Extracellular Vesicle-Induced Classical Complement Activation Leads to Retinal Endothelial Cell Damage via MAC Deposition

Circulating small extracellular vesicles mediate vascular hyperpermeability in diabetes

AIMS/HYPOTHESIS

A hallmark chronic complication of type 2 diabetes mellitus is vascular hyperpermeability, which encompasses dysfunction of the cerebrovascular endothelium and the subsequent development of associated cognitive impairment. The present study tested the hypothesis that during type 2 diabetes circulating small extracellular vesicles (sEVs) exhibit phenotypic changes that facilitate pathogenic disruption of the vascular barrier.

METHODS

sEVs isolated from the plasma of a mouse model of type 2 diabetes and from diabetic human individuals were characterised for their ability to disrupt the endothelial cell (EC) barrier. The contents of sEVs and their effect on recipient ECs were assessed by proteomics and identified pathways were functionally interrogated with small molecule inhibitors.

RESULTS

Using intravital imaging, we found that diabetic mice (Leprdb/db) displayed hyperpermeability of the cerebrovasculature. Enhanced vascular leakiness was recapitulated following i.v. injection of sEVs from diabetic mice into non-diabetic recipient mice. Characterisation of circulating sEV populations from the plasma of diabetic mice and humans demonstrated increased quantity and size of sEVs compared with those isolated from non-diabetic counterparts. Functional experiments revealed that sEVs from diabetic mice or humans induced the rapid and sustained disruption of the EC barrier through enhanced paracellular and transcellular leak but did not induce inflammation. Subsequent sEV proteome and recipient EC phospho-proteome analysis suggested that extracellular vesicles (sEVs) from diabetic mice and humans modulate the MAPK/MAPK kinase (MEK) and Rho-associated protein kinase (ROCK) pathways, cell-cell junctions and actin dynamics. This was confirmed experimentally. Treatment of sEVs with proteinase K or pre-treatment of recipient cells with MEK or ROCK inhibitors reduced the hyperpermeability-inducing effects of circulating sEVs in the diabetic state.

CONCLUSIONS/INTERPRETATION

Diabetes is associated with marked increases in the concentration and size of circulating sEVs. The modulation of sEV-associated proteins under diabetic conditions can induce vascular leak through activation of the MEK/ROCK pathway. These data identify a new paradigm by which diabetes can induce hyperpermeability and dysfunction of the cerebrovasculature and may implicate sEVs in the pathogenesis of cognitive decline during type 2 diabetes.

Contribution of extracellular vesicles for the pathogenesis of retinal diseases: shedding light on blood-retinal barrier dysfunction

Retinal degenerative diseases, including diabetic retinopathy (DR) and age-related macular degeneration (AMD), loom as threats to vision, causing detrimental effects on the structure and function of the retina. Central to understanding these diseases, is the compromised state of the blood-retinal barrier (BRB), an effective barrier that regulates the influx of immune and inflammatory components. Whether BRB breakdown initiates retinal distress, or is a consequence of disease progression, remains enigmatic. Nevertheless, it is an indication of retinal dysfunction and potential vision loss.The intricate intercellular dialogues among retinal cell populations remain unintelligible in the complex retinal milieu, under conditions of inflammation and oxidative stress. The retina, a specialized neural tissue, sustains a ceaseless demand for oxygen and nutrients from two vascular networks. The BRB orchestrates the exchange of molecules and fluids within this specialized region, comprising the inner BRB (iBRB) and the outer BRB (oBRB). Extracellular vesicles (EVs) are small membranous structures, and act as messengers facilitating intercellular communication in this milieu.EVs, both from retinal and peripheral immune cells, increase complexity to BRB dysfunction in DR and AMD. Laden with bioactive cargoes, these EVs can modulate the retinal microenvironment, influencing disease progression. Our review delves into the multifaceted role of EVs in retinal degenerative diseases, elucidating the molecular crosstalk they orchestrate, and their microRNA (miRNA) content. By shedding light on these nanoscale messengers, from their biogenesis, release, to interaction and uptake by target cells, we aim to deepen the comprehension of BRB dysfunction and explore their therapeutic potential, therefore increasing our understanding of DR and AMD pathophysiology.

