Cardioprotection in cardiovascular surgery.

Since the invention of cardiopulmonary bypass, cardioprotective strategies have been investigated to mitigate ischemic injury to the heart during aortic cross-clamping and reperfusion injury with cross-clamp release. With advances in cardiac surgical and percutaneous techniques and post-operative management strategies including mechanical circulatory support, cardiac surgeons are able to operate on more complex patients. Therefore, there is a growing need for improved cardioprotective strategies to optimize outcomes in these patients. This review provides an overview of the basic principles of cardioprotection in the setting of cardiac surgery, including mechanisms of cardiac injury in the context of cardiopulmonary bypass, followed by a discussion of the specific approaches to optimizing cardioprotection in cardiac surgery, including refinements in cardiopulmonary bypass and cardioplegia, ischemic conditioning, use of specific anesthetic and pharmaceutical agents, and novel mechanical circulatory support technologies. Finally, translational strategies that investigate cardioprotection in the setting of cardiac surgery will be reviewed, with a focus on promising research in the areas of cell-based and gene therapy. Advances in this area will help cardiologists and cardiac surgeons mitigate myocardial ischemic injury, improve functional post-operative recovery, and optimize clinical outcomes in patients undergoing cardiac surgery.

Effects of diet-induced metabolic syndrome on cardiac function and angiogenesis in response to the sodium-glucose cotransporter-2 inhibitor canagliflozin.

INTRODUCTION: Sodium-glucose cotransporter-2 inhibitors are antidiabetic medications that have been shown to decrease cardiovascular events and heart failure-related mortality in clinical studies. We attempt to examine the complex interplay between metabolic syndrome and the sodium-glucose cotransporter-2 inhibitor canagliflozin (CAN) in a clinically relevant model of chronic myocardial ischemia. METHODS: Twenty-one Yorkshire swine were fed a high-fat diet starting at 6 weeks of age to induce metabolic syndrome. At 11 weeks, all underwent placement of an ameroid constrictor around the left circumflex coronary artery to induce chronic myocardial ischemia. After 2 weeks, swine received either control (CON) (n = 11) or CAN 300 mg by mouth daily (n = 10) for 5 weeks, whereupon all underwent terminal harvest. RESULTS: There was a significant increase in cardiac output and heart rate with a decrease in pulse pressure in the CAN group compared with CON (all P values < .05). The CAN group had a significant increase in capillary density (P = .02). There was no change in myocardial perfusion or arteriolar density. CAN induced a significant increase in markers of angiogenesis, including Phospho-endothelial nitric oxide synthase, Endothelial nitric oxide synthase, vascular endothelial growth factor receptor-1, heat shock protein 70, and extracellular signal-regulated kinases (all P values < .05), plausibly resulting in capillary angiogenesis. CONCLUSIONS: CAN treatment leads to a significant increase in capillary density and augmented cardiac function in a swine model of chronic myocardial ischemia in the setting of metabolic syndrome. This work further elucidates the mechanism of sodium-glucose cotransporter-2 inhibitors in patients with cardiac disease; however, more studies are needed to determine if this increase in capillary density plays a role in the improvements seen in clinical studies.

Patients with uncontrolled hypertension subjected to cardiopulmonary bypass have altered coronary vasomotor responses to serotonin.

BACKGROUND: We previously found that cardioplegic arrest and cardiopulmonary bypass are associated with altered coronary arteriolar response to serotonin in patients undergoing cardiac surgery. In this study, we investigated the effects of hypertension on coronary microvascular vasomotor tone in response to serotonin and alterations in serotonin receptor protein expression in the setting of cardioplegic arrest and cardiopulmonary bypass. METHODS: Coronary arterioles were dissected from harvested pre- and post-cardioplegic arrest and cardiopulmonary bypass right atrial tissue samples of patients undergoing cardiac surgery with normotension, well-controlled hypertension, and uncontrolled hypertension. Vasomotor tone was assessed by video-myography, and protein expression was measured with immunoblotting. RESULTS: Pre-cardioplegic arrest and cardiopulmonary bypass, serotonin induced moderate relaxation responses of coronary arterioles in normotension and well-controlled hypertension patients, whereas serotonin caused moderate contractile responses in uncontrolled hypertension patients. Post-cardioplegic arrest and cardiopulmonary bypass, serotonin caused contractile responses of coronary arterioles in all 3 groups. The post-cardioplegic arrest and cardiopulmonary bypass contractile response to serotonin was significantly higher in the uncontrolled hypertension group compared with the normotension or well-controlled hypertension groups (P < .05). Pre-cardioplegic arrest and cardiopulmonary bypass, expression of the serotonin 1A receptor was significantly lower in the uncontrolled hypertension group compared with the well-controlled hypertension and normotension groups (P = .01 and P < .001). Serotonin 1B receptor expression was higher in the uncontrolled hypertension group compared with the normotension or well-controlled hypertension groups post-cardioplegic arrest and cardiopulmonary bypass (P = .03 and P = .046). CONCLUSION: Uncontrolled hypertension is associated with an increased coronary contractile response of coronary microvessels to serotonin and altered serotonin receptor protein expression after cardioplegic arrest and cardiopulmonary bypass. These findings may contribute to a worse postoperative coronary spasm and worsened recovery of coronary perfusion in patients with uncontrolled hypertension after cardioplegic arrest and cardiopulmonary bypass and cardiac surgery.

