Lipoprotein-apheresis reduces circulating microparticles in individuals with familial hypercholesterolemia

Lipoprotein apheresis affects the concentration of extracellular vesicles in patients with elevated lipoprotein (a)

Lipoprotein apheresis (LA) is a therapeutic option for hyperlipoproteinemia(a) (hyper-Lp(a)) and atherosclerotic cardiovascular disease (ASCVD). LA improves blood rheology, reduces oxidative stress parameters and improves endothelial function. The underlying molecular mechanisms of LA beneficial effects are unknown, but it has been suggested that LA exhibits multiple activities beyond simply removing lipoproteins. We hