Extracellular Vesicles in Metabolic and Vascular Insulin Resistance.

BACKGROUND: Insulin resistance is a major etiological factor in obesity, type 2 diabetes, and cardiovascular disease (CVD). Endothelial dysfunction may precede impairments in insulin-stimulated glucose uptake, thereby making it a key feature in development of CVD. However, the mechanism by which vascular tissue becomes dysfunctional is not clear. SUMMARY: Extracellular vesicles (EVs) have emerged as potential mediators of insulin resistance and vascular dysfunction. EVs are membrane-bound particles released by tissues following cellular stress or activation. They carry "cargo" (e.g., insulin signaling proteins, eNOS-nitric oxide, and miRNA) that are believed to promote inter-cellular and interorgan communications. Herein, we review the underlying physiology of EVs in relation to type 2 diabetes and CVD risk. Specifically, we discuss how EVs may modulate metabolic (e.g., skeletal muscle, liver, and adipose) insulin sensitivity, and propose that EVs may modulate vascular insulin action to influence both endothelial function and arterial stiffness. We lastly identify how EVs may play a unique role following exercise to promote metabolic and vascular insulin sensitivity changes. KEY MESSAGE: Gaining insight toward insulin-mediated EV mechanism has potential to identify novel pathways regulating cardiometabolic health and provide foundation for examining EVs as unique biomarkers and targets to prevent and/or treat chronic diseases.

Acute exercise decreases insulin-stimulated extracellular vesicles in conjunction with augmentation index in adults with obesity.

Extracellular vesicles (EVs) are often elevated in obesity and may modulate disease risk. Although acute exercise reduces fasting EVs in adults with obesity, no data exist on insulin-mediated EV responses. This study evaluated the effects of exercise on EV responses to insulin in relation to vascular function. Ten (5M/5F) sedentary adults with obesity (34.3 ± 3.7 kg/m2 ) completed an evening control and acute exercise condition (70% V ̇ O 2 max ${\dot{V}_{{{\rm{O}}_{\rm{2}}}{\rm{max}}}}$ to expend 400 kcal). Following an overnight fast, participants underwent a 2 h euglycaemic-hyperinsulinaemic clamp (90 mg/dl; 40 mU/m2 /min) to determine metabolic insulin sensitivity (M-value), phenotypes of medium- to large-sized EVs, and aortic waveform measures. Endothelial (CD105+ , CD41- /CD31+ )-, leukocyte (CD45+ )-, platelet (CD41+ , CD41+ /31+ )- and tetraspanin (TX+ )-derived EVs, as well as platelet endothelial cell adhesion molecule (CD31+ ), were determined before and after the clamp using high resolution spectral flow cytometry. Although exercise did not alter fasting haemodynamics, it lowered the augmentation index (AIx75, P = 0.024) and increased the M-value (P = 0.042). Further, exercise decreased all fasting EVs (P < 0.01) and decreased insulin-stimulated TX+ (P = 0.060), CD31+ (P = 0.060) and CD41- /31+ (P = 0.045) compared to rest. Interestingly, greater insulin-stimulated decreases in CD41- /31+ were associated with reduced AIx75 during the clamp (r = 0.62, P = 0.059), while insulin-stimulated decreases in CD41+ (r = -0.68, P = 0.031), CD41+ /31+ (r = -0.69, P = 0.262), TX+ (r = -0.66, P = 0.037) and CD31+ (r = -0.69, P = 0.028) correlated with M-value following exercise. Thus, acute exercise may decrease fasting and insulin-stimulated medium- to large-size EVs in conjunction with improved M-value and AIx75. More research is needed to understand effects of exercise on EVs in the regulation of glucose homeostasis and vascular function. KEY POINTS: Extracellular vesicles (EVs) are increased in states of obesity and may play a role in altered insulin sensitivity and blood pressure; aerobic exercise decreases fasting EV concentrations the following day in adults with obesity. This study directly tested the effects of insulin on EVs and how a single bout of exercise impacts these responses. Together, these data highlight the positive effects of a single bout of exercise on fasting and insulin-stimulated EVs, with the latter relating to increased insulin sensitivity and decreased augmentation index. These results support future research identifying EVs as mechanistic factors in glucose regulation and vascular function as well as clinical use of exercise to reduce cardiovascular disease risk.

