Background: Autologous adipose tissue–derived mesenchymal stem cells ( ATMSC s) therapy is a promising strategy to improve post–myocardial infarction outcomes. In a porcine model of acute myocardial infarction, we studied the long‐term effects and the mechanisms involved in allogeneic ATMSC s administration on myocardial performance. Methods and Results: Thirty‐eight pigs underwent 50 minutes of coronary occlusion; the study was completed in 33 pigs. After reperfusion, allogeneic ATMSC s or culture medium (vehicle) were intracoronarily administered. Follow‐ups were performed at short (2 days after acute myocardial infarction vehicle‐treated, n=10; ATMSC s‐treated, n=9) or long term (60 days after acute myocardial infarction vehicle‐treated, n=7; ATMSC s‐treated, n=7). At short term, infarcted myocardium analysis showed reduced apoptosis in the ATMSC s‐treated animals (48.6±6% versus 55.9±5.7% in vehicle; P =0.017); enhancement of the reparative process with up‐regulated vascular endothelial growth factor, granulocyte macrophage colony‐stimulating factor, and stromal‐derived factor‐1α gene expression; and increased M2 macrophages (67.2±10% versus 54.7±10.2% in vehicle; P =0.016). In long‐term groups, increase in myocardial perfusion at the anterior infarct border was observed both on day‐7 and day‐60 cardiac magnetic resonance studies in ATMSC s‐treated animals, compared to vehicle (87.9±28.7 versus 57.4±17.7 mL/min per gram at 7 days; P =0.034 and 99±22.6 versus 43.3±14.7 22.6 mL/min per gram at 60 days; P =0.0001, respectively). At day 60, higher vascular density was detected at the border zone in the ATMSC s‐treated animals (118±18 versus 92.4±24.3 vessels/mm ² in vehicle; P =0.045). Cardiac magnetic resonance–measured left ventricular ejection fraction of left ventricular volumes was not different between groups at any time point. Conclusions: In this porcine acute myocardial infarction model, allogeneic ATMSC s‐based therapy was associated with increased cardioprotective and reparative mechanisms and with better cardiac magnetic resonance–measured perfusion. No effect on left ventricular volumes or ejection fraction was observed.

Endothelial cell dysfunction is the principal cause of several cardiovascular diseases that are increasing in prevalence, healthcare costs, and mortality. Developing a standardized, representative in vitro model of endothelial cell dysfunction is fundamental to a greater understanding of the pathophysiology, and to aiding the development of novel pharmacological therapies. We subjected human umbilical vein endothelial cells (HUVECs) to different periods of nutrient deprivation or increasing doses of H₂O₂ to represent starvation or elevated oxidative stress, respectively, to investigate changes in cellular function. Both in vitro cellular models of endothelial cell dysfunction-associated senescence developed in this study, starvation and oxidative stress, were validated by markers of cellular senescence (increase in β-galactosidase activity, and changes in senescence gene markers SIRT1 and P21) and endothelial dysfunction as denoted by reductions in angiogenic and migratory capabilities. HUVECs showed a significant H₂O₂ concentration-dependent reduction in cell viability (p < 0.0001), and a significant increase in oxidative stress (p < 0.0001). Furthermore, HUVECs subjected to 96 h of starvation, or exposed to concentrations of H₂O₂ of 400 to 1000 μM resulted in impaired angiogenic and migratory potentials. These models will enable improved physiological studies of endothelial cell dysfunction, and the rapid testing of cellular efficacy and toxicity of future novel therapeutic compounds.

Background: Hypothermia has been associated with therapeutic benefits including reduced mortality and better neurologic outcomes in survivors of cardiac arrest. However, undesirable side effects have been reported in patients undergoing coronary interventions. Using a large animal model of temperature management, we aimed to describe how temperature interferes with the coronary vasculature. Methods and Results: Coronary hemodynamics and endothelial function were studied in 12 pigs at various core temperatures. Left circumflex coronary artery was challenged with intracoronary nitroglycerin, bradykinin, and adenosine at normothermia (38°C) and mild hypothermia (34°C), followed by either rewarming (38°C; n=6) or moderate hypothermia (Mo HT ; 32°C, n=6). Invasive coronary hemodynamics by Doppler wire revealed a slower coronary blood velocity at 32°C in the Mo HT protocol (normothermia 20.2±11.2 cm/s versus mild hypothermia 18.7±4.3 cm/s versus Mo HT 11.3±5.3 cm/s, P =0.007). Mo HT time point was also associated with high values of hyperemic microvascular resistance (>3 mm Hg/cm per second) (normothermia 2.0±0.6 mm Hg/cm per second versus mild hypothermia 2.0±0.8 mm Hg/cm per second versus Mo HT 3.4±1.6 mm Hg/cm per second, P =0.273). Assessment of coronary vasodilation by quantitative coronary analysis showed increased endothelium‐dependent (bradykinin) vasodilation at 32°C when compared with normothermia (normothermia 6.96% change versus mild hypothermia 9.01% change versus Mo HT 25.42% change, P =0.044). Results from coronary reactivity in vitro were in agreement with angiography data and established that endothelium‐dependent relaxation in Mo HT completely relies on NO production. Conclusions: In this porcine model of temperature management, 34°C hypothermia and rewarming (38°C) did not affect coronary hemodynamics or endothelial function. However, 32°C hypothermia altered coronary vasculature physiology by slowing coronary blood flow, increasing microvascular resistance, and exacerbating endothelium‐dependent vasodilatory response.