Extracellular Vesicles Promote Arteriogenesis in Chronically Ischemic Myocardium in the Setting of Metabolic Syndrome

Metformin Preconditioning Augments Cardiac Perfusion and Performance in a Large Animal Model of Chronic Coronary Artery Disease

OBJECTIVE

To test the efficacy of metformin (MET) during the induction of coronary ischemia on myocardial performance in a large animal model of coronary artery disease (CAD) and metabolic syndrome (MS), with or without concomitant extracellular vesicular (EV) therapy.

BACKGROUND

Although surgical and endovascular revascularization are durably efficacious for many patients with CAD, up to one-third are poor candidates for standard therapies. For these patients, many of whom have comorbid MS, adjunctive strategies are needed. EV therapy has shown promise in this context, but its efficacy is attenuated by MS. We investigated whether MET pretreatment could ameliorate therapeutic decrements associated with MS.

METHODS

Yorkshire swine (n = 29) were provided a high-fat diet to induce MS, whereupon an ameroid constrictor was placed to induce CAD. Animals were initiated on 1000 mg oral MET or placebo; all then underwent repeat thoracotomy for intramyocardial injection of EVs or saline. Swine were maintained for 5 weeks before the acquisition of functional and perfusion data immediately before terminal myocardial harvest. Immunoblotting and immunofluorescence were performed on the most ischemic tissue from all groups.

RESULTS

Regardless of EV administration, animals that received MET exhibited significantly improved ejection fraction, cardiac index, and contractility at rest and during rapid myocardial pacing, improved perfusion to the most ischemic myocardial region at rest and during pacing, and markedly reduced apoptosis.

CONCLUSIONS

MET administration reduced apoptotic cell death, improved perfusion, and augmented both intrinsic and load-dependent myocardial performance in a highly translatable large animal model of chronic myocardial ischemia and MS.

Postoperative Organ Dysfunction Risk Stratification Using Extracellular Vesicle-Derived circRNAs in Pediatric Congenital Heart Surgery

Breakthroughs in surgical and medical techniques have significantly improved outcomes for children with congenital heart disease (CHD), but research continues to address the ongoing challenge of organ dysfunction after surgery, particularly in neonates and infants. Our study explored circular RNAs (circRNAs) within plasma-derived extracellular vesicles (EVs) in neonates and infants undergoing CHD surgery. Post-surgery EV circRNAs showed dramatic expression changes between organ dysfunction (OD) and control groups. Tissue injury-related pathways were consistent across pre- and post-surgery in OD. The top two significant predicted tissue sources of these circRNAs originated from the respiratory system, aligning with the fact that all patients in the OD arm experienced respiratory dysfunction. Five of these circRNAs, namely circ-CELSR1, circ-PLXNA1, circ-OBSL1, circ-DAB2IP, and circ-KANK1, significantly correlated with PELOD (Pediatric Logistic Organ Dysfunction) score and demonstrated high performance (AUC = 0.95), supporting the potential of circRNAs as prognostic markers. These findings pave the way for EV circRNAs as promising tools for managing post-surgical organ dysfunction and potentially guiding therapeutic strategies in children with CHD.

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.

Intramyocardial injection of hypoxia-conditioned extracellular vesicles increases myocardial perfusion in a swine model of chronic coronary disease

Objective

Coronary artery disease remains a leading cause of morbidity and mortality worldwide. Patients with advanced coronary artery disease who are not eligible for endovascular or surgical revascularization have limited options. Extracellular vesicles have shown potential to improve myocardial function in preclinical models. Extracellular vesicles can be conditioned to modify their components. Hypoxia-conditioned extracellular vesicles have demonstrated the ability to reduce infarct size and apoptosis in small animals. Our objective is to assess the potential benefits of hypoxia-conditioned extracellular vesicles in a large animal model of coronary artery disease.

Methods

Coronary artery disease was induced in 14 Yorkshire swine by ameroid constriction of the left circumflex coronary artery. Two weeks postsurgery, swine underwent a repeat left thoracotomy for injections of hypoxia-conditioned extracellular vesicles (n = 7) or saline (control, n = 7). Five weeks later, all animals underwent terminal harvest for perfusion measurements and myocardial sectioning.

