Exosomal miR-21a-5p mediates cardioprotection by mesenchymal stem cells

Native and bioengineered extracellular vesicles for cardiovascular therapeutics

Extracellular vesicles (EVs) are a heterogeneous group of natural particles that are relevant to the treatment of cardiovascular diseases. These endogenous vesicles have certain properties that allow them to survive in the extracellular space, bypass biological barriers and deliver their biologically active molecular cargo to recipient cells. Moreover, EVs can be bioengineered to increase their stability, bioactivity, presentation to acceptor cells and capacity for on-target binding at both cell-type-specific and tissue-specific levels. Bioengineering of EVs involves the modification of the donor cell before EV isolation or direct modification of the EV properties after isolation. The therapeutic potential of native EVs and bioengineered EVs has been only minimally explored in the context of cardiovascular diseases. Efforts to harness the therapeutic potential of EVs will require innovative approaches and a comprehensive integration of knowledge gathered from decades of research into molecular-compound delivery. In this Review, we outline the endogenous properties of EVs that make them natural delivery agents as well as the features that can be improved by bioengineering. We also discuss the therapeutic applications of native and bioengineered EVs to cardiovascular diseases and examine the opportunities and challenges that need to be addressed to advance this research area, with an emphasis on clinical translation.

Mesenchymal stromal cell-derived extracellular vesicles modulate microglia/macrophage polarization and protect the brain against hypoxia-ischemic injury in neonatal mice by targeting delivery of miR-21a-5p

Mesenchymal stromal cell (MSC)-derived extracellular vesicles (EVs) (MSC-EVs) exhibit protective effects in damaged or diseased tissues. However, the role of EVs secreted by MSC in hypoxia-ischemic (HI) injury in neonatal mice remains unknown. Systemic administration of MSC-EVs attenuated acute brain damage and neuroinflammation, and skewed CD11b⁺/CD45^low microglia and CD11b⁺/CD45^high brain monocyte/macrophage towards a more anti-inflammatory property as determined at 72 h post-HI. In addition, MSC-EVs remarkably improve the injury outcomes pups prior to weaning (P21), while no effect on long-term memory impairment (P42). Importantly, these effects were preceded by incorporation of MSC-EVs into a large number of neurons and microglia within HI group. Abundant levels of miR-21a-5p were present in EVs as determined with next-generation sequencing. Notably, MSC-EVs treatment further increased miR-21a-5p levels at 72 h post HI. Knockdown analyses revealed that miR-21a-5p, and its target-Timp3, were essential for this neuroprotective property of MSC-EVs following HI exposure as demonstrated in both in vitro and in vivo models. These findings suggest that a systemic administration of EVs derived from MSC, have the capacity to incorporated into neurons and microglia where they can then exert neuroprotection against HI-induced injury in neonates through the delivery of miR-21a-5p.

Mesenchymal stem cell-derived exosomes: Toward cell-free therapeutic strategies in regenerative medicine

Mesenchymal stem cells (MSCs) are multipotent stem cells with marked potential for regenerative medicine because of their strong immunosuppressive and regenerative abilities. The therapeutic effects of MSCs are based in part on their secretion of biologically active factors in extracellular vesicles known as exosomes. Exosomes have a diameter of 30-100 nm and mediate intercellular communication and material exchange. MSC-derived exosomes (MSC-Exos) have potential for cell-free therapy for diseases of, for instance, the kidney, liver, heart, nervous system, and musculoskeletal system. Hence, MSC-Exos are an alternative to MSC-based therapy for regenerative medicine. We review MSC-Exos and their therapeutic potential for a variety of diseases and injuries.

Ultrasound targeted microbubble destruction assisted exosomal delivery of miR-21 protects the heart from chemotherapy associated cardiotoxicity

Chemotherapy related cardiotoxicity is now becoming one of the biggest hurdles for the prognosis of cancer patients. Therapeutically delivering protective small RNAs holds promise for the cardiotoxicity prevention and therapy. However, heart is intrinsically refractory to the nanoparticle-mediated drug delivery. In this study, we found that the exosome-mediated miRNA delivery into the heart could be significantly augmented with the aid of ultrasound targeted microbubble destruction (UTMD). Moreover, we found that UTMD assisted exosomal miR-21 delivery into the heart significantly decreased the cell death, and restored the cardiac function in a doxorubicin induced cardiotoxicity mouse model. Our study here not only provides a promising strategy to protect the heart from the chemotherapy related cardiotoxicity, but also sheds light on gene therapy of other heart diseases.

Biomimetic nanovesicle design for cardiac tissue repair

Cardiovascular disease is a major cause of mortality and morbidity worldwide. Exosome therapies are promising for cardiac repair. Exosomes transfer cargo between cells, have high uptake by native cells and are ideal natural carriers for proteins and nucleic acids. Despite their proreparative potential, exosome production is dependent on parent cell state with typically low yields and cargo variability. Therefore, there is potential value in engineering exosomes to maximize their benefits by delivering customized, potent cargo for cardiovascular disease. Here, we outline several methods of exosome engineering focusing on three important aspects: optimizing cargo, homing to target tissue and minimizing clearance. Finally, we put these methods in context of the cardiac field and discuss the future potential of vesicle design.

Extracellular vesicles derived from microRNA-150-5p-overexpressing mesenchymal stem cells protect rat hearts against ischemia/reperfusion

An intriguing area of research has demonstrated the ability of extracellular vesicles (EVs) as biological vehicles for microRNAs (miRNAs) transfer. Mesenchymal stem cells (MSCs) produce large amounts of EVs. Rat models of ischemia/reperfusion (I/R) were established to explore the expression profile of thioredoxin-interacting protein (TXNIP), which was then knocked-down to investigate its effects on myocardial remodeling, followed by detection on myocardial infarction size (MIS), myocardial collagen volume fraction (CVF) and cardiomyocyte apoptosis. MSCs-derived EVs carrying miR-150-5p were cultured with neonatal cardiomyocytes under hypoxia/hypoglycemia condition for in vitro exploration and intramyocardially injected into I/R rats for in vivo exploration. I/R-induced rats presented higher TXNIP levels and lower miR-150-5p levels, along with increased cardiomyocyte apoptosis. miR-150-5p in MSCs was transferred through EVs to cardiomyocytes, leading to suppressed myocardial remodeling, as reflected by smaller MIS and CVF and suppressed cardiomyocyte apoptosis. I/R-treated rats injected with MSCs-derived EVs containing miR-150-5p showed a reduction in myocardial remodeling associated with the downregulation of TXNIP, which may be clinically applicable for treatment of I/R.

Adult mesenchymal stem cells and their exosomes: Sources, characteristics, and application in regenerative medicine

Human mesenchymal stem cells (MSCs) have become a hot topic in the development of cell therapies and bioengineering. All kinds of MSCs are genomic stable and have the self-renewal ability. Main sources of MSCs are bone marrow, adipose tissues, umbilical cord and placental tissues. MSCs can be cultured in many undifferentiated passages to grow into more specialized cells, produce secretory factors and also support trophic functions in the body. Exosomes, derived from MSCs also have great potential in regenerative medicine and tissue engineering. Exosomes are secreted by MSCs and have the same therapeutic potential as their parent cells. MSCs and their exosomes combined with biomaterials can also be more effective in promoting the regeneration of tissues and organs. However, for use of MSCs-exosomes as a clinical agent different MSCs-exosomes have been manufactured and their therapeutics effects demonstrated in clinical studies. But there are still many characteristics which are unknown and many barriers still need to be conquered. In this review, we not only highlighted the characteristics of human MSCs and their exosomes, but also provided their latest therapeutic strategies in regenerative medicine.

Cardiovascular Exosomes and MicroRNAs in Cardiovascular Physiology and Pathophysiology

Cardiac exosomes mediate cell-to-cell communication, stimulate or inhibit the activities of target cells, and affect myocardial hypertrophy, injury and infarction, ventricular remodeling, angiogenesis, and atherosclerosis. The exosomes that are released in the heart from cardiomyocytes, vascular cells, fibroblasts, and resident stem cells are hypoimmunogenic, are physiologically more stable than cardiac cells, can circulate in the body, and are able to cross the blood-brain barrier. Exosomes utilize three mechanisms for cellular communication: (1) internalization by cells, (2) direct fusion to the cell membrane, and (3) receptor-ligand interactions. Cardiac exosomes transmit proteins, mRNA, and microRNAs to other cells during both physiological and pathological process. Cardiac-specific exosome miRNAs can regulate the expression of sarcomeric genes, ion channel genes, autophagy, anti-apoptotic and anti-fibrotic activity, and angiogenesis. This review discusses the role of exosomes and microRNAs in normal myocardium, myocardial injury and infarction, atherosclerosis, and the importance of circulating microRNAs as biomarkers of cardiac disease. Graphical Abstract.

Small but significant: Insights and new perspectives of exosomes in cardiovascular disease

Cardiovascular diseases (CVDs) are a major health problem worldwide, and health professionals are still actively seeking new and effective approaches for CVDs treatment. Presently, extracellular vesicles, particularly exosomes, have gained its popularity for CVDs treatment because of their function as messengers for inter- and extra-cellular communications to promote cellular functions in cardiovascular system. However, as a newly developed field, researchers are still trying to fully understand the role of exosomes, and their mechanism in mediating cardiac repair process. Therefore, a comprehensive review of this topic can be timely and favourable. In this review, we summarized the basic biogenesis and characterization of exosomes and then further extended the focus on the circulating exosomes in cellular communication and stem cell-derived exosomes in cardiac disease treatment. In addition, we covered interactions between the heart and other organs through exosomes, leading to the diagnostic characteristics of exosomes in CVDs. Future perspectives and limitations of exosomes in CVDs were also discussed with a special focus on exploring the potential delivery routes, targeting the injured tissue and engineering novel exosomes, as well as its potential as one novel target in the metabolism-related puzzle.

Novel Findings and Therapeutic Targets on Cardioprotection of Ischemia/ Reperfusion Injury in STEMI

Acute ST-segment elevation myocardial infarction (STEMI) remains a leading cause of morbidity and mortality around the world. A large number of STEMI patients after the infarction gradually develop heart failure due to the infarcted myocardium. Timely reperfusion is essential to salvage ischemic myocardium from the infarction, but the restoration of coronary blood flow in the infarct-related artery itself induces myocardial injury and cardiomyocyte death, known as ischemia/reperfusion injury (IRI). The factors contributing to IRI in STEMI are complex, and microvascular obstruction, inflammation, release of reactive oxygen species, myocardial stunning, and activation of myocardial cell death are involved. Therefore, additional cardioprotection is required to prevent the heart from IRI. Although many mechanical conditioning procedures and pharmacological agents have been identified as effective cardioprotective approaches in animal studies, their translation into the clinical practice has been relatively disappointing due to a variety of reasons. With new emerging data on cardioprotection in STEMI over the past few years, it is mandatory to reevaluate the effectiveness of "old" cardioprotective interventions and highlight the novel therapeutic targets and new treatment strategies of cardioprotection.

Serum Exosomal MicroRNA-21, MicroRNA-126, and PTEN Are Novel Biomarkers for Diagnosis of Acute Coronary Syndrome

Acute coronary syndrome (ACS) is a serious threat to public health. Based on clinical manifestations, ACS can be classified into unstable angina (UA) pectoris and acute myocardial infarction (AMI). The purpose of this study was to explore the possibility of using serum exosomal microRNA (miR)-126, miR-21, and phosphatase and tensin homolog (PTEN) expression levels as biomarkers of UA and AMI and to investigate whether these levels were positively correlated with the severity of coronary stenosis based on the Gensini score. Exosomes were isolated by ultracentrifugation from the serum of 34 patients with AMI, 31 patients with UA, and 22 healthy controls. The isolated exosomes were characterized by electron microscopy and particle size analysis; exosomal identity was further confirmed by western blotting using exosome-specific antibodies. Real-time quantitative polymerase chain reaction indicated that the serum exosomal levels of miR-126 and miR-21 were significantly higher in the patients with UA and AMI than in the healthy controls. Enzyme-linked immunosorbent assay showed that the serum exosomal PTEN levels were significantly higher in the UA and AMI groups than in the control group. Receiving operating characteristic curve analysis demonstrated the diagnostic efficiency of serum exosomal miR-126, miR-21, and PTEN levels for predicting AMI and UA. In addition, the circulating exosomal miR-126 level was positively correlated with the severity of coronary artery stenosis in patients with UA and AMI based on the Gensini score.

Mesenchymal and Induced Pluripotent Stem Cells-Derived Extracellular Vesicles: The New Frontier for Regenerative Medicine?

Regenerative medicine aims to repair damaged, tissues or organs for the treatment of various diseases, which have been poorly managed with conventional drugs and medical procedures. To date, multimodal regenerative methods include transplant of healthy organs, tissues, or cells, body stimulation to activate a self-healing response in damaged tissues, as well as the combined use of cells and bio-degradable scaffold to obtain functional tissues. Certainly, stem cells are promising tools in regenerative medicine due to their ability to induce de novo tissue formation and/or promote organ repair and regeneration. Currently, several studies have shown that the beneficial stem cell effects, especially for mesenchymal stem cells (MSCs) and induced pluripotent stem cells (iPSCs) in damaged tissue restore are not dependent on their engraftment and differentiation on the injury site, but rather to their paracrine activity. It is now well known that paracrine action of stem cells is due to their ability to release extracellular vesicles (EVs). EVs play a fundamental role in cell-to-cell communication and are directly involved in tissue regeneration. In the present review, we tried to summarize the molecular mechanisms through which MSCs and iPSCs-derived EVs carry out their therapeutic action and their possible application for the treatment of several diseases.

Mesenchymal stromal/stem cell-derived extracellular vesicles in tissue repair: challenges and opportunities

Mesenchymal stem/stromal cells (MSCs) are important players in tissue homeostasis and regeneration owing to their immunomodulatory potential and release of trophic factors that promote healing. They have been increasingly used in clinical trials to treat multiple conditions associated with inflammation and tissue damage such as graft versus host disease, orthopedic injuries and cardiac and liver diseases. Recent evidence demonstrates that their beneficial effects are derived, at least in part, from their secretome. In particular, data from animal models and first-in-man studies indicate that MSC-derived extracellular vesicles (MSC-EVs) can exert similar therapeutic potential as their cells of origin. MSC-EVs are membranous structures loaded with proteins, lipids, carbohydrates and nucleic acids, which play an important role in cell-cell communication and may represent an attractive alternative for cell-based therapy. In this article we summarize recent advances in the use of MSC-EVs for tissue repair. We highlight several isolation and characterization approaches used to enrich MSC-derived EVs. We discuss our current understanding of the relative contribution of the MSC-EVs to the immunomodulatory and regenerative effects mediated by MSCs and MSC secretome. Finally we highlight the challenges and opportunities, which come with the potential use of MSC-EVs as cell free therapy for conditions that require tissue repair.

miR-21 and Pellino-1 Expression Profiling in Autoimmune Premature Ovarian Insufficiency

Background

Premature ovarian insufficiency (POI) represents the hypergonadotropic hypoestrogenic symptoms that result in the loss of ovarian follicles. 5-30% POI cases are suggested to be involved in autoimmune etiology. MicroRNA-21 (miR-21) plays a vital role in ovarian folliculogenesis via regulating and interacting with multiple target genes. Here, we conduct the target prediction of miR-21, identify the expression and correlation of miR-21 and its putative target Pellino-1 (Peli1), and confirm their relationship with clinical characteristics in autoimmune POI.