Emerging role of extracellular vesicles in diabetic retinopathy

Diabetic retinopathy (DR), a complex complication of diabetes mellitus (DM), is a leading cause of adult blindness. Hyperglycemia triggers DR, resulting in microvascular damage, glial apoptosis, and neuronal degeneration. Inflammation and oxidative stress play crucial roles during this process. Current clinical treatments for DR primarily target the advanced retinal disorder but offer limited benefits with inevitable side effects. Extracellular vesicles (EVs) exhibit unique morphological features, contents, and biological properties and can be found in cell culture supernatants, various body fluids, and tissues. In DR, EVs with specific cargo composition would induce the reaction of receptor cell once internalized, mediating cellular communication and disease progression. Increasing evidence indicates that monitoring changes in EV quantity and content in DR can aid in disease diagnosis and prognosis. Furthermore, extensive research is investigating the potential of these nanoparticles as effective therapeutic agents in preclinical models of DR. This review explores the current understanding of the pathological effects of EVs in DR development, discusses their potential as biomarkers and therapeutic strategies, and paves the way for further research and therapeutic advancements.

Extracellular vesicles in degenerative retinal diseases: A new therapeutic paradigm

Nanoscale extracellular vesicles (EVs), consisting of exomers, exosomes and microvesicles/ectosomes, have been extensively investigated in the last 20 years, although their biological role is still something of a mystery. EVs are involved in the transfer of lipids, nucleic acids and proteins from donor to recipient cells or distant organs as well as regulating cell-cell communication and signaling. Thus, EVs are important in intercellular communication and this is not limited to sister cells, but may also mediate the crosstalk between different cell types even over long distances. EVs play crucial functions in both cellular homeostasis and the pathogenesis of diseases, and since their contents reflect the status of the donor cell, they represent an additional valuable source of information for characterizing complex biological processes. Recent advances in isolation and analytical methods have led to substantial improvements in both characterizing and engineering EVs, leading to their use either as novel biomarkers for disease diagnosis/prognosis or even as novel therapies. Due to their capacity to carry biomolecules, various EV-based therapeutic applications have been devised for several pathological conditions, including eye diseases. In the eye, EVs have been detected in the retina, aqueous humor, vitreous body and also in tears. Experiences with other forms of intraocular drug applications have opened new ways to use EVs in the treatment of retinal diseases. We here provide a comprehensive summary of the main in vitro, in vivo, and ex vivo literature-based studies on EVs' role in ocular physiological and pathological conditions. We have focused on age-related macular degeneration, diabetic retinopathy, glaucoma, which are common eye diseases leading to permanent blindness, if not treated properly. In addition, the putative use of EVs in retinitis pigmentosa and other retinopathies is discussed. Finally, we have reviewed the potential of EVs as therapeutic tools and/or biomarkers in the above-mentioned retinal disorders. Evidence emerging from experimental disease models and human material strongly suggests future diagnostic and/or therapeutic exploitation of these biological agents in various ocular disorders with a good possibility to improve the patient's quality of life.

Ultrafast and Controlled Capturing, Loading, and Release of Extracellular Vesicles by a Portable Microstructured Electrochemical Fluidic Device