Results

Myocardial perfusion analysis demonstrated a trend toward increase at rest and a significant increase during rapid pacing (P = .09, P < .001). There were significant increases in activated phosphorylated endothelial nitric oxide synthase, endothelial nitric oxide synthase, phosphatidylinositol 3-kinase, phosphorylated protein kinase B, and the phosphorylated protein kinase B/protein kinase B ratio in the hypoxia-conditioned extracellular vesicles group compared with the control group (all P < .05). Additionally, there was a significant decrease in the antiangiogenic proteins collagen 18 and angiostatin (P = .01, P = .01) in the hypoxia-conditioned extracellular vesicles group.

Conclusions

Intramyocardial injection of hypoxia-conditioned extracellular vesicles results in increased myocardial perfusion without a corresponding change in vessel density. Therefore, this improvement in perfusion is possibly due to changes in nitric oxide signaling. Hypoxia-conditioned extracellular vesicles represent a potential therapeutic strategy to increase myocardial perfusion in patients with advanced coronary artery disease.

Unlocking the Potential of Extracellular Vesicles as the Next Generation Therapy: Challenges and Opportunities

BACKGROUND

Mesenchymal stem cells (MSCs) have undergone extensive investigation for their potential therapeutic applications, primarily attributed to their paracrine activity. Recently, researchers have been exploring the therapeutic potential of extracellular vesicles (EVs) released by MSCs.

METHODS

MEDLINE/PubMed and Google scholar databases were used for the selection of literature. The keywords used were mesenchymal stem cells, extracellular vesicles, clinical application of EVs and challenges EVs production.

RESULTS

These EVs have demonstrated robust capabilities in transporting intracellular cargo, playing a critical role in facilitating cell-to-cell communication by carrying functional molecules, including proteins, RNA species, DNAs, and lipids. Utilizing EVs as an alternative to stem cells offers several benefits, such as improved safety, reduced immunogenicity, and the ability to traverse biological barriers. Consequently, EVs have emerged as an increasingly attractive option for clinical use.

CONCLUSION

From this perspective, this review delves into the advantages and challenges associated with employing MSC-EVs in clinical settings, with a specific focus on their potential in treating conditions like lung diseases, cancer, and autoimmune disorders.

Crafting a Rigorous, Clinically Relevant Large Animal Model of Chronic Myocardial Ischemia: What Have We Learned in 20 Years?

The past several decades have borne witness to several breakthroughs and paradigm shifts within the field of cardiovascular medicine, but one component that has remained constant throughout this time is the need for accurate animal models for the refinement and elaboration of the hypotheses and therapies crucial to our capacity to combat human disease. Numerous sophisticated and high-throughput molecular strategies have emerged, including rational drug design and the multi-omics approaches that allow extensive characterization of the host response to disease states and their prospective resolutions, but these technologies all require grounding within a faithful representation of their clinical context. Over this period, our lab has exhaustively tested, progressively refined, and extensively contributed to cardiovascular discovery on the basis of one such faithful representation. It is the purpose of this paper to review our porcine model of chronic myocardial ischemia using ameroid constriction and the subsequent myriad of physiological and molecular-biological insights it has allowed our lab to attain and describe. We hope that, by depicting our methods and the insight they have yielded clearly and completely-drawing for this purpose on comprehensive videographic illustration-other research teams will be empowered to carry our work forward, drawing on our experience to refine their own investigations into the pathogenesis and eradication of cardiovascular disease.

Comparative effects of canagliflozin and sitagliptin in chronically ischemic myocardium

Aim

Recent studies demonstrate that sodium-glucose cotransporter 2 inhibitors (SGLT2i) and dipeptidyl peptidase-4 inhibitors (DPP4i), two classes of antidiabetic drugs, are cardioprotective. However, the mechanisms of these benefits and their comparative efficacy remain unclear. We aimed to compare the effects of these antidiabetic agents on cardiac function, perfusion, and microvascular density using a swine model of chronic myocardial ischemia.

Methods

Chronic myocardial ischemia was induced in Yorkshire swine by ameroid constrictor placement to the left circumflex artery. Two weeks later, pigs were administered vehicle ("CON", 8 pigs), 300 mg SGLT2i canagliflozin, ("CANA", 8 pigs), or 100 mg DPP4i sitagliptin ("SIT", 5 pigs) daily. Five weeks later, pigs were euthanized. Cardiac function, perfusion, collateralization, and protein expression were determined by pressure-volume catheter, microsphere analysis, immunofluorescence, and immunoblotting, respectively.

Results

Compared with SIT, CANA was associated with improved stroke volume and cardiac output, with a trend towards reduced left ventricular stiffness. Both CANA and SIT trended towards improved perfusion compared to CON, but there were no differences between the two treatment groups. SIT was associated with improved capillary density with a trend towards improved arteriolar density compared to CANA. Both CANA and SIT were associated with increased expression of vascular endothelial cadherin compared to CON, without differences in treatment groups. SIT pigs had decreased 5' adenosine monophosphate-activated protein kinase activation compared to CON and CANA. There was a trend towards increased endothelial nitric oxide synthase activation in the SIT group compared to CON. There were no differences in activation of extracellular signal-regulated kinase 1/2 across groups.

Conclusions

In the setting of chronic myocardial ischemia, canagliflozin is associated with improved cardiac function compared to sitagliptin, with similar effects on perfusion despite differences in microvascular collateralization.

Extracellular Vesicles' Role in Angiogenesis and Altering Angiogenic Signaling

Angiogenesis, the process of new blood vessels formation from existing vasculature, plays a vital role in development, wound healing, and various pathophysiological conditions. In recent years, extracellular vesicles (EVs) have emerged as crucial mediators in intercellular communication and have gained significant attention for their role in modulating angiogenic processes. This review explores the multifaceted role of EVs in angiogenesis and their capacity to modulate angiogenic signaling pathways. Through comprehensive analysis of a vast body of literature, this review highlights the potential of utilizing EVs as therapeutic tools to modulate angiogenesis for both physiological and pathological purposes. A good understanding of these concepts holds promise for the development of novel therapeutic interventions targeting angiogenesis-related disorders.

Lack of cardiac benefit after intramyocardial or intravenous injection of mesenchymal stem cell-derived extracellular vesicles supports the need for optimized cardiac delivery

Aim

To determine the differences in improvement in cardiac function by intramyocardial (IM) vs. intravenous (IV) injection of human bone mesenchymal stem cell-derived extracellular vesicles (HBMSC-EV) after acute MI.

Methods

FVB mice underwent acute MI via left anterior descending coronary artery ligation and subsequent injection of: (1) IM saline control; (2) IM HBMSC-EV; (3) IV saline control; and (4) IV HBMSC-EV. Cardiac function was evaluated with weekly postoperative echocardiography. On postoperative day 28, the mice were euthanized, and the heart, lungs, liver, spleen, and kidneys were harvested. Given previous studies showing HBMSC-EV hepatic uptake after IV injection, the liver was evaluated for changes in inflammation, fibrosis, and proliferation.

Results

On postoperative day 28, there were no significant differences in left ventricular ejection fraction (P = 0.6151), fractional shortening (P = 0.1135), or anterior border zone fibrosis (P = 0.6333) in any of the experimental groups. Interestingly, there was a strong trend demonstrating improvement in infarct size on fibrosis staining, which did not reach significance (P = 0.05620). There were no differences in hepatic inflammation, fibrosis, and proliferation.

Conclusions

Although there was a trend in the improvement in infarct size, a single-dose administration of neither IM nor IV injection of HBMSC-EV resulted in significant improvement in post-MI cardiac function. A major limitation of this study is the lack of trials determining the optimal dose of HBMSC-EV needed in this model. However, the current study demonstrates that future studies are required to either optimize administration or bioengineer HBMSC-EV with cardiac-homing properties.

Diabetic state of human coronary artery endothelial cells results in altered effects of bone mesenchymal stem cell-derived extracellular vesicles

Human bone mesenchymal stem cell-derived extracellular vesicles (HBMSC-EV) have been used successfully in animal models of myocardial ischemia, yet have dampened effects in metabolic syndrome through unknown mechanisms. This study demonstrates the basal differences between non-diabetic human coronary artery endothelial cells (HCAEC) and diabetic HCAEC (DM-HCAEC), and how these cells respond to the treatment of HBMSC-EV. HCAEC and DM-HCAEC were treated with HBMSC-EV for 6 h. Proteomics, western blot analysis, and tube formation assays were performed. Key metabolic, growth, and stress/starvation cellular responses were significantly altered in DM-HCAEC in comparison to that of HCAEC at baseline. Proteomics demonstrated increased phosphorus metabolic process and immune pathways and decreased RNA processing and biosynthetic pathways in DM-HCAEC. Similar to previous in vivo findings, HCAEC responded to the HBMSC-EV with regenerative and anti-inflammatory effects through the upregulation of multiple RNA pathways and downregulation of immune cell activation pathways. In contrast, DM-HCAEC had a significantly diminished response to HBMSC-EV, likely due to the baseline abnormalities in DM-HCAEC. To achieve the full benefits of HBMSC-EV and for a successful transition of this potential therapeutic agent to clinical studies, the abnormalities found in DM-HCAEC will need to be further studied.

Mechanisms and Optimization Strategies of Paracrine Exosomes from Mesenchymal Stem Cells in Ischemic Heart Disease

The morbidity and mortality of myocardial infarction (MI) are increasing worldwide. Mesenchymal stem cells (MSCs) are multipotent stem cells with self-renewal and differentiation capabilities that are essential in tissue healing and regenerative medicine. However, the low implantation and survival rates of transplanted cells hinder the widespread clinical use of stem cells. Exosomes are naturally occurring nanovesicles that are secreted by cells and promote the repair of cardiac function by transporting noncoding RNA and protein. In recent years, MSC-derived exosomes have been promising cell-free treatment tools for improving cardiac function and reversing cardiac remodeling. This review describes the biological properties and therapeutic potential of exosomes and summarizes some engineering approaches for exosomes optimization to enhance the targeting and therapeutic efficacy of exosomes in MI.

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.

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.

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.

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.

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.

Comparative Analysis of Normoxia- and Hypoxia-Modified Extracellular Vesicle Therapy in Function, Perfusion, and Collateralization in Chronically Ischemic Myocardium

We have previously shown that normoxia serum-starved extracellular vesicle (EV) therapy improves myocardial function, perfusion, and angiogenesis in a swine model of chronic myocardial ischemia. Hypoxia-modified EVs have increased abundance of anti-oxidant, pro-angiogenic, and pro-survival proteins. The purpose of this study is to investigate the differential effects of normoxia serum-starved EVs and hypoxia-modified EVs on myocardial function, perfusion, and microvascular density in chronically ischemic myocardium. Yorkshire swine underwent placement of an ameroid constrictor to the left circumflex artery to induce chronic myocardial ischemia. Two weeks later, the pigs underwent intramyocardial injection of either normoxia serum-starved EVs (NOR, n = 10) or hypoxia-modified EVs (HYP, n = 7). Five weeks later, pigs were euthanized, and ischemic myocardium was harvested. Hypoxia EV treatment was associated with improved contractility compared to NOR, as well as improved capillary density, without changes in arteriolar density. There were trends towards improved perfusion at rest and during pacing in the HYP group compared to NOR. Ischemic myocardium in the HYP group had increased pro-angiogenic Akt and ERK signaling and decreased expression of anti-angiogenic markers compared to the NOR group. In the setting of chronic myocardial ischemia, hypoxia-modified EVs may enhance contractility, capillary density, and angiogenic signaling pathways compared to normoxia serum-starved EVs.

Reduction in mitochondrial ROS improves oxidative phosphorylation and provides resilience to coronary endothelium in non-reperfused myocardial infarction

Recent studies demonstrated that mitochondrial antioxidant MnSOD that reduces mitochondrial (mito) reactive oxygen species (ROS) helps maintain an optimal balance between sub-cellular ROS levels in coronary vascular endothelial cells (ECs). However, it is not known whether EC-specific mito-ROS modulation provides resilience to coronary ECs after a non-reperfused acute myocardial infarction (MI). This study examined whether a reduction in endothelium-specific mito-ROS improves the survival and proliferation of coronary ECs in vivo. We generated a novel conditional binary transgenic animal model that overexpresses (OE) mitochondrial antioxidant MnSOD in an EC-specific manner (MnSOD-OE). EC-specific MnSOD-OE was validated in heart sections and mouse heart ECs (MHECs). Mitosox and mito-roGFP assays demonstrated that MnSOD-OE resulted in a 50% reduction in mito-ROS in MHEC. Control and MnSOD-OE mice were subject to non-reperfusion MI surgery, echocardiography, and heart harvest. In post-MI hearts, MnSOD-OE promoted EC proliferation (by 2.4 ± 0.9 fold) and coronary angiogenesis (by 3.4 ± 0.9 fold), reduced myocardial infarct size (by 27%), and improved left ventricle ejection fraction (by 16%) and fractional shortening (by 20%). Interestingly, proteomic and Western blot analyses demonstrated upregulation in mitochondrial complex I and oxidative phosphorylation (OXPHOS) proteins in MnSOD-OE MHECs. These MHECs also showed increased mitochondrial oxygen consumption rate (OCR) and membrane potential. These findings suggest that mito-ROS reduction in EC improves coronary angiogenesis and cardiac function in non-reperfused MI, which are associated with increased activation of OXPHOS in EC-mitochondria. Activation of an energy-efficient mechanism in EC may be a novel mechanism to confer resilience to coronary EC during MI.

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.

Extracellular Vesicles and Ischemic Cardiovascular Diseases

Characterized by coronary artery obstruction or stenosis, ischemic cardiovascular diseases as advanced stages of coronary heart diseases commonly lead to left ventricular aneurysm, ventricular septal defect, and mitral insufficiency. Extracellular vesicles (EVs) secreted by diverse cells in the body exert roles in cell-cell interactions and intrinsic cellular regulations. With a lipid double-layer membrane and biological components such as DNA, protein, mRNA, microRNAs (miRNA), and siRNA inside, the EVs function as paracrine signaling for the pathophysiology of ischemic cardiovascular diseases and maintenance of the cardiac homeostasis. Unlike stem cell transplantation with the potential tumorigenicity and immunogenicity, the EV-based therapeutic strategy is proposed to satisfy the demand for cardiac repair and regeneration while the circulating EVs detected by a noninvasive approach can act as precious biomarkers. In this chapter, we extensively summarize the cardioprotective functions of native EVs and bioengineered EVs released from stem cells, cardiomyocytes, cardiac progenitor cells (CPCs), endothelial cells, fibroblast, smooth muscle cells, and immune cells. In addition, the potential of EVs as robust molecule biomarkers is discussed for clinical diagnosis of ischemic cardiovascular disease, attributed to the same pathology of EVs as that of their origin. Finally, we highlight EV-based therapy as a biocompatible alternative to direct cell-based therapy for ischemic cardiovascular diseases.

Extracellular vesicles improve diastolic function and substructure in normal and high-fat diet models of chronic myocardial ischemia

OBJECTIVE

The burden of mortality and morbidity of cardiovascular disease is in part due to substantial fibrosis accelerated by coexisting risk factors. This study aims to evaluate the effect of extracellular vesicle therapy on diastolic function and myocardial fibrosis in the setting of chronic myocardial ischemia with and without a high-fat diet.

METHODS

Forty male Yorkshire swine were administered a normal or high-fat diet. At 11 weeks of age, they underwent placement of an ameroid constrictor on their left circumflex coronary artery. Both dietary groups then received either intramyocardial injection of vehicle saline as controls or extracellular vesicles as treatment into the ischemic territory (normal diet control, n = 8; high-fat diet controls, n = 11) or extracellular vesicles (normal diet extracellular vesicles, n = 9; high-fat diet extracellular vesicles, n = 12). Five weeks later, hemodynamic parameters, histology, and selected protein expression were evaluated.

RESULTS

Extracellular vesicles reduced end-diastolic pressure volume relationship (P = .002), perivascular collagen density (P = .031), calcium mineralization (P = .026), and cardiomyocyte diameter (P < .0001), and upregulated osteopontin (P = .0046) and mechanistic target of rapamycin (P = .021). An interaction between extracellular vesicles and diet was observed in the vimentin area (P = .044) and fraction of myofibroblast markers to total vimentin (P = .049). Significant changes across diet were found with reductions in muscle fiber area (P = .026), tumor necrosis factor α (P = .0002), NADPH oxidase 2 and 4 (P = .0036, P = .008), superoxide dismutase 1 (P = .034), and phosphorylated glycogen synthase kinase 3β (P = .020).

CONCLUSIONS

Extracellular vesicle therapy improved the myocardium's ability to relax and is likely due to structural improvements at the extracellular matrix and cellular levels.

Non-Invasive imaging of extracellular vesicles: Quo vaditis in vivo?

Extracellular vesicles (EVs) are lipid-bilayer delimited vesicles released by nearly all cell types that serve as mediators of intercellular signalling. Recent evidence has shown that EVs play a key role in many normal as well as pathological cellular processes. EVs can be exploited as disease biomarkers and also as targeted, cell-free therapeutic delivery and signalling vehicles for use in regenerative medicine and other clinical settings. Despite this potential, much remains unknown about the in vivo biodistribution and pharmacokinetic profiles of EVs after administration into living subjects. The ability to non-invasively image exogeneous EVs, especially in larger animals, will allow a better understanding of their in vivo homing and retention patterns, blood and tissue half-life, and excretion pathways, all of which are needed to advance clinical diagnostic and/or therapeutic applications of EVs. We present the current state-of-the-art methods for labeling EVs with various diagnostic contrast agents and tracers and the respective imaging modalities that can be used for their in vivo visualization: magnetic resonance imaging (MRI), X-ray computed tomography (CT) imaging, magnetic particle imaging (MPI), single-photon emission computed tomography (SPECT), positron emission tomography (PET), and optical imaging (fluorescence and bioluminescence imaging). We review here the strengths and weaknesses of each of these EV imaging approaches, with special emphasis on clinical translation.

