Endothelial Progenitor Cell-Derived Extracellular Vesicles: A Novel Candidate for Regenerative Medicine and Disease Treatment

Endothelial progenitor cell-derived conditioned medium mitigates chronic cerebral ischemic injury through macrophage migration inhibitory factor-activated AKT pathway

BACKGROUND

Chronic cerebral ischemia (CCI) is a significant health issue characterized by hypoperfusion due to damage or occlusion of the cerebral or carotid arteries. CCI may lead to progressive cognitive impairment that is considered as a prelude to neurodegenerative diseases, including dementia and Alzheimer's disease (AD). Endothelial progenitor cells (EPCs) have been implicated in vascular repair in ischemic cerebrovascular diseases, primarily by differentiating into endothelial cells (ECs) or through paracrine effects. However, the clinical transplantation of stem cell therapies remains limited. In this study, we investigated the effects of EPC-derived conditioned medium (EPC-CM) on the impaired vasculature and neurological function in a rodent model of CCI and the mechanism involved.

METHODS

EPC-CM was analyzed by cytokine array to identify key factors involved in angiogenesis and cellular senescence. The effects and mechanism of the candidate factors in the EPC-CM were validated in vitro using oxygen-glucose deprivation (OGD)-injured ECs and EPCs. The therapeutic effects of EPC-CM and the identified key factor were further examined in a rat model of CCI, which was induced by bilateral internal carotid artery ligation (BICAL). EPC-CM was administered via intracisternal injection one week post BICAL. The cerebral microvasculature and neurobehavior of the rats were examined three weeks after BICAL.

RESULTS

Macrophage migration inhibitory factor (MIF) was identified as a key factor in the EPC-CM. Recombinant MIF protein promoted angiogenesis and prevented senescence in the injured EPCs and ECs. The effect was similar to that of the EPC-CM. These therapeutic effects were diminished when the EPC-CM was co-treated with MIF-specific antibody (Ab). Additionally, the vascular, motor, and cognitive improvements observed in the BICAL rats treated with EPC-CM were abolished by co-treated with MIF Ab. Furthermore, we found MIF promoted angiogenesis and anti-senescence via activating the AKT pathway. Inhibition of the AKT pathway diminished the protective effects of MIF in the in vitro study.

CONCLUSIONS

We demonstrated that EPC-CM protected the brain from chronic ischemic injury and promoted functional recovery through MIF-mediated AKT pathway. These findings suggest EPC-CM holds potential as a novel cell-free therapeutic approach for treating CCI through the actions of MIF.

Exosome-based cell therapy for diabetic foot ulcers: Present and prospect

Diabetic foot ulcers (DFUs) represent a serious complication of diabetes with high incidence, requiring intensive treatment, prolonged hospitalization, and high costs. It poses a severe threat to the patient's life, resulting in substantial burdens on patient and healthcare system. However, the therapy of DFUs remains challenging. Therefore, exploring cell-free therapies for DFUs is both critical and urgent. Exosomes, as crucial mediators of intercellular communication, have been demonstrated potentially effective in anti-inflammation, angiogenesis, cell proliferation and migration, and collagen deposition. These functions have been proven beneficial in all stages of diabetic wound healing. This review aims to summarize the role and mechanisms of exosomes from diverse cellular sources in diabetic wound healing research. In addition, we elaborate on the challenges for clinical application, discuss the advantages of membrane vesicles as exosome mimics in wound healing, and present the therapeutic potential of exosomes and their mimetic vesicles for future clinical applications.

The Angiogenic Repertoire of Stem Cell Extracellular Vesicles: Demystifying the Molecular Underpinnings for Wound Healing Applications

Stem cells-derived extracellular vesicles (SC-EVs) have emerged as promising therapeutic agents for wound repair, recapitulating the biological effects of parent cells while mitigating immunogenic and tumorigenic risks. These EVs orchestrate wound healing processes, notably through modulating angiogenesis-a critical event in tissue revascularization and regeneration. This study provides a comprehensive overview of the multifaceted mechanisms underpinning the pro-angiogenic capacity of EVs from various stem cell sources within the wound microenvironment. By elucidating the molecular intricacies governing their angiogenic prowess, we aim to unravel the mechanistic repertoire underlying their remarkable potential to accelerate wound healing. Additionally, methods to enhance the angiogenic effects of SC-EVs, current limitations, and future perspectives are highlighted, emphasizing the significant potential of this rapidly advancing field in revolutionizing wound healing strategies.

α7nAChR Activation Combined with Endothelial Progenitor Cell Transplantation Attenuates Lung Injury in Diabetic Rats with Sepsis through the NF-κB Pathway

Chronic diabetes mellitus compromises the vascular system, which causes organ injury, including in the lung. Due to the strong compensatory ability of the lung, patients always exhibit subclinical symptoms. Once sepsis occurs, the degree of lung injury is more severe under hyperglycemic conditions. The α7 nicotinic acetylcholine receptor (α7nAChR) plays an important role in regulating inflammation and metabolism and can improve endothelial progenitor cell (EPC) functions. In the present study, lung injury caused by sepsis was compared between diabetic rats and normal rats. We also examined whether α7nAChR activation combined with EPC transplantation could ameliorate lung injury in diabetic sepsis rats. A type 2 diabetic model was induced in rats via a high-fat diet and streptozotocin. Then, a rat model of septic lung injury was established by intraperitoneal injection combined with endotracheal instillation of LPS. The oxygenation indices, wet-to-dry ratios, and histopathological scores of the lungs were tested after PNU282987 treatment and EPC transplantation. IL-6, IL-8, TNF-α, and IL-10 levels were measured. Caspase-3, Bax, Bcl-2, and phosphorylated NF-κB (p-NF-κB) levels were determined by blotting. Sepsis causes obvious lung injury, which is exacerbated by diabetic conditions. α7nAChR activation and endothelial progenitor cell transplantation reduced lung injury in diabetic sepsis rats, alleviating inflammation and decreasing apoptosis. This treatment was more effective when PNU282987 and endothelial progenitor cells were administered together. p-NF-κB levels decreased following treatment with PNU282987 and EPCs. In conclusion, α7nAChR activation combined with EPC transplantation can alleviate lung injury in diabetic sepsis rats through the NF-κB signaling pathway.

Exosomes derived from induced cardiopulmonary progenitor cells alleviate acute lung injury in mice

Cardiopulmonary progenitor cells (CPPs) constitute a minor subpopulation of cells that are commonly associated with heart and lung morphogenesis during embryonic development but completely subside after birth. This fact offers the possibility for the treatment of pulmonary heart disease (PHD), in which the lung and heart are both damaged. A reliable source of CPPs is urgently needed. In this study, we reprogrammed human cardiac fibroblasts (HCFs) into CPP-like cells (or induced CPPs, iCPPs) and evaluated the therapeutic potential of iCPP-derived exosomes for acute lung injury (ALI). iCPPs were created in passage 3 primary HCFs by overexpressing GLI1, WNT2, ISL1 and TBX5 (GWIT). Exosomes were isolated from the culture medium of passage 6-8 GWIT-iCPPs. A mouse ALI model was established by intratracheal instillation of LPS. Four hours after LPS instillation, ALI mice were treated with GWIT-iCPP-derived exosomes (5 × 109, 5 × 1010 particles/mL) via intratracheal instillation. We showed that GWIT-iCPPs could differentiate into cell lineages, such as cardiomyocyte-like cells, endothelial cells, smooth muscle cells and alveolar epithelial cells, in vitro. Transcription analysis revealed that GWIT-iCPPs have potential for heart and lung development. Intratracheal instillation of iCPP-derived exosomes dose-dependently alleviated LPS-induced ALI in mice by attenuating lung inflammation, promoting endothelial function and restoring capillary endothelial cells and the epithelial cells barrier. This study provides a potential new method for the prevention and treatment of cardiopulmonary injury, especially lung injury, and provides a new cell model for drug screening.

Endothelial Cell Derived Extracellular Vesicles and Hematopoiesis

Extracellular vesicles (EVs) have been recognized as a novel way of cell-to-cell communication in the last several decades. It is believed that EVs exert their functions on nearby or distant cells through transfer of the cargo that they carry. In this review, we focus on EVs produced by endothelial cells, with emphasis on their role in hematopoiesis. We first describe how endothelial cells interact with hematopoietic stem/progenitor cells during development and in disease conditions. We then discuss EVs, ranging from their subtypes to isolation methods and analysis of EVs. With the above background information, we next review the literature related to endothelial cell derived EVs (ECEVs), including physiological functions and their clinical uses. In the last sections, we summarize the current results about the effect of ECEVs on hematopoiesis under physiological and stress conditions.

HOXD9 regulated mitophagy to promote endothelial progenitor cells angiogenesis and deep vein thrombosis recanalization and resolution

BACKGROUND

Deep vein thrombosis (DVT) is a common vascular surgical disease caused by the coagulation of blood in the deep veins, and predominantly occur in the lower limbs. Endothelial progenitor cells (EPCs) are multi-functional stem cells, which are precursors of vascular endothelial cells. EPCs have gradually evolved into a promising treatment strategy for promoting deep vein thrombus dissolution and recanalization through the stimulation of various physical and chemical factors.

METHODS

In this study, we utilized a mouse DVT model and performed several experiments including qRT-PCR, Western blot, tube formation, wound healing, Transwell assay, immunofluorescence, flow cytometry analysis, and immunoprecipitation to investigate the role of HOXD9 in the function of EPCs cells. The therapeutic effect of EPCs overexpressing HOXD9 on the DVT model and its mechanism were also explored.

RESULTS

Overexpression of HOXD9 significantly enhanced the angiogenesis and migration abilities of EPCs, while inhibiting cell apoptosis. Additionally, results indicated that HOXD9 specifically targeted the HRD1 promoter region and regulated the downstream PINK1-mediated mitophagy. Interestingly, intravenous injection of EPCs overexpressing HOXD9 into mice promoted thrombus dissolution and recanalization, significantly decreasing venous thrombosis.

CONCLUSIONS

The findings of this study reveal that HOXD9 plays a pivotal role in stimulating vascular formation in endothelial progenitor cells, indicating its potential as a therapeutic target for DVT management.

Endothelial progenitor cell-derived extracellular vesicles: the world of potential prospects for the treatment of cardiovascular diseases

Cardiovascular diseases (CVDs) have emerged as a predominant threat to human health, surpassing the incidence and mortality rates of neoplastic diseases. Extracellular vesicles (EVs) serve as vital mediators in intercellular communication and material exchange. Endothelial progenitor cells (EPCs), recognized as precursors of vascular endothelial cells (ECs), have garnered considerable attention in recent years due to the potential therapeutic value of their derived extracellular vesicles (EPC-EVs) in the context of CVDs. This comprehensive review systematically explores the origins, characteristics, and functions of EPCs, alongside the classification, properties, biogenesis, and extraction techniques of EVs, with particular emphasis on their protective roles in CVDs. Additionally, we delve into the essential bioactive components of EPC-EVs, including microRNAs, long non-coding RNAs, and proteins, analyzing their beneficial effects in promoting angiogenesis, anti-inflammatory and anti-oxidant activities, anti-fibrosis, anti-apoptosis, and myocardial regeneration. Furthermore, this review comprehensively investigates the therapeutic potential of EPC-EVs across various CVDs, encompassing acute myocardial infarction, myocardial ischemia-reperfusion injury, atherosclerosis, non-ischemic cardiomyopathies, and diabetic cardiovascular disease. Lastly, we summarize the potential challenges associated with the clinical application of EPC-EVs and outline future directions, aiming to offer a valuable resource for both theoretical insights and practical applications of EPC-EVs in managing CVDs.