Tracking Biomarker Responses to Exercise in Hypertension.

PURPOSE OF REVIEW: Strong evidence is evolving that physical exercise prevents hypertension and reduces blood pressure in patients with pre- and manifest HTN. Yet, identifying and confirming the effectiveness of exercise are challenging. Herein, we discuss conventional and novel biomarkers such as extracellular vesicles (EVs) which may track responses to HTN before and after exercise. RECENT FINDINGS: Evolving data shows that improved aerobic fitness and vascular function as well as lowered oxidative stress, inflammation, and gluco-lipid toxicity are leading biomarkers considered to promote HTN, but they explain only about a half of the pathophysiology. Novel biomarkers such as EVs or microRNA are providing additional input to understand the complex mechanisms involved in exercise therapy for HTN patients. Conventional and novel biomarkers are needed to fully understand the integrative "cross-talk" between tissues to regulate vasculature physiology for blood pressure control. These biomarker studies will lead to more specific disease markers and the development of even more personalized therapy in this field. However, more systematic approaches and randomized controlled trials in larger cohorts are needed to assess exercise effectiveness across the day and with different exercise types.

Insulin infusion decreases medium-sized extracellular vesicles in adults with metabolic syndrome.

Elevated extracellular vesicles (EVs) are associated with glucose dysmetabolism. However, the effects of insulin on EVs and subsequent relationships with insulin sensitivity, substrate oxidation, and inflammation are unknown. We tested the hypothesis that insulin would lower EVs and relate to insulin action. Fifty-one sedentary adults (54.8 ± 1.0 yr; V̇o2peak : 22.1 ± 0.6 mL/kg/min) with metabolic syndrome (MetS) and obesity (36.4 ± 0.65 kg/m2) underwent a 2-h euglycemic-hyperinsulinemic clamp (5 mmol/L; 40 mU/m2/min). Count and size (medium: 200-624 nm; larger: 625-1,000 nm) for total particle count, endothelial- (CD105+), leukocyte- (CD45+), platelet- (CD41+), and tetraspanin- (TX+: CD9/CD81/CD63), as well as platelet endothelial cell adhesion molecule- (CD31+) derived EVs were determined before and following the clamp using Full Spectrum Profiling (FSPM). Size and MESF (molecules of equivalent soluble fluorochrome) data were generated using FCMPASS Software. Fat and carbohydrate oxidation, in addition to high-sensitivity c-reactive protein (hsCRP), were measured to understand insulin effects and associations between EVs, metabolic flexibility, and inflammation. Despite low metabolic insulin sensitivity (M-Value = 2.56 ± 0.17 mg/kg/min), insulin increased carbohydrate (P = 0.015) and decreased fat oxidation (P = 0.048) and hsCRP (P = 0.016) compared with fasting. Insulin also decreased total particle count (P < 0.001), attributable to decreased medium-sized CD105+ (P = 0.052) and CD45+ EVs (P < 0.001). Elevated fasting insulin was associated with reduced insulin-stimulated changes in all EVs phenotypes (P < 0.001). Interestingly, fasting EVs were associated with increased fasting carbohydrate oxidation (all P < 0.05). These findings suggest that insulin decreases medium-sized EVs in conjunction with metabolic flexibility under euglycemic conditions in adults with MetS. More research is needed to determine how therapies alter EV phenotype/size and consequent cardiometabolic risk.NEW & NOTEWORTHY This study is one of the first to investigate the effects of insulin on medium and larger extracellular vesicles (EVs) in relation to metabolic insulin sensitivity and fuel use in adults with metabolic syndrome. Our data suggest that insulin infusion decreases the concentration of total particle counts, mainly due to reductions in medium-sized EVs. Furthermore, EVs, predominantly medium-sized, are inversely associated with metabolic flexibility.