Extracellular vesicles (EVs) are secreted by all living cells and are found in body fluids. They exert numerous physiological and pathological functions and serve as cargo shuttles. Due to their safety and inherent bioactivity, they have emerged as versatile therapeutic agents, biomarkers, and potential drug carriers. Despite the growing interest in EVs, current progress in this field is, in part, limited by relatively inefficient isolation techniques. Conventional methods are indeed slow, laborious, require specialized laboratory equipment, and may result in low yield and purity. This work describes an electrochemically controlled "all-in-one" device enabling capturing, loading, and releasing of EVs. The device is composed of a fluidic channel confined within antibody-coated microstructured electrodes. It rapidly isolates EVs with a high level of purity from various biofluids. As a proof of principle, the device is applied to isolate EVs from skin wounds of healthy and diabetic mice. Strikingly, it is found that EVs from healing wounds of diabetic mice are enriched in mitochondrial proteins compared to those of healthy mice. Additionally, the device improves the loading protocol of EVs with polyplexes, and may therefore find applications in nucleic acid delivery. Overall, the electrochemical device can greatly facilitate the development of EVs-based technologies.

Extracellular vesicles: an emerging player in retinal homeostasis

Extracellular vesicles (EVs) encompass secreted membrane vesicles of varied sizes, including exosomes (-30-200 nm) and microvesicles (MVs) that are ∼100-1,000 nm in size. EVs play an important role in autocrine, paracrine, and endocrine signaling and are implicated in myriad human disorders including prominent retinal degenerative diseases, like age related macular degeneration (AMD) and diabetic retinopathy (DR). Studies of EVs in vitro using transformed cell lines, primary cultures, and more recently, induced pluripotent stem cell derived retinal cell type(s) (e.g., retinal pigment epithelium) have provided insights into the composition and function of EVs in the retina. Furthermore, consistent with a causal role of EVs in retinal degenerative diseases, altering EV composition has promoted pro-retinopathy cellular and molecular events in both in vitro and in vivo models. In this review, we summarize the current understanding of the role of EVs in retinal (patho)physiology. Specifically, we will focus on disease-associated EV alterations in specific retinal diseases. Furthermore, we discuss the potential utility of EVs in diagnostic and therapeutic strategies for targeting retinal diseases.

The Role of Intravesicular Proteins and the Protein Corona of Extracellular Vesicles in the Development of Drug-Induced Polyneuropathy

Extracellular vesicles (EVs) as membrane structures of cellular origin participating in intercellular communication are involved in the molecular mechanisms of the development of various variants of polyneuropathy. Taking into account the increasing role of the protein corona of EVs and protein-protein interactions on the surface of EVs in the pathogenesis of various diseases, we focused our attention in this review on the role of intravesicular proteins and the protein corona of EVs in the development of chemotherapy-induced polyneuropathy (CIPN). It has been shown that EVs are effectively internalized by the mechanisms of endocytosis and macropinocytosis by neurocytes and glial cells, carry markers of insulin resistance, functionally active proteins (receptors, cytokines, enzymes), and may be involved in the pathogenesis of CIPN. The mechanisms of CIPN associated with the EVs protein corona can be related with the accumulation of heavy chains of circulating IgG in it. G-class immunoglobulins in EVs are likely to have myelin hydrolyzing, superoxide dismutase, and oxidoreductase enzymatic activities. Moreover, circulating IgG-loaded EVs are a place for complement activation that can lead to membrane attack complex deposition in neuroglia and neurons. The mechanisms of CIPN development that are not associated with IgG in the EVs protein corona are somehow related to the fact that many anticancer drugs induce apoptosis of tumor cells, neurons, and neuroglial cells by various mechanisms. This process may be accompanied by the secretion of EVs with modified cargo (HSPs, 20S proteasomes, miRNAs).

Salivary Exosomes in Health and Disease: Future Prospects in the Eye

Exosomes are a group of vesicles that package and transport DNA, RNA, proteins, and lipids to recipient cells. They can be derived from blood, saliva, urine, and/or other biological tissues. Their impact on several diseases, such as neurodegenerative, autoimmune, and ocular diseases, have been reported, but not fully unraveled. The exosomes that are derived from saliva are less studied, but offer significant advantages over exosomes from other sources, due to their accessibility and ease of collection. Thus, their role in the pathophysiology of diseases is largely unknown. In the context of ocular diseases, salivary exosomes have been under-utilized, thus creating an enormous gap in the literature. The current review discusses the state of exosomes research on systemic and ocular diseases and highlights the role and potential of salivary exosomes as future ocular therapeutic vehicles.