Methods

Bioinformatic analysis was conducted to screen the miR-21 putative target gene. Autoimmune POI mouse models were established by ZP3 immunization. Serum miR-21, Peli1 mRNA of peripheral blood mononuclear cells (PBMCs) and regulatory T cells (Tregs), general status, spleen Tregs ratio, inflammatory factors, ovarian endocrine function, and ovarian structure were evaluated. For autoimmune POI patients, serum miR-21, PBMCs Peli1 mRNA levels, general data, immune parameters, hormone levels, and ultrasound examinations were obtained. The correlations of miR-21 with Peli1 and clinical characteristics in patients were analyzed.

Results

Peli1 was selected based on four microRNA prediction databases and literature retrieval. In mouse models, serum miR-21 level, PBMCs and Tregs Peli1 mRNA, and spleen Tregs ratio were 0.61 ± 0.09, 0.12 ± 0.12, 0.27±0.23 and 4.82 ± 0.58, respectively, lower than those in the control group. In patients, miR-21 level (0.60 ± 0.14) and Peli1 mRNA (0.30 ± 0.14) were lower than those in the control group (1.01 ± 0.07 and 1.63 ± 0.54); miR-21 was positively related with Peli1, AMH, E₂, the size of the uterus, and ovarian volume and negatively related with FSH, LH, and the number of positive immune parameters (AOAb, EMAb, ACL, ANA, ds-DNA, ACA, IgG, IgA, IgM, IgE, C3, and C4).

Conclusions

Low expressions of miR-21 and Peli1 were detected in autoimmune POI mice and patients. Positive correlation between miR-21 and Peli1 was observed in autoimmune POI patients, suggesting that miR-21 and Peli1 might be associated with the pathogenesis of autoimmune POI.

MicroRNA Mediated Cardioprotection - Is There a Path to Clinical Translation?

In the past 20 years, there have been several approaches to achieve cardioprotection or cardiac regeneration using a vast variety of cell therapies and remote ischemic pre-conditioning (RIPC). To date, substantial proof that either cell therapy or RIPC has the potential for clinically relevant cardiac repair or regeneration of cardiac tissue is still pending. Preclinical trials indicate that the secretome of cells in situ (during RIPC) as well as of transplanted cells may exhibit cardioprotective properties in the acute setting of cardiac injury. The secretome generally consists of cell-specific cytokines and extracellular vesicles (EVs) containing microRNAs (miRNAs). It is currently hypothesized that a subset of known miRNAs play a crucial part in the facilitation of cardioprotective effects. miRNAs are small non-coding RNA molecules that inhibit post-transcriptional translation of messenger RNAs (mRNAs) and play an important role in gene translation regulation. It is also known that one miRNAs usually targets multiple mRNAs. This makes predictability of pharmacokinetics and mechanism of action very difficult and could in part explain the inferior performance of various progenitor cells in clinical studies. Identification of miRNAs involved in cardioprotection and remodeling, the composition of miRNA profiles, and the exact mechanism of action are important to the design of future cell-based but also cell-free cardioprotective therapeutics. This review will give a description of miRNA with cardioprotective properties and a current overview on known mechanism of action and potential missing links. Additionally, we will give an outlook on the potential for clinical translation of miRNAs in the setting of myocardial infarction and heart failure.

Paracrine Mechanisms of Mesenchymal Stromal Cells in Angiogenesis

The role of the mesenchymal stromal cell- (MSC-) derived secretome is becoming increasingly intriguing from a clinical perspective due to its ability to stimulate endogenous tissue repair processes as well as its effective regulation of the immune system, mimicking the therapeutic effects produced by the MSCs. The secretome is a composite product secreted by MSC in vitro (in conditioned medium) and in vivo (in the extracellular milieu), consisting of a protein soluble fraction (mostly growth factors and cytokines) and a vesicular component, extracellular vesicles (EVs), which transfer proteins, lipids, and genetic material. MSC-derived secretome differs based on the tissue from which the MSCs are isolated and under specific conditions (e.g., preconditioning or priming) suggesting that clinical applications should be tailored by choosing the tissue of origin and a priming regimen to specifically correct a given pathology. MSC-derived secretome mediates beneficial angiogenic effects in a variety of tissue injury-related diseases. This supports the current effort to develop cell-free therapeutic products that bring both clinical benefits (reduced immunogenicity, persistence in vivo, and no genotoxicity associated with long-term cell cultures) and manufacturing advantages (reduced costs, availability of large quantities of off-the-shelf products, and lower regulatory burden). In the present review, we aim to give a comprehensive picture of the numerous components of the secretome produced by MSCs derived from the most common tissue sources for clinical use (e.g., AT, BM, and CB). We focus on the factors involved in the complex regulation of angiogenic processes.

Isolation of extracellular vesicles from intestinal tissue in a mouse model of intestinal ischemia/reperfusion injury

Extracellular vesicles (EVs) are small membranous particles that contribute to intercellular communications. Separating EVs from tissue is still a technical challenge. Here, we present a rigorous method for extracting EVs from intestinal tissue in a mouse intestinal ischemia/reperfusion (I/R) model, and for analyzing their miRNA content. The isolated EVs show a typical cup shape with a size peak of 120-130 nm in diameter, confirmed by TEM and NTA. They also express EV markers such as CD9, CD63, CD81, Tsg101 and Alix. Real-time qPCR confirmed that these pellets contain miRNAs related to I/R injury. Our study presents a practical way to isolate EVs from intestinal tissue which is suitable for downstream applications such as miRNA analysis, and provides a novel method for investigating the mechanism of intestinal I/R injury.

Extracellular vesicles isolated from patients undergoing remote ischemic preconditioning decrease hypoxia-evoked apoptosis of cardiomyoblasts after isoflurane but not propofol exposure

Remote ischemic preconditioning (RIPC) can evoke cardioprotection following ischemia/reperfusion and this may depend on the anesthetic used. We tested whether 1) extracellular vesicles (EVs) isolated from humans undergoing RIPC protect cardiomyoblasts against hypoxia-induced apoptosis and 2) this effect is altered by cardiomyoblast exposure to isoflurane or propofol. EVs were isolated before and 60 min after RIPC or Sham from ten patients undergoing coronary artery bypass graft surgery with isoflurane anesthesia and quantified by Nanoparticle Tracking Analysis. Following EV-treatment for 6 hours under exposure of isoflurane or propofol, rat H9c2 cardiomyoblasts were cultured for 18 hours in normoxic or hypoxic atmospheres. Apoptosis was detected by flow cytometry. Serum nanoparticle concentrations in patients had increased sixty minutes after RIPC compared to Sham (2.5x10¹¹±4.9x10¹⁰ nanoparticles/ml; Sham: 1.2x10¹¹±2.0x10¹⁰; p = 0.04). Hypoxia increased apoptosis of H9c2 cells (hypoxia: 8.4%±0.6; normoxia: 2.5%±0.1; p<0.0001). RIPC-EVs decreased H9c2 cell apoptosis compared to control (apoptotic ratio: 0.83; p = 0.0429) while Sham-EVs showed no protection (apoptotic ratio: 0.97). Prior isoflurane exposure in vitro even increased protection (RIPC-EVs/control, apoptotic ratio: 0.79; p = 0.0035; Sham-EVs/control, apoptotic ratio:1.04) while propofol (50μM) abrogated protection by RIPC-EVs (RIPC-EVs/control, Apoptotic ratio: 1.01; Sham-EVs/control, apoptotic ratio: 0.94; p = 0.602). Thus, EVs isolated from patients undergoing RIPC under isoflurane anesthesia protect H9c2 cardiomyoblasts against hypoxia-evoked apoptosis and this effect is abrogated by propofol. This supports a role of human RIPC-generated EVs in cardioprotection and underlines propofol as a possible confounder in RIPC-signaling mediated by EVs.

