MicroRNA-containing extracellular vesicles released from endothelial colony-forming cells modulate angiogenesis during ischaemic retinopathy

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.

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.

Elucidating glial responses to products of diabetes-associated systemic dyshomeostasis

Diabetic retinopathy (DR) is a leading cause of blindness in working age adults. DR has non-proliferative stages, characterized in part by retinal neuroinflammation and ischemia, and proliferative stages, characterized by retinal angiogenesis. Several systemic factors, including poor glycemic control, hypertension, and hyperlipidemia, increase the risk of DR progression to vision-threatening stages. Identification of cellular or molecular targets in early DR events could allow more prompt interventions pre-empting DR progression to vision-threatening stages. Glia mediate homeostasis and repair. They contribute to immune surveillance and defense, cytokine and growth factor production and secretion, ion and neurotransmitter balance, neuroprotection, and, potentially, regeneration. Therefore, it is likely that glia orchestrate events throughout the development and progression of retinopathy. Understanding glial responses to products of diabetes-associated systemic dyshomeostasis may reveal novel insights into the pathophysiology of DR and guide the development of novel therapies for this potentially blinding condition. In this article, first, we review normal glial functions and their putative roles in the development of DR. We then describe glial transcriptome alterations in response to systemic circulating factors that are upregulated in patients with diabetes and diabetes-related comorbidities; namely glucose in hyperglycemia, angiotensin II in hypertension, and the free fatty acid palmitic acid in hyperlipidemia. Finally, we discuss potential benefits and challenges associated with studying glia as targets of DR therapeutic interventions. In vitro stimulation of glia with glucose, angiotensin II and palmitic acid suggests that: 1) astrocytes may be more responsive than other glia to these products of systemic dyshomeostasis; 2) the effects of hyperglycemia on glia are likely to be largely osmotic; 3) fatty acid accumulation may compound DR pathophysiology by promoting predominantly proinflammatory and proangiogenic transcriptional alterations of macro and microglia; and 4) cell-targeted therapies may offer safer and more effective avenues for DR treatment as they may circumvent the complication of pleiotropism in retinal cell responses. Although several molecules previously implicated in DR pathophysiology are validated in this review, some less explored molecules emerge as potential therapeutic targets. Whereas much is known regarding glial cell activation, future studies characterizing the role of glia in DR and how their activation is regulated and sustained (independently or as part of retinal cell networks) may help elucidate mechanisms of DR pathogenesis and identify novel drug targets for this blinding disease.

Stem cells and diabetic retinopathy: From models to treatment

Diabetic retinopathy is a common yet complex microvascular disease, caused as a complication of diabetes mellitus. Associated with hyperglycemia and subsequent metabolic abnormalities, advanced stages of the disease lead to fibrosis, subsequent visual impairment and blindness. Though clinical postmortems, animal and cell models provide information about the progression and prognosis of diabetic retinopathy, its underlying pathophysiology still needs a better understanding. In addition to it, the loss of pericytes, immature retinal angiogenesis and neuronal apoptosis portray the disease treatment to be challenging. Indulged with cell loss of both vascular and neuronal type cells, novel therapies like cell replacement strategies by various types of stem cells have been sightseen as a possible treatment of the disease. This review provides insight into the pathophysiology of diabetic retinopathy, current models used in modelling the disease, as well as the varied aspects of stem cells in generating three-dimensional retinal models. Further outlook on stem cell therapy and the future directions of stem cell treatment in diabetic retinopathy have also been contemplated.

CD34 positive cells as endothelial progenitor cells in biology and medicine

CD34 is a cell surface antigen expressed in numerous stem/progenitor cells including hematopoietic stem cells (HSCs) and endothelial progenitor cells (EPCs), which are known to be rich sources of EPCs. Therefore, regenerative therapy using CD34⁺ cells has attracted interest for application in patients with various vascular, ischemic, and inflammatory diseases. CD34⁺ cells have recently been reported to improve therapeutic angiogenesis in a variety of diseases. Mechanistically, CD34⁺ cells are involved in both direct incorporation into the expanding vasculature and paracrine activity through angiogenesis, anti-inflammatory, immunomodulatory, and anti-apoptosis/fibrosis roles, which support the developing microvasculature. Preclinical, pilot, and clinical trials have well documented a track record of safety, practicality, and validity of CD34⁺ cell therapy in various diseases. However, the clinical application of CD34⁺ cell therapy has triggered scientific debates and controversies in last decade. This review covers all preexisting scientific literature and prepares an overview of the comprehensive biology of CD34⁺ cells as well as the preclinical/clinical details of CD34⁺ cell therapy for regenerative medicine.

