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

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 Modulates Response to Oxidative Stress in the Chronically Ischemic Myocardium

INTRODUCTION

Patients with advanced coronary artery disease (CAD) who are not eligible for stenting or surgical bypass procedures have limited treatment options. Extracellular vesicles (EVs) have emerged as a potential therapeutic target for the treatment of advanced CAD. These EVs can be conditioned to modify their contents. In our previous research, we demonstrated increased perfusion, decreased inflammation, and reduced apoptosis with intramyocardial injection of hypoxia-conditioned EVs (HEVs). The goal of this study is to further understand the function of HEVs by examining their impact on oxidative stress using our clinically relevant and extensively validated swine model of chronic myocardial ischemia.

METHODS

Fourteen Yorkshire swine underwent a left thoracotomy for the placement of an ameroid constrictor on the left circumflex coronary artery to model chronic myocardial ischemia. After two weeks of recovery, the swine underwent a redo thoracotomy with injection of either HEVs (n = 7) or a saline control (CON, n = 7) into the ischemic myocardium. Five weeks after injection, the swine were subjected to terminal harvest. Protein expression was measured using immunoblotting. OxyBlot analysis and 3-nitrotyrosine staining were used to quantify total oxidative stress.

RESULTS

There was a significant increase in myocardial expression of the antioxidants SOD 2, GPX-1, HSF-1, UCP-2, catalase, and HO-1 (all p ≤ 0.05) in the HEV group when compared to control animals. The HEVs also exhibited a significant increase in pro-oxidant NADPH oxidase (NOX) 1, NOX 3, p47phox, and p67phox (all p ≤ 0.05). However, no change was observed in the expression of NFkB, KEAP 1, and PRDX1 (all p > 0.05) between the HEV and CON groups. There were no significant differences in total oxidative stress as determined by OxyBlot and 3-nitrotyrosine staining (p = 0.64, p = 0.32) between the groups.

CONCLUSIONS

Administration of HEVs in ischemic myocardium induces a significant increase in pro- and antioxidant proteins without a net change in total oxidative stress. These findings suggest that HEV-induced changes in redox signaling pathways may play a role in increased perfusion, decreased inflammation, and reduced apoptosis in ischemic myocardium. Further studies are required to determine if HEVs alter the net oxidative stress in ischemic myocardium at an earlier time point of HEV administration.

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.

Extracellular vesicle treatment partially reverts epigenetic alterations in chronically ischemic porcine myocardium

Introduction

Research has shown epigenetic change via alternation of the methylation profile of human skeletal muscle DNA after Cardio-Pulmonary Bypass (CPB). In this study, we investigated the change in epigenome-wide DNA methylation profiles of porcine myocardium after ischemic insult in the setting of treatment with extracellular vesicle (EV) therapy in normal vs. high-fat diet (HFD) pigs.

Methods

Four groups of three pigs underwent ameroid constrictor placement to the left circumflex artery (LCx) and were assigned to the following groups: (1) normal diet saline injection; (2) normal diet EV injection; (3) HFD saline injection; and (4) HFD EV injection. DNA methylation was profiled via reduced-representation bisulfite sequencing (RRBS) and compared using a custom bioinformatic pipeline.

Results

After initial analysis, 441 loci had a nominal P value < 0.05 when examining the effect of ischemia vs. normal heart tissue on a normal diet in the absence of treatment. 426 loci at P value threshold < 0.05 were identified when comparing the ischemic vs. normal tissue from high-fat diet animals. When examining the effect of EV treatment in ischemic tissue in subjects on a normal diet, there were 574 loci with nominal P value < 0.05 with two loci Fructosamine 3 kinase related protein [(FN3KRP) (P < 0.001)] and SNTG1 (P = 0.03) significant after Bonferroni correction. When examining the effect of EV treatment in ischemic tissue in HFD, there were 511 loci with nominal P values < 0.05. After Bonferroni correction, two loci had P values less than 0.05, betacellulin [(BTC) (P = 0.008)] and [proprotein convertase subtilisin/kexin type 7 (PCSK7) (P = 0.01)].

Conclusions

Alterations in DNA methylation were identified in pig myocardium after ischemic insult, change in diet, and treatment with EVs. Hundreds of differentially methylated loci were detected, but the magnitude of the effects was low. These changes represent significant alterations in DNA methylation and merit further investigation.

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.

The Long Journey of Extracellular Vesicles towards Global Scientific Acclamation

Extracellular vesicles (EVs) are a heterogeneous class of cell-derived vesicles that are responsible for eliciting a wide array of biological processes. After decades of intense investigation, the therapeutic potential of EVs will be finally explored in a series of upcoming clinical trials. EVs are rapidly changing the understanding of human physiology and will undoubtedly transform the field of medicine. The applicability of EVs as diagnostic biomarkers and treatment vectors has captured the attention of the scientific community and investors, facilitating the rapid progression of numerous EVs-based platforms. This mini-review provides an outline of the pioneering discoveries, and their respective significances, on progressing EVs toward clinical use. We focus the attention of the readers on several promising classes of EVs that hold major opportunities to translate in clinical practice. Market analysis and future challenges facing EVs-based therapies are also discussed.

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.

Lyophilized Extracellular Vesicles from Adipose-Derived Stem Cells Increase Muscle Reperfusion but Degrade Muscle Structural Proteins in a Mouse Model of Hindlimb Ischemia-Reperfusion Injury

Ischemia-reperfusion (I/R) injury is a complication impacting multiple organs and tissues in clinical conditions ranging from peripheral arterial disease to musculoskeletal trauma and myocardial infarction. Stem cell-derived extracellular vesicles (EVs) may represent one therapeutic resource for preventing the tissue damage associated with I/R injury. Here we tested the hypothesis that lyophilized extracellular vesicles derived from adipose stem cells could serve as an "off-the-shelf" treatment modality for I/R injury in a mouse hindlimb ischemia model. Ischemia was induced for 90 min using a rubber band tourniquet and extracellular vesicles (0, 50, or 100 µg) administered via tail vein injection immediately prior to reperfusion. Perfusion was measured prior to, during, and after ischemia using laser Doppler imaging. Serum and tissue were collected 24 h after reperfusion. Mass spectrometry (MS)-based proteomics was used to characterize the EV cargo and proteins from the ischemic and non-ischemic hindlimb. Inflammatory cytokines were measured in muscle and serum using a multiplex array. Results indicate that EVs significantly increase reperfusion and significantly increase expression of the anti-inflammatory factor annexin a1 in skeletal muscle; however, the increased reperfusion was also associated with a marked decrease in muscle structural proteins such as dystrophin, plectin, and obscurin. Circulating inflammatory cytokines TNF-alpha and IL-6 were increased with EV treatment, and serum TNF-alpha showed a significant, positive correlation with reperfusion level. These findings suggest that, while EVs may enhance reperfusion, the increased reperfusion can negatively impact muscle tissue and possibly remote organs. Alternative approaches, such as targeting mitochondrial permeability, may be more effective at mitigating I/R injury.

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.

Proteomic Assessment of Hypoxia-Pre-Conditioned Human Bone Marrow Mesenchymal Stem Cell-Derived Extracellular Vesicles Demonstrates Promise in the Treatment of Cardiovascular Disease

Human bone marrow mesenchymal stem cell derived-extracellular vesicles (HBMSC-EV) are known for their regenerative and anti-inflammatory effects in animal models of myocardial ischemia. However, it is not known whether the efficacy of the EVs can be modulated by pre-conditioning of HBMSC by exposing them to either starvation or hypoxia prior to EV collection. HBMSC-EVs were isolated following normoxia starvation (NS), normoxia non-starvation (NNS), hypoxia starvation (HS), or hypoxia non-starvation (HNS) pre-conditioning. The HBMSC-EVs were characterized by nanoparticle tracking analysis, electron microscopy, Western blot, and proteomic analysis. Comparative proteomic profiling revealed that starvation pre-conditioning led to a smaller variety of proteins expressed, with the associated lesser effect of normoxia versus hypoxia pre-conditioning. In the absence of starvation, normoxia and hypoxia pre-conditioning led to disparate HBMSC-EV proteomic profiles. HNS HBMSC-EV was found to have the greatest variety of proteins overall, with 74 unique proteins, the greatest number of redox proteins, and pathway analysis suggestive of improved angiogenic properties. Future HBMSC-EV studies in the treatment of cardiovascular disease may achieve the most therapeutic benefits from hypoxia non-starved pre-conditioned HBMSC. This study was limited by the lack of functional and animal models of cardiovascular disease and transcriptomic studies.

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.

Pharmacokinetics and biodistribution of extracellular vesicles administered intravenously and intranasally to Macaca nemestrina

Extracellular vesicles (EVs) have potential in disease treatment since they can be loaded with therapeutic molecules and engineered for retention by specific tissues. However, questions remain on optimal dosing, administration, and pharmacokinetics. Previous studies have addressed biodistribution and pharmacokinetics in rodents, but little evidence is available for larger animals. Here, we investigated the pharmacokinetics and biodistribution of Expi293F-derived EVs labelled with a highly sensitive nanoluciferase reporter (palmGRET) in a non-human primate model (Macaca nemestrina), comparing intravenous (IV) and intranasal (IN) administration over a 125-fold dose range. We report that EVs administered IV had longer circulation times in plasma than previously reported in mice and were detectable in cerebrospinal fluid (CSF) after 30-60 minutes. EV association with PBMCs, especially B-cells, was observed as early as one minute post-administration. EVs were detected in liver and spleen within one hour of IV administration. However, IN delivery was minimal, suggesting that pretreatment approaches may be needed in large animals. Furthermore, EV circulation times strongly decreased after repeated IV administration, possibly due to immune responses and with clear implications for xenogeneic EV-based therapeutics. We hope that our findings from this baseline study in macaques will help to inform future research and therapeutic development of EVs.

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.

Nephronectin promotes cardiac repair post myocardial infarction via activating EGFR/JAK2/STAT3 pathway

Background: ECM proteins are instrumental for angiogenesis, which plays momentous roles during development and repair in various organs, including post cardiac insult. After a screening based on an open access RNA-seq database, we identified Nephronectin (NPNT), an extracellular protein, might be involved in cardiac repair post myocardial infarction (MI). However, the specific impact of nephronectin during cardiac repair in MI remains elusive. Methods and Results: In the present study, we established a system overexpressing NPNT locally in mouse heart by utilizing a recombinant adeno-associated virus. One-to-four weeks post MI induction, we observed improved cardiac function, limited infarct size, alleviated cardiac fibrosis, with promoted angiogenesis in infarct border zone in NPNT overexpressed mice. And NPNT treatment enhanced human umbilical vascular endothelial cell (HUVEC) migration and tube formation, putatively through advocating phosphorylation of EGFR/JAK2/STAT3. The migration and capillary-like tube formation events could be readily revoked by EGFR or STAT3 inhibition. Notably, phosphorylation of EGFR, JAK2 and STAT3 were markedly upregulated in AAV2/9-cTnT-NPNT-treated mice with MI. Conclusions: Our study thus identifies the beneficial effects of NPNT on angiogenesis and cardiac repair post MI by enhancing the EGFR/JAK2/STAT3 signaling pathway, implying the potential therapeutic application of NPNT on myocardial dysfunction post MI.

Therapeutic Applications of Extracellular Vesicles for Myocardial Repair

Cardiovascular disease is the leading cause of human death worldwide. Drug thrombolysis, percutaneous coronary intervention, coronary artery bypass grafting and other methods are used to restore blood perfusion for coronary artery stenosis and blockage. The treatments listed prolong lifespan, however, rate of mortality ultimately remains the same. This is due to the irreversible damage sustained by myocardium, in which millions of heart cells are lost during myocardial infarction. The lack of pragmatic methods of myocardial restoration remains the greatest challenge for effective treatment. Exosomes are small extracellular vesicles (EVs) actively secreted by all cell types that act as effective transmitters of biological signals which contribute to both reparative and pathological processes within the heart. Exosomes have become the focus of many researchers as a novel drug delivery system due to the advantages of low toxicity, little immunogenicity and good permeability. In this review, we discuss the progress and challenges of EVs in myocardial repair, and review the recent development of extracellular vesicle-loading systems based on their unique nanostructures and physiological functions, as well as the application of engineering modifications in the diagnosis and treatment of myocardial repair.

Amniotic stromal stem cell-loaded hydrogel repairs cardiac tissue in infarcted rat hearts via paracrine mediators

The use of stem cells to repair the heart after a myocardial infarction (MI) remains promising, yet clinical trials over the past 20 years suggest that cells fail to integrate into the native tissue, resulting in limited improvements in cardiac function. Here, we demonstrate the cardioprotective potential of a composite inserting human amniotic stromal mesenchymal stem cells (ASMCs) in a chitosan and hyaluronic acid (C/HA) based hydrogel in a rat MI model. Mechanical characterization of the C/HA platform indicated a swift elastic conversion at 40°C and a rapid sol-gel transition time at 37°C. Cell viability assay presented active and proliferating AMSCs in the C/HA. The ASMCs + C/HA injected composite significantly increased left ventricular ejection fraction, fractional shortening, and neovessel formation. The encapsulated AMSCs were abundantly detected in the infarcted myocardium 6 weeks post-administration and co-expressed cardiac proteins and notably proliferative markers. Proteomic profiling revealed that extracellular vesicles released from hypoxia preconditioned ASMCs contained proteins involved in cytoprotection, angiogenesis, cardiac differentiation and non-canonical Wnt-signaling. Independent activation of non-canonical Wnt-signaling pathways in ASMCs induced cardiogenesis. Despite a low injected cellular density at baseline, the encapsulated AMSCs were abundantly retained and increased cardiac function. Furthermore, the C/HA hydrogel provided an active milieu for the AMSCs to proliferate, co-express cardiac proteins, and induce new vessel formation. Hence, this novel composite of AMSCs + C/HA scaffold is a conceivable candidate that could restore cardiac function and reduce remodeling.

Extracellular Vesicles in Cardiac Regeneration: Potential Applications for Tissues-on-a-Chip

Strategies to regenerate cardiac tissue postinjury are limited and heart transplantation remains the only 'cure' for a failing heart. Extracellular vesicles (EVs), membrane-bound cell secretions important in intercellular signaling, have been shown to play a crucial role in regulating heart function. A mechanistic understanding of the role of EVs in the heart remains elusive due to the challenges in studying the native human heart. Tissue-on-a-chip platforms, comprising functional, physiologically relevant human tissue models, are an emerging technology that has yet to be fully applied to the study of EVs. In this review, we summarize recent advances in cardiac tissue-on-a-chip (CTC) platforms and discuss how they are uniquely situated to advance our understanding of EVs in cardiac disease and regeneration.

Extracellular vesicles as a drug delivery system: A systematic review of preclinical studies

During the past decades, extracellular vesicles (EVs) have emerged as an attractive drug delivery system. Here, we assess their pre-clinical applications, in the form of a systematic review. For each study published in the past decade, disease models, animal species, EV donor cell types, active pharmaceutical ingredients (APIs), EV surface modifications, API loading methods, EV size and charge, estimation of EV purity, presence of biodistribution studies and administration routes were quantitatively analyzed in a defined and reproducible way. We have interpreted the trends we observe over the past decade, to define the niches where to apply EVs for drug delivery in the future and to provide a basis for regulatory guidelines.

Mesenchymal Stem Cells Therapies on Fibrotic Heart Diseases

Stem cell therapy is a promising alternative approach to heart diseases. The most prevalent source of multipotent stem cells, usually called somatic or adult stem cells (mesenchymal stromal/stem cells, MSCs) used in clinical trials is bone marrow (BM-MSCs), adipose tissue (AT-MSCs), umbilical cord (UC-MSCs) and placenta. Therapeutic use of MSCs in cardiovascular diseases is based on the benefits in reducing cardiac fibrosis and inflammation that compose the cardiac remodeling responsible for the maintenance of normal function, something which may end up causing progressive and irreversible dysfunction. Many factors lead to cardiac fibrosis and failure, and an effective therapy is lacking to reverse or attenuate this condition. Different approaches have been shown to be promising in surpassing the poor survival of transplanted cells in cardiac tissue to provide cardioprotection and prevent cardiac remodeling. This review includes the description of pre-clinical and clinical investigation of the therapeutic potential of MSCs in improving ventricular dysfunction consequent to diverse cardiac diseases.

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.

Current Status and Limitations of Myocardial Infarction Large Animal Models in Cardiovascular Translational Research

Establishing an appropriate disease model that mimics the complexities of human cardiovascular disease is critical for evaluating the clinical efficacy and translation success. The multifaceted and complex nature of human ischemic heart disease is difficult to recapitulate in animal models. This difficulty is often compounded by the methodological biases introduced in animal studies. Considerable variations across animal species, modifications made in surgical procedures, and inadequate randomization, sample size calculation, blinding, and heterogeneity of animal models used often produce preclinical cardiovascular research that looks promising but is irreproducible and not translatable. Moreover, many published papers are not transparent enough for other investigators to verify the feasibility of the studies and the therapeutics' efficacy. Unfortunately, successful translation of these innovative therapies in such a closed and biased research is difficult. This review discusses some challenges in current preclinical myocardial infarction research, focusing on the following three major inhibitors for its successful translation: Inappropriate disease model, frequent modifications to surgical procedures, and insufficient reporting transparency.

