW and HCV, whereas phospho-mammalian target of rapamycin was increased only in the HCV group. Expression of Sirt-1 and downstream antioxidant phospho-FoxO1 was increased only in the HCW group. Protein oxidative stress was decreased in the HCW group alone, whereas capillary density was increased only in the HCV group. There was no significant difference in platelet function between groups. Moderate consumption of red wine and vodka may reduce cardiovascular risk by improving collateral-dependent perfusion through different mechanisms. Red wine may offer increased cardioprotection related to its antioxidant properties.

Functional Exhaustion of Bone Marrow Derived Endothelial Progenitor Cells in a Chronic Swine Model of Myocardial Ischemia

The functional impairment of bone marrow derived endothelial progenitor cells remains an important barrier for cardiac cell-based therapies. Our aim was to create a relevant swine model of chronic ischemia and document its effect on bone derived progenitor cells. We hypothesized that bone marrow derived endothelial progenitor cells would be functionally impaired in the setting of chronic cardiac dysfunction of ischemic origin. At baseline, Landrace miniswine was instrumented with a fixed occluder to the proximal left anterior descending coronary artery. We evaluated the animals over a 3-month period (0, 45 and 90 days). Focal proximal left anterior descending stenosis was angiographically confirmed in all animals (mean diameter stenosis = 96±4%, n=12). The resulting ischemic myocardium had evidence of contractile dysfunction but preserved viability. A progressive decline in circulating levels of endothelial progenitor cells was documented 3 months following instrumentation (P<0.001). Quantitative polymerase chain reaction analysis revealed that chronic myocardial ischemia produced a biphasic response in both hypoxic-inducible factor 1 and stromal-derived factor 1 mRNA expression. While initially unregulated, a gradual decline in hypoxic-inducible factor 1 and stromal-derived factor 1 mRNA expression was observed over time (from day 45 to 90). On serial assessment, endothelial progenitor cell migration in response to chemo attractant gradients of vascular endothelial growth factor (10-200 ng/mL) and stromal cell-derived factor-1 (10-100 ng/mL) was progressively impaired. Decreased circulating levels and migratory dysfunction of bone marrow derived endothelial progenitor cells were documented in a reproducible clinically relevant model of myocardial ischemia. Our model of chronic ischemic cardiac dysfunction could contribute to improved understanding of cellular mechanisms involved in the mobilization and exhaustion of endothelial progenitor cells in patients with heart failure.

Effects of cyclooxygenase inhibition on cardiovascular function in a hypercholesterolemic swine model of chronic ischemia

The cardiovascular effects of cyclooxygenase (COX) inhibition remain controversial, especially in the setting of cardiovascular comorbidities. We examined the effects of nonselective and selective COX inhibition on cardiovascular function in a hypercholesterolemic swine model of chronic ischemia. Twenty-four intact male Yorkshire swine underwent left circumflex ameroid constrictor placement and were subsequently given either no drug (HCC; n = 8), a nonselective COX inhibitor (440 mg/day naproxen; HCNS; n = 8), or a selective COX-2 inhibitor (200 mg/day celecoxib; HCCX; n = 8). After 7 wk, myocardial functional was measured and myocardium from the nonischemic ventricle and ischemic area-at-risk (AAR) were analyzed. Regional function as measured by segmental shortening was improved in the AAR of HCCX compared with HCC. There was no significant difference in perfusion to the nonischemic ventricle between groups, but myocardial perfusion in the AAR was significantly improved in the HCCX group compared with controls at rest and during pacing. Endothelium-dependent microvessel relaxation was diminished by ischemia in HCC animals, but both naproxen and celecoxib improved vessel relaxation in the AAR compared with controls, and also decreased the vasoconstrictive response to serotonin. Thromboxane levels in the AAR were decreased in both HCNS and HCCX compared with HCC, whereas prostacyclin levels were decreased only in HCNS, corresponding to a decrease in prostacyclin synthase expression. Chronic ischemia increased apoptosis in Troponin T negative cells and intramyocardial fibrosis, both of which were reduced by celecoxib administration in the AAR. Capillary density was decreased in both the HCNS and HCCX groups. Protein oxidative stress was decreased in both HCNS and HCCX, whereas lipid oxidative stress was decreased only in the HCCX group. Thus nonselective and especially selective COX inhibition may have beneficial myocardial effects in the setting of hypercholesterolemia and chronic ischemia. Whether these effects modulate cardiovascular risk in patients taking these drugs remains to be seen, but evidence to date suggests that they do not.