Extracellular vesicles derived from different sources play various roles in diabetic retinopathy

Extracellular vesicles (EVs) are present in almost all biological fluids and secreted by almost all cell types. A growing number of studies have revealed the potential roles of EVs in the diagnosis and treatment of the diabetic retinopathy (DR). Changes in the quantity and content of EVs may serve as biomarkers of cause or consequence of pathological status of DR, such as inflammation, neovascularization and epithelial-mesenchymal transition. In addition, as natural, safe and efficient drug carrier, EVs have been reported to play important roles in intercellular communication by acting for essential cell-specific information to target cells. In this review, we summarize the roles of EVs, secreted by various types of cells and participated in various biological processes, in the pathogenesis, diagnosis, and treatment of DR.

Effect of plasma-derived extracellular vesicles on angiogenesis and the ensuing proliferative diabetic retinopathy through a miR-30b-dependent mechanism

BACKGROUND/PURPOSE

Proliferative diabetic retinopathy (PDR) is a major diabetic microvascular complication, characterized by pathological angiogenesis. This study sets out to investigate the potential molecular mechanism in the angiogenesis during PDR.

METHODS

The expression of microRNA-30b (miR-30b) was quantified in a streptozotocin (STZ)-induced mouse model of PDR. The binding affinity between SIRT1 and miR-30b was then identified and validated. After transduction with In-miR-30b or combined with sh-SIRT1, high-glucose (HG)-induced retinal microvascular endothelial cells (RMECs) were co-cultured with extracellular vesicles (EVs) derived from the plasma of PDR mice (plasma-EVs). The proliferation and angiogenesis of RMECs were then detected in vitro.

RESULTS

miR-30b expression was upregulated in the retinal tissue of PDR mice. SIRT1 was a target gene of miR-30b and under the negative regulation by miR-30b in RMECs. In contrast, inhibition of miR-30b resulted in elevated SIRT1 expression, thus alleviating the angiogenesis of RMECs. miR-30b was enriched in the plasma-EVs and could be delivered to RMECs, in which miR-30b exerted pro-angiogenic effects. Furthermore, inhibition of miR-30b arrested the progression of PDR in mice by promoting the expression of SIRT1.

CONCLUSION

Collectively, the present study pinpointed the involvement of miR-30b delivered by plasma-EVs in PDR angiogenesis, thus laying the basis for the development of novel therapeutic targets for the treatment of PDR.

Endothelial cell-derived extracellular vesicles impair the angiogenic response of coronary artery endothelial cells

Cardiovascular disease (CVD) is the most prominent cause of death of adults in the United States with coronary artery disease being the most common type of CVD. Following a myocardial event, the coronary endothelium plays an important role in the recovery of the ischemic myocardium. Specifically, endothelial cells (EC) must be able to elicit a robust angiogenic response necessary for tissue revascularization and repair. However, local or distant cues may prevent effective revascularization. Extracellular vesicles (EV) are produced by all cells and endothelium is a rich source of EVs that have access to the main circulation thereby potentially impacting local and distant tissue function. Systemic inflammation associated with conditions such as obesity as well as the acute inflammatory response elicited by a cardiac event can significantly increase the EV release by endothelium and alter their miRNA, protein or lipid cargo. Our laboratory has previously shown that EVs released by adipose tissue endothelial cells exposed to chronic inflammation have angiostatic effects on naïve adipose tissue EC in vitro. Whether the observed effect is specific to EVs from adipose tissue endothelium or is a more general feature of the endothelial EVs exposed to pro-inflammatory cues is currently unclear. The objective of this study was to investigate the angiostatic effects of EVs produced by EC from the coronary artery and adipose microvasculature exposed to pro-inflammatory cytokines (PIC) on naïve coronary artery EC. We have found that EVs from both EC sources have angiostatic effects on the coronary endothelium. EVs produced by cells in a pro-inflammatory environment reduced proliferation and barrier function of EC without impacting cellular senescence. Some of these functional effects could be attributed to the miRNA cargo of EVs. Several miRNAs such as miR-451, let-7, or miR-23a impact on multiple pathways responsible for proliferation, cellular permeability and angiogenesis. Collectively, our data suggests that EVs may compete with pro-angiogenic cues in the ischemic myocardium therefore slowing down the repair response. Acute treatments with inhibitors that prevent endogenous EV release immediately after an ischemic event may contribute to better efficacy of therapeutic approaches using functionalized exogenous EVs or other pro-angiogenic approaches.