Responses of Endothelial Progenitor Cells to Chronic and Acute Physical Activity in Healthy Individuals

Endothelial progenitor cells (EPCs) are circulating cells of various origins that possess the capacity for renewing and regenerating the endothelial lining of blood vessels. During physical activity, in response to factors such as hypoxia, changes in osmotic pressure, and mechanical forces, endothelial cells undergo intense physiological stress that results in endothelial damage. Circulating EPCs participate in blood vessel repair and vascular healing mainly through paracrine signalling. Furthermore, physical activity may play an important role in mobilising this important cell population. In this narrative review, we summarise the current knowledge on the biology of EPCs, including their characteristics, assessment, and mobilisation in response to both chronic and acute physical activity in healthy individuals.

The Immunomodulatory effect of exosomes in diabetes: a novel and attractive therapeutic tool in diabetes therapy

Exosomes carry proteins, metabolites, nucleic acids and lipids from their parent cell of origin. They are derived from cells through exocytosis, are ingested by target cells, and can transfer biological signals between local or distant cells. Therefore, exosomes are often modified in reaction to pathological processes, including infection, cancer, cardiovascular diseases and in response to metabolic perturbations such as obesity and diabetes, all of which involve a significant inflammatory aspect. Here, we discuss how immune cell-derived exosomes origin from neutrophils, T lymphocytes, macrophages impact on the immune reprogramming of diabetes and the associated complications. Besides, exosomes derived from stem cells and their immunomodulatory properties and anti-inflammation effect in diabetes are also reviewed. Moreover, As an important addition to previous reviews, we describes promising directions involving engineered exosomes as well as current challenges of clinical applications in diabetic therapy. Further research on exosomes will explore their potential in translational medicine and provide new avenues for the development of effective clinical diagnostics and therapeutic strategies for immunoregulation of diabetes.

Recent advances in endothelial colony-forming cells: from the transcriptomic perspective

Endothelial colony-forming cells (ECFCs) are progenitors of endothelial cells with significant proliferative and angiogenic ability. ECFCs are a promising treatment option for various diseases, such as ischemic heart disease and peripheral artery disease. However, some barriers hinder the clinical application of ECFC therapeutics. One of the current obstacles is that ECFCs are dysfunctional due to the underlying disease states. ECFCs exhibit dysfunctional phenotypes in pathologic states, which include but are not limited to the following: premature neonates and pregnancy-related diseases, diabetes mellitus, cancers, haematological system diseases, hypoxia, pulmonary arterial hypertension, coronary artery diseases, and other vascular diseases. Besides, ECFCs are heterogeneous among donors, tissue sources, and within cell subpopulations. Therefore, it is important to elucidate the underlying mechanisms of ECFC dysfunction and characterize their heterogeneity to enable clinical application. In this review, we summarize the current and potential application of transcriptomic analysis in the field of ECFC biology. Transcriptomic analysis is a powerful tool for exploring the key molecules and pathways involved in health and disease and can be used to characterize ECFC heterogeneity.

Extracellular Vesicles in Atherosclerosis: State of the Art

Atherosclerosis is a chronic inflammatory disease driven by lipid accumulation in the arteries, leading to narrowing and thrombosis that causes mortality. Emerging evidence has confirmed that atherosclerosis affects younger people and is involved in the majority of deaths worldwide. EVs are associated with critical steps in atherosclerosis, cholesterol metabolism, immune response, endothelial dysfunction, vascular inflammation, and remodeling. Endothelial cell-derived EVs can interact with platelets and monocytes, thereby influencing endothelial dysfunction, atherosclerotic plaque destabilization, and the formation of thrombus. EVs are potential diagnostic and prognostic biomarkers in atherosclerosis (AS) and cardiovascular disease (CVD). Importantly, EVs derived from stem/progenitor cells are essential mediators of cardiogenesis and cardioprotection and may be used in regenerative medicine and tissue engineering.

CXCR7 Agonist TC14012 Improves Angiogenic Function of Endothelial Progenitor Cells via Activating Akt/eNOS Pathway and Promotes Ischemic Angiogenesis in Diabetic Limb Ischemia

PURPOSE

Endothelial progenitor cells (EPCs) play a critical role in repairing damaged vessels and triggering ischemic angiogenesis, but their number is reduced and function is impaired under diabetic conditions. Improving EPC function has been considered a promising strategy to ameliorate diabetic vascular complications. In the present study, we aim to investigate whether and how CXCR7 agonist TC14012 promotes the angiogenic function of diabetic EPCs.

METHODS

High glucose (HG) treatment was used to mimic the hyperglycemia in diabetes. Tube formation, cell scratch recovery and transwell assay, terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay, and cleaved-caspase3 expression were used to evaluate the angiogenic capability, cell migration, and apoptosis of EPCs, respectively. Hind limb ischemia (HLI) model was used to appraise the ability of TC14012 in promoting diabetic ischemic angiogenesis in vivo.

RESULTS

HG treatment impaired EPC tube formation and migration, and induced EPC apoptosis and oxidative damage, while TC14012 rescued tube formation and migration, and prevented HG-induced apoptosis and oxidative damage of EPCs. Furthermore, these beneficial effects of TC14012 on EPCs were attenuated by specific siRNAs against CXCR7, validating that CXCR7 is a functional target of TC14012 in EPCs. Mechanistic studies demonstrated that HG treatment reduced CXCR7 expression in EPCs, and impaired Akt and endothelial nitric oxide synthase (eNOS) phosphorylation and nitric oxide (NO) production; similarly, these signal impairments in HG-exposed EPCs could be rescued by TC14012. However, the protective effects of TC14012 on tube formation and migration, Akt and eNOS phosphorylation, and NO production in HG-treated EPCs were almost completely abolished by siRNAs against CXCR7 or Akt specific inhibitor wortmannin. More importantly, in vivo study showed that TC14012 administration enhanced blood perfusion recovery and angiogenesis in the ischemic hind limb and increased the EPC number in peripheral circulation of db/db mice, demonstrating the capability of TC14012 in promoting EPC mobilization and ischemia angiogenic function.

CONCLUSION

TC14012 can prevent EPCs from HG-induced dysfunction and apoptosis, improve eNOS activity and NO production via CXCR7/Akt signal pathway, and promote EPC mobilization and diabetic ischemia angiogenesis.