Resveratrol supplementation abrogates pro-arteriogenic effects of intramyocardial vascular endothelial growth factor in a hypercholesterolemic swine model of chronic ischemia

Clinical trials of therapeutic angiogenesis with vascular endothelial growth factor (VEGF) have been disappointing, owing likely to endothelial dysfunction. We used a swine model of chronic ischemia and endothelial dysfunction to determine whether resveratrol coadministration would improve the angiogenic response to VEGF therapy. Yorkshire swine fed a high-cholesterol diet underwent left circumflex ameroid constrictor placement, and were given either no drug (high cholesterol control [HCC], n = 8), perivascular VEGF (2 μg sustained release [high cholesterol VEGF-treated; HCV], n = 8), or VEGF plus oral resveratrol (10 mg/kg, [high cholesterol VEGF- and resveratrol-treated; HCVR], n = 8). After 7 weeks, myocardial contractility, perfusion, and microvessel reactivity in the ischemic territory were assessed. Tissue was analyzed for vessel density, oxidative stress, and protein expression. Myocardial perfusion was significantly improved in the HCV group compared with the HCC group; resveratrol coadministration abrogated this improvement. There were no differences in regional myocardial contractility between groups. Endothelium-dependent microvessel relaxation was improved in the HCVR group, and endothelium-independent relaxation response was similar between groups. Arteriolar density was greatest in the HCV group, whereas capillary density was similar between groups. Expression of Akt and phospho-endothelial nitric oxide synthase were increased in the HCVR group. Total protein oxidative stress and myeloperoxidase expression were reduced in the HCVR group, but so was the oxidative-stress dependent phosphorylation of vascular endothelial cadherin (VE-cadherin) and β-catenin. Although resveratrol coadministration decreases oxidative stress and improves endothelial function, it abolishes improvements in myocardial perfusion and arteriolar density afforded by VEGF treatment alone. This effect is due likely to inhibition of the oxidative stress-dependent phosphorylation of VE-cadherin, an essential step in the initiation of arteriogenesis.

Resveratrol Supplementation Abrogates Pro-angiogenic Effects of Intramyocardial VEGF in a Hypercholesterolemic Swine Model of Chronic Ischemia

Introduction: Therapeutic angiogenesis with VEGF improves myocardial perfusion in animal models of chronic ischemia, but results in human trials have been disappointing, likely owing to endothelial dysfunction brought on by comorbidities such as hypercholesterolemia. We used a hypercholesterolemic swine model of chronic ischemia to determine whether resveratrol supplementation would improve the angiogenic response to VEGF therapy. Methods: Twenty-four Yorkshire swine fed high cholesterol diet (total 11 weeks) underwent left circumflex ameroid constrictor placement to create chronic myocardial ischemia.

Endogenous myocardial angiogenesis and revascularization using a gastric submucosal patch

Background The gastrointestinal submucosa physiologically produces angiogenic proteins. We examined whether these properties could lead to endogenous myocardial angiogenesis in a swine model of chronic ischemia. Methods Fifteen Yorkshire swine underwent ameroid constrictor placement around the circumflex artery and either lateral epicardial abrasion, creation of a gastroepiploic artery (GEA) based gastric patch, mucosal avulsion, transdiaphragmatic transfer, and apposition of the patch against the circumflex myocardial territory (number = 8; test animals), or lateral epicardial abrasion alone (number = 7; controls). Seven weeks later, lateral myocardial perfusion, endothelial cell density, and expression of VEGFR-1 and VE-cadherin were determined using isotope-labeled microsphere assays, immunohistochemistry, and immunoblotting, respectively. Results Microsphere assays showed equivalent lateral/anterior myocardial perfusion indices at rest (1.10 ± 0.49 vs 0.95 ± 0.23, test vs control animals; p = 0.54), but higher perfusion in test animals versus controls during pacing (1.05 ± 0.29 vs 0.69 ± 0.09, test vs controls; p = 0.02). Increased myocardial endothelial cell density (42.6 ± 8.5 vs 26.1 ± 11.6 cells per 3850 μm 2, test vs controls; p = 0.02) and expression of VE-cadherin (3.10 ± 0.60-fold change, test vs controls; p = 0.001) were also observed in the lateral territory of test animals versus controls. Reconstitution of the proximally occluded circumflex artery from patch collaterals was demonstrated on gastroepiploic arteriography in a subset of test animals. Conclusions This model results in an angiogenic process of significantly greater magnitude than that resulting from chronic myocardial ischemia alone, without the need for exogenous angiogenic agents.