Proteomics of Vitreous Humor Reveals PPARA, RXR, and LXR Are Possible Upstream Regulators of Proliferative Diabetic Retinopathy

Purpose: To investigate the key regulators of the disease by comparing the abundance of vitreous proteins between the patients with proliferative diabetic retinopathy (PDR) and the controls with idiopathic epiretinal membrane (iERM).

Methods: Vitreous humor (VH) samples were derived from patients with PDR or iERM through the pars plana vitrectomy. The VH proteins were identified by liquid chromatography tandem mass spectrometry (LC-MS/MS) analysis. MaxQuant software and Metascape were applied to explore the enrichment of differentially expressed proteins in biological processes, cellular components, and molecular functions. Enrichr online tool and Gene Set Enrichment Analysis (GSEA) were performed to detect upstream transcriptional regulators of the highly expressed proteins.

Results: The present study collected 8 vitreous humor samples from 5 PDR eyes and 3 iERM eyes and identified 88 highly expressed proteins in PDR patients. We validated our highly expressed proteome was able to distinguish the PDR patients from the non-PDR patients by using the VH proteomics data from a previous study. The majority of highly expressed proteins were involved in complement and coagulation cascades, regulating exocytosis, and hemostasis. Using the Gene Set Enrichment Analysis (GSEA), we identified that transcription factors (TFs) PPAR-α, RXR, LXR regulate these proteins.

Conclusions: In this study, we identified a highly expressed proteome in VH of PDR patients. The role of the complement and coagulation system, regulating exocytosis, and hemostasis has been of great significance to PDR. Nuclear receptors PPARA, RXR, LXR were possible upstream regulators of disease progression and required further study.

Extracellular vesicle- and particle-mediated communication shapes innate and adaptive immune responses

Intercellular communication among immune cells is vital for the coordination of proper immune responses. Extracellular vesicles and particles (EVPs) act as messengers in intercellular communication, with important consequences for target cell and organ physiology in both health and disease. Under normal physiological conditions, immune cell-derived EVPs participate in immune responses by regulating innate and adaptive immune responses. EVPs play a major role in antigen presentation and immune activation. On the other hand, immune cell-derived EVPs exert immunosuppressive and regulatory effects. Consequently, EVPs may contribute to pathological conditions, such as autoimmune and inflammatory diseases, graft rejection, and cancer progression and metastasis. Here, we provide an overview of the role of EVPs in immune homeostasis and pathophysiology, with a particular focus on their contribution to innate and adaptive immunity and their potential use for immunotherapies.

Emerging Role of Exosomes in Retinal Diseases

Retinal diseases, the leading causes of vison loss and blindness, are associated with complicated pathogeneses such as angiogenesis, inflammation, immune regulation, fibrous proliferation, and neurodegeneration. The retina is a complex tissue, where the various resident cell types communicate between themselves and with cells from the blood and immune systems. Exosomes, which are bilayer membrane vesicles with diameters of 30–150 nm, carry a variety of proteins, lipids, and nucleic acids, and participate in cell-to-cell communication. Recently, the roles of exosomes in pathophysiological process and their therapeutic potential have been emerging. Here, we critically review the roles of exosomes as possible intracellular mediators and discuss the possibility of using exosomes as therapeutic agents in retinal diseases.