Macrophages redirect phagocytosis by non-professional phagocytes and influence inflammation.

Professional phagocytes (such as macrophages) and non-professional phagocytes (such as epithelial cells) clear billions of apoptotic cells and particles on a daily basis. Although professional and non-professional macrophages reside in proximity in most tissues, whether they communicate with each other during cell clearance, and how this might affect inflammation, is not known. Here we show that macrophages, through the release of a soluble growth factor and microvesicles, alter the type of particles engulfed by non-professional phagocytes and influence their inflammatory response. During phagocytosis of apoptotic cells or in response to inflammation-associated cytokines, macrophages released insulin-like growth factor 1 (IGF-1). The binding of IGF-1 to its receptor on non-professional phagocytes redirected their phagocytosis, such that uptake of larger apoptotic cells was reduced whereas engulfment of microvesicles was increased. IGF-1 did not alter engulfment by macrophages. Macrophages also released microvesicles, whose uptake by epithelial cells was enhanced by IGF-1 and led to decreased inflammatory responses by epithelial cells. Consistent with these observations, deletion of IGF-1 receptor in airway epithelial cells led to exacerbated lung inflammation after allergen exposure. These genetic and functional studies reveal that IGF-1- and microvesicle-dependent communication between macrophages and epithelial cells can critically influence the magnitude of tissue inflammation in vivo.

T cell-derived extracellular vesicles are elevated in essential HTN.

Extracellular vesicles (EVs) are novel mediators of cell-to-cell communication and appear to mediate the pathogenesis of hypertension (HTN). However, the mechanisms underlying the involvement of EVs in HTN remain unclear. The adaptive and innate immune systems play an important role affecting the kidney and vasculature in animal models of HTN. Evolving evidence shows that immune cell-derived EVs can modulate the immune system in a paracrine fashion and therefore may mediate the effects of inflammation in the pathogenesis of HTN. Therefore, we aimed to understand if specific subtypes of leukocyte/immune cell-derived EVs are altered in essential HTN using an in vivo model of angiotensin II (ANG II)-induced HTN. After 4 wk of ANG II treatment, EVs were isolated from the blood and kidney. EV origin and counts were characterized with Imaging Flow Cytometry, antibody panels targeting platelets, endothelial cells, and leukocytes including B and T cells, monocytes, and neutrophils. Leukocyte-derived EVs (CD45+) were elevated in the circulation and kidney tissue in ANG II-induced HTN. Subgroup analysis depicted T cell-derived EVs (CD3+) to be significantly elevated in ANG II-induced HTN (3.50e+5 particles/mL) compared with control groups (9.16e+4 particles/mL, P = 0.0106). T cell-derived EVs also significantly correlated with systolic blood pressure levels (r2 = 0.898, P = 0.0012). In summary, leukocyte-derived EVs, and more specifically T cell-derived EVs (CD3+), are elevated in ANG II-induced HTN in the circulation and kidney tissue and correlate well with blood pressure severity. EVs from the circulation and kidney may be sensitive biomarkers for HTN and end-organ damage and may lead to new mechanistic insights in this silent disease.

Extracellular Vesicles in Essential Hypertension: Hidden Messengers.