Selective Loading and Variations in the miRNA Profile of Extracellular Vesicles from Endothelial-like Cells Cultivated under Normoxia and Hypoxia

Endothelial-like cells may be obtained from CD133⁺ mononuclear cells isolated from human umbilical cord blood (hUCB) and expanded using endothelial-inducing medium (E-CD133 cells). Their use in regenerative medicine has been explored by the potential not only to form vessels but also by the secretion of bioactive elements. Extracellular vesicles (EVs) are prominent messengers of this paracrine activity, transporting bioactive molecules that may guide cellular response under different conditions. Using RNA-Seq, we characterized the miRNA content of EVs derived from E-CD133 cells cultivated under normoxia (N-EVs) and hypoxia (H-EVs) and observed that changing the O₂ status led to variations in the selective loading of miRNAs in the EVs. In silico analysis showed that among the targets of differentially loaded miRNAs, there are transcripts involved in pathways related to cell growth and survival, such as FoxO and HIF-1 pathways. The data obtained reinforce the pro-regenerative potential of EVs obtained from E-CD133 cells and shows that fine tuning of their properties may be regulated by culture conditions.

Advances in cell therapies using stem cells/progenitors as a novel approach for neurovascular repair of the diabetic retina

BACKGROUND

Diabetic retinopathy, a major complication of diabetes mellitus, is a leading cause of sigh-loss in working age adults. Progressive loss of integrity of the retinal neurovascular unit is a central element in the disease pathogenesis. Retinal ischemia and inflammatory processes drive interrelated pathologies such as blood retinal barrier disruption, fluid accumulation, gliosis, neuronal loss and/or aberrant neovascularisation. Current treatment options are somewhat limited to late-stages of the disease where there is already significant damage to the retinal architecture arising from degenerative, edematous and proliferative pathology. New preventive and interventional treatments to target early vasodegenerative and neurodegenerative stages of the disease are needed to ensure avoidance of sight-loss.

MAIN BODY

Historically, diabetic retinopathy has been considered a primarily microvascular disease of the retina and clinically it is classified based on the presence and severity of vascular lesions. It is now known that neurodegeneration plays a significant role during the pathogenesis. Loss of neurons has been documented at early stages in pre-clinical models as well as in individuals with diabetes and, in some, even prior to the onset of clinically overt diabetic retinopathy. Recent studies suggest that some patients have a primarily neurodegenerative phenotype. Retinal pigment epithelial cells and the choroid are also affected during the disease pathogenesis and these tissues may also need to be addressed by new regenerative treatments. Most stem cell research for diabetic retinopathy to date has focused on addressing vasculopathy. Pre-clinical and clinical studies aiming to restore damaged vasculature using vasoactive progenitors including mesenchymal stromal/stem cells, adipose stem cells, CD34+ cells, endothelial colony forming cells and induced pluripotent stem cell derived endothelial cells are discussed in this review. Stem cells that could replace dying neurons such as retinal progenitor cells, pluripotent stem cell derived photoreceptors and ganglion cells as well as Müller stem cells are also discussed. Finally, challenges of stem cell therapies relevant to diabetic retinopathy are considered.

CONCLUSION

Stem cell therapies hold great potential to replace dying cells during early and even late stages of diabetic retinopathy. However, due to the presence of different phenotypes, selecting the most suitable stem cell product for individual patients will be crucial for successful treatment.

Bioactive extracellular vesicles from a subset of endothelial progenitor cells rescue retinal ischemia and neurodegeneration

Disruption of the neurovascular unit (NVU) underlies the pathophysiology of various CNS diseases. One strategy to repair NVU dysfunction uses stem/progenitor cells to provide trophic support to the NVU's functionally coupled and interdependent vasculature and surrounding CNS parenchyma. A subset of endothelial progenitor cells, endothelial colony-forming cells (ECFCs) with high expression of the CD44 hyaluronan receptor (CD44hi), provides such neurovasculotrophic support via a paracrine mechanism. Here, we report that bioactive extracellular vesicles from CD44hi ECFCs (EVshi) are paracrine mediators, recapitulating the effects of intact cell therapy in murine models of ischemic/neurodegenerative retinopathy; vesicles from ECFCs with low expression levels of CD44 (EVslo) were ineffective. Small RNA sequencing comparing the microRNA cargo from EVshi and EVslo identified candidate microRNAs that contribute to these effects. EVshi may be used to repair NVU dysfunction through multiple mechanisms to stabilize hypoxic vasculature, promote vascular growth, and support neural cells.

Exploring Endothelial Colony-Forming Cells to Better Understand the Pathophysiology of Disease: An Updated Review

Endothelial cell (EC) dysfunction has been implicated in a variety of pathological conditions. The collection of ECs from patients is typically conducted postmortem or through invasive procedures, such as surgery and interventional procedures, hampering efforts to clarify the role of ECs in disease onset and progression. In contrast, endothelial colony-forming cells (ECFCs), also termed late endothelial progenitor cells, late outgrowth endothelial cells, blood outgrowth endothelial cells, or endothelial outgrowth cells, are obtained in a minimally invasive manner, namely, by the culture of human peripheral blood mononuclear cells in endothelial growth medium. ECFCs resemble mature ECs phenotypically, genetically, and functionally, making them excellent surrogates for ECs. Numerous studies have been performed that examined ECFC function in conditions such as coronary artery disease, diabetes mellitus, hereditary hemorrhagic telangiectasia, congenital bicuspid aortic valve disease, pulmonary arterial hypertension, venous thromboembolic disease, and von Willebrand disease. Here, we provide an updated review of studies using ECFCs that were performed to better understand the pathophysiology of disease. We also discuss the potential of ECFCs as disease biomarkers and the standardized methods to culture, quantify, and evaluate ECFCs and suggest the future direction of research in this field.