Mesenchymal Stromal Cell Exosomes in Cardiac Repair

PURPOSE OF THE REVIEW

Mesenchymal stromal cells (MSCs) are considered an attractive option for cell-based therapy because of their immune-privileged phenotype and paracrine activity. Substantial preclinical evidence indicates that MSC exosomes recapitulate MSC cellular function in cardiac regeneration and repair. Therefore, in this review, we briefly discuss the latest research progress of MSC exosomes in cardiac repair and regeneration.

RECENT FINDINGS

The recent revolutionary advance in controlling the contents of the exosomes by manipulating parental cells through bioengineering methods to alter specific signaling pathways in ischemic myocardium has proven to be beneficial in the treatment of heart failure. MSC Exosomes appear to be leading candidates to treat myocardial infarction and subsequent heart failure by carrying rich cargo from their parental cells. However, more clinical and pre-clinical studies on MSC exosomes will be required to confirm the beneficial effect to treat cardiovascular diseases.

Lactobacillus plantarum probiotic induces Nrf2-mediated antioxidant signaling and eNOS expression resulting in improvement of myocardial diastolic function

Yorkshire swine were fed standard diet (n = 7) or standard diet containing applesauce rich in caffeic acid with Lactobacillus plantarum (n = 7) for 3 wk. An ameroid constrictor was next placed around the left coronary circumflex artery, and the dietary regimens were continued. At 14 wk, cardiac function, myocardial perfusion, vascular density, and molecular signaling in ischemic myocardium were evaluated. The L. plantarum-applesauce augmented NF-E2-related factor 2 (Nrf2) in the ischemic myocardium and induced Nrf2-regulated antioxidant enzymes heme oxygenase-1 (HO-1), NADPH dehydrogenase quinone 1 (NQO-1), and thioredoxin reductase (TRXR-1). Improved left ventricular diastolic function and decreased myocardial collagen expression were seen in animals receiving the L. plantarum-applesauce supplements. The expression of endothelial nitric oxide synthase (eNOS) was increased in ischemic myocardial tissue of the treatment group, whereas levels of asymmetric dimethyl arginine (ADMA), hypoxia inducible factor 1α (HIF-1α), and phosphorylated MAPK (pMAPK) were decreased. Collateral-dependent myocardial perfusion was unaffected, whereas arteriolar and capillary densities were reduced as determined by α-smooth muscle cell actin and CD31 immunofluorescence in ischemic myocardial tissue. Dietary supplementation with L. plantarum-applesauce is a safe and effective method of enhancing Nrf2-mediated antioxidant signaling cascade in ischemic myocardium. Although this experimental diet was associated with a reduction in hypoxic stimuli, decreased vascular density, and without any change in collateral-dependent perfusion, the net effect of an increase in antioxidant activity and eNOS expression resulted in improvement in diastolic function.NEW & NOTEWORTHY Colonization of the gut microbiome with certain strains of L. Plantarum has been shown to convert caffeic acid readily available in applesauce to 4-vinyl-catechol, a potent activator of the Nrf2 antioxidant defense pathway. In this exciting study, we show that simple dietary supplementation with L. Plantarum-applesauce-mediated Nrf2 activation supports vascular function, ameliorates myocardial ischemic diastolic dysfunction, and upregulates expression of eNOS.

Pulmonary arterial hypertension induces the release of circulating extracellular vesicles with oxidative content and alters redox and mitochondrial homeostasis in the brains of rats

Pulmonary arterial hypertension (PAH) is characterized by increased resistance of the pulmonary vasculature and afterload imposed on the right ventricle (RV). Two major contributors to the worsening of this disease are oxidative stress and mitochondrial impairment. This study aimed to explore the effects of monocrotaline (MCT)-induced PAH on redox and mitochondrial homeostasis in the RV and brain and how circulating extracellular vesicle (EV) signaling is related to these phenomena. Wistar rats were divided into control and MCT groups (60 mg/kg, intraperitoneal), and EVs were isolated from blood on the day of euthanasia (21 days after MCT injections). There was an oxidative imbalance in the RV, brain, and EVs of MCT rats. PAH impaired mitochondrial function in the RV, as seen by a decrease in the activities of mitochondrial complex II and citrate synthase and manganese superoxide dismutase (MnSOD) protein expression, but this function was preserved in the brain. The key regulators of mitochondrial biogenesis, namely, proliferator-activated receptor gamma coactivator 1-alpha and sirtuin 1, were poorly expressed in the EVs of MCT rats, and this result was positively correlated with MnSOD expression in the RV and negatively correlated with MnSOD expression in the brain. Based on these findings, we can conclude that the RV is severely impacted by the development of PAH, but this pathological injury may signal the release of circulating EVs that communicate with different organs, such as the brain, helping to prevent further damage through the upregulation of proteins involved in redox and mitochondrial function.