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.

Mesenchymal stem cell-derived exosomes ameliorate cardiomyocyte apoptosis in hypoxic conditions through microRNA144 by targeting the PTEN/AKT pathway

Background

A growing body of evidence suggests that stem cell-derived exosomal microRNAs (miRNAs) could be a promising cardioprotective therapy in the context of hypoxic conditions. The present study aims to explore how miRNA-144 (miR-144), a miRNA contained in bone marrow mesenchymal stem cell (MSC)-derived exosomes, exerts a cardioprotective effect on cardiomyocyte apoptosis in the context of hypoxic conditions and identify the underlying mechanisms.

Methods

MSCs were cultured using the whole bone marrow adherent method. MSC-derived exosomes were isolated using the total exosome isolation reagent and confirmed by nanoparticle trafficking analysis as well as western blotting using TSG101 and CD63 as markers. The hypoxic growth conditions for the H9C2 cells were established using the AnaeroPack method. Treatment conditions tested included H9C2 cells pre-incubated with exosomes, transfected with miR-144 mimics or inhibitor, or treated with the PTEN inhibitor SF1670, all under hypoxic growth conditions. Cell apoptosis was determined by flow cytometry using 7-ADD and Annexin V together. The expression levels of the miRNAs were detected by real-time PCR, and the expression levels of AKT/p-AKT, Bcl-2, caspase-3, HIF-1α, PTEN, and Rac-1 were measured by both real-time PCR and western blotting.

Results

Exosomes were readily internalized by H9C2 cells after co-incubation for 12 h. Exosome-mediated protection of H9C2 cells from apoptosis was accompanied by increasing levels of p-AKT. MiR-144 was found to be highly enriched in MSC-derived exosomes. Transfection of cells with a miR-144 inhibitor weakened exosome-mediated protection from apoptosis. Furthermore, treatment of cells grown in hypoxic conditions with miR-144 mimics resulted in decreased PTEN expression, increased p-AKT expression, and prevented H9C2 cell apoptosis, whereas treatment with a miR-144 inhibitor resulted in increased PTEN expression, decreased p-AKT expression, and enhanced H9C2 cell apoptosis in hypoxic conditions. We also validated that PTEN was a target of miR-144 by using luciferase reporter assay. Additionally, cells treated with SF1670, a PTEN-specific inhibitor, resulted in increased p-AKT expression and decreased H9C2 cell apoptosis.

Conclusions

These findings demonstrate that MSC-derived exosomes inhibit cell apoptotic injury in hypoxic conditions by delivering miR-144 to cells, where it targets the PTEN/AKT pathway. MSC-derived exosomes could be a promising therapeutic vehicle to facilitate delivery of miRNA therapies to ameliorate ischemic conditions.

Electronic supplementary material

The online version of this article (10.1186/s13287-020-1563-8) contains supplementary material, which is available to authorized users.

Exosomes from mesenchymal stem cells overexpressing MIF enhance myocardial repair

Accumulating evidence has shown that mesenchymal stem cell (MSC)-derived exosomes (exo) mediate cardiac repair following myocardial infarction (MI). Macrophage migration inhibitory factor (MIF), a proinflammatory cytokine, plays a critical role in regulating cell homeostasis. This study aimed to investigate the cardioprotective effects of exo secreted from bone marrow-MSCs (BM-MSCs) overexpressing MIF in a rat model of MI. MIF plasmid was transducted in BM-MSCs. Exo were isolated from the supernatants of BM-MSCs and MIF-BM-MSCs, respectively. The morphology of mitochondria in neonatal mice cardiomyocytes (NRCMs) was determined by MitoTracker staining. The apoptosis of NRCMs was examined by deoxynucleotidyl transferase-mediated dUTP nick end-labeling. BM-MSC-exo and MIF-BM-MSC-exo were intramuscularly injected into the peri-infarct region in a rat model of MI. The heart function of rats was assessed by echocardiography. The expression of MIF was greatly enhanced in MIF-BM-MSCs compared with BM-MSCs. Both BM-MSC-exo and MIF-BM-MSC-exo expressed CD63 and CD81. NRCMs treated with MIF-BM-MSC-exo exhibited less mitochondrial fragmentation and cell apoptosis under hypoxia/serum deprivation (H/SD) challenge than those treated with BM-MSC-exo via activating adenosine 5'-monophosphate-activated protein kinase signaling. Moreover, these effects were partially abrogated by Compound C. Injection of BM-MSC-exo or MIF-BM-MSC-exo greatly restored heart function in a rat model of MI. Compared with BM-MSC-exo, injection of MIF-BM-MSC-exo was associated with enhanced heart function, reduced heart remodeling, less cardiomyocyte mitochondrial fragmentation, reactive oxygen species generation, and apoptosis. Our study reveals a new mechanism of MIF-BM-MSC-exo-based therapy for MI and provides a novel strategy for cardiovascular disease treatment.

Mononuclear phagocyte system blockade improves therapeutic exosome delivery to the myocardium

Rationale: Exosomes are emerging as a promising drug delivery carrier. However, rapid uptake of exosomes by the mononuclear phagocyte system (MPS) remains an obstacle for drug delivery into other targeted organs, including the heart. We hypothesized that prior blocking of uptake of exosomes by the MPS would improve their delivery to the targeted organs.

Methods: Exosomes were isolated from the cell culture medium. Fluorescence-labeled exosomes were tracked in vitro and in vivo by fluorescence imaging. The expression of clathrin heavy chain (Cltc), cavolin1, Pak1 and Rhoa, known genes for endocytosis, were profiled in various cell lines and organs by qPCR. The knockdown efficiency of siRNA against Cltc was analyzed by Western blotting. Exosome^control and exosome^blocking were constructed by encapsulating isolated exosomes with siControl or siClathrin via electroporation, while exosome^therapeutic was constructed by encapsulating isolated exosomes with miR-21a. Doxorubicin-induced cardiotoxicity model was used to verify the therapeutic efficiency of the exosome-based miR-21a delivery by echocardiography.

Results: Exosomes were preferentially accumulated in the liver and spleen, mainly due to the presence of abundant macrophages. Besides the well-known phagocytic effect, efficient endocytosis also contributes to the uptake of exosomes by macrophages. Cltc was found to be highly expressed in the macrophages compared with other endocytosis-associated genes. Accordingly, knockdown of Cltc significantly decreased the uptake of exosomes by macrophages in vitro and in vivo. Moreover, prior injection of exosome^blocking strikingly improved the delivery efficiency of exosomes to organs other than spleen and liver. Consistently, compared with the direct injection of exosome^therapeutic, prior injection of exosome^blocking produced a much better therapeutic effect on cardiac function in the doxorubicin-induced cardiotoxicity mouse model.

Conclusions: Prior blocking of endocytosis of exosomes by macrophages with exosome^blocking successfully and efficiently improves the distribution of following exosome^therapeutic in targeted organs, like the heart. The established two-step exosome delivery strategy (blocking the uptake of exosomes first followed by delivery of therapeutic exosomes) would be a promising method for gene therapy.

The Contrasting Role of Extracellular Vesicles in Vascular Inflammation and Tissue Repair

Extracellular vesicles are a heterogeneous family of vesicles, generated from different subcellular compartments and released into the extracellular space. Composed of a lipid bilayer encompassing both soluble cytosolic material and nuclear components, these organelles have been recently described as novel regulators of intercellular communication between adjacent and remote cells. Due to their diversified composition and biological content, they portray specific signatures of cellular activation and pathological processes, their potential as diagnostic and prognostic biomarkers has raised significant interest in cardiovascular diseases. Circulating vesicles, especially those released from platelets, leukocytes, and endothelial cells are found to play a critical role in activating several fundamental cells within the vasculature, including endothelial cells and vascular smooth muscle cells. Their intrinsic activity and immunomodulatory properties lends them to not only promote vascular inflammation, but also enhance tissue regeneration, vascular repair, and indeed resolution. In this review we aim to recapitulate the recent findings concerning the roles played by EVs that originate from different circulating cells, with particular reference to their action on the endothelium. We focus herein, on the interaction of platelet and leukocyte EVs with the endothelium. In addition, their potential biological function in promoting tissue resolution and vascular repair will also be discussed.