Extracellular vesicles engineering by silicates-activated endothelial progenitor cells for myocardial infarction treatment in male mice

Extracellular vesicles have shown good potential in disease treatments including ischemic injury such as myocardial infarction. However, the efficient production of highly active extracellular vesicles is one of the critical limitations for their clinical applications. Here, we demonstrate a biomaterial-based approach to prepare high amounts of extracellular vesicles with high bioactivity from endothelial progenitor cells (EPCs) by stimulation with silicate ions derived from bioactive silicate ceramics. We further show that hydrogel microspheres containing engineered extracellular vesicles are highly effective in the treatment of myocardial infarction in male mice by significantly enhancing angiogenesis. This therapeutic effect is attributed to significantly enhanced revascularization by the high content of miR-126a-3p and angiogenic factors such as VEGF and SDF-1, CXCR4 and eNOS in engineered extracellular vesicles, which not only activate endothelial cells but also recruit EPCs from the circulatory system.

MiR-17-5p Mediates the Effects of ACE2-Enriched Endothelial Progenitor Cell-Derived Exosomes on Ameliorating Cerebral Ischemic Injury in Aged Mice

Aging is one of the key mechanisms of vascular dysfunction and contributes to the initiation and progression of ischemic stroke (IS). Our previous study demonstrated that ACE2 priming enhanced the protective effects of exosomes derived from endothelial progenitor cells (EPC-EXs) on hypoxia-induced injury in aging endothelial cells (ECs). Here, we aimed to investigate whether ACE2-enriched EPC-EXs (ACE2-EPC-EXs) could attenuate brain ischemic injury by inhibiting cerebral EC damage through their carried miR-17-5p and the underlying molecular mechanisms. The enriched miRs in ACE2-EPC-EXs were screened using the miR sequencing method. EPC-EXs, ACE2-EPC-EXs, and ACE2-EPC-EXs with miR-17-5p deficiency (ACE2-EPC-EXs^{antagomiR-17-5p}) were administered to transient middle cerebral artery occlusion (tMCAO)-operated aged mice or coincubated with hypoxia/reoxygenation (H/R)-treated aging ECs. The results showed that (1) the level of brain EPC-EXs and their carried ACE2 were significantly decreased in aged mice compared to in young mice, and (2) after tMCAO, aged mice displayed increases in brain cell senescence, infarct volume, and neurological deficit score (NDS) and a decrease in cerebral blood flow (CBF). (3) Compared with EPC-EXs, ACE2-EPC-EXs were enriched with miR-17-5p and more effective in increasing ACE2 and miR-17-5p expression in cerebral microvessels, accompanied by obvious increases in cerebral microvascular density (cMVD) and cerebral blood flow (CBF) and decreases in brain cell senescence, infarct volume, neurological deficit score (NDS), cerebral EC ROS production, and apoptosis in tMCAO-operated aged mice. Moreover, silencing of miR-17-5p partially abolished the beneficial effects of ACE2-EPC-EXs. (4) In H/R-treated aging ECs, ACE2-EPC-EXs were more effective than EPC-EXs in decreasing cell senescence, ROS production, and apoptosis and increasing cell viability and tube formation. In a mechanistic study, ACE2-EPC-EXs more effectively inhibited PTEN protein expression and increased the phosphorylation of PI3K and Akt, which were partially abolished by miR-17-5p knockdown. Altogether, our data suggest that ACE-EPC-EXs have better protective effects on ameliorating aged IS mouse brain neurovascular injury by inhibiting cell senescence, EC oxidative stress, apoptosis, and dysfunction by activating the miR-17-5p/PTEN/PI3K/Akt signaling pathway.

Endothelial Progenitor Cells Affect the Growth and Apoptosis of Renal Cells by Secreting Microvesicles Carrying Dysregulated miR-205 and miR-206

Background

This study investigated the mechanism of microRNA (miRNA, miR) in microvesicles (MVs) secreted by endothelial progenitor cells (EPCs) involved in renal function in vivo and in vitro injury repair of rat primary kidney cells (PRKs).

Methods

Gene Expression Omnibus analysis of potential target miRNAs in nephrotic rats. Real-time quantitative polymerase chain reaction verified the correlation of these miRNAs and screened the effective target miRNAs and their downstream putative target mRNAs. Western blot analyzes the protein levels of DEAD-box helicase 5 (DDX5) and the activation of the proapoptotic factor caspase-3/9 (cleaved). Dil-Ac-LDL staining, immunofluorescence, and a transmission electron microscope (TEM) were used to identify the successful isolation of EPCs and PRKs and the morphology of MVs. Cell Counting Kit-8 was used to detect the effect of miRNA-mRNA on the proliferation of PRKs. Standard biochemical kits were used to detect biochemical indicators in rat blood and urine. Dual-luciferase analysis of miRNA binding to mRNA was conducted. The effect of miRNA-mRNA interaction on the apoptosis level of PRKs was analyzed by flow cytometry.

Results

A total of 13 rat-derived miRNAs were potential therapeutic targets, and miR-205 and miR-206 were screened as the targets of this study. We found that the EPC-MVs alleviated the increase of blood urea nitrogen and urinary albumin excretion and the decrease in creatinine clearance caused by hypertensive nephropathy in vivo. The effect of MVs in improving renal function indicators was promoted by miR-205 and miR-206 and inhibited by knockdown of expressed miR-205 and miR-206. In vitro, angiotensin II (Ang II) promoted growth inhibition and apoptosis of PRKs, and similarly, dysregulated miR-205 and miR-206 affected the induction of Ang II. We then observed that miR-205 and miR-206 cotargeted the downstream target DDX5 and regulated its transcriptional activity and translational levels, while also reducing the activation of proapoptotic factors caspase-3/9. Overexpressed DDX5 reversed the effects of miR-205 and miR-206.