Current status of myocardial restoration via the paracrine function of mesenchymal stromal cells

Mesenchymal stromal cells (MSCs) have been studied for nearly two decades as a therapy for myocardial restoration. An emerging direction to repair myocardium is through their paracrine function, which includes the utilization of MSC-derived conditioned medium or extracellular vesicles. In this review, we go over the unique characteristics of MSCs that make it suitable for "off the shelf," cell-free regenerative therapy, current MSC-derived cell-free approaches including their advantages and disadvantages, and the known mechanisms of action of the paracrine effect of MSCs. With a summary of the clinical trials and preclinical studies of MSC-derived cell-free therapy, we classify the aforementioned mechanisms into angiogenesis, immunomodulation, extracellular matrix remodeling, antiapoptosis, and antioxidation. Particularly, we discuss on ways researchers have worked toward enhancing these desired properties to improve the therapeutic outcomes and the investigation of mechanobiology involved in MSC paracrine function. Lastly, we bring up the remaining challenges in this arising field and suggestions for future directions to improve our understanding and control over the potential of MSC paracrine function for myocardial restoration.

Extracellular vesicles (EVs) in ischemic conditioning and angiogenesis: Focus on endothelial derived EVs

During myocardial ischemia, timely reperfusion is critical to limit infarct area and the overall loss of cardiac contractile function. However, reperfusion further exacerbates the damage of the ischemic heart. This type of injury is known as ischemia-reperfusion injury (IRI). Ischemic conditioning is a procedure which consists of brief cycles of ischemia and reperfusion in order to protect the myocardium against IRI. Remote ischemic conditioning (RIC), namely transient brief episodes of ischemia at a remote site before a subsequent damaging ischemia/reperfusion procedure of the target organ (e.g., the heart), protects against IRI. However, how the stimulus of RIC is transduced from the remote organ to the ischemic heart is still unknown. Recently, extracellular vesicles (EVs) have been proposed to have a role in the RIC procedure. The endothelium releases EVs and is also one of the tissues mostly exposed to EVs during their journey to the target organ. Moreover, EVs may have important roles in angiogenesis and, therefore, in the remodeling of post-ischemic organs. Here we analyze how EVs may contribute to the overall cardioprotective effect and the implication of the endothelium and its EVs in RIC mediated acute cardioprotection as well as in angiogenesis.

Mesenchymal stem cell-derived extracellular vesicles in the failing heart: past, present, and future

Cardiovascular disease (CVD) is the leading cause of death globally. Current treatment options include lifestyle changes, medication, and surgical intervention. However, many patients are unsuitable candidates for surgeries due to comorbidities, diffuse coronary artery disease, or advanced stages of heart failure. The search for new treatment options has recently transitioned from cell-based therapies to stem-cell-derived extracellular vesicles (EVs). A number of challenges remain in the EV field, including the effect of comorbidities, characterization, and delivery. However, recent revolutionary developments and insight into the potential of personalizing EV contents by bioengineering methods to alter specific signaling pathways in the ischemic myocardium hold promise. Here, we discuss the past limitations of cell-based therapies and recent EV studies involving in vivo, in vitro, and omics, and future challenges and opportunities in EV-based treatments in CVD.

Effects of High Fat Versus Normal Diet on Extracellular Vesicle-Induced Angiogenesis in a Swine Model of Chronic Myocardial Ischemia