Human umbilical cord mesenchymal stem cell derived exosomes encapsulated in functional peptide hydrogels promote cardiac repair

Stem cell-derived exosomes have been recognized as a potential therapy for cardiovascular disease. However, the low retention rate of exosomes after transplantation in vivo remains a major challenge in clinical applications. The aim of this study is to investigate whether human umbilical cord mesenchymal stem cell derived exosomes (UMSC-Exo) encapsulated in functional peptide hydrogels could increase the retention and stability of exosomes and improve heart function in a rat myocardial infarction model. Our results demonstrated that the PA-GHRPS peptide protected H9C2 cells from H2O2-induced oxidative stress. The gelatinization ability of PA-GHRPS can be enhanced by peptide NapFF. Therefore, these two peptides were mixed to form the PGN hydrogel, which was used to encapsulate exosomes. Our data showed that the PGN hydrogel was able to encapsulate exosomes effectively and ensured a stable and sustained release of exosomes. The exosome/PGN hydrogel mixture was injected into the infarcted border zone of rat hearts. Compared to the exosome treatment alone, the mixture improved the myocardial function by reducing inflammation, fibrosis and apoptosis, and by promoting angiogenesis. The strategy used in this study provided a practical and effective method to harness exosomes for myocardial regeneration.

Substantial Overview on Mesenchymal Stem Cell Biological and Physical Properties as an Opportunity in Translational Medicine

Mesenchymal stem cells (MSC) have piqued worldwide interest for their extensive potential to treat a large array of clinical indications, their unique and controversial immunogenic and immune modulatory properties allowing ample discussions and debates for their possible applications. Emerging data demonstrating that the interaction of biomaterials and physical cues with MSC can guide their differentiation into specific cell lineages also provide new interesting insights for further MSC manipulation in different clinical applications. Moreover, recent discoveries of some regulatory molecules and signaling pathways in MSC niche that may regulate cell fate to distinct lineage herald breakthroughs in regenerative medicine. Although the advancement and success in the MSC field had led to an enormous increase in the amount of ongoing clinical trials, we still lack defined clinical therapeutic protocols. This review will explore the exciting opportunities offered by human and animal MSC, describing relevant biological properties of these cells in the light of the novel emerging evidence mentioned above while addressing the limitations and challenges MSC are still facing.

Incorporation of small extracellular vesicles in sodium alginate hydrogel as a novel therapeutic strategy for myocardial infarction

Bone marrow mesenchymal stem cell (MSC)-derived small extracellular vesicles (sEVs) have been widely used for treating myocardial infarction (MI). However, low retention and short-lived therapeutic effects are still significant challenges. This study aimed to determine whether incorporation of MSC-derived sEVs in alginate hydrogel increases their retention in the heart thereby improving therapeutic effects.

Methods: The optimal sodium alginate hydrogel incorporating sEVs system was determined by its release ability of sEVs and rheology of hydrogel. Ex vivo fluorescence imaging was utilized to evaluate the retention of sEVs in the heart. Immunoregulation and effects of sEVs on angiogenesis were analyzed by immunofluorescence staining. Echocardiography and Masson's trichrome staining were used to estimate cardiac function and infarct size.

Results: The delivery of sEVs incorporated in alginate hydrogel (sEVs-Gel) enhanced their retention in the heart. Compared with sEVs only treatment (sEVs), sEVs-Gel treatment significantly decreased cardiac cell apoptosis and promoted the polarization of macrophages at day 3 after MI. sEVs-Gel treatment also increased scar thickness and angiogenesis at four weeks post-infarction. Measurement of cardiac function and infarct size were significantly better in the sEVs-Gel group than in the group treated with sEVs only.

Conclusion: Delivery of sEVs incorporated in alginate hydrogel provides a novel approach of cell-free therapy and optimizes the therapeutic effect of sEVs for MI.

Exosomes in ischemic heart disease: novel carriers for bioinformation

The occurrence of ischemic heart disease(IHD) is a multi-step chain process from potential risk factors to overt clinical diseases. Vascular cells, blood cells, cardiomyocytes and stem cells are all involved in the pathophysiological links via continual and polynary crosstalk. Exosomes,as powerful vectors for intercellular communication,have been a hotspot for basic and clinical research. Plenty of evidence has shown that exosomes largely participate in the evolution of IHD, including endothelial dysfunction, lipid deposition, atheromatous plaque formation and rupture, myocardial ischemia-reperfusion(I/R) injury,and heart failure (HF), while the rules for detailed communication in the different stages of this continuous disease are still poorly understood. This review will systematically describe characteristics of exosomal crosstalk between different cells in the diverse periods, and also cast light on the potential and challenges for exosome application as therapeutic targets, hoping to offer supporting background for the following research.

Strategies to inhibit arsenic trioxide-induced cardiotoxicity in acute promyelocytic leukemia

OBJECTIVE

Arsenic trioxide (ATO) is a drug commonly used for the treatment of acute promyelocytic leukemia (APL). Although ATO has been shown to cause significant improvement in patients, it is associated with serious side effects, which sometimes lead to the patient's death. In this review paper, we examine the reports of ATO-induced cardiotoxicity in APL patients and evaluate the strategies to reduce the incidence of such toxicity.

METHODS

The key search terms were "arsenic trioxide," "acute promyelocytic leukemia," "cardiotoxicity," "molecular pathway," and "biomarker."

RESULTS

Studies have indicated the involvement of several molecular pathways in ATO-induced cardiotoxicity. These pathways increase the production of reactive oxygen species by interfering with intracellular calcium homeostasis as well as impairing the transfer of calcium into endoplasmic reticulum and mitochondria. On the other hand, increasing or decreasing expressions of some microRNAs (miRs) have been shown to play a role in cardiotoxicity.

CONCLUSION

Finally, it can be stated that given the essential role of molecular pathways in cardiotoxicity and considering the fact these pathways impair the regulation of miRs expression, identification of molecular pathways involved in ATO-induced cardiotoxicity aimed at targeting miRs could be a new therapeutic strategy to prevent cardiotoxicity.

The relationship between molecular content of mesenchymal stem cells derived exosomes and their potentials: Opening the way for exosomes based therapeutics

At least, more than half of our understanding of extracellular vesicles owes to the studies conducted over the past few years. When it became clear that the exosomes have various potentials in medicine, extensive research has focused on these potentials in a variety of areas including cancer, drug delivery and regenerative medicine. The growing understanding of molecular structure and functions of exosomes causes the vision to become brighter in the exosomes complexity, and our attitude toward these vesicles has undergone changes accordingly. Proteomic and transcriptomic studies on exosomes have highlighted their molecular diversity. In this review, we explicitly examine the exosomes composition, molecular structure and their therapeutic potentials in some diseases. Due to the very heterogeneous nature of exosomes, the process of their use as a therapeutic agent in the clinic has been challenged. We are still at the beginning of recognizing the molecular composition of exosomes and mechanisms that affect their physiology and biology. The growing trend of engineering of exosomes has shown a promising future to further utilize them in a different field. Molecular profiling of exosomes and their content for their related potentials in regenerative medicine should be done exactly for further defining a minimum content for specific therapeutic potentials.