Sodium-glucose co-transporter 2 inhibitor canagliflozin modulates myocardial metabolism and inflammation in a swine model for chronic myocardial ischemia.

BACKGROUND: Inflammation and disruption of cardiac metabolism are prevalent in the setting of myocardial ischemia. Canagliflozin, a sodium-glucose costransporter-2 inhibitor, has beneficial effects on the heart, though the precise mechanisms are unknown. This study investigated the effects of canagliflozin therapy on metabolic pathways and inflammation in ischemic myocardial tissue using a swine model of chronic myocardial ischemia. METHODS: Sixteen Yorkshire swine underwent placement of an ameroid constrictor to the left circumflex artery to induce chronic ischemia. Two weeks later, pigs received either no drug (n = 8) or 300 mg canagliflozin (n = 8) daily. Five weeks later, pigs underwent terminal harvest and tissue collection. RESULTS: Canagliflozin treatment was associated with a trend toward decreased expression of fatty acid oxidation inhibitor acetyl-CoA carboxylase and decreased phosphorylated/inactivated acetyl-CoA carboxylase, a promotor of fatty acid oxidation, compared with control ischemic myocardium (P = .08, P = .03). There was also a significant modulation in insulin resistance markers p-IRS1, p-PKCα, and phosphoinositide 3-kinase in ischemic myocardium of the canagliflozin group compared with the control group (all P < .05). Canagliflozin treatment was associated with a significant increase in inflammatory markers interleukin 6, interleukin 17, interferon-gamma, and inducible nitric oxide synthase (all P < .05). There was a trend toward decreased expression of the anti-inflammatory cytokines interleukin 10 (P = .16) and interleukin 4 (P = .31) with canagliflozin treatment. CONCLUSION: The beneficial effects of canagliflozin therapy appear to be associated with inhibition of fatty acid oxidation and enhancement of insulin signaling in ischemic myocardium. Interestingly, canagliflozin appears to increase the levels of several inflammatory markers, but further studies are required to better understand how canagliflozin modulates inflammatory signaling pathways.

Association Between Marijuana Use and Clinical Outcomes After Coronary Artery Bypass Grafting.

INTRODUCTION: Though marijuana use has been linked to an increase in heart failure admissions, no prior study has explored the association between its use and outcomes after coronary artery bypass grafting (CABG). This study examines the relationship between marijuana use and postoperative outcomes in CABG patients. METHODS: We utilized data from the National Inpatient Sample database from 2008 to 2018 for CABG patients ≥18 y old. Patients were divided into two groups based on marijuana use (abuse/dependency versus nonuse). Primary outcomes include in-hospital mortality, favorable discharge, and length of stay (LOS). Secondary outcomes include acute kidney injury (AKI), acute myocardial infarction (AMI), and transient ischemic attack (TIA)/stroke. A multivariable model, adjusted for confounding variables, was utilized for each outcome. RESULTS: A total of 343,796 patients met inclusion criteria for the study, 590 of which were marijuana users. In both marijuana user and nonuser groups, most patients were male and White with an average age of 56.0 and 66.3 y, respectively. There was a nonsignificant decreased odds of in-hospital mortality among marijuana users (odds ratio [OR] = 0.41, [0.141-1.124]). Marijuana users exhibited significantly decreased odds of home discharge (OR = 1.50, [1.24-1.81]), and increased odds of longer LOS (mean 10.4 d versus 9.8 d; OR = 1.14, [1.09-1.20]), AKI (OR = 1.40, [1.11-1.78]), AMI (OR = 1.56, [1.32-1.84]), and TIA/stroke (OR = 1.64, [1.21-2.22]). CONCLUSIONS: Marijuana use and dependency are associated with increased nonhome discharge, AKI, AMI, TIA/stroke, and longer LOS. Further studies are needed to delineate the pathophysiologic derangements that contribute to these unfavorable post-CABG outcomes.

Increased Coronary Contraction to Thromboxane A2 in Cardiac Surgery Patients With Poorly Controlled Hypertension.

INTRODUCTION: Cardioplegia and cardiopulmonary bypass (CP/CPB) alters coronary arteriolar response to thromboxane A2 (TXA2) in patients undergoing cardiac surgery. Comorbidities, including hypertension (HTN), can further alter coronary vasomotor tone. This study investigates the effects of HTN on coronary arteriolar response to TXA2 pre and post-CP/CPB and cardiac surgery. MATERIALS AND METHODS: Coronary arterioles pre and post-CP/CPB were dissected from atrial tissue samples in patients with no HTN (NH, n = 9), well-controlled HTN (WC, n = 12), or uncontrolled HTN (UC, n = 12). In-vitro coronary microvascular reactivity was examined in the presence of TXA2 analog U46619 (10-9-10-4M). Protein expression of TXA2 receptor in the harvested right atrial tissue samples were measured by immunoblotting. RESULTS: TXA2 analog U46619 induced dose-dependent contractile responses of coronary arterioles in all groups. Pre-CPB contractile responses to U46619 were significantly increased in microvessels in the UC group compared to the NH group (P < 0.05). The pre-CP/CPB contractile responses of coronary arterioles were significantly diminished post-CP/CPB among the three groups (P < 0.05), but there remained an increased contractile response in the microvessels of the UC group compared to the WC and NH groups (P < 0.05). There were no significant differences in U46619-induced vasomotor tone between patients in the NH and WC groups (P > 0.05). There were no differences in expression of TXA2R among groups. CONCLUSIONS: Poorly controlled HTN is associated with increased contractile response of coronary arterioles to TXA2. This alteration may contribute to worsened recovery of coronary microvascular function in patients with poorly controlled HTN after CP/CPB and cardiac surgery.

Intramyocardial injection of hypoxia-conditioned extracellular vesicles modulates apoptotic signaling in chronically ischemic myocardium.

Objective: Limited treatments exist for nonoperative chronic coronary artery disease. Previously, our laboratory has investigated extracellular vesicle (EV) therapy as a potential treatment for chronic coronary artery disease using a swine model and demonstrated improved cardiac function in swine treated with intramyocardial EV injection. Here, we seek to investigate the potential cardiac benefits of EVs by using hypoxia-conditioned EVs (HEV). Specifically, this study aims to investigate the effect of HEV on apoptosis in chronically ischemic myocardium in swine. Methods: Fourteen Yorkshire swine underwent placement of an ameroid constrictor on the left circumflex artery. Two weeks later, swine underwent redo left thoracotomy with injection of either saline (control, n = 7) or HEVs (n = 7). After 5 weeks, swine were euthanized for tissue collection. Terminal deoxynucleotidyl transferase dUTP nick end labeling was used to quantify apoptosis. Immunoblotting was used for protein quantification. Results: Terminal deoxynucleotidyl transferase dUTP nick end labeling staining showed a decrease in apoptosis in the HEV group compared with the control (P = .049). The HEV group exhibited a significant increase in the anti-apoptotic signaling molecule phospho-BAD (P = .005), a significant decrease in B-cell lymphoma 2 (P = .006) and an increase in the phospho-B-cell lymphoma to B-cell lymphoma 2 ratio (P < .001). Furthermore, the HEV group exhibited increased levels of prosurvival signaling markers including phosphoinositide 3-kinase, phosphor-extracellular signal-regulated kinase 1/2, phospho-forkhead box protein O1, and phospho-protein kinase B to protein kinase B ratio (all P < .05). Conclusions: In chronic myocardial ischemia, treatment with HEV results in a decrease in overall apoptosis, possibly through the activation of both pro-survival and anti-apoptotic signaling pathways.

Canagliflozin improves coronary microvascular vasodilation and increases absolute blood flow to the myocardium independent of angiogenesis.

OBJECTIVES: Sodium-glucose cotransporter-2 inhibitor, canagliflozin, improves myocardial perfusion to ischemic territory without accompanying changes in vascular density. We aimed to (1) characterize effects on angiogenic pathways, (2) use multiomics to identify gene expression and metabolite profiles relevant to regulation of myocardial blood flow, and (3) investigate drug effect on coronary microvascular reactivity. METHODS: A nondiabetic swine model of chronic myocardial ischemia and nondiabetic rat model were used to study functional and molecular effects of canagliflozin on myocardium and in vitro microvascular reactivity. RESULTS: Canagliflozin resulted in increased coronary microvascular vasodilation and decreased vasoconstriction (P < .05) without changes in microvascular density (P > .3). Expression of the angiogenic modulator, endostatin, increased (P = .008), along with its precursor, collagen 18 (P < .001), and factors that increase its production, including cathepsin L (P = .004). Endostatin and collagen 18 levels trended toward an inverse correlation with blood flow to ischemic territory at rest. Proangiogenic fibroblast growth factor receptor was increased (P = .03) and matrix metalloproteinase-9 was decreased (P < .001) with canagliflozin treatment. Proangiogenic vascular endothelial growth factor A (P = .13), Tie-2 (P = .10), and Ras (P = .18) were not significantly altered. Gene expression related to the cardiac renin-angiotensin system was significantly decreased. CONCLUSIONS: In chronic myocardial ischemia, canagliflozin increased absolute blood flow to the myocardium without robustly increasing vascular density or proangiogenic signaling. Canagliflozin resulted in altered coronary microvascular reactivity to favor vasodilation, likely through direct effect on vascular smooth muscle. Downregulation of cardiac renin-angiotensin system demonstrated local regulation of perfusion. VIDEO ABSTRACT.

One Billion hiPSC-Cardiomyocytes: Upscaling Engineered Cardiac Tissues to Create High Cell Density Therapies for Clinical Translation in Heart Regeneration.

Despite the overwhelming use of cellularized therapeutics in cardiac regenerative engineering, approaches to biomanufacture engineered cardiac tissues (ECTs) at clinical scale remain limited. This study aims to evaluate the impact of critical biomanufacturing decisions-namely cell dose, hydrogel composition, and size-on ECT formation and function-through the lens of clinical translation. ECTs were fabricated by mixing human induced pluripotent stem-cell-derived cardiomyocytes (hiPSC-CMs) and human cardiac fibroblasts into a collagen hydrogel to engineer meso-(3 × 9 mm), macro- (8 × 12 mm), and mega-ECTs (65 × 75 mm). Meso-ECTs exhibited a hiPSC-CM dose-dependent response in structure and mechanics, with high-density ECTs displaying reduced elastic modulus, collagen organization, prestrain development, and active stress generation. Scaling up, cell-dense macro-ECTs were able to follow point stimulation pacing without arrhythmogenesis. Finally, we successfully fabricated a mega-ECT at clinical scale containing 1 billion hiPSC-CMs for implantation in a swine model of chronic myocardial ischemia to demonstrate the technical feasibility of biomanufacturing, surgical implantation, and engraftment. Through this iterative process, we define the impact of manufacturing variables on ECT formation and function as well as identify challenges that must still be overcome to successfully accelerate ECT clinical translation.

Microvascular dysfunction following cardiopulmonary bypass plays a central role in postoperative organ dysfunction.

Despite significant advances in surgical technique and strategies for tissue/organ protection, cardiac surgery involving cardiopulmonary bypass is a profound stressor on the human body and is associated with numerous intraoperative and postoperative collateral effects across different tissues and organ systems. Of note, cardiopulmonary bypass has been shown to induce significant alterations in microvascular reactivity. This involves altered myogenic tone, altered microvascular responsiveness to many endogenous vasoactive agonists, and generalized endothelial dysfunction across multiple vascular beds. This review begins with a survey of in vitro studies that examine the cellular mechanisms of microvascular dysfunction following cardiac surgery involving cardiopulmonary bypass, with a focus on endothelial activation, weakened barrier integrity, altered cell surface receptor expression, and changes in the balance between vasoconstrictive and vasodilatory mediators. Microvascular dysfunction in turn influences postoperative organ dysfunction in complex, poorly understood ways. Hence the second part of this review will highlight in vivo studies examining the effects of cardiac surgery on critical organ systems, notably the heart, brain, renal system, and skin/peripheral tissue vasculature. Clinical implications and possible areas for intervention will be discussed throughout the review.

Visualization of cardiac uptake of bone marrow mesenchymal stem cell-derived extracellular vesicles after intramyocardial or intravenous injection in murine myocardial infarction.

In animal models, human bone marrow mesenchymal stem cell-derived extracellular vesicles (MSC-EV) have been found to have beneficial effects in cardiovascular disease, but only when administered via intramyocardial injection. The biodistribution of either intravenous or intramyocardial injection of MSC-EV in the presence of myocardial injury is uncharacterized at this time. We hypothesized that intramyocardial injection will ensure delivery of MSC-EV to the ischemic myocardium, while intravenous injection will not. Human bone marrow mesenchymal stem cells were cultured and the MSC-EV were isolated and characterized. The MSC-EVs were then labeled with DiD lipid dye. FVB mice with normal cardiac function underwent left coronary artery ligation followed by either peri-infarct intramyocardial or tail vein injection of 3*106 or 2*109 particles of DiD-labeled MSC-EV or a DiD-saline control. The heart, lungs, liver, spleen and kidneys were harvested 2 h post-injection and were submitted for fluorescent molecular tomography imaging. Myocardial uptake of MSC-EV was only visualized after intramyocardial injection of 2*109 MSC-EV particles (p = 0.01) compared to control, and there were no differences in cardiac fluorescence after tail vein injection of MSC-EV (p = 0.5). There was no significantly detectable MSC-EV uptake in other organs after intramyocardial injection. After tail vein injection of 2*109 particles of MSC-EV, the liver (p = 0.02) and spleen (p = 0.04) appeared to have diffuse MSC-EV uptake compared to controls. Even in the presence of myocardial injury, only intramyocardial but not intravenous administration resulted in detectable levels of MSC-EV in the ischemic myocardium. This study confirms the role for intramyocardial injection in maximal and effective delivery of MSC-EV. Our ongoing studies aimed at developing bioengineered MSC-EV for targeted delivery to the heart may render MSC-EV clinically applicable for cardiovascular disease.

Canagliflozin Improves Myocardial Perfusion, Fibrosis, and Function in a Swine Model of Chronic Myocardial Ischemia.

Background Sodium-glucose cotransporter-2 inhibitors are cardioprotective independent of glucose control, as demonstrated in animal models of acute myocardial ischemia and clinical trials. The functional and molecular mechanisms of these benefits in the setting of chronic myocardial ischemia are poorly defined. The purpose of this study is to determine the effects of canagliflozin therapy on myocardial perfusion, fibrosis, and function in a large animal model of chronic myocardial ischemia. Methods and Results Yorkshire swine underwent placement of an ameroid constrictor to the left circumflex artery to induce chronic myocardial ischemia. Two weeks later, pigs received either no drug (n=8) or 300 mg sodium-glucose cotransporter-2 inhibitor canagliflozin orally, daily (n=8). Treatment continued for 5 weeks, followed by hemodynamic measurements, harvest, and tissue analysis. Canagliflozin therapy was associated with increased stroke volume and stroke work and decreased left ventricular stiffness compared with controls. The canagliflozin group had improved perfusion to ischemic myocardium compared with controls, without differences in arteriolar or capillary density. Canagliflozin was associated with decreased interstitial and perivascular fibrosis in chronically ischemic tissue, with reduced Jak/STAT (Janus kinase/signal transducer and activator of transcription) signaling compared with controls. In ischemic myocardium of the canagliflozin group, there was increased expression and activation of adenosine monophosphate-activated protein kinase, decreased activation of endothelial nitric oxide synthase, and unchanged total endothelial nitric oxide synthase. Canagliflozin therapy reduced total protein oxidation and increased expression of mitochondrial antioxidant superoxide dismutase 2 compared with controls. Conclusions In the setting of chronic myocardial ischemia, canagliflozin therapy improves myocardial function and perfusion to ischemic territory, without changes in collateralization. Attenuation of fibrosis via reduced Jak/STAT signaling, activation of adenosine monophosphate-activated protein kinase, and antioxidant signaling may contribute to these effects.

Poorly controlled hypertension is associated with increased coronary myogenic tone in patients undergoing cardiac surgery with cardiopulmonary bypass.

OBJECTIVE: Cardioplegia and cardiopulmonary bypass dysregulate coronary vasomotor tone, which can be further affected by common comorbidities in patients undergoing cardiac surgery. This study investigates differences in coronary myogenic tone and vasomotor responses to phenylephrine before and after cardioplegia and cardiopulmonary bypass based on hypertension history. METHODS: Coronary arterioles before and after cardioplegia and cardiopulmonary bypass were dissected from atrial tissue samples in patients with no hypertension, well-controlled hypertension, or uncontrolled hypertension, as determined by documented history of hypertension, antihypertensive agent use, and clinical blood pressure measurements averaged over 1 year. Myogenic tone in response to stepwise increases in intraluminal pressure was studied between pressure steps. Microvascular reactivity in response to phenylephrine was assessed via vessel myography. Protein expression was measured with immunoblotting. RESULTS: Coronary myogenic tone was significantly increased in the uncontrolled hypertension group compared with the no hypertension and well-controlled hypertension groups before cardioplegia and cardiopulmonary bypass at higher intraluminal pressures, and after cardioplegia and cardiopulmonary bypass across all intraluminal pressures (P < .05). Contractile responses to phenylephrine were significantly enhanced in patients in the uncontrolled hypertension group compared with the well-controlled hypertension group before cardioplegia and cardiopulmonary bypass, and in the uncontrolled hypertension group compared with the no hypertension and well-controlled hyertension groups after cardioplegia and cardiopulmonary bypass (P < .05). There were no differences in myogenic tone or phenylephrine-induced reactivity between the no hypertension and well-controlled hypertension groups (P > .05). There was increased expression of phosphorylated protein kinase C alpha in the uncontrolled hypertension group after cardiopulmonary bypass compared with before cardiopulmonary bypass and increased phosphorylated extracellular signal-regulated kinase 1/2 in the uncontrolled hypertension compared with the no hypertension group after cardiopulmonary bypass (P < .05). CONCLUSIONS: Uncontrolled hypertension is associated with increased coronary myogenic tone and vasoconstrictive response to phenylephrine that persists after cardioplegia and cardiopulmonary bypass.