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.

The emerging role of extracellular vesicles in retinal diseases

As a type of nanosized membranous vesicles secreted by living cells, extracellular vesicles (EVs) mediate intercellular communications with excellent physicochemical stability and biocompatibility. By delivering biologically active molecules including proteins, nucleic acids and lipids, EVs participate in many physiological and pathological processes. Increasing studies have suggested that EVs may be biomarkers for liquid biopsy of retinal diseases due to the ability to transfer through the blood-retinal barrier. EVs also represent a novel cell-free strategy to repair tissue damage in regenerative medicine. Evidence has indicated that EVs can be engineered and modified to enhance their efficacy. In this review, an overview of the characteristics, isolation, and identification of EVs is provided. Moreover, recent advances with EVs in the diagnosis and treatment of retinal diseases and the engineering approaches to elevate their effects are introduced, and opportunities and challenges for clinical application are discussed.

MicroRNAs are minor constituents of extracellular vesicles that are rarely delivered to target cells

Mammalian cells release different types of vesicles, collectively termed extracellular vesicles (EVs). EVs contain cellular microRNAs (miRNAs) with an apparent potential to deliver their miRNA cargo to recipient cells to affect the stability of individual mRNAs and the cells’ transcriptome. The extent to which miRNAs are exported via the EV route and whether they contribute to cell-cell communication are controversial. To address these issues, we defined multiple properties of EVs and analyzed their capacity to deliver packaged miRNAs into target cells to exert biological functions. We applied well-defined approaches to produce and characterize purified EVs with or without specific viral miRNAs. We found that only a small fraction of EVs carried miRNAs. EVs readily bound to different target cell types, but EVs did not fuse detectably with cellular membranes to deliver their cargo. We engineered EVs to be fusogenic and document their capacity to deliver functional messenger RNAs. Engineered fusogenic EVs, however, did not detectably alter the functionality of cells exposed to miRNA-carrying EVs. These results suggest that EV-borne miRNAs do not act as effectors of cell-to-cell communication.

The majority of metazoan cells release vesicles of different types and origins, such as exosomes and microvesicles, now collectively termed extracellular vesicles (EVs). EVs have gained much attention because they contain microRNAs (miRNAs) and thus could regulate their specific mRNA targets in recipient or acceptor cells that take up EVs. Using a novel fusion assay with superior sensitivity and specificity, we revisited this claim but found no convincing evidence for an efficient functional uptake of EVs in many different cell lines and primary human blood cells. Even EVs engineered to fuse and deliver their miRNA cargo to recipient cells had no measurable effect on target mRNAs in very carefully controlled, quantitative experiments. Our negative results clearly indicate that EVs do not act as vehicles for miRNA-based cell-to-cell communication.

Endothelial repair by stem and progenitor cells

The integrity of the endothelial barrier is required to maintain vascular homeostasis and fluid balance between the circulatory system and surrounding tissues and to prevent the development of vascular disease. However, the origin of the newly developed endothelial cells is still controversial. Stem and progenitor cells have the potential to differentiate into endothelial cell lines and stimulate vascular regeneration in a paracrine/autocrine fashion. The one source of new endothelial cells was believed to come from the bone marrow, which was challenged by the recent findings. By administration of new techniques, including genetic cell lineage tracing and single cell RNA sequencing, more solid data were obtained that support the concept of stem/progenitor cells for regenerating damaged endothelium. Specifically, it was found that tissue resident endothelial progenitors located in the vessel wall were crucial for endothelial repair. In this review, we summarized the latest advances in stem and progenitor cell research in endothelial regeneration through findings from animal models and discussed clinical data to indicate the future direction of stem cell therapy.

Latest Advances in Endothelial Progenitor Cell-Derived Extracellular Vesicles Translation to the Clinic

Almost all nucleated cells secrete extracellular vesicles (EVs) that are heterogeneous spheroid patterned or round shape particles ranging from 30 to 200 nm in size. Recent preclinical and clinical studies have shown that endothelial progenitor cell-derived EVs (EPC-EVs) have a beneficial therapeutic effect in various diseases, including cardiovascular diseases and kidney, and lung disorders. Moreover, some animal studies have shown that EPC-EVs selectively accumulate at the injury site with a specific mechanism of binding along with angiogenic and restorative effects that are superior to those of their ancestors. This review article highlights current advances in the biogenesis, delivery route, and long-term storage methods of EPC-EVs and their favorable effects such as anti-inflammatory, angiogenic, and tissue protection in various diseases. Finally, we review the possibility of therapeutic application of EPC-EVs in the clinic.

Preparing Adipogenic Hydrogel with Neo-Mechanical Isolated Adipose-Derived Extracellular Vesicles for Adipose Tissue Engineering

BACKGROUND

Subcutaneous transplantation of decellularized adipose tissue was capable of recellularization during soft tissue repair. However, further improvements are required to promote angiogenesis and adipogenesis. Here, the authors proposed a neo-mechanical protocol to isolate adipose tissue-derived extracellular vesicles (ATEVs) through lipoaspirate as a mediator for both angiogenesis and adipogenesis, and prepared ATEV-rich decellularized adipose tissue hydrogel for adipose tissue engineering.