Exosomes from adipose-derived mesenchymal stem cells ameliorate cardiac damage after myocardial infarction by activating S1P/SK1/S1PR1 signaling and promoting macrophage M2 polarization

Exosomes derived from mesenchymal stem cells (MSCs) are known to participate in myocardial repair after myocardial infarction (MI), but the mechanism remains unclear. Here, we isolated exosomes from adipose-derived MSCs (ADSCs) and examined their effect on MI-induced cardiac damage. To examine the underlying mechanism, H9c2 cells, cardiac fibroblasts, and HAPI cells were used to study the effect of ADSC-exosomes on hypoxia-induced H9c2 apoptosis, TGF-β1-induced fibrosis of cardiac fibroblasts, and hypoxia-induced macrophage M1 polarization using qRT-PCR, western blot, ELISA, immunohistochemistry, immunofluorescence and flow cytometry. ADSC-exosome treatment mitigated MI-induced cardiac damage by suppressing cardiac dysfunction, cardiac apoptosis, cardiac fibrosis, and inflammatory responses in vitro and in vivo. In addition, ADSC-exosome treatment promoted macrophage M2 polarization. Further experiments found that S1P/SK1/S1PR1 signaling was involved in the ADSC-exosome-mediated myocardial repair. Silencing of S1PR1 reversed the inhibitory effect of ADSC-exosomes on MI-induced cardiac apoptosis and fibrosis in vitro. ADSC-exosome-induced macrophage M2 polarization was also reversed after downregulation of S1PR1 under hypoxia conditions, which promoted NFκB and TGF-β1 expression, and suppressed the MI-induced cardiac fibrosis and inflammatory response. In sum, these results indicate that ADSC-derived exosomes ameliorate cardiac damage after MI by activating S1P/SK1/S1PR1 signaling and promoting macrophage M2 polarization.

Mesenchymal stem cell derived EVs mediate neuroprotection after spinal cord injury in rats via the microRNA-21-5p/FasL gene axis

Spinal cord injury (SCI) represents a relatively common type of motor system trauma. While the SCI patient will experience varying degrees of paraplegia and quadriplegia, which severely affects their quality of life, a heavy burden is also placed on the family and society as a whole. The exact pathogenic mechanisms underlying this condition remain unknown and no specific treatments are currently available. Findings from recent studies have shown that mesenchymal stem cells (MSCs), derived from extracellular vesicles (EVs) can reduce apoptosis, inflammation and promote angiogenesis after SCI. However, the mechanisms through which EVs exert these effects have yet to be identified, indicating the necessity for further investigation. In the present study, we report that treatment with MSCs-EVs significantly improved functional recovery and attenuated lesion size and apoptosis in a rat model of SCI. These MSCs-EVs were found to be directed to the spinal injury site and mainly incorporated into neurons within the lesioned site of the spinal cord. Tandem Mass Tags quantitative proteomics was applied to compare protein changes after SCI and MSCs-EVs treatment. A total of 883 differential proteins were identified, many of which being associated with apoptosis and inflammation. Subsequently, miRNA contents of MSCs-EVs were determined using qRT-PCR, with the result that miR-21-5p was one of the most highly expressed miRNA in these MSCs-EVs. Moreover, inhibition of miR-21-5p in MSCs-EVs significantly reversed the beneficial effects of MSCs-EVs on motor function and apoptosis, an effect which was associated with modulating FasL expression. The data suggest that modulation of the MSCs-EVs miR-21-5p/FasL gene axis may serve as a promising strategy for clinical treatment of SCI and other neurological diseases.

microRNA-21-5p dysregulation in exosomes derived from heart failure patients impairs regenerative potential

Exosomes, as functional paracrine units of therapeutic cells, can partially reproduce the reparative properties of their parental cells. The constitution of exosomes, as well as their biological activity, largely depends on the cells that secrete them. We isolated exosomes from explant-derived cardiac stromal cells from patients with heart failure (FEXO) or from normal donor hearts (NEXO) and compared their regenerative activities in vitro and in vivo. Patients in the FEXO group exhibited an impaired ability to promote endothelial tube formation and cardiomyocyte proliferation in vitro. Intramyocardial injection of NEXO resulted in structural and functional improvements in a murine model of acute myocardial infarction. In contrast, FEXO therapy exacerbated cardiac function and left ventricular remodeling. microRNA array and PCR analysis revealed dysregulation of miR-21-5p in FEXO. Restoring miR-21-5p expression rescued FEXO's reparative function, whereas blunting miR-21-5p expression in NEXO diminished its therapeutic benefits. Further mechanistic studies revealed that miR-21-5p augmented Akt kinase activity through the inhibition of phosphatase and tensin homolog. Taken together, the heart failure pathological condition altered the miR cargos of cardiac-derived exosomes and impaired their regenerative activities. miR-21-5p contributes to exosome-mediated heart repair by enhancing angiogenesis and cardiomyocyte survival through the phosphatase and tensin homolog/Akt pathway.

[Research progress on miR-21 in heart diseases]

Pathological processes such as myocardial apoptosis, cardiac hypertrophy, myocardial fibrosis, and cardiac electrical remodeling are involved in the development and progression of most cardiac diseases. MicroRNA-21 (miR-21) has been found to play an important role in heart diseases as a novel type of endogenous regulators, which can inhibit cardiomyocyte apoptosis, improve hypertension and cardiac hypertrophy, promote myocardial fibrosis and atrial electrical remodeling. In this review, we summarize the research progress on the function of miR-21 in heart diseases and its mechanism, and discuss its potential application in diagnosis and treatment of heart diseases.

Cardioprotective microRNAs: Lessons from stem cell-derived exosomal microRNAs to treat cardiovascular disease

The stem cell-based therapy has emerged as a promising therapeutic strategy for treating cardiovascular ischemic diseases (CVIDs), such as myocardial infarction (MI). However, some important functional shortcomings of stem cell transplantation, such as immune rejection, tumorigenicity and infusional toxicity, have overshadowed stem cell therapy in the setting of cardiovascular diseases (CVDs). Accumulating evidence suggests that the therapeutic effects of transplanted stem cells are predominately mediated by secreting paracrine factors, importantly, microRNAs (miRs) present in the secreted exosomes. Therefore, novel cell-free therapy based on the stem cell-secreted exosomal miRs can be considered as a safe and effective alternative tool to stem cell therapy for the treatment of CVDs. Stem cell-derived miRs have recently been found to transfer, via exosomes, from a transplanted stem cell into a recipient cardiac cell, where they regulate various cellular process, such as proliferation, apoptosis, stress responses, as well as differentiation and angiogenesis. The present review aimed to summarize cardioprotective exosomal miRs secreted by transplanted stem cells from various sources, including embryonic stem cells (ESCs), induced pluripotent stem cells (iPSCs), mesenchymal stem cells (MSCs), and cardiac stem/progenitor cells, which showed beneficial modulatory effects on the myocardial infracted heart. In summary, stem cell-exosomal miRs, including miR-19a, mirR-21, miR-21-5p, miR-21-a5p, miR-22 miR-24, miR-26a, miR-29, miR-125b-5p, miR-126, miR-201, miR-210, and miR-294, have been shown to have cardioprotective effects by enhancing cardiomyocyte survival and function and attenuating cardiac fibrosis. Additionally, MCS-exosomal miRs, including miR-126, miR-210, miR-21, miR-23a-3p and miR-130a-3p, are found to exert cardioprotective effects through induction of angiogenesis in ischemic heart after MI.