Extracellular Vesicles: Novel Opportunities to Understand and Detect Neoplastic Diseases

With a size range from 30 to 1000 nm, extracellular vesicles (EVs) are one of the smallest cell components able to transport biologically active molecules. They mediate intercellular communications and play a fundamental role in the maintenance of tissue homeostasis and pathogenesis in several types of diseases. In particular, EVs actively contribute to cancer initiation and progression, and there is emerging understanding of their role in creation of the metastatic niche. This fact underlies the recent exponential growth in EV research, which has improved our understanding of their specific roles in disease and their potential applications in diagnosis and therapy. EVs and their biomolecular cargo reflect the state of the diseased donor cells, and can be detected in body fluids and exploited as biomarkers in cancer and other diseases. Relatively few studies have been published on EVs in the veterinary field. This review provides an overview of the features and biology of EVs as well as recent developments in EV research including techniques for isolation and analysis, and will address the way in which the EVs released by diseased tissues can be studied and exploited in the field of veterinary pathology. Uniquely, this review emphasizes the important contribution that pathologists can make to the field of EV research: pathologists can help EV scientists in studying and confirming the role of EVs and their molecular cargo in diseased tissues and as biomarkers in liquid biopsies.

Clinical Application of Novel Therapies for Coronary Angiogenesis: Overview, Challenges, and Prospects

Cardiovascular diseases continue to be the leading cause of death worldwide, with ischemic heart disease as the most significant contributor. Pharmacological and surgical interventions have improved clinical outcomes, but are unable to ameliorate advanced stages of end-heart failure. Successful preclinical studies of new therapeutic modalities aimed at revascularization have shown short lasting to no effects in the clinical practice. This lack of success may be attributed to current challenges in patient selection, endpoint measurements, comorbidities, and delivery systems. Although challenges remain, the field of therapeutic angiogenesis is evolving, as novel strategies and bioengineering approaches emerge to optimize delivery and efficacy. Here, we describe the structure, vascularization, and regulation of the vascular system with particular attention to the endothelium. We proceed to discuss preclinical and clinical findings and present challenges and future prospects in the field.

Potential Mechanisms and Perspectives in Ischemic Stroke Treatment Using Stem Cell Therapies

Ischemic stroke (IS) remains one of the major causes of death and disability due to the limited ability of central nervous system cells to regenerate and differentiate. Although several advances have been made in stroke therapies in the last decades, there are only a few approaches available to improve IS outcome. In the acute phase of IS, mechanical thrombectomy and the administration of tissue plasminogen activator have been widely used, while aspirin or clopidogrel represents the main therapy used in the subacute or chronic phase. However, in most cases, stroke patients fail to achieve satisfactory functional recovery under the treatments mentioned above. Recently, cell therapy, especially stem cell therapy, has been considered as a novel and potential therapeutic strategy to improve stroke outcome through mechanisms, including cell differentiation, cell replacement, immunomodulation, neural circuit reconstruction, and protective factor release. Different stem cell types, such as mesenchymal stem cells, marrow mononuclear cells, and neural stem cells, have also been considered for stroke therapy. In recent years, many clinical and preclinical studies on cell therapy have been carried out, and numerous results have shown that cell therapy has bright prospects in the treatment of stroke. However, some cell therapy issues are not yet fully understood, such as its optimal parameters including cell type choice, cell doses, and injection routes; therefore, a closer relationship between basic and clinical research is needed. In this review, the role of cell therapy in stroke treatment and its mechanisms was summarized, as well as the function of different stem cell types in stroke treatment and the clinical trials using stem cell therapy to cure stroke, to reveal future insights on stroke-related cell therapy, and to guide further studies.

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.

Recent Approaches for Angiogenesis in Search of Successful Tissue Engineering and Regeneration

Angiogenesis plays a central role in human physiology from reproduction and fetal development to wound healing and tissue repair/regeneration. Clinically relevant therapies are needed for promoting angiogenesis in order to supply oxygen and nutrients after transplantation, thus relieving the symptoms of ischemia. Increase in angiogenesis can lead to the restoration of damaged tissues, thereby leading the way for successful tissue regeneration. Tissue regeneration is a broad field that has shown the convergence of various interdisciplinary fields, wherein living cells in conjugation with biomaterials have been tried and tested on to the human body. Although there is a prevalence of various approaches that hypothesize enhanced tissue regeneration via angiogenesis, none of them have been successful in gaining clinical relevance. Hence, the current review summarizes the recent cell-based and cell free (exosomes, extracellular vesicles, micro-RNAs) therapies, gene and biomaterial-based approaches that have been used for angiogenesis-mediated tissue regeneration and have been applied in treating disease models like ischemic heart, brain stroke, bone defects and corneal defects. This review also puts forward a concise report of the pre-clinical and clinical studies that have been performed so far; thereby presenting the credible impact of the development of biomaterials and their 3D concepts in the field of tissue engineering and regeneration, which would lead to the probable ways for heralding the successful future of angiogenesis-mediated approaches in the greater perspective of tissue engineering and regenerative medicine.