PURPOSE OF REVIEW: Hypertension affects about half of all Americans, yet in the vast majority of cases, the factors causing the hypertension cannot be clearly delineated. Developing a more precise understanding of the molecular pathogenesis of HTN and its various phenotypes is therefore a pressing priority. Circulating and urinary extracellular vesicles (EVs) are potential novel candidates as biomarkers and bioactivators in HTN. EVs are a heterogeneous population of small membrane fragments shed from various cell types into various body fluids. As EVs carry protein, RNA, and lipids, they also play a role as effectors and novel cell-to-cell communicators. In this review, we discuss the diagnostic, functional, and regenerative role of EVs in essential HTN and focus on EV protein and RNA cargo as the most extensively studied EV cargo. RECENT FINDINGS: The field of EVs in HTN is still a young one and earlier studies have not used the novel EV detection tools currently available. More rigor and transparency in EV research are needed. Current data suggest that EVs represent potential novel biomarkers in HTN. EVs correlate with HTN severity and possibly end-organ damage. However, it has yet to be discerned which specific subtype(s) of EV reflects best HTN pathophysiology. Evolving studies are also showing that EVs might be novel regulators in vascular and renal tubular function and also be therapeutic. RNA in EVs has been studied in the context of hypertension, largely in the form of studies of miRNA, which are reviewed herein. Beyond miRNAs, mRNA in urinary EVs changed in response to sodium loading in humans. EVs represent promising novel biomarkers and bioactivators in essential HTN. Novel tools are being developed to apply more rigor in EV research including more in vivo models and translation to humans.

Extracellular vesicles as a novel diagnostic and research tool for patients with HTN and kidney disease.

Hypertension (HTN) affects one in three adults in the United States and is a major risk factor for cardiovascular disease and kidney failure. There is emerging evidence that more intense blood pressure lowering reduces mortality in patients with kidney disease who are at risk of cardiovascular disease and progression to end-stage renal disease. However, the ideal blood pressure threshold for patients with kidney disease remains a question of debate. Novel tools to more precisely diagnose HTN, tailor treatment, and predict the risk of end-organ damage such as kidney disease are needed. Analysis of circulating and urinary extracellular vesicles (EVs) and their cargo (protein and RNA) has the potential to identify novel noninvasive biomarkers that can also reflect a specific pathological mechanism of different HTN phenotypes. We will discuss the use of extracellular vesicles as markers of HTN severity and explain their profile change with antihypertensive medicine and potential to detect early end-organ damage. However, more studies with enhanced rigor in this field are needed to define the blood pressure threshold to prevent or delay kidney disease progression and decrease cardiovascular risk.

Extracellular Vesicles in Renal Diseases: More than Novel Biomarkers?

Extracellular vesicles from the urine and circulation have gained significant interest as potential diagnostic biomarkers in renal diseases. Urinary extracellular vesicles contain proteins from all sections of the nephron, whereas most studied circulating extracellular vesicles are derived from platelets, immune cells, and the endothelium. In addition to their diagnostic role as markers of kidney and vascular damage, extracellular vesicles may have functional significance in renal health and disease by facilitating communication between cells and protecting against kidney injury and bacterial infection in the urinary tract. However, the current understanding of extracellular vesicles has derived mostly from studies with very small numbers of patients or in vitro data. Moreover, accurate assessment of these vesicles remains a challenge, in part because of a lack of consensus in the methodologies to measure extracellular vesicles and the inability of most techniques to capture the entire size range of these vesicles. However, newer techniques and standardized protocols to improve the detection of extracellular vesicles are in development. A clearer understanding of the composition and biology of extracellular vesicles will provide insights into their pathophysiologic, diagnostic, and therapeutic roles.

Analytical challenges of extracellular vesicle detection: A comparison of different techniques.

The interest in extracellular vesicles (EVs) has grown exponentially over the last decade. Evolving evidence is demonstrating that these EVs are playing an important role in health and disease. They are involved in intercellular communication and have been shown to transfer proteins, lipids, and nucleic acids. This review focuses on the most commonly used techniques for detection of EVs, to include microparticles, 100-1,000 nm in size, and exosomes, 50-100 nm in size. Conventional flow cytometry is the most prevalent technique, but nanoparticle tracking analysis (NTA), dynamic light scattering (DLS), and resistive pulse sensing have also been used to detect EVs. The accurate measurement of these vesicles is challenged by size heterogeneity, low refractive index, and the lack of dynamic measurement range for most of the available technologies. Sample handling during the preanalytical phase can also affect the accuracy of measurements. Currently, there is not one single method which allows phenotyping, sizing, and enumerating the whole range of EVs and, therefore, providing all the necessary information to truly understand the biology of these particles. A combination of methods is probably needed which might also include electron and atomic force microscopy and full RNA, lipid, and protein profiling.