Bone marrow mesenchymal stem cell-derived exosomes alleviate high phosphorus-induced vascular smooth muscle cells calcification by modifying microRNA profiles

Vascular calcification is a common complication in patients with chronic kidney disease (CKD). It is an important predictor of cardiovascular disease and all-cause mortality. Previous studies have confirmed that bone marrow mesenchymal stem cell (BMSC) therapy can reduce vascular calcification, but the specific mechanism is still controversial. In this study, we aimed to investigate the mechanisms of BMSC-derived exosomes (EXO) in improving vascular calcification. BMSCs were cultured and EXO were isolated using the Total Exosome Isolation Reagent. Human aortic vascular smooth muscle cells (HA-VSMCs) were cultured into three groups: control group, high phosphorus group, and high phosphorus plus EXO group. Then, indicators related to smooth muscle cell calcification and microRNA profiles were analyzed. BMSC-derived exosomes inhibited high phosphorus-induced calcification in HA-VSMCs. Besides, EXO treatment reduced calcium content and decreased the alkaline phosphatase (AKP) activity in high phosphorus co-incubated HA-VSMCs. MicroRNA (miRNA) and mRNA expression profiles analyses revealed that 63 miRNAs were significantly upregulated and 1424 genes were significantly downregulated in HA-VSMCs after EXO treatment. Functional miRNA-gene regulatory network revealed that mTOR, MAPK, and Wnt signaling pathway were involved in vascular calcification. BMSC-derived exosomes alleviated high phosphorus-induced calcification in HA-VSMC through modifying miRNA profiles.

Extracellular vesicles secreted by hypoxia pre-challenged mesenchymal stem cells promote non-small cell lung cancer cell growth and mobility as well as macrophage M2 polarization via miR-21-5p delivery

Objective

To investigate the lung cancer-promoting mechanism of mesenchymal stem cell-secreted extracellular vesicles (MSC-EV).

Methods

EV were isolated from culture media of human bone marrow-derived MSCs that were pre-challenged with or without hypoxia (referred to as H-EV and N-EV, respectively). After treatment with N-EV or H-EV, A549 and H23 cell proliferation, apoptosis, trans-well invasion and epithelial-to-mesenchymal transition (EMT) were examined. Polarization of human primary monocytes-derived macrophages with or without N-EV or H-EV induction were analyzed by flow cytometry and ELISA. PTEN, PDCD4 or RECK gene was overexpressed in A549 cells, while miR-21-5p was knocked down in MSCs, A549 or H23 lung cancer cells or primary monocytes by miR-21-5p inhibitor transfection. Protein level of PTEN, PDCD4, RECK, AKT or STAT3 as well as phosphorylation level of AKT or STAT3 protein were assayed by western blot. Tumorigenicity of A549 and H23 cells with or without MSC-EV co-injection was assayed on immunocompromised mice. The xenograft tumor were examined for cell proliferation, angiogenesis, apoptosis and intra-tumoral M1/M2 macrophage polarization.

Results

Comparing to N-EV, H-EV treatment significantly increased A549 and H23 cell proliferation, survival, invasiveness and EMT as well as macrophage M2 polarization. MiR-21-5p knocked down significantly abrogated the cancer-promoting and macrophage M2 polarizing effects of H-EV treatment. H-EV treatment downregulated PTEN, PDCD4 and RECK gene expression largely through miR-21-5p. Overexpressing PTEN, PDCD4 and RECK in A549 cells significantly reduced the miR-21-5p-mediated anti-apoptotic and pro-metastatic effect of H-EV, while overexpressing PTEN in monocytes significantly reduced macrophage M2 polarization after induction with the presence of H-EV. H-EV co-injection significantly increased tumor growth, cancer cell proliferation, intra-tumoral angiogenesis and M2 polarization of macrophages in vivo partially through miR-21-5p.

Conclusions

Increased miR-21-5p delivery by MSC-EV after hypoxia pre-challenge can promote lung cancer development by reducing apoptosis and promoting macrophage M2 polarization.

Electronic supplementary material

The online version of this article (10.1186/s13046-019-1027-0) contains supplementary material, which is available to authorized users.

Extracellular Vesicles as Conduits of Non-Coding RNA Emission and Intercellular Transfer in Brain Tumors

Non-coding RNA (ncRNA) species have emerged in as molecular fingerprints and regulators of brain tumor pathogenesis and progression. While changes in ncRNA levels have been traditionally regarded as cell intrinsic there is mounting evidence for their extracellular and paracrine function. One of the key mechanisms that enables ncRNA to exit from cells is their selective packaging into extracellular vesicles (EVs), and trafficking in the extracellular space and biofluids. Vesicular export processes reduce intracellular levels of specific ncRNA in EV donor cells while creating a pool of EV-associated ncRNA in the extracellular space and biofluids that enables their uptake by other recipient cells; both aspects have functional consequences. Cancer cells produce several EV subtypes (exosomes, ectosomes), which differ in their ncRNA composition, properties and function. Several RNA biotypes have been identified in the cargo of brain tumor EVs, of which microRNAs are the most studied, but other species (snRNA, YRNA, tRNA, and lncRNA) are often more abundant. Of particular interest is the link between transforming oncogenes and the biogenesis, cargo, uptake and function of tumor-derived EV, including EV content of oncogenic RNA. The ncRNA repertoire of EVs isolated from cerebrospinal fluid and serum is being developed as a liquid biopsy platform in brain tumors.

Comparison of Cardiac miRNA Transcriptomes Induced by Diabetes and Rapamycin Treatment and Identification of a Rapamycin-Associated Cardiac MicroRNA Signature

Rapamycin (Rap), an inhibitor of mTORC1, reduces obesity and improves lifespan in mice. However, hyperglycemia and lipid disorders are adverse side effects in patients receiving Rap treatment. We previously reported that diabetes induces pansuppression of cardiac cytokines in Zucker obese rats (ZO-C). Rap treatment (750 μg/kg/day for 12 weeks) reduced their obesity and cardiac fibrosis significantly; however, it increased their hyperglycemia and did not improve their cardiac diastolic parameters. Moreover, Rap treatment of healthy Zucker lean rats (ZL-C) induced cardiac fibrosis. Rap-induced changes in ZL-C's cardiac cytokine profile shared similarities with that of diabetes-induced ZO-C. Therefore, we hypothesized that the cardiac microRNA transcriptome induced by diabetes and Rap treatment could share similarities. Here, we compared the cardiac miRNA transcriptome of ZL-C to ZO-C, Rap-treated ZL (ZL-Rap), and ZO (ZO-Rap). We report that 80% of diabetes-induced miRNA transcriptome (40 differentially expressed miRNAs by minimum 1.5-fold in ZO-C versus ZL-C; p ≤ 0.05) is similar to 47% of Rap-induced miRNA transcriptome in ZL (68 differentially expressed miRNAs by minimum 1.5-fold in ZL-Rap versus ZL-C; p ≤ 0.05). This remarkable similarity between diabetes-induced and Rap-induced cardiac microRNA transcriptome underscores the role of miRNAs in Rap-induced insulin resistance. We also show that Rap treatment altered the expression of the same 17 miRNAs in ZL and ZO hearts indicating that these 17 miRNAs comprise a unique Rap-induced cardiac miRNA signature. Interestingly, only four miRNAs were significantly differentially expressed between ZO-C and ZO-Rap, indicating that, unlike the nondiabetic heart, Rap did not substantially change the miRNA transcriptome in the diabetic heart. In silico analyses showed that (a) mRNA-miRNA interactions exist between differentially expressed cardiac cytokines and miRNAs, (b) human orthologs of rat miRNAs that are strongly correlated with cardiac fibrosis may modulate profibrotic TGF-β signaling, and (c) changes in miRNA transcriptome caused by diabetes or Rap treatment include cardioprotective miRNAs indicating a concurrent activation of an adaptive mechanism to protect the heart in conditions that exacerbate diabetes.

Mesenchymal stem cell-derived extracellular vesicles affect disease outcomes via transfer of microRNAs

Mesenchymal stem cells (MSCs) are adult stromal cells with the capacity to differentiate into multiple types of cells. MSCs represent an attractive option in regenerative medicine due to their multifaceted abilities for tissue repair, immunosuppression, and anti-inflammation. Recent studies demonstrate that MSCs exert their effects via paracrine activity, which is at least partially mediated by extracellular vesicles (EVs). MSC-derived EVs (MSC-EVs) could mimic the function of parental MSCs by transferring their components such as DNA, proteins/peptides, mRNA, microRNA (miRNA), lipids, and organelles to recipient cells. In this review, we aim to summarize the mechanism and role of miRNA transfer in mediating the effects of MSC-EVs in the models of human diseases. The first three sections of the review discuss the sorting of miRNAs into EVs, uptake of EVs by target cells, and functional transfer of miRNAs via EVs. Then, we describe the composition of miRNAs in MSC-EVs. Next, we provide the existing evidence that MSC-EVs affect the outcomes of renal, liver, heart, and brain diseases by transferring their miRNA contents. In conclusion, EV-mediated miRNA transfer plays an important role in disease-modulating capacity of MSCs.

Endothelial cells release cardioprotective exosomes that may contribute to ischaemic preconditioning

Extracellular vesicles (EVs) such as exosomes are nano-sized vesicles that carry proteins and miRNAs and can transmit signals between cells. We hypothesized that exosomes from endothelial cells can transmit protective signals to cardiomyocytes. Co-culture of primary adult rat cardiomyocytes with normoxic HUVEC cells separated by a cell-impermeable membrane reduced the percentage of cardiomyocyte death following simulated ischaemia and reperfusion (sIR) from 80 ± 11% to 51 ± 4% (P < 0.05; N = 5). When EVs were removed from the HUVEC-conditioned medium it was no longer protective. Exosomes were purified from HUVEC-conditioned medium using differential centrifugation and characterized by nanoparticle tracking analysis, electron microscopy, and flow cytometry. Pre-incubation of cardiomyocytes with HUVEC exosomes reduced the percentage of cell death after sIR from 88 ± 4% to 55 ± 3% (P < 0.05; N = 3). This protection required ERK1/2 activity as it was prevented by inhibitors PD98059 and U0126. Ischaemic preconditioning caused about ~3-fold higher rate of exosome production from HUVEC and from isolated, perfused rat hearts. This increase resulted in significantly greater protection against sIR in cardiomyocytes. In conclusion, exosomes released from endothelial cells can confer resistance to sIR injury in cardiomyocytes via the activation of the ERK1/2 MAPK signalling pathway, and may contribute to IPC.

Triggering Endogenous Cardiac Repair and Regeneration via Extracellular Vesicle-Mediated Communication

A variety of paracrine signals create networks within the myocardium and mediate intercellular communications. Indeed, paracrine stimulation of the endogenous regenerative program of the heart, mainly based on resident cardiac progenitor cell (CPC) activation together with cardiomyocyte proliferation, has become increasingly relevant for future cardiac medicine. In the last years, it has been shown that extracellular vesicles (EV), including exosomes (Ex), are powerful conveyors of relevant biological effects. EV have been proposed not only as promising therapeutic tool for triggering cardiac regeneration and improving repair, but also as means of better understanding the physiological and pathological relationships between specific cardiac components, including cardiomyocytes and fibroblasts. Actually, EV from different kinds of exogenous stem cells have been shown to mediate beneficial effects on the injured myocardium. Moreover, endogenous cells, like CPC can instruct cardiovascular cell types, including cardiomyocytes, while cardiac stromal cells, especially fibroblasts, secrete EV that modulate relevant aspects of cardiomyocyte biology, such as hypertrophy and electrophysiological properties. Finally, cardiomyocytes too may release EV influencing the function of other cardiac cell types. Therefore, EV-based crosstalk is thought to be important in both physiology and pathology, being involved in the responses of the heart to noxious stimuli. In this review we will discuss the role of EV in both regulating cardiac homeostasis and driving heart regeneration. In particular, we will address their role in: (i) providing cardio-protection and enhancing cardiac repair mechanisms; (ii) CPC biology; and (iii) influencing adult cardiomyocyte behavior.

Transplantation of Cardiac Mesenchymal Stem Cell-Derived Exosomes Promotes Repair in Ischemic Myocardium

Our previous study demonstrated the beneficial effects of exosomes secreted by cardiac mesenchymal stem cells (C-MSC-Exo) in protecting acute ischemic myocardium from reperfusion injury. Here, we investigated the effect of exosomes from C-MSC on angiogenesis in ischemic myocardium. We intramyocardially injected C-MSC-Exo or PBS into the infarct border zone after induction of acute mouse myocardial infarction (MI). We observed that hearts treated with C-MSC-Exo exhibit improved cardiac function compared to control hearts treated with PBS at one month after MI. Capillary density and Ki67-postive cells were significantly higher following treatment with C-MSC-Exo as compared with PBS. Moreover, C-MSC-Exo treatment increased cardiomyocyte proliferation in infarcted hearts. In conclusion, intramyocardial delivery of C-MSC-Exo after myocardial infarction enhances cardiac angiogenesis, promotes cardiomyocyte proliferation, and preserves heart function. C-MSC-Exo constitute a novel form of cell-free therapy for cardiac repair.

AMSC-derived exosomes alleviate lipopolysaccharide/d-galactosamine-induced acute liver failure by miR-17-mediated reduction of TXNIP/NLRP3 inflammasome activation in macrophages

Background

Mesenchymal stem cell (MSC)-derived exosome administration has been considered as a novel cell-free therapy for liver diseases through cell-cell communication. This study was aimed to determine the effects and mechanisms of AMSC-derived exosomes (AMSC-Exo) for acute liver failure (ALF) treatment.

Methods

AMSC-Exo were intravenously administrated into the mice immediately after lipopolysaccharide and D-galactosamine (LPS/GalN)-exposure and their effects were evaluated by liver histological and serum biochemical analysis. To elucidate its mechanisms in ALF therapy, the expression levels of miRNAs and inflammasome-related genes in macrophages were evaluated by qPCR and Western blot analysis, respectively. The exosomes from miR-17-knockdowned AMSCs (AMSC-Exo^miR-17-KD) were used for further determine the role of miR-17 in AMSC-Exo-based therapy.

Findings

AMSC-Exo administration significantly ameliorated ALF as determined by reduced serum alanine aminotransferase and aspartate aminotransferase levels and hepatic inflammasome activation. Further experiments revealed that AMSC-Exo were colocalized with hepatic macrophages and could reduce inflammatory factor secretion by suppressing inflammasome activation in macrophages. Moreover, miR-17, which can suppress NLRP3 inflammasome activation by targeting TXNIP, was abundant in AMSC-Exo cargo. While, the therapeutic effects of AMSC-Exo^miR-17-KD on ALF were significantly abolished as they could not effectively suppress TXNIP expression and consequent inflammasome activation in vitro and in vivo.

Interpretation: Exosome-shuttled miR-17 plays an essential role in AMSC-Exo therapy for ALF by targeting TXNIP and suppressing inflammasome activation in hepatic macrophages. AMSC-Exo-based therapy may present as a promising approach for TXNIP/NLRP3 inflammasome-related inflammatory liver diseases.

Fund

Key R&D projects of Zhejiang province (2018C03019) and National Natural Science Fund (81470851 and 81500616).

Emerging roles of extracellular vesicles in cardiac repair and rejuvenation

Cell therapy has received significant attention as a therapeutic approach to restore cardiac function after myocardial infarction. Accumulating evidence supports that beneficial effects observed with cell therapy are due to paracrine secretion of multiple factors from transplanted cells, which alter the tissue microenvironment and orchestrate cardiac repair processes. Of these paracrine factors, extracellular vesicles (EVs) have emerged as a key effector of cell therapy. EVs regulate cellular function through the transfer of cargo, such as microRNAs and proteins, which act on multiple biological pathways within recipient cells. These discoveries have led to the development of cell-free therapies using EVs to improve cardiac repair after a myocardial infarction. Here, we present an overview of the current use of EVs to enhance cardiac repair after myocardial infarction. We also discuss the emerging use of EVs for rejuvenation-based therapies. Finally, future directions for the use of EVs as therapeutic agents for cardiac regenerative medicine are also discussed.