Conclusion

By upregulating the expression of miR-205 and miR-206 in MVs secreted by EPC, the transcriptional activity of DDX5 and the activation of caspase-3/9 can be inhibited, thereby promoting the growth of PRKs and protecting the injury caused by hypertensive nephropathy.

Unraveling the potential of endothelial progenitor cells as a treatment following ischemic stroke

Ischemic stroke is becoming one of the most common causes of death and disability in developed countries. Since current therapeutic options are quite limited, focused on acute reperfusion therapies that are hampered by a very narrow therapeutic time window, it is essential to discover novel treatments that not only stop the progression of the ischemic cascade during the acute phase, but also improve the recovery of stroke patients during the sub-acute or chronic phase. In this regard, several studies have shown that endothelial progenitor cells (EPCs) can repair damaged vessels as well as generate new ones following cerebrovascular damage. EPCs are circulating cells with characteristics of both endothelial cells and adult stem cells presenting the ability to differentiate into mature endothelial cells and self-renew, respectively. Moreover, EPCs have the advantage of being already present in healthy conditions as circulating cells that participate in the maintenance of the endothelium in a direct and paracrine way. In this scenario, EPCs appear as a promising target to tackle stroke by self-promoting re-endothelization, angiogenesis and vasculogenesis. Based on clinical data showing a better neurological and functional outcome in ischemic stroke patients with higher levels of circulating EPCs, novel and promising therapeutic approaches would be pharmacological treatment promoting EPCs-generation as well as EPCs-based therapies. Here, we will review the latest advances in preclinical as well as clinical research on EPCs application following stroke, not only as a single treatment but also in combination with new therapeutic approaches.

Advances for the treatment of lower extremity arterial disease associated with diabetes mellitus

Lower extremity arterial disease (LEAD) is a major vascular complication of diabetes. Vascular endothelial cells dysfunction can exacerbate local ischemia, leading to a significant increase in amputation, disability, and even mortality in patients with diabetes combined with LEAD. Therefore, it is of great clinical importance to explore proper and effective treatments. Conventional treatments of diabetic LEAD include lifestyle management, medication, open surgery, endovascular treatment, and amputation. As interdisciplinary research emerges, regenerative medicine strategies have provided new insights to treat chronic limb threatening ischemia (CLTI). Therapeutic angiogenesis strategies, such as delivering growth factors, stem cells, drugs to ischemic tissues, have also been proposed to treat LEAD by fundamentally stimulating multidimensional vascular regeneration. Recent years have seen the rapid growth of tissue engineering technology; tissue-engineered biomaterials have been used to study the treatment of LEAD, such as encapsulation of growth factors and drugs in hydrogel to facilitate the restoration of blood perfusion in ischemic tissues of animals. The primary purpose of this review is to introduce treatments and novel biomaterials development in LEAD. Firstly, the pathogenesis of LEAD is briefly described. Secondly, conventional therapies and therapeutic angiogenesis strategies of LEAD are discussed. Finally, recent research advances and future perspectives on biomaterials in LEAD are proposed.

The Inhibitory Effect of Regulatory T Cells on the Intimal Hyperplasia of Tissue-Engineered Blood Vessels in Diabetic Pigs

Severe inflammatory response and functional impairment of endothelial progenitor cells (EPCs) often lead to the implantation failure of EPC-captured tissue-engineered blood vessels (TEBVs) in diabetes. Regulatory T cells (Treg cells) are the most important inhibitory immune cells, but their effects in angiogenesis remain undefined, and the differences in the microenvironment may be an important reason. Here, we constructed a TEBV coated with an anti-CD34 antibody-functionalized heparin-collagen multilayer (anti-CD34 antibody-modified TEBV) using layer-by-layer self-assembly. Then, TEBVs were implanted into diabetic pigs. All TEBVs remained unobstructed 60 days after implantation, although varying degrees of intimal hyperplasia were detectable. Severe intimal hyperplasia was observed in the control group and peripheral injection of Treg cells group. Intravenous injection of Treg cells significantly inhibited intimal hyperplasia, inflammation, and cell apoptosis. Moreover, intravenous injection increased the proportion of circulating EPCs, while peripheral injection did not have these effects and reduced microvessel density around the TEBV. Interestingly, many Nestin+ cells could be detected in TEBVs, most of which were fusiform, showing the characteristics of smooth-muscle cells. Treg cell intravenous transplantation markedly reduced the number of Nestin+ cells in the TEBV. In conclusion, Treg cells inhibited the intimal hyperplasia of TEBVs in diabetic pigs by promoting EPC mobilization, anti-inflammatory action, and cellular protection.

Comprehensive insight into endothelial progenitor cell-derived extracellular vesicles as a promising candidate for disease treatment

Endothelial progenitor cells (EPCs), which are a type of stem cell, have been found to have strong angiogenic and tissue repair capabilities. Extracellular vesicles (EVs) contain many effective components, such as cellular proteins, microRNAs, messenger RNAs, and long noncoding RNAs, and can be secreted by different cell types. The functions of EVs depend mainly on their parent cells. Many researchers have conducted functional studies of EPC-derived EVs (EPC-EVs) and showed that they exhibit therapeutic effects on many diseases, such as cardiovascular disease, acute kidney injury, acute lung injury, and sepsis. In this review article, we comprehensively summarized the biogenesis and functions of EPCs and EVs and the potent role of EPC-EVs in the treatment of various diseases. Furthermore, the current problems and future prospects have been discussed, and further studies are needed to compare the therapeutic effects of EVs derived from various stem cells, which will contribute to the accelerated translation of these applications in a clinical setting.