Imaging flow cytometry elucidates limitations of microparticle analysis by conventional flow cytometry.

Microparticles (MPs) are submicron vesicles released from cell membranes in response to activation, cell injury, or apoptosis. The clinical importance of MPs has become increasingly recognized, although no standardized method exists for their measurement. Flow cytometry (FCM) is the most commonly used technique, however, because of the small size of MPs, and the limitations of current FCM instrumentation, accurate identification is compromised by this methodology. We decided to investigate whether the use of FCM combined with imaging, such as is possible with the ImagestreamX imaging FC (ISX), would be a more sensitive approach to characterizing MPs. Combining FCM with imaging eliminates some of the limitations demonstrated by conventional FCM, whereas also providing morphological confirmation and the ability to distinguish true single events from aggregates and cell debris. The detection limit of standard nonspecialized FCM is suboptimal when compared to ISX. Evaluating MPs below 0.200 µm and sizing remain a challenge as some MPs remain below the detection limit of ISX. Standardized calibrators, that more closely reflect the physical characteristics of MPs, need further development.

B cells secrete functional antigen-specific IgG antibodies on extracellular vesicles.

B cells and the antibodies they produce are critical in host defense against pathogens and contribute to various immune-mediated diseases. B cells responding to activating signals in vitro release extracellular vesicles (EV) that carry surface antibodies, yet B cell production of EVs that express antibodies and their function in vivo is incompletely understood. Using transgenic mice expressing the Cre recombinase in B cells switching to IgG1 to induce expression of fusion proteins between emerald green fluorescent protein (emGFP) and the EV tetraspanin CD63 as a model, we identify emGFP expression in B cells responding to foreign antigen in vivo and characterize the emGFP+ EVs they release. Our data suggests that emGFP+ germinal center B cells undergoing immunoglobulin class switching to express IgG and their progeny memory B cells and plasma cells, also emGFP+, are sources of circulating antigen-specific IgG+ EVs. Furthermore, using a mouse model of influenza virus infection, we find that IgG+ EVs specific for the influenza hemagglutinin antigen protect against virus infection. In addition, crossing the B cell Cre driver EV reporter mice onto the Nba2 lupus-prone strain revealed increased circulating emGFP+ EVs that expressed surface IgG against nuclear antigens linked to autoimmunity. These data identify EVs loaded with antibodies as a novel route for antibody secretion in B cells that contribute to adaptive immune responses, with important implications for different functions of IgG+ EVs in infection and autoimmunity.

Minimal information for studies of extracellular vesicles (MISEV2023): From basic to advanced approaches.

Extracellular vesicles (EVs), through their complex cargo, can reflect the state of their cell of origin and change the functions and phenotypes of other cells. These features indicate strong biomarker and therapeutic potential and have generated broad interest, as evidenced by the steady year-on-year increase in the numbers of scientific publications about EVs. Important advances have been made in EV metrology and in understanding and applying EV biology. However, hurdles remain to realising the potential of EVs in domains ranging from basic biology to clinical applications due to challenges in EV nomenclature, separation from non-vesicular extracellular particles, characterisation and functional studies. To address the challenges and opportunities in this rapidly evolving field, the International Society for Extracellular Vesicles (ISEV) updates its 'Minimal Information for Studies of Extracellular Vesicles', which was first published in 2014 and then in 2018 as MISEV2014 and MISEV2018, respectively. The goal of the current document, MISEV2023, is to provide researchers with an updated snapshot of available approaches and their advantages and limitations for production, separation and characterisation of EVs from multiple sources, including cell culture, body fluids and solid tissues. In addition to presenting the latest state of the art in basic principles of EV research, this document also covers advanced techniques and approaches that are currently expanding the boundaries of the field. MISEV2023 also includes new sections on EV release and uptake and a brief discussion of in vivo approaches to study EVs. Compiling feedback from ISEV expert task forces and more than 1000 researchers, this document conveys the current state of EV research to facilitate robust scientific discoveries and move the field forward even more rapidly.