Large Animal Models of Cell-Free Cardiac Regeneration

The adult mammalian heart lacks the ability to sufficiently regenerate itself, leading to the progressive deterioration of function and heart failure after ischemic injuries such as myocardial infarction. Thus far, cell-based therapies have delivered unsatisfactory results, prompting the search for cell-free alternatives that can induce the heart to repair itself through cardiomyocyte proliferation, angiogenesis, and advantageous remodeling. Large animal models are an invaluable step toward translating basic research into clinical applications. In this review, we give an overview of the state-of-the-art in cell-free cardiac regeneration therapies that have been tested in large animal models, mainly pigs. Cell-free cardiac regeneration therapies involve stem cell secretome- and extracellular vesicles (including exosomes)-induced cardiac repair, RNA-based therapies, mainly regarding microRNAs, but also modified mRNA (modRNA) as well as other molecules including growth factors and extracellular matrix components. Various methods for the delivery of regenerative substances are used, including adenoviral vectors (AAVs), microencapsulation, and microparticles. Physical stimulation methods and direct cardiac reprogramming approaches are also discussed.

Extracellular Vesicle miRNAs in the Promotion of Cardiac Neovascularisation

Cardiovascular disease (CVD) is the leading cause of mortality worldwide claiming almost 17. 9 million deaths annually. A primary cause is atherosclerosis within the coronary arteries, which restricts blood flow to the heart muscle resulting in myocardial infarction (MI) and cardiac cell death. Despite substantial progress in the management of coronary heart disease (CHD), there is still a significant number of patients developing chronic heart failure post-MI. Recent research has been focused on promoting neovascularisation post-MI with the ultimate goal being to reduce the extent of injury and improve function in the failing myocardium. Cardiac cell transplantation studies in pre-clinical models have shown improvement in cardiac function; nonetheless, poor retention of the cells has indicated a paracrine mechanism for the observed improvement. Cell communication in a paracrine manner is controlled by various mechanisms, including extracellular vesicles (EVs). EVs have emerged as novel regulators of intercellular communication, by transferring molecules able to influence molecular pathways in the recipient cell. Several studies have demonstrated the ability of EVs to stimulate angiogenesis by transferring microRNA (miRNA, miR) molecules to endothelial cells (ECs). In this review, we describe the process of neovascularisation and current developments in modulating neovascularisation in the heart using miRNAs and EV-bound miRNAs. Furthermore, we critically evaluate methods used in cell culture, EV isolation and administration.

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.

Mesenchymal stem cell-derived extracellular vesicles: a new impetus of promoting angiogenesis in tissue regeneration

Over the past few decades, extracellular vesicles (EVs) have emerged as crucial mediators of intercellular communication. EVs encapsulate and convey information to surrounding cells or distant cells, where they mediate cellular biological responses. Among their multifaceted roles in the modulation of biological responses, the involvement of EVs in vascular development, growth and maturation has been widely documented and their potential therapeutic application in regenerative medicine or in the treatment of angiogenesis-related diseases is drawing increasing interest. In this review, we have summarized the details about the current knowledge on biogenesis of EVs and conventional isolation methods. Evidence supporting the use of EVs derived from mesenchymal stromal cells (MSCs) to enhance angiogenesis in the development of insufficient angiogenesis, such as chronic wounds, stroke and myocardial infarction, will also be discussed critically. Finally, the main challenges and prerequisites for their therapeutic applications will be evaluated.

Small extracellular vesicles secreted from human amniotic fluid mesenchymal stromal cells possess cardioprotective and promigratory potential