Extracellular vesicles modulate inflammatory signaling in chronically ischemic myocardium of swine with metabolic syndrome.

OBJECTIVE: Extracellular vesicle (EV) therapy has been shown to mitigate inflammation in animal models of acute myocardial ischemia/reperfusion. This study evaluates the effect of EV therapy on inflammatory signaling in a porcine model of chronic myocardial ischemia and metabolic syndrome. METHODS: Yorkshire swine were fed a high-cholesterol diet for 4 weeks to induce metabolic syndrome, then underwent placement of an ameroid constrictor to the left circumflex artery to induce chronic myocardial ischemia. Two weeks later, pigs received intramyocardial injection of either saline (control) (n = 6) or EVs (n = 8). Five weeks later, pigs were put to death and left ventricular myocardial tissue in ischemic and nonischemic territories were harvested. Protein expression was measured with immunoblotting, and macrophage count was determined by immunofluorescent staining of cluster of differentiation 68. Data were statistically analyzed via Wilcoxon rank-sum test. RESULTS: EV treatment was associated with decreased expression of proinflammatory markers nuclear factor kappa B (P = .002), pro-interleukin (IL) 1ß (P = .020), and cluster of differentiation 11c (P = .001) in ischemic myocardium, and decreased expression of nuclear factor kappa B in nonischemic myocardium (P = .03) compared with control. EV treatment was associated with increased expression of anti-inflammatory markers IL-10 (P = .020) and cluster of differentiation 163 (P = .043) in ischemic myocardium compared with control. There were no significant differences in expression of IL-6, tumor necrosis factor alpha, arginase, HLA class II histocompatibility antigen DR alpha chain, nuclear factor of kappa light polypeptide gene enhancer in B-cells inhibitor alpha, or phosphorylated nuclear factor of kappa light polypeptide gene enhancer in B-cells inhibitor alpha in ischemic myocardium or pro-IL1ß, IL-6, tumor necrosis factor alpha, IL-10, or nuclear factor of kappa light polypeptide gene enhancer in B-cells inhibitor alpha in nonischemic myocardium of EV-treated pigs compared with control. There were no differences in macrophage count in ischemic myocardium between EV-treated pigs and control. CONCLUSIONS: In the setting of metabolic syndrome and chronic myocardial ischemia, intramyocardial EV therapy attenuates proinflammatory signaling.

Extracellular vesicle therapy attenuates antiangiogenic signaling in ischemic myocardium of swine with metabolic syndrome.

OBJECTIVE: Our recent studies using a porcine model of metabolic syndrome (MS) and chronic myocardial ischemia show that extracellular vesicle (EV) therapy improves blood flow and arteriogenesis in ischemic myocardium, although mechanisms of these changes are unclear. We hypothesized that in the setting of MS, EV therapy would decrease antiangiogenic signaling to mediate increased blood flow to chronically ischemic myocardium. METHODS: Yorkshire swine were fed a high-fat diet for 4 weeks to induce MS, then underwent placement of an ameroid constrictor to the left circumflex artery to induce chronic myocardial ischemia. Two weeks later, pigs underwent intramyocardial injection of vehicle (control, n = 6) or human bone marrow-derived EVs (n = 8). Five weeks later, left ventricular myocardium in ischemic territory was harvested. Protein expression was measured using immunoblot analysis, and data were analyzed using Wilcoxon rank sum test. Myocardial perfusion was measured with isotope-labeled microspheres, and correlation data were analyzed using Spearman rank correlation coefficient. RESULTS: EV treatment was associated with decreased expression of antiangiogenic proteins, angiostatin (P < .001) and endostatin (P = .043) in ischemic myocardium compared with control. In EV-treated pigs, there was a negative correlation between blood flow to ischemic myocardium and angiostatin (rs = -0.76; P = .037), but not endostatin expression (rs = .02; P = .98). EV treatment was also associated with decreased cathepsin D, which cleaves precursors to produce angiostatin and endostatin, in ischemic myocardium (P = .020). CONCLUSIONS: In the setting of MS and chronic myocardial ischemia, EV therapy is associated with decreased expression of antiangiogenic proteins, which might contribute to increased blood flow to chronically ischemic myocardium.

Ischemic myocardial inflammatory signaling in starvation versus hypoxia-derived extracellular vesicles: A comparative analysis.