Extracellular Vesicles in Acute Kidney Injury.

Extracellular vesicles (EVs) are promising novel cellular communicators and biomarkers in acute kidney injury (AKI). These submicron vesicles derive from all cell types along the urinary tract and reflect molecular processes of their parent cells and physiological and pathological conditions in AKI. Several EV protein and RNA biomarker candidates have been identified. They have shown to differentiate AKI etiology and pinpoint to disease mechanisms. In fact, EV research has opened up a new frontier of biomarker discovery since some less abundant biomarkers are concentrated in EVs, which makes them more easily detectable. EVs are also functional and are involved in intra-nephron communication. Tubular-interstitial communication is current focus in EV research in AKI as it can help to understand maladaptive processes in AKI. EVs are also promising therapeutic tools and have been shown to be regenerative in many different models of AKI. Rigorous studies are needed to validate these findings, and more sensitive EV detection and characterization tools need to be developed to dissect EV biology in renal disease and AKI.

Extracellular Vesicles in Kidney Diseases: Moving Forward.

Extracellular vesicles (EVs) are evolving as novel cell mediators, biomarkers, and therapeutic targets in kidney health and disease. They are naturally derived from cells both within and outside the kidney and carry cargo which mirrors the state of the parent cell. Thus, they are potentially more sensitive and disease-specific as biomarkers and messengers in various kidney diseases. Beside their role as novel communicators within the nephron, they likely communicate between different organs affected by various kidney diseases. Study of urinary EVs (uEVs) can help to fill current knowledge gaps in kidney diseases. However, separation and characterization are challenged by their heterogeneity in size, shape, and cargo. Fortunately, more sensitive and direct EV measuring tools are in development. Many clinical syndromes in nephrology from acute to chronic kidney and glomerular to tubular diseases have been studied. Yet, validation of biomarkers in larger cohorts is warranted and simpler tools are needed. Translation from in vitro to in vivo studies is also urgently needed. The therapeutic role of uEVs in kidney diseases has been studied extensively in rodent models of AKI. On the basis of the current exponential growth of EV research, the field of EV diagnostics and therapeutics is moving forward.

Extracellular vesicles and insulin-mediated vascular function in metabolic syndrome.

Metabolic Syndrome (MetS) raises cardiovascular disease risk. Extracellular vesicles (EVs) have emerged as important mediators of insulin sensitivity, although few studies on vascular function exist in humans. We determined the effect of insulin on EVs in relation to vascular function. Adults with MetS (n = 51, n = 9 M, 54.8 ± 1.0 years, 36.4 ± 0.7 kg/m2 , ATPIII: 3.5 ± 0.1 a.u., VO2 max: 22.1 ± 0.6 ml/kg/min) were enrolled in this cross-sectional study. Peripheral insulin sensitivity (M-value) was determined during a euglycemic clamp (40 mU/m2 /min, 90 mg/dl), and blood was collected for EVs (CD105+, CD45+, CD41+, TX+, and CD31+; spectral flow cytometry), inflammation, insulin, and substrates. Central hemodynamics (applanation tonometry) was determined at 0 and 120 min via aortic waveforms. Pressure myography was used to assess insulin-induced arterial vasodilation from mouse 3rd order mesenteric arteries (100-200 µm in diameter) at 0.2, 2 and 20 nM of insulin with EVs from healthy and MetS adults. Adults with MetS had low peripheral insulin sensitivity (2.6 ± 0.2 mg/kg/min) and high HOMA-IR (4.7 ± 0.4 a.u.) plus Adipose-IR (13.0 ± 1.3 a.u.). Insulin decreased total/particle counts (p < 0.001), CD45+ EVs (p = 0.002), AIx75 (p = 0.005) and Pb (p = 0.04), FFA (p < 0.001), total adiponectin (p = 0.006), ICAM (p = 0.002), and VCAM (p = 0.03). Higher M-value related to lower fasted total EVs (r = -0.40, p = 0.004) while higher Adipose-IR associated with higher fasted EVs (r = 0.42, p = 0.004) independent of VAT. Fasting CD105+ and CD45+ derived total EVs correlated with fasting AIx75 (r = 0.29, p < 0.05) and Pb (r = 0.30, p < 0.05). EVs from MetS participants blunted insulin-induced vasodilation in mesenteric arteries compared with increases from healthy controls across insulin doses (all p < 0.005). These data highlight EVs as potentially novel mediators of vascular insulin sensitivity and disease risk.