METHODS

Adipose liquid extract and lipid-devoid adipose tissue were extracted through homogenization and repeated freeze and thaw cycles. ATEVs were isolated from adipose liquid extract by ultracentrifugation. Decellularized adipose tissue hydrogel was prepared by optimized decellularization of lipid-devoid adipose tissue. The optimum dose of ATEVs for angiogenesis and adipogenesis was estimated by co-culturing with vascular endothelial cells and 3T3-L1 cells, then mixed with the hydrogel. ATEV-enriched hydrogel was injected subcutaneously into the back of severe combined immunodeficiency mice, and then subjected to supplementary injection of ATEVs on postoperative day 14. ATEV-free decellularized adipose tissue hydrogel was injected as control. The newly formed tissue samples were harvested at postoperative weeks 2, 4, and 8 and subjected to volume measurement, hematoxylin and eosin staining, and immunofluorescence (CD31 and perilipin) staining.

RESULTS

The optimum dose of ATEVs for promoting angiogenesis and adipogenesis was 50 μg/ml. The newly formed tissue mediated by ATEV-enriched hydrogel had increased volume well as improved angiogenesis and adipogenesis at postoperative week 4 and 8.

CONCLUSION

ATEV-enriched adipogenic hydrogel promotes enhanced angiogenesis and adipogenesis and could serve as a promising biomaterial for adipose tissue engineering.

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

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

Extracellular vesicles in Inter-Kingdom communication in gastrointestinal cancer

The production and secretion of extracellular vesicles (EVs) are common features of cells (including various normal cells, neoplastic cell lines as well as bacteria) that span all domains of life. Tumor-derived exosomes are enriched with kinds of tumorigenesis mediators which are derived from the cytoplasm of cancer cells and fully reflect the tumor conditions. Indeed, the major topics and challenges on current oncological research are the identification of tumorigenic and metastatic molecules in tumor-cell-derived exosomes as well as elucidating the pathways that guarantee these components to be included in exosomes. The bacterial EVs have also been implicated in the pathogenesis of gastrointestinal (GI) tumors and chronic inflammatory diseases; however, the possible function of outer membrane vesicles (OMVs) in tumorigenesis remains largely underestimated. We suggest that EVs from both eukaryotic cells and different microbes in GI tract act as regulators of intracellular and cross-species communication, thus particularly facilitate tumor cell survival and multi-drug resistance. Therefore, our review introduces comprehensive knowledge on the promising role of EVs (mainly exosomes and OMVs) production of GI cancer development and gut microbiome, as well as its roles in developing novel therapeutic strategies.

Endothelium-dependent remote signaling in ischemia and reperfusion: Alterations in the cardiometabolic continuum

Intact endothelial function plays a fundamental role for the maintenance of cardiovascular (CV) health. The endothelium is also involved in remote signaling pathway-mediated protection against ischemia/reperfusion (I/R) injury. However, the transfer of these protective signals into clinical practice has been hampered by the complex metabolic alterations frequently observed in the cardiometabolic continuum, which affect redox balance and inflammatory pathways. Despite recent advances in determining the distinct roles of hyperglycemia, insulin resistance (InR), hyperinsulinemia, and ultimately diabetes mellitus (DM), which define the cardiometabolic continuum, our understanding of how these conditions modulate endothelial signaling remains challenging. It is widely accepted that endothelial cells (ECs) undergo functional changes within the cardiometabolic continuum. Beyond vascular tone and platelet-endothelium interaction, endothelial dysfunction may have profound negative effects on outcome during I/R. In this review, we summarize the current knowledge of the influence of hyperglycemia, InR, hyperinsulinemia, and DM on endothelial function and redox balance, their influence on remote protective signaling pathways, and their impact on potential therapeutic strategies to optimize protective heterocellular signaling.

Exosome-derived miR-196b-5p facilitates intercellular interaction in infantile hemangioma via down-regulating CDKN1B

Background

Though infantile hemangioma (IH) is a common benign vascular tumor, its pathogenesis remains unclear. This study explored the function of hemangioma-derived stem cells (HemSCs) derived exosomes, which exerted an intercellular effect on hemangioma-derived endothelial cells (HemECs).

Methods

First, HemSCs and HemECs were extracted and cultured. HemSCs derived exosomes (HemSCs-exos) were harvested. miRNA sequencing and target prediction were used to explore differentially expressed miRNAs and potential binding targets. After HemECs were co-cultured with HemSCs-exos, a series of in vitro assays were then performed including cell counting kit-8 (CCK-8) assay, cell apoptosis assay, cell cycle assay and tube formation assay to evaluate proliferation, angiogenesis abilities, etc. qRT-PCR and Western blot were conducted to detect the expression level of target genes and proteins.