Background: Coronary artery disease remains a leading cause of death worldwide. Bone mesenchymal stem cell-derived extracellular vesicles (EVs) have shown promise in the setting of myocardial ischemia. Furthermore, the properties of the EVs can be modified via preconditioning of progenitor cells. Previous research from our lab demonstrated a significant decrease in proinflammatory signaling following treatment with EVs derived from starvation preconditioning of human bone mesenchymal stem cells (MVM EVs) in a porcine model of chronic myocardial ischemia. However, rodent models have demonstrated that the use of EVs derived from hypoxia preconditioning of bone mesenchymal stem cells (HYP EVs) may have extended benefits compared to MVM EVs. This study evaluated the effect of HYP EVs on inflammation in a swine model of chronic myocardial ischemia. We hypothesized that HYP EVs would have a greater anti-inflammatory effect than MVM EVs or saline (CON). Methods: Yorkshire swine fed a standard diet underwent placement of an ameroid constrictor to the left circumflex artery. Two weeks later, the animals received intramyocardial injection of saline (CON; n = 6), starvation-derived EVs (MVM; n = 10), or hypoxia-derived EVs (HYP; n = 7). After 5 weeks, myocardial perfusion was assessed, and left ventricular myocardial tissue was harvested. Protein expression was measured using immunoblotting. Data were analyzed via the Kruskal-Wallis test or one-way analysis of variance based on the results of a Shapiro-Wilk test. Coronary perfusion was plotted against relative cytokine concentration and analyzed with the Spearman rank-sum test. Results: HYP EV treatment was associated with decreased expression of proinflammatory markers interleukin (IL)-6 (P = .03), Pro-IL-1ß (P = .01), IL-17 (P < .01), and NOD-like receptor protein 3 (NLRP3; P < .01) compared to CON. Ischemic tissue from the MVM group showed significantly decreased expression of pro-inflammatory markers NLRP3 (P < .01), IL-17 (P < .01), and HLA class II histocompatibility antigen (P < .01) compared to CON. The MVM group also had decreased expression of anti-inflammatory IL-10 (P = .01) compared to CON counterparts. There were no significant differences in expression of tumor necrosis factor-α, interferon-γ, IL-12, Toll-like receptor-2, and nuclear factor kappa-light-chain-enhancer of activated B cells in either group . There was no correlation between coronary perfusion and cytokine concentration in the MVM or HYP groups, either at rest or with pacing. Conclusions: HYP EVs and MVM EVs appear to result in relative decreases in the degree of inflammation in chronically ischemic swine myocardium, independent of coronary perfusion. It is possible that this observed decrease may partially explain the myocardial benefits seen with both HYP and MVM EV treatment.

Risk Factors for Heart Failure Readmission After Cardiac Surgery.

Background: Heart failure (HF) is a leading cause of readmission after cardiac surgery, yet risk factors for HF readmission after cardiac surgery remain poorly characterized. Objectives: This study aimed to identify risk factors associated with 30-day HF-specific readmissions after cardiac surgery using a national database. Methods: We queried the 2016 to 2018 National Readmissions Database to identify U.S. patients who underwent coronary artery bypass grafting (CABG), mitral valve repair/replacement, and/or aortic valve repair/replacement. Exclusion criteria included history of ventricular assist device or heart transplant, dialysis-dependent renal insufficiency, and death during index admission. Clinical variables were defined using International Classification of Diseases-10th Revision codes. The primary outcome was a 30-day readmission for HF following discharge. Multivariable logistic regression was used to account for relevant clinical and demographic covariates and identify independent risk factors for HF readmissions following cardiac surgery. Results: Our study included 394,050 patients who underwent cardiac surgery (mean age 66 ± 12 years, 63% isolated CABG, 27% isolated valve, 11% CABG + valve). Of these patients, 7,318 were readmitted within 30 days of discharge for a principal diagnosis of HF. Independent risk factors of HF-specific readmission included older age, female sex, prolonged length of stay, comorbid congestive HF, nondialysis dependent chronic kidney disease, chronic obstructive pulmonary disease, chronic liver disease, obesity, atrial fibrillation, and acute kidney injury. Prior CABG was marginally protective for HF-specific readmission. Conclusions: Using a national registry, we identified risk factors associated with HF readmission after cardiac surgery. Further analysis of these risk factors and their association with HF readmission is warranted.

Calpain inhibition decreases myocardial fibrosis in chronically ischemic hypercholesterolemic swine.