Hydrogel Loaded with VEGF/TFEB-Engineered Extracellular Vesicles for Rescuing Critical Limb Ischemia by a Dual-Pathway Activation Strategy

Critical limb ischemia (CLI) is the most severe clinical manifestation of peripheral arterial disease, which causes many amputations and deaths. Conventional treatment strategies for CLI (e.g., stent implantation and vascular surgery) bring surgical risk, which are not suitable for each patient. Extracellular vesicles (EVs) can be a potential solution for CLI. Herein, vascular endothelial growth factor (VEGF; i.e., a crucial molecule related to angiogenesis) and transcription factor EB (TFEB; i.e., a pivotal regulator of autophagy) are chosen as the target gene to improve the bioactivity of EVs derived from endothelial cells. The VEGF/TFEB-engineered EVs (Engineered-EVs) are fabricated by genetically engineering the parent cells, and their versatile functions are confirmed using three cell models (human umbilical vein endothelial cells, myoblast, and monocytes). Injectable thermal-responsive hydrogel are then combined with Engineered-EVs to combat CLI. These results reveal that the hydrogel can enhance the stability of Engineered-EVs in vivo and release EVs at different temperatures. Moreover, the results of animal studies indicate that Engineered-EV/Hydrogel can significantly improve neovascularization, attenuate muscle injury, and recover limb function after CLI. Finally, mechanistic studies shed light on the therapeutic effect of Engineered-EV/Hydrogel due to the activated VEGF/VEGFR pathway and autophagy-lysosomal pathway.

Targeting angiogenesis in myocardial infarction: Novel therapeutics (Review)

Acute myocardial infarction (AMI) remains the main cause of mortality worldwide. Despite surgery and medical treatment, the non-regeneration of dead cardiomyocytes and the limited contractile ability of scar tissue can lead to heart failure. Therefore, restoring blood flow in the infarcted area is important for the repair of myocardial injury. The objective of the present review was to summarize the factors influencing angiogenesis after AMI, and to describe the application of angiogenesis for cardiac repair. Collectively, this review may be helpful for relevant studies and to provide insight into future therapeutic applications in clinical practice.

Paracrine mechanisms of endothelial progenitor cells in vascular repair

Endothelial progenitor cells (EPCs) play an important role in repairing damaged blood vessels and promoting neovascularization. However, the specific mechanism of EPCs promoting vascular repair is still unclear. Currently, there are two different views on the repair of damaged vessels by EPCs, one is that EPCs can directly differentiate into endothelial cells (ECs) and integrate into injured vessels, the other is that EPCs act on cells and blood vessels by releasing paracrine substances. But more evidence now supports the latter. Therefore, the paracrine mechanisms of EPCs are worth further study. This review describes the substances secreted by EPCs, some applications based on paracrine effects of EPCs, and the studies of paracrine mechanisms in cardiovascular diseases--all of these are to support the view that EPCs repair blood vessels through paracrine effects rather than integrating directly into damaged vessels.

Recent Advances on Cell-Based Co-Culture Strategies for Prevascularization in Tissue Engineering

Currently, the fabrication of a functional vascular network to maintain the viability of engineered tissues is a major bottleneck in the way of developing a more advanced engineered construct. Inspired by vasculogenesis during the embryonic period, the in vitro prevascularization strategies have focused on optimizing communications and interactions of cells, biomaterial and culture conditions to develop a capillary-like network to tackle the aforementioned issue. Many of these studies employ a combination of endothelial lineage cells and supporting cells such as mesenchymal stem cells, fibroblasts, and perivascular cells to create a lumenized endothelial network. These supporting cells are necessary for the stabilization of the newly developed endothelial network. Moreover, to optimize endothelial network development without impairing biomechanical properties of scaffolds or differentiation of target tissue cells, several other factors, including target tissue, endothelial cell origins, the choice of supporting cell, culture condition, incorporated pro-angiogenic factors, and choice of biomaterial must be taken into account. The prevascularization method can also influence the endothelial lineage cell/supporting cell co-culture system to vascularize the bioengineered constructs. This review aims to investigate the recent advances on standard cells used in in vitro prevascularization methods, their co-culture systems, and conditions in which they form an organized and functional vascular network.

Cardioprotective Roles of Endothelial Progenitor Cell-Derived Exosomes

With the globally increasing prevalence, cardiovascular diseases (CVDs) have become the leading cause of mortality. The transplantation of endothelial progenitor cells (EPCs) holds a great promise due to their potential for vasculogenesis, angiogenesis, and protective cytokine release, whose mechanisms are essential for CVD therapies. In reality, many investigations have attributed the therapeutic effects of EPC transplantation to the secretion of paracrine factors rather than the differentiation function. Of note, previous studies have suggested that EPCs could also release exosomes (diameter range of 30–150 nm), which carry various lipids and proteins and are abundant in microRNAs. The EPC-derived exosomes (EPC-EXs) were reported to act on the heart and blood vessels and were implicated in anti-inflammation, anti-oxidation, anti-apoptosis, the inhibition of endothelial-to-mesenchymal transition (EndMT), and cardiac fibrosis, as well as anti-vascular remodeling and angiogenesis, which were considered as protective effects against CVDs. In this review, we summarize the current knowledge on using EPC-EXs as therapeutic agents and provide a detailed description of their identified mechanisms of action to promote the prognosis of CVDs.

RETRACTED: MicroRNA-375-3p in endothelial progenitor cells-derived extracellular vesicles relieves myocardial injury in septic rats via BRD4-mediated PI3K/AKT signaling pathway

This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy). This article has been retracted at the request of the Editor-in-Chief. Concern was raised about the reliability of the Western blot results in Figs. 1E, 4A+F, 5A+B and Supplementary Fig. 1O+P, which appear to have the same eyebrow shaped phenotype as many other publications tabulated here (https://docs.google.com/spreadsheets/d/149EjFXVxpwkBXYJOnOHb6RhAqT4a2llhj9LM60MBffM/edit#gid=0 [docs.google.com]). The journal requested the corresponding author comment on these concerns and provide the raw data. However, the authors were not responsive to the request for comment. Since original data could not be provided, the overall validity of the results could not be confirmed. Therefore, the Editor-in-Chief decided to retract the article.

[Experimental study of endothelial progenitor cells derived small extracellular vesicles for spinal cord injury repair in mice]

Objective

To explore the potential therapeutic effects of endothelial progenitor cells derived small extracellular vesicles (EPCs-sEVs) on spinal cord injury in mice.