Background Mesenchymal stem cell-derived extracellular vesicles (EVs) promote angiogenesis in the ischemic myocardium. This study examines the difference in vascular density, myocardial perfusion, molecular signaling, and gene expression between normal diet (ND) and high fat diet (HFD) groups at baseline and following intramyocardial injection of EVs. Methods and Results Intact male Yorkshire swine fed either an ND (n=17) or HFD (n=14) underwent placement of an ameroid constrictor on the left circumflex coronary artery. Subsequently, animals received either intramyocardial injection of vehicle-saline as controls; (ND-controls n=7, HFD-controls, n=6) or EVs; (ND-EVs n=10, HFD-EVs n=8) into the ischemic territory. Five weeks later, myocardial function, perfusion, vascular density, cell signaling, and gene expression were examined. EVs improved indices of myocardial contractile function, myocardial perfusion, and arteriogenesis in both dietary cohorts. Interestingly, quantification of alpha smooth muscle actin demonstrated higher basal arteriolar density in HFD swine compared with their ND counterparts; whereas EVs were associated with increased CD31-labeled endothelial cell density only in the ND tissue, which approached significance. Levels of total endothelial nitric oxide synthase, FOXO1 (forkhead box protein O1) , transforming growth factor-β, phosphorylated VEGFR2 (vascular endothelial growth factor receptor 2), and phosphorylated MAPK ERK1/ERK2 (mitogen-activated protein kinase) were higher in ischemic myocardial lysates from ND-controls compared with HFD-controls. Conversely, HFD-control tissue showed increased expression of phosphorylated endothelial nitric oxide synthase, phosphorylated FOXO1, VEGFR2, and MAPK ERK1/ERK2 with respect to ND-controls. Preliminary gene expression studies indicate differential modulation of transcriptional activity by EVs between the 2 dietary cohorts. Conclusions HFD produces a profound metabolic disorder that dysregulates the molecular mechanisms of collateral vessel formation in the ischemic myocardium, which may hinder the therapeutic angiogenic effects of EVs.

Intravenous injection of extracellular vesicles to treat chronic myocardial ischemia

Background

Mesenchymal stem cell-derived extracellular vesicles (EVs) appear to be a very exciting treatment option for heart disease. Here, we used a swine model of chronic myocardial ischemia to evaluate the efficacy of a less-invasive method of injection of EVs via a peripheral intravenous route.

Methods

Sixteen Yorkshire swine underwent placement of an ameroid constrictor on the left circumflex (LCx) artery at age 11 weeks to induce chronic myocardial ischemia. Two weeks later, they were divided into two groups: control (CON; n = 8), and intravenous injection of EVs (EVIV; n = 8). At 18 weeks of age, animals underwent final analysis and euthanasia. The chronically ischemic myocardium (LCx territory) was harvested for analysis.

Results

Intravenous injection (IV) of EVs induced several pro-angiogenic markers such as MAPK, JNK but not Akt. Whereas IV injections of EVs decreased VEGFR2 expression and inhibited apoptotic signaling (caspase 3), they increased expression of VEGFR1 that is believed to be anti-angiogenic. Injection of EVs did not result in an increase in vessel density and blood flow when compared to the control group.

Conclusions

Although IV injection of EVs upregulated several pro-angiogenic signaling pathways, it failed to induce changes in vascular density in the chronically ischemic myocardium. Thus, a lack of increase in vascular density at the doses tested failed to elicit a functional response in ischemic myocardium.

Extracellular Vesicles Promote Arteriogenesis in Chronically Ischemic Myocardium in the Setting of Metabolic Syndrome

Background

Ischemic heart disease continues to be a leading cause of mortality in patients. Extracellular vesicles (EVs) provide a potential for treatment that may induce collateral vessel growth to increase myocardial perfusion.

Methods and Results

Nineteen male Yorkshire pigs were given a high‐fat diet for 4 weeks, then underwent placement of an ameroid constrictor on the left circumflex artery to induce chronic myocardial ischemia. Two weeks later, the pigs received either intramyocardial vehicle (n=6), EVs (high‐fat diet with myocardial EV injection [HVM]; n=8), or HVM and calpain inhibition (n=5). Five weeks later, myocardial function, perfusion, coronary vascular density, and cell signaling were examined. Perfusion in the collateral‐dependent myocardium was increased during rapid ventricular pacing in the HVM group in both nonischemic (P=0.04) and ischemic areas of the ventricle (P=0.05). Cardiac output and stroke volume were significantly improved in the HVM group compared with the control group during ventricular pacing (P=0.006). Increased arteriolar density was seen in the HVM group in both nonischemic and ischemic myocardium (P=0.003 for both). However, no significant changes in the capillary density were observed between the control, HVM, and HVM and calpain inhibition groups (P=0.07). The group that received EVs with oral calpain inhibition had neither increased vessel density (P>0.99) nor improvement in blood flow or cardiac function (P=0.48) when compared with the control group.

Conclusions

These findings suggest that EVs promote angiogenesis in areas of chronic myocardial ischemia and improve cardiac function under conditions of diet‐induced metabolic syndrome.