Extracellular Vesicles and Their Emerging Roles as Cellular Messengers in Endocrinology: An Endocrine Society Scientific Statement.

During the last decade, there has been great interest in elucidating the biological role of extracellular vesicles (EVs), particularly, their hormone-like role in cell-to-cell communication. The field of endocrinology is uniquely placed to provide insight into the functions of EVs, which are secreted from all cells into biological fluids and carry endocrine signals to engage in paracellular and distal interactions. EVs are a heterogeneous population of membrane-bound vesicles of varying size, content, and bioactivity. EVs are specifically packaged with signaling molecules, including lipids, proteins, and nucleic acids, and are released via exocytosis into biofluid compartments. EVs regulate the activity of both proximal and distal target cells, including translational activity, metabolism, growth, and development. As such, EVs signaling represents an integral pathway mediating intercellular communication. Moreover, as the content of EVs is cell-type specific, it is a "fingerprint" of the releasing cell and its metabolic status. Recently, changes in the profile of EV and bioactivity have been described in several endocrine-related conditions including diabetes, obesity, cardiovascular diseases, and cancer. The goal of this statement is to highlight relevant aspects of EV research and their potential role in the field of endocrinology.

In sickness and in health: The functional role of extracellular vesicles in physiology and pathology in vivo: Part I: Health and Normal Physiology: Part I: Health and Normal Physiology.

Previously thought to be nothing more than cellular debris, extracellular vesicles (EVs) are now known to mediate physiological and pathological functions throughout the body. We now understand more about their capacity to transfer nucleic acids and proteins between distant organs, the interaction of their surface proteins with target cells, and the role of vesicle-bound lipids in health and disease. To date, most observations have been made in reductionist cell culture systems, or as snapshots from patient cohorts. The heterogenous population of vesicles produced in vivo likely act in concert to mediate both beneficial and detrimental effects. EVs play crucial roles in both the pathogenesis of diseases, from cancer to neurodegenerative disease, as well as in the maintenance of system and organ homeostasis. This two-part review draws on the expertise of researchers working in the field of EV biology and aims to cover the functional role of EVs in physiology and pathology. Part I will outline the role of EVs in normal physiology.

In sickness and in health: The functional role of extracellular vesicles in physiology and pathology in vivo: Part II: Pathology: Part II: Pathology.

It is clear from Part I of this series that extracellular vesicles (EVs) play a critical role in maintaining the homeostasis of most, if not all, normal physiological systems. However, the majority of our knowledge about EV signalling has come from studying them in disease. Indeed, EVs have consistently been associated with propagating disease pathophysiology. The analysis of EVs in biofluids, obtained in the clinic, has been an essential of the work to improve our understanding of their role in disease. However, to interfere with EV signalling for therapeutic gain, a more fundamental understanding of the mechanisms by which they contribute to pathogenic processes is required. Only by discovering how the EV populations in different biofluids change-size, number, and physicochemical composition-in clinical samples, may we then begin to unravel their functional roles in translational models in vitro and in vivo, which can then feedback to the clinic. In Part II of this review series, the functional role of EVs in pathology and disease will be discussed, with a focus on in vivo evidence and their potential to be used as both biomarkers and points of therapeutic intervention.