Methods

EPCs were separated from femur and tibia bone marrow of 20 C57BL/6 male mice, and identified by double fluorescence staining and flow cytometry. Then the EPCs were passaged and the cell supernatants from P2-P4 generations EPCs were collected; the EPCs-sEVs were extracted by ultracentrifugation and identified by transmission electron microscopy, nanoflow cytometry, and Western blot. Forty C57BL/6 female mice were randomly divided into 4 groups ( n=10). The mice were only removed T ₁₀ lamina in sham group, and prepared T ₁₀ spinal cord injury models in the model group and the low and high concentration intervention groups. After 30 minutes, 3 days, and 7 days of operation, the mice in low and high concentration intervention groups were injected with EPCs-sEVs at concentrations of 1×10 ⁹ and 1×10 ¹⁰cells/mL through the tail vein, respectively. The behavioral examinations [Basso Mouse Scale (BMS) score, inclined plate test, Von Frey test] , and the gross, HE staining, and immunohistochemical staining were performed to observe the structural changes of the spinal cord at 4 weeks after operation. Another 3 C57BL/6 female mice were taken to prepare T ₁₀ spinal cord injury models, and DiR-labeled EPCs- sEVs were injected through the tail vein. After 30 minutes, in vivo imaging was used to observe whether the EPCs-sEVs reached the spinal cord injury site.

Results

After identification, EPCs and EPCs-sEVs derived from mouse bone marrow were successfully obtained. In vivo imaging of the spinal cord showed that EPCs-sEVs were recruited to the spinal cord injury site within 30 minutes after injection. There was no significant difference in BMS scores and the maximum angle of the inclined plate test between two intervention groups and the model group within 2 weeks after operation ( P>0.05), while both were significantly better than the model group ( P<0.05) after 2 weeks. The Von Frey test showed that the mechanical pain threshold of the two intervention groups were significantly higher than that of model group and lower than that of sham group ( P<0.05); there was no significant difference between two intervention groups ( P>0.05). Compared with the model group, the injured segment of the two intervention groups had smaller spinal cord tissue defects, less mononuclear cells infiltration, more obvious tissue structure recovery, and more angiogenesis, and these differences were significant ( P<0.05); there was no significant difference between the two intervention groups.

Conclusion

EPCs-sEVs can promote the repair of spinal cord injury in mice and provide a new plan for the biological treatment of spinal cord injury.

miR-144 delivered by nasopharyngeal carcinoma-derived EVs stimulates angiogenesis through the FBXW7/HIF-1α/VEGF-A axis

The current study aimed to explore the role of tumor-derived extracellular vesicles (EVs) in angiogenesis during nasopharyngeal carcinoma (NPC). NPC biopsy specimens were initially collected. Human umbilical vein endothelial cells (HUVECs) were co-cultured with EVs isolated from NPC cells, after which their migration, invasion, as well as vessel-like tube formation were evaluated by Transwell chamber systems and Matrigel-based angiogenesis assays. The pro-angiogenic activities of EVs as well as the candidate microRNA (miRNA or miR) were examined using an in vivo Matrigel angiogenesis model. The results indicated that the levels of miR-144 in the NPC tissues were upregulated when compared to the nasopharyngeal normal tissues in addition to the identification of a positive correlation with the expression of CD31. Moreover, our data indicated that miR-144 was highly enriched in EVs from NPC cells and then ultimately enhanced the migration and invasion of HUVECs and vessel-like tubes in vitro and in vivo. Notably, miR-144 was identified as a mediator in NPC-EV-induced regulatory effects through the inhibition of the target gene FBXW7 and promotion of the transcriptional factor HIF-1α-dependent vascular endothelial growth factor (VEGF-A). Taken together, the key findings of the current study highlighted the role of miR-144 as an extracellular pro-angiogenic mediator in NPC tumorigenesis.

FO-SPR biosensor calibrated with recombinant extracellular vesicles enables specific and sensitive detection directly in complex matrices

Extracellular vesicles (EVs) have drawn huge attention for diagnosing myriad of diseases, including cancer. However, the EV detection and analyses procedures often lack much desired sample standardization. To address this, we used well-characterized recombinant EVs (rEVs) for the first time as a biological reference material in developing a fiber optic surface plasmon resonance (FO-SPR) bioassay. In this context, EV binding on the FO-SPR probes was achieved only with EV-specific antibodies (e.g. anti-CD9 and anti-CD63) but not with non-specific anti-IgG. To increase detection sensitivity, we tested six different combinations of EV-specific antibodies in a sandwich bioassay. Calibration curves were generated with two most effective combinations (anti-CD9/^Banti-CD81 and anti-CD63/^Banti-CD9), resulting in 10³ and 10⁴ times higher sensitivity than the EV concentration in human blood plasma from healthy or cancer patients, respectively. Additionally, by using anti-CD63/^Banti-CD9, we detected rEVs spiked in cell culture medium and HEK293 endogenous EVs in the same matrix without any prior EV purification or enrichment. Lastly, we selectively captured breast cancer cell EVs spiked in blood plasma using anti-EpCAM antibody on the FO-SPR surface. The obtained results combined with FO-SPR real-time monitoring, fast response time and ease of operation, demonstrate its outstanding potential for EV quantification and analysis.

Exosomes in atherosclerosis: performers, bystanders, biomarkers, and therapeutic targets

Exosomes are nanosized lipid vesicles originating from the endosomal system that carry many macromolecules from their parental cells and play important roles in intercellular communication. The functions and underlying mechanisms of exosomes in atherosclerosis have recently been intensively studied. In this review, we briefly introduce exosome biology and then focus on advances in the roles of exosomes in atherosclerosis, specifically exosomal changes associated with atherosclerosis, their cellular origins and potential functional cargos, and their detailed impacts on recipient cells. We also discuss the potential of exosomes as biomarkers and drug carriers for managing atherosclerosis.