OBJECTIVES: Calpain activation during ischemia is known to play critical roles in myocardial remodeling. We hypothesize that calpain inhibition (CI) may serve to reverse and/or prevent fibrosis in chronically ischemic myocardium. METHODS: Yorkshire swine were fed a high-cholesterol diet for 4 weeks followed by placement of an ameroid constrictor on the left circumflex artery to induce myocardial ischemia. 3 weeks later, animals received either: no drug; high-cholesterol control group (CON; n = 8); low-dose CI (0.12 mg/kg; LCI, n = 9); or high-dose CI (0.25 mg/kg; HCI, n = 8). The high-cholesterol diet and CI were continued for 5 weeks, after which myocardial tissue was harvested. Tissue samples were analyzed by western blot for changes in protein content. RESULTS: In the setting of hypercholesterolemia and chronic myocardial ischemia, CI decreased the expression of collagen in ischemic and nonischemic myocardial tissue. This reduced collagen content was associated with a corresponding decrease in Jak/STAT/MCP-1 signaling pathway, suggesting a role for Jak 2 signaling in calpain activity. CI also decreases the expression of focal adhesion proteins (vinculin) and stabilizes the expression of cytoskeletal and structural proteins (N-cadherin, α-fodrin, desmin, vimentin, filamin, troponin-I). CI had no significant effect on metabolic and hemodynamic parameters. CONCLUSIONS: Calpain inhibition may be a beneficial medical therapy to decrease collagen formation in patients with coronary artery disease and associated comorbidities.

Decreased contractile response of peripheral arterioles to serotonin after CPB in patients with diabetes.

BACKGROUND: Regulation of coronary vasomotor tone by serotonin is significantly changed after cardioplegic arrest and reperfusion. The current study investigates whether cardiopulmonary bypass may also affect peripheral arteriolar response to serotonin in patients with or without diabetes. METHODS: Human peripheral microvessels (90-180 µm diameter) were dissected from harvested skeletal muscle tissues from diabetic and non-diabetic patients before and after cardiopulmonary bypass and cardiac surgery (n = 8/group). In vitro contractile response to serotonin was assessed by videomicroscopy in the presence or absence of serotonin alone (10-9-10-5M) or combined with the selective serotonin 1B receptor (5-HT1B) antagonist, SB224289 (10-6M). 5-HT1A/1B protein expression in the skeletal muscle was measured by Western-blot and immunohistochemistry. RESULTS: There were no significant differences in contractile response of peripheral arterioles to serotonin (10-5M) pre-cardiopulmonary bypass between diabetic and non-diabetic patients. After cardiopulmonary bypass, contractile response to serotonin was significantly impaired in both diabetic and non-diabetic patients compared to their pre-cardiopulmonary bypass counterparts (P < .05). This effect was more pronounced in diabetic patients than non-diabetic patients (P < .05 versus non-diabetic). The contractile response to serotonin was significantly inhibited by the 5-HT1B antagonist in both diabetic and non-diabetic vessels (P < .05 versus serotonin alone). There were no significant differences in the expression/distribution of 5-HT1A/1B between non-diabetic and diabetic groups or between pre- versus post- cardiopulmonary bypass vessels. CONCLUSIONS: Cardiopulmonary bypass is associated with decreased contractile response of peripheral arterioles to serotonin and this effect was exaggerated in the presence of diabetes. Serotonin-induced contractile response of the peripheral arterioles was via 5-HT1B in both diabetic and non-diabetic patients.

Glycogen synthase kinase 3ß inhibition reduces mitochondrial oxidative stress in chronic myocardial ischemia.

OBJECTIVES: Glycogen synthase kinase 3ß (GSK-3ß) inhibition has been reported to increase microvascular density and improve myocardial blood flow in a porcine model of chronic myocardial ischemia and metabolic syndrome. Inhibition of GSK-3ß can also be cardioprotective by modulating fibrosis signaling and mitochondrial-induced apoptosis. We hypothesized GSK-3ß inhibition would have a beneficial effect on myocardial fibrosis and oxidative stress in a porcine model of chronic myocardial ischemia and metabolic syndrome. METHODS: Pigs were fed a high fat diet for 4 weeks followed by placement of an ameroid constrictor to the left circumflex coronary artery. Three weeks later animals received either no drug or a GSK-3ß inhibitor. The diets and placebo/GSK-3ß inhibition were continued for an additional 5 weeks, the pigs were then euthanized, and the myocardial tissue was harvested. Collagen expression was analyzed via Picrosirius staining. Oxidative stress was analyzed via Oxyblot analysis. Protein expression was analyzed via Western blot. RESULTS: GSK-3ß inhibition was associated with decreased collagen expression and oxidative stress in the ischemic and nonischemic myocardial tissue compared with control. There was a decrease in profibrotic proteins transforming growth factor-ß, p-SMAD2/3, and matrix metalloproteinase-9, and in proapoptotic and oxidative stress proteins, apoptosis inducing factor, the cleaved caspase 3/caspase 3 protein ratio and phosphorylated myeloid cell leukemia sequence-1 in the GSK-3ß inhibited group compared with the control. CONCLUSIONS: In the setting of metabolic syndrome and chronic myocardial ischemia, inhibition of GSK-3ß decreases collagen formation and oxidative stress in myocardial tissue. GSK-3ß inhibition might be having this beneficial effect by downregulating transforming growth factor-ß/SMAD2/3 signaling and decreasing mitochondrial induced cellular stress.