Results

After co-culturing with HemSCs-exos, proliferation, and angiogenesis abilities of HemECs were enhanced, while apoptosis and cell cycle arrest rate were decreased. MiR-196b-5p was observed to be significantly highly expressed in HemSCs-exos. CDKN1B was identified as the binding target of miR-196b-5p. HemECs' proliferation and angiogenesis abilities were elevated when co-cultured with exosomes from HemSCs transfected with miR-196b-5p mimic. In addition, apoptosis rate declined, and lower cells were arrested in G0/G1 phases. Cyclin E, bcl-2 were significantly highly expressed, whereas p27, Bax expression were significantly down-regulated. The positive effect of miR-196b-5p in HemSCs-exos was dramatically reversed when HemECs were transfected with oe-CDKN1B.

Conclusions

The current study found a novel intercellular interaction between IH cells. Briefly, exosome-derived miRNA-196b-5p in HemSCs could facilitate proliferation and angiogenesis abilities, and attenuate apoptosis and cell cycle repression rate of HemECs by directly binding with CDKN1B.

Therapeutic Potential of Endothelial Colony-Forming Cells in Ischemic Disease: Strategies to Improve their Regenerative Efficacy

Cardiovascular disease (CVD) comprises a range of major clinical cardiac and circulatory diseases, which produce immense health and economic burdens worldwide. Currently, vascular regenerative surgery represents the most employed therapeutic option to treat ischemic disorders, even though not all the patients are amenable to surgical revascularization. Therefore, more efficient therapeutic approaches are urgently required to promote neovascularization. Therapeutic angiogenesis represents an emerging strategy that aims at reconstructing the damaged vascular network by stimulating local angiogenesis and/or promoting de novo blood vessel formation according to a process known as vasculogenesis. In turn, circulating endothelial colony-forming cells (ECFCs) represent truly endothelial precursors, which display high clonogenic potential and have the documented ability to originate de novo blood vessels in vivo. Therefore, ECFCs are regarded as the most promising cellular candidate to promote therapeutic angiogenesis in patients suffering from CVD. The current briefly summarizes the available information about the origin and characterization of ECFCs and then widely illustrates the preclinical studies that assessed their regenerative efficacy in a variety of ischemic disorders, including acute myocardial infarction, peripheral artery disease, ischemic brain disease, and retinopathy. Then, we describe the most common pharmacological, genetic, and epigenetic strategies employed to enhance the vasoreparative potential of autologous ECFCs by manipulating crucial pro-angiogenic signaling pathways, e.g., extracellular-signal regulated kinase/Akt, phosphoinositide 3-kinase, and Ca²⁺ signaling. We conclude by discussing the possibility of targeting circulating ECFCs to rescue their dysfunctional phenotype and promote neovascularization in the presence of CVD.

The future of Extracellular Vesicles as Theranostics - an ISEV meeting report

The utilization of extracellular vesicles (EVs) in clinical theranostics has rapidly advanced in the past decade. In November 2018, the International Society for Extracellular Vesicles (ISEV) held a workshop on “EVs in Clinical Theranostic”. Here, we report the conclusions of roundtable discussions on the current advancement in the analysis technologies and we provide some guidelines to researchers in the field to consider the use of EVs in clinical application. The main challenges and the requirements for EV separation and characterization strategies, quality control and clinical investigation were discussed to promote the application of EVs in future clinical studies.

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

Extracellular vesicles (EVs) are a heterogeneous group of membranous structures, which can be secreted by most cell types. As a product of paracrine secretion, EVs are considered to be a regulatory mediator for intercellular communication. There are many bioactive cargos in EVs, such as proteins, lipids, and nucleic acids. As the precursor cell of vascular endothelial cells (ECs), endothelial progenitor cells (EPCs) are first discovered in peripheral blood. With the development of studies about the functions of EPCs, an increasing number of researchers focus on EPC-derived EVs (EPC-EVs). EPC-EVs exert key functions for promoting angiogenesis in regenerative medicine and show significant therapeutic effects on a variety of diseases such as circulatory diseases, kidney diseases, diabetes, bone diseases, and tissue/organ damages. This article reviews the current knowledge on the role of EPC-EVs in regenerative medicine and disease treatment, discussing the main challenges and future directions in this field.

Vascular Regeneration for Ischemic Retinopathies: Hope from Cell Therapies

Retinal vascular diseases, such as diabetic retinopathy, retinopathy of prematurity, retinal vein occlusion, ocular ischemic syndrome and ischemic optic neuropathy, are leading causes of vision impairment and blindness. Whilst drug, laser or surgery-based treatments for the late stage complications of many of these diseases are available, interventions that target the early vasodegenerative stages are lacking. Progressive vasculopathy and ensuing ischemia is an underpinning pathology in many of these diseases, leading to hypoperfusion, hypoxia, and ultimately pathological neovascularization and/or edema in the retina and other ocular tissues, such as the optic nerve and iris. Therefore, repairing the retinal vasculature may prevent progression of ischemic retinopathies into late stage vascular complications. Various cell types have been explored for their vascular repair potential. Endothelial progenitor cells, mesenchymal stem cells and induced pluripotent stem cells are studied for their potential to integrate with the damaged retinal vasculature and limit ischemic injury. Clinical trials for some of these cell types have confirmed safety and feasibility in the treatment of ischemic diseases, including some retinopathies. Another promising avenue is mobilization of endogenous endothelial progenitors, whereby reparative cells are moved from their niche to circulating blood to target and home into ischemic tissues. Several aspects and properties of these cell types have yet to be elucidated. Nevertheless, we foresee that cell therapy, whether through delivery of exogenous or enhancement of endogenous reparative cells, will become a valuable and beneficial treatment for ischemic retinopathies.

Heart Failure with Reduced Ejection Fraction (HFrEF) and Preserved Ejection Fraction (HFpEF): The Diagnostic Value of Circulating MicroRNAs

Circulating microRNAs offer attractive potential as epigenetic disease biomarkers by virtue of their biological stability and ready accessibility in liquid biopsies. Numerous clinical cohort studies have revealed unique microRNA profiles in different disease settings, suggesting utility as markers with diagnostic and prognostic applications. Given the complex network of microRNA functions in modulating gene expression and post-transcriptional modifications, the circulating microRNA landscape in disease may reflect pathophysiological status, providing valuable information for delineating distinct subtypes and/or stages of complex diseases. Heart failure (HF) is an increasingly significant global health challenge, imposing major economic liability and health care burden due to high hospitalization, morbidity, and mortality rates. Although HF is defined as a syndrome characterized by symptoms and findings on physical examination, it may be further differentiated based on left ventricular ejection fraction (LVEF) and categorized as HF with reduced ejection fraction (HFrEF) and HF with preserved ejection fraction (HFpEF). The presenting clinical syndromes in HFpEF and HFrEF are similar but mortality differs, being somewhat lower in HFpEF than in HFrEF. However, while HFrEF is responsive to an array of therapies, none has been shown to improve survival in HFpEF. Herein, we review recent HF cohort studies focusing on the distinct microRNA profiles associated with HF subtypes to reveal new insights to underlying mechanisms and explore the possibility of exploiting these differences for diagnostic/prognostic applications.

Correlation between Diabetic Retinopathy Severity and Oxygen Metabolism in Patients with Diabetic Macular Edema during Treatment with Intravitreal Aflibercept

PURPOSE

To attribute data on changes in diabetic retinopathy (DR) severity during treatment of diabetic macular edema (DME) with vascular endothelial growth factor inhibitors (anti-VEGF), this study aimed to (1) examine the correlation between oxygen saturations in retinal vessels and the number of DR lesions on ultra-wide field color fundus photographs prior to anti-VEGF treatment and (2) compare changes in oxygen saturations in retinal vessels with changes in the number of DR lesions after a loading dose of three monthly intravitreal injections of 2.0 mg of aflibercept.

METHODS

This 3-month prospective study included 37 eyes of patients with DME and varying severity of peripheral DR lesions. DR lesions were graded on wide field images and retinal oxygen saturations were evaluated by retinal oximetry. Patients were then treated with three monthly intravitreal injections of 2 mg aflibercept and wide field imaging and retinal oximetry were repeated 4 weeks after the last injection. Patients with proliferative DR or previous panretinal photocoagulation were excluded.

RESULTS

Baseline retinal arteriolar oxygen saturation increased with increasing DR severity and numbers of microaneurysms, hemorrhages, and cotton wool spots (p = 0.03, 0.01, 0.03, and <0.001), while no correlation between the severity of DR lesions and retinal venular oxygen saturation was found. After treatment with intravitreal aflibercept, the severity of DR lesions significantly reduced, while retinal arteriolar and venular oxygen saturation as well as the arteriolar-venular difference remained unchanged (95.5 vs. 95.8%, p = 0.44; 62.9 vs. 64.5%, p = 0.08; 32.5 vs. 31.4%, p = 0.33).

CONCLUSION

This study demonstrated that structural DR lesions correlate with retinal arteriolar oxygen saturation in patients with DME prior to anti-VEGF treatment and that improvement in the severity of DR lesions can occur without corresponding changes in retinal oxygen metabolism during intravitreal therapy. Our results suggest that DR severity on color fundus photographs should be interpreted with caution once intravitreal therapy is initiated.

Role of Mesenchymal Stem Cell-Derived Extracellular Vesicles in Epithelial-Mesenchymal Transition

Epithelial–mesenchymal transition (EMT) is a process that takes place during embryonic development, wound healing, and under some pathological processes, including fibrosis and tumor progression. The molecular changes occurring within epithelial cells during transformation to a mesenchymal phenotype have been well studied. However, to date, the mechanism of EMT induction remains to be fully elucidated. Recent findings in the field of intercellular communication have shed new light on this process and indicate the need for further studies into this important mechanism. New evidence supports the hypothesis that intercellular communication between mesenchymal stroma/stem cells (MSCs) and resident epithelial cells plays an important role in EMT induction. Besides direct interactions between cells, indirect paracrine interactions by soluble factors and extracellular vesicles also occur. Extracellular vesicles (EVs) are important mediators of intercellular communication, through the transfer of biologically active molecules, genetic material (mRNA, microRNA, siRNA, DNA), and EMT inducers to the target cells, which are capable of reprogramming recipient cells. In this review, we discuss the role of intercellular communication by EVs to induce EMT and the acquisition of stemness properties by normal and tumor epithelial cells.

Endothelial progenitor cell-derived exosomes facilitate vascular endothelial cell repair through shuttling miR-21-5p to modulate Thrombospondin-1 expression

Background: Our previous studies observed that administration of exosomes from endothelial progenitor cells (EPC) facilitated vascular repair in the rat model of balloon injury. However, the molecular events underlying this process remain elusive. Here, we aim to interrogate the key miRNAs within EPC-derived exosomes (EPC-exosomes) responsible for the activation of endothelial cell (EC) repair. Methods: The efficacy of EPC-exosomes in re-endothelialization was examined by Evans Blue dye and histological examination in the rat model of balloon-induced carotid artery injury. The effects of EPC-exosomes on human vascular EC (HUVEC) were also studied by evaluating the effects on growth, migratory and tube formation. To dissect the underlying mechanism, RNA-sequencing assays were performed to determine miRNA abundance in exosomes and mRNA profiles in exosome-treated HUVECs. Meanwhile, in vitro loss of function assays identified an exosomal miRNA and its target gene in EC, which engaged in EPC-exosomes-induced EC repair. Results: Administration of EPC-exosomes potentiated re-endothelialization in the early phase after endothelial damage in the rat carotid artery. The uptake of exogenous EPC-exosomes intensified HUVEC in proliferation rate, migration and tube-forming ability. Integrative analyses of miRNA-mRNA interactions revealed that miR-21-5p was highly enriched in EPC-exosomes and specifically suppressed the expression of an angiogenesis inhibitor Thrombospondin-1 (THBS1) in the recipient EC. The following functional studies demonstrated a fundamental role of miR-21-5p in the pro-angiogenic activities of EPC-exosomes. Conclusions: The present work highlights a critical event for the regulation of EC behavior by EPC-exosomes, which EPC-exosomes may deliver miR-21-5p and inhibit THBS1 expression to promote EC repair.

Vasculogenic Stem and Progenitor Cells in Human: Future Cell Therapy Product or Liquid Biopsy for Vascular Disease

New blood vessel formation in adults was considered to result exclusively from sprouting of preexisting endothelial cells, a process referred to angiogenesis. Vasculogenesis, the formation of new blood vessels from endothelial progenitor cells, was thought to occur only during embryonic life. Discovery of adult endothelial progenitor cells (EPCs) in 1997 opened the door for cell therapy in vascular disease. Endothelial progenitor cells contribute to vascular repair and are now well established as postnatal vasculogenic cells in humans. It is now admitted that endothelial colony-forming cells (ECFCs) are the vasculogenic subtype. ECFCs could be used as a cell therapy product and also as a liquid biopsy in several vascular diseases or as vector for gene therapy. However, despite a huge interest in these cells, their tissue and molecular origin is still unclear. We recently proposed that endothelial progenitor could come from very small embryonic-like stem cells (VSELs) isolated in human from CD133 positive cells. VSELs are small dormant stem cells related to migratory primordial germ cells. They have been described in bone marrow and other organs. This chapter discusses the reported findings from in vitro data and also preclinical studies that aimed to explore stem cells at the origin of vasculogenesis in human and then explore the potential use of ECFCs to promote newly formed vessels or serve as liquid biopsy to understand vascular pathophysiology and in particular pulmonary disease and haemostasis disorders.

miR-30a-5p inhibition promotes interaction of Fas+ endothelial cells and FasL+ microglia to decrease pathological neovascularization and promote physiological angiogenesis

Ischemia-induced angiogenesis contributes to various neuronal and retinal diseases, and often results in neurodegeneration and visual impairment. Current treatments involve the use of anti-VEGF agents but are not successful in all cases. In this study we determined that miR-30a-5p is another important mediator of retinal angiogenesis. Using a rodent model of ischemic retinopathy, we show that inhibiting miR-30a-5p reduces neovascularization and promotes tissue repair, through modulation of microglial and endothelial cell cross-talk. miR-30a-5p inhibition results in increased expression of the death receptor Fas and CCL2, to decrease endothelial cell survival and promote microglial migration and phagocytic function in focal regions of ischemic injury. Our data suggest that miR-30a-5p inhibition accelerates tissue repair by enhancing FasL-Fas crosstalk between microglia and endothelial cells, to promote endothelial cell apoptosis and removal of dead endothelial cells. Finally, we found that miR-30a levels were increased in the vitreous of patients with proliferative diabetic retinopathy. Our study identifies a role for miR-30a in the pathogenesis of neovascular retinal disease by modulating microglial and endothelial cell function, and suggests it may be a therapeutic target to treat ischemia-mediated conditions.

Receptor-Ligand Interaction Mediates Targeting of Endothelial Colony Forming Cell-derived Exosomes to the Kidney after Ischemic Injury

Endothelial colony forming cell (ECFC)-derived exosomes protect mice against ischemic kidney injury, via transfer of microRNA-(miR)-486-5p. Mechanisms mediating exosome recruitment to tissues are unclear. We hypothesized that ECFC exosomes target ischemic kidneys, involving interaction between exosomal CXC chemokine receptor type 4 (CXCR4) and stromal cell-derived factor (SDF)-1α. Ischemia-reperfusion was induced in mice by bilateral renal vascular clamp, with intravenous infusion of exosomes at reperfusion. Optical imaging determined exosome biodistribution, and miR-486-5p was measured by real-time PCR. Human umbilical vein endothelial cells (HUVECs) were cultured to study the CXCR4/SDF-1α interaction. Targeting of administered exosomes to ischemic kidneys was detected 30 min and 4 hrs after reperfusion. Exosomes increased miR-486-5p levels only in kidneys, within proximal tubules, glomeruli, and endothelial cells. Uptake of fluorescently-labeled exosomes into HUVECs, and exosomal transfer of miR-486-5p were enhanced by hypoxia, effects blocked by neutralizing antibody to SDF-1α or by the CXCR4 inhibitor plerixafor. Infusion of ECFC exosomes prevented ischemic kidney injury in vivo, an effect that was not observed when exosomes were pre-incubated with plerixafor. These data indicate that ECFC exosomes selectively target the kidneys after ischemic injury, with rapid cellular transfer of miR486-5p. Targeting of exosomes may involve interaction of CXCR4 with endothelial cell SDF-1α.

Recent Advances in Endothelial Colony Forming Cells Toward Their Use in Clinical Translation

The term “Endothelial progenitor cell” (EPC) has been used to describe multiple cell populations that express endothelial surface makers and promote vascularisation. However, the only population that has all the characteristics of a real “EPC” is the Endothelial Colony Forming Cells (ECFC). ECFC possess clonal proliferative potential, display endothelial and not myeloid cell surface markers, and exhibit pronounced postnatal vascularisation ability in vivo. ECFC have been used to investigate endothelial molecular dysfunction in several diseases, as they give access to endothelial cells from patients in a non-invasive way. ECFC also represent a promising tool for revascularization of damaged tissue. Here we review the translational applications of ECFC research. We discuss studies which have used ECFC to investigate molecular endothelial abnormalities in several diseases and review the evidence supporting the use of ECFC for autologous cell therapy, gene therapy and tissue regeneration. Finally, we discuss ways to improve the therapeutic efficacy of ECFC in clinical applications, as well as the challenges that must be overcome to use ECFC in clinical trials for regenerative approaches.

Endothelial cell regulation through epigenetic mechanisms: Depicting parallels and its clinical application within an intra-islet microenvironment

The intra-islet endothelial cells (ECs), the building blocks of islet microvasculature, govern a number of cellular and pathophysiological processes associated with the pancreatic tissue. These cells are key to the angiogenic process and essential for islet revascularization after transplantation. Understanding fundamental mechanisms by which ECs regulate the angiogenic process is important as these cells maintain and regulate the intra-islet environment facilitated by a complex signaling crosstalk with the surrounding endocrine cells. In recent years, many studies have demonstrated the impact of epigenetic regulation on islet cell development and function. This review will present an overview of the reports involving endothelial epigenetic mechanisms particularly focusing on histone modifications which have been identified to play a critical role in governing EC functions by modifying the chromatin structure. A better understanding of epigenetic mechanisms by which these cells regulate gene expression and function to orchestrate cellular physiology and pathology is likely to offer improved insights on the functioning and regulation of an intra-islet endothelial microvascular environment.

Mesenchymal Stem Cell-Derived Small Extracellular Vesicles Promote Neuroprotection in Rodent Models of Glaucoma

Purpose

To investigate the benefit of bone marrow mesenchymal stem cell (BMSC)-derived small extracellular vesicles (sEV) as an intravitreal (ivit) therapy in two rat models of glaucoma and to determine and identify candidate miRNA involved in the mechanism.

Methods

sEV were isolated from human BMSC and fibroblasts and ivit injected into adult rats after induction of elevated IOP. IOP was elevated using either intracameral injection of microbeads or laser photocoagulation of circumferential limbal vessels and the trabecular meshwork. Retinal nerve fiber layer (RNFL) thickness was measured using optical coherence tomography, positive scotopic threshold response (pSTR) recorded using ERG, and RNA binding protein with multiple splicing (RBPMS⁺) retinal ganglion cell (RGC) counted using retinal wholemounts. sEV miRNA were sequenced using RNAseq.

Results

sEV isolated from BMSC promoted significant neuroprotection of RGC while preventing RNFL degenerative thinning and loss of pSTR. sEV proved therapeutically efficacious when ivit injected every week or every month, but ineffective with longer delays between treatments. Knockdown of Argonaute2 (AGO2), a protein critical for miRNA function and packing into sEV prior to sEV isolation, significantly attenuated the above effects. Addition of BMSC sEV (but not fibroblast sEV) reduced death of cultured purified RGC. RNAseq identified 43 miRNA upregulated in BMSC sEV in comparison to fibroblast sEV, which yielded no neuroprotective effects.

Conclusions

Injection of BMSC-derived sEV into the vitreous provided significant therapeutic benefit to glaucomatous eyes. The neuroprotective effect of sEV, at least partially, may be explained by direct action on RGC through miRNA-dependent mechanisms.