Innate Immunity Communicates Using the Language of Extracellular Microvesicles

The innate immunity system and extracellular microvesicles (ExMVs) both emerged early in the evolution of life, which is why its innate immunity cellular arm and its soluble-component arm learned, understood, and adapted to the “language” of ExMVs. This was most likely the first language of cell–cell communication during evolution, which existed before more specific intercellular crosstalk involving specific ligands and receptors emerged. ExMVs are involved in several processes in the body, including immune and coagulation responses, which are part of inflammation. In this review we will briefly highlight what is known about how ExMVs regulate the function of the cellular arm of innate immunity, including macrophages, monocytes, granulocytes, natural killer cells, and dendritic cells, and affect the soluble components of this system, which consists of the complement cascade (ComC) and soluble, circulating, pattern-recognition receptors (collectins, ficolins, and pentaxrins). These effects are direct, due to the fact that ExMVs affect the biological functions of innate immunity cells and may directly interact with soluble components of this system. Moreover, by activating coagulation proteases, ExMVs may also indirectly activate the ComC. In this review, we will use the term “extracellular microvesicles” (ExMVs) to refer to these small, spheroidal blebs of different sizes, which are surrounded by a membrane lipid layer. We will focus on the role of both ExMVs released during cell-surface membrane budding and smaller ExMVs, known as exosomes, which are derived from the budding of the endosomal membrane compartment. Finally, we will provide a brief update on the potential therapeutic applications of ExMVs, with a special emphasis on innate immunity.

Extracellular vesicles: new players in regulating vascular barrier function

Extracellular vesicles (EVs) have attracted rising interests in the cardiovascular field not only because they serve as serological markers for circulatory disorders but also because they participate in important physiological responses to stress and inflammation. In the circulation, these membranous vesicles are mainly derived from blood or vascular cells, and they carry cargos with distinct molecular signatures reflecting the origin and activation state of parent cells that produce them, thus providing a powerful tool for diagnosis and prognosis of pathological conditions. Functionally, circulating EVs mediate tissue-tissue communication by transporting bioactive cargos to local and distant sites, where they directly interact with target cells to alter their function. Recent evidence points to the critical contributions of EVs to the pathogenesis of vascular endothelial barrier dysfunction during inflammatory response to injury or infection. In this review, we provide a brief summary of the current knowledge on EV biology and advanced techniques in EV isolation and characterization. This is followed by a discussion focusing on the role and mechanisms of EVs in regulating blood-endothelium interactions and vascular permeability during inflammation. We conclude with a translational perspective on the diagnostic and therapeutic potential of EVs in vascular injury or infectious diseases, such as COVID-19.

Extracellular Vesicles and MicroRNA: Putative Role in Diagnosis and Treatment of Diabetic Retinopathy

Diabetic retinopathy (DR) is a complex, progressive, and heterogenous retinal degenerative disease associated with diabetes duration. It is characterized by glial, neural, and microvascular dysfunction, being the blood-retinal barrier (BRB) breakdown a hallmark of the early stages. In advanced stages, there is formation of new blood vessels, which are fragile and prone to leaking. This disease, if left untreated, may result in severe vision loss and eventually legal blindness. Although there are some available treatment options for DR, most of them are targeted to the advanced stages of the disease, have some adverse effects, and many patients do not adequately respond to the treatment, which demands further research. Oxidative stress and low-grade inflammation are closely associated processes that play a critical role in the development of DR. Retinal cells communicate with each other or with another one, using cell junctions, adhesion contacts, and secreted soluble factors that can act in neighboring or long-distance cells. Another mechanism of cell communication is via secreted extracellular vesicles (EVs), through exchange of material. Here, we review the current knowledge on deregulation of cell-to-cell communication through EVs, discussing the changes in miRNA expression profiling in body fluids and their role in the development of DR. Thereafter, current and promising therapeutic agents for preventing the progression of DR will be discussed.