Mesenchymal stromal cells (MSCs) exhibit antiapoptotic and proangiogenic functions in models of myocardial infarction which may be mediated by secreted small extracellular vesicles (sEVs). However, MSCs have frequently been harvested from aged or diseased patients, while the isolated sEVs often contain high levels of impurities. Here, we studied the cardioprotective and proangiogenic activities of size-exclusion chromatography-purified sEVs secreted from human foetal amniotic fluid stem cells (SS-hAFSCs), possessing superior functional potential to that of adult MSCs. We demonstrated for the first time that highly pure (up to 1.7 × 1010 particles/µg protein) and thoroughly characterised SS-hAFSC sEVs protect rat hearts from ischaemia-reperfusion injury in vivo when administered intravenously prior to reperfusion (38 ± 9% infarct size reduction, p < 0.05). SS-hAFSC sEVs did not protect isolated primary cardiomyocytes in models of simulated ischaemia-reperfusion injury in vitro, indicative of indirect cardioprotective effects. SS-hAFSC sEVs were not proangiogenic in vitro, although they markedly stimulated endothelial cell migration. Additionally, sEVs were entirely responsible for the promigratory effects of the medium conditioned by SS-hAFSC. Mechanistically, sEV-induced chemotaxis involved phosphatidylinositol 3-kinase (PI3K) signalling, as its pharmacological inhibition in treated endothelial cells reduced migration by 54 ± 7% (p < 0.001). Together, these data indicate that SS-hAFSC sEVs have multifactorial beneficial effects in a myocardial infarction setting.

Mesenchymal stem cell-derived extracellular vesicles alone or in conjunction with a SDKP-conjugated self-assembling peptide improve a rat model of myocardial infarction

PURPOSE

The aim of this study was to investigate the cardiac repair effect of human bone marrow mesenchymal stromal cells-derived extracellular vesicles (MSC-EVs) after intramyocardial injection in free form or encapsulated within a self-assembling peptide hydrogel modified with SDKP motif, in a rat model of myocardial infarction (MI).

METHODS

MSC-EVs were isolated by ultracentrifuge and characterized for physical parameters and surface proteins. Furthermore, cellular uptake and cardioprotective effects of MSC-EVs were evaluated in vitro using neonatal mouse cardiomyocytes (NMCMs). In vivo effects of MSC-EVs on cardiac repair were studied in rat MI model by comparing the vehicle group (injected with PBS), EV group (injected with MSC-EVs) and Gel + EV group (injected with MSC-EVs encapsulated in (RADA)₄-SDKP hydrogel) with respect to cardiac function and fibrotic area using echocardiography and Masson's trichrome staining, respectively. Histological sections were assessed by α-SMA and CD68 immunostaining to investigate the angiogenic and anti-inflammatory effects of the MSC-EVs.

RESULTS

We observed the uptake of MSC-EVs into NMCMs which led to NMCMs protection against H₂O₂-induced oxidative stress by substantial reduction of apoptosis. In myocardial infarcted rats, cardiac function was improved after myocardial injection of MSC-EVs alone or in conjunction with (RADA)₄-SDKP hydrogel. This functional restoration coincided with promotion of angiogenesis and decrement of fibrosis and inflammation.

CONCLUSION

These data demonstrated that MSC-EVs can be used alone as a potent therapeutic agent for improvement of myocardial infarction.

Expression of angiogenic factors in the uteroplacental unit is altered at time of placentation in a porcine model of von Willebrand disease type 1

Von Willebrand disease (VWD) affects blood coagulation and correlates with angiodysplasia. Data on VWD-affected women point to slightly increased miscarriage rates. We aimed to investigate the impact of VWD on angiogenesis in the uteroplacental unit of pregnant pigs of a model of VWD type 1 (T1). Uteri, placentae, and embryos were harvested at time of placentation (day 29 to 31) from four sows (two wildtype (WT) and two heterozygous for a von Willebrand factor (VWF) mutation diagnosed with T1). T1 sows were bred to a T1 boar creating embryos of three different genotypes: WT, T1 or homozygous for the VWF mutation corresponding with VWD type 3 (T3). Uteroplacental tissues were examined histologically. Embryos were genotyped. Gene expression of angiogenic factors possibly related to VWF was determined by quantitative real-time PCR. Corresponding protein expression was analyzed by immunohistochemistry. Genotyping revealed 35.3% WT, 52.9% T1 and 5.9% T3 embryos (5.9% not classified confidently). No histological alterations were found. Gene expression of VEGF was significantly increased in T1 placentae while expression of ANG1, ANG2, TIE2, and ITGB3 was significantly reduced, confirmed on protein level for different cell types. TIE2/TIE1 ratios were significantly lower in T1 placentae. Distribution of embryo genotypes indicates selection favoring the WT. Significant expression differences of angiogenic factors in placentae suggest influence of VWF on these factors during placentation, although angiodysplasia was not observed. The alterations concerning VEGF/VEGFR-2 signaling, integrin expression and the ANG/TIE system may influence angiogenesis and vascular adaptation during placentation and thus the overall outcome of pregnancy.

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.

Drug Delivery with Extracellular Vesicles: From Imagination to Innovation

Extracellular vesicles are nanoparticles produced by cells. They are composed of cellular membrane with associated membrane proteins that surrounds an aqueous core containing soluble molecules such as proteins and nucleic acids, like miRNA and mRNA. They are important in many physiological and pathological processes as they can transfer biological molecules from producer cells to acceptor cells. Preparation of the niche for cancer metastasis, stimulation of tissue regeneration and orchestration of the immune response are examples of the diverse processes in which extracellular vesicles have been implicated. As a result, these vesicles have formed a source of inspiration for many scientific fields. They could be used, for example, as liquid biopsies in diagnostics, as therapeutics in regenerative medicine, or as drug delivery vehicles for transport of medicines. In this Account, we focus on drug delivery applications. As we learn more and more about these vesicles, the complexity increases. What originally appeared to be a relatively uniform population of cellular vesicles is increasingly subdivided into different subsets. Cells make various distinct vesicle types whose physicochemical aspects and composition is influenced by parental cell type, cellular activation state, local microenvironment, biogenesis pathway, and intracellular cargo sorting routes. It has proven difficult to assess the effects of changes in production protocol on the characteristics of the cell-derived vesicle population. On top of that, each isolation method for vesicles necessarily enriches certain vesicle classes and subpopulations while depleting others. Also, each method is associated with a varying degree of vesicle purity and concomitant coisolation of nonvesicular material. What emerges is a staggering heterogeneity. This constitutes one of the main challenges of the field as small changes in production and isolation protocols may have large impact on the vesicle characteristics and on subsequent vesicle activity. We try to meet this challenge by careful experimental design and development of tools that enable robust readouts. By engineering the surface and cargo of extracellular vesicles through chemical and biological techniques, favorable characteristics can be enforced while unfavorable qualities can be overruled or masked. This is coupled to the precise evaluation of the interaction of extracellular vesicles with cells to determine the extracellular vesicle uptake routes and intracellular routing. Sensitive reporter assays enable reproducible analysis of functional delivery. This systematic evaluation and optimization of extracellular vesicles improves our insight into the critical determinants of extracellular vesicle activity and should improve translation into clinical application of engineered extracellular vesicles as a new class of drug delivery systems.

Extracellular micro/nanovesicles rescue kidney from ischemia-reperfusion injury

Acute renal failure (ARF) is a clinical challenge that is highly resistant to treatment, and its high rate of mortality is alarming. Ischemia-reperfusion injury (IRI) is the most common cause of ARF. Especially IRI is implicated in kidney transplantation and can determine graft survival. Although the exact pathophysiology of renal IRI is unknown, the role of inflammatory responses has been elucidated. Because mesenchymal stromal cells (MSCs) have strong immunomodulatory properties, they are under extensive investigation as a therapeutic modality for renal IRI. Extracellular vesicles (EVs) play an integral role in cell-to-cell communication. Because the regenerative potential of the MSCs can be recapitulated by their EVs, the therapeutic appeal of MSC-derived EVs has dramatically increased in the past decade. Higher safety profile and ease of preservation without losing function are other advantages of EVs compared with their producing cells. In the current review, the preliminary results and potential of MSC-derived EVs to alleviate kidney IRI are summarized. We might be heading toward a cell-free approach to treat renal IRI.

(Re) Solving Repair After Myocardial Infarction

Cardiovascular diseases, including myocardial infarction and its complications such as heart failure, are the leading cause of death worldwide. To date, basic and translational research becomes necessary to unravel the mechanisms of cardiac repair post-myocardial infarction. The local inflammatory tissue response after acute myocardial infarction determines the subsequent healing process. The diversity of leukocytes such as neutrophils, macrophages and lymphocytes contribute to the clearance of dead cells while activating reparative pathways necessary for myocardial healing. Cardiomyocyte death triggers wall thinning, ventricular dilatation, and fibrosis that can cause left ventricular dysfunction and heart failure. The ultimate goal of cardiac repair is to regenerate functionally viable myocardium after myocardial infarction to prevent cardiac death. Current therapies for heart failure after myocardial infarction are limited and non-curative. At the moment in clinic, conventional surgical interventions such as coronary artery bypass graft or percutaneous coronary interventions are only able to partially restore heart function, with a minor improvement in the left ventricular ejection fraction. The goal of this review is to provide an overview of endogenous myocardial repair mechanisms possibly transferable to future treatment strategies. Among the innovative factors identified as essential in cardiac healing, we highlight specialized pro-resolving mediators as the emerging factors that provide the key molecular signals for the activation of the reparative cells in the myocardium.