Reversal of Endothelial Extracellular Vesicle-Induced Smooth Muscle Phenotype Transition by Hypercholesterolemia Stimulation: Role of NLRP3 Inflammasome Activation

Recent studies reported that vascular endothelial cells (ECs) secrete NLR family pyrin domain-containing 3 (NLRP3) inflammasome products such as interleukin-1β (IL-1β) via extracellular vesicles (EVs) under various pathological conditions. EVs represent one of the critical mechanisms mediating the cell-to-cell communication between ECs and vascular smooth muscle cells (VSMCs). However, whether or not the inflammasome-dependent EVs directly participate in the regulation of VSMC function remains unknown. In the present study, we found that in cultured carotid ECs, atherogenic stimulation by oxysterol 7-ketocholesterol (7-Ket) induced NLRP3 inflammasome formation and activation, reduced lysosome-multivesicular bodies (MVBs) fusion, and increased secretion of EVs that contain inflammasome product IL-1β. These EC-derived IL-1β-containing EVs promoted synthetic phenotype transition of co-cultured VSMCs, whereas EVs from unstimulated ECs have the opposite effects. Moreover, acid ceramidase (AC) deficiency or lysosome inhibition further exaggerated the 7-Ket-induced release of IL-1β-containing EVs in ECs. Using a Western diet (WD)-induced hypercholesterolemia mouse model, we found that endothelial-specific AC gene knockout mice (Asah1^fl/fl/EC^Cre) exhibited augmented WD-induced EV secretion with IL-1β and more significantly decreased the interaction of MVBs with lysosomes in the carotid arterial wall compared to their wild-type littermates (WT/WT). The endothelial AC deficiency in Asah1^fl/fl/EC^Cre mice also resulted in enhanced VSMC phenotype transition and accelerated neointima formation. Together, these results suggest that NLRP3 inflammasome-dependent IL-1β production during hypercholesterolemia promotes VSMC phenotype transition to synthetic status via EV machinery, which is controlled by lysosomal AC activity. Our findings provide novel mechanistic insights into understanding the pathogenic role of endothelial NLRP3 inflammasome in vascular injury through EV-mediated EC-to-VSMC regulation.

Endothelial progenitor cells promote osteogenic differentiation in co-cultured with mesenchymal stem cells via the MAPK-dependent pathway

BACKGROUND

The role of bone tissue engineering is to regenerate tissue using biomaterials and stem cell-based approaches. Combination of two or more cell types is one of the strategies to promote bone formation. Endothelial progenitor cells (EPCs) may enhance the osteogenic properties of mesenchymal stem cells (MSCs) and promote bone healing; this study aimed to investigate the possible mechanisms of EPCs on promoting osteogenic differentiation of MSCs.

METHODS

MSCs and EPCs were isolated and co-cultured in Transwell chambers, the effects of EPCs on the regulation of MSC biological properties were investigated. Real-time PCR array, and western blotting were performed to explore possible signaling pathways involved in osteogenesis. The expression of osteogenesis markers and calcium nodule formation was quantified by qRT-PCR, western blotting, and Alizarin Red staining.

RESULTS

Results showed that MSCs exhibited greater alkaline phosphatase (ALP) activity and increased calcium mineral deposition significantly when co-cultured with EPCs. The mitogen-activated protein kinase (MAPK) signaling pathway was involved in this process. p38 gene expression and p38 protein phosphorylation levels showed significant upregulation in co-cultured MSCs. Silencing expression of p38 in co-cultured MSCs reduced osteogenic gene expression, protein synthesis, ALP activity, and calcium nodule formation.

CONCLUSIONS

These data suggest paracrine signaling from EPCs influences the biological function and promotes MSCs osteogenic differentiation. Activation of the p38MAPK pathway may be the key to enhancing MSCs osteogenic differentiation via indirect interactions with EPCs.

The potential roles of exosomal noncoding RNAs in osteosarcoma

Clinically, it is difficult to efficaciously screen and diagnose osteosarcoma (OS) in advance due to the low sensitivity and poor specificity of the existing tumor markers. Exosomes (Exos) are nanoscale vesicles containing RNAs, lipids, and proteins with a diameter of 30-100 nm. They are multivesicular bodies formed during the invagination of lysosomal particles in cells and released extracellularly after fusing with cell membranes. Besides, Exos are important carriers of cell-to-cell communication signals and genetic materials in the tumor microenvironment. During tumorigenesis, the tumor cells interplay with immune cells, endothelial cells, and related fibroblasts through Exos and boost cancer development. After altering the surrounding microenvironment, the Exos drive tumor cells to proliferate, speed up angiogenesis, and boost cancers to develop along with body fluid transportation. Currently, Exos are becoming novel noninvasive tumor diagnostic markers with high sensitivity, exerting pivotal impacts in fundamental research and clinical applications. Here, we review the existing literature on the roles of exosomal noncoding RNAs in OS progression and their potential clinical applications as novel biomarkers and therapeutics.

Advances in Exosomes Derived from Different Cell Sources and Cardiovascular Diseases

Exosomes can reach distant tissues through blood circulation to communicate directly with target cells and rapidly regulate intracellular signals. Exosomes play an important role in cardiovascular pathophysiology. Different exosomes derived from different sources, and their cargos have different mechanisms of action. In addition to being biomarkers, exosomes also have a certain significance in the diagnosis, treatment, and even prevention of cardiovascular diseases. Here, we provide a review of the up-to-date applications of exosomes, derived from various sources, in the prognosis and diagnosis of cardiovascular diseases.

Extracellular Vesicle Therapeutics in Regenerative Medicine

Extracellular vesicles (EVs) are nano-sized, cell-released vesicles which contain lipids, proteins, and nucleic acids derived from the parental cells. EVs play an important role in intercellular communication and influence both physiological and pathological conditions. They are increasingly explored as potential therapeutic agents since they can cross biological barriers, their cargo is protected from degradation and they are involved in the transfer of bioactive components. EVs can promote tissue regeneration and might be alternatives to cell therapy. They can be used both in their native form, and as delivery vehicles for therapeutic agents. However, there are many hurdles to overcome for broad clinical application of EVs as therapeutics. Here, we review recent conditions regarding EVs therapeutics in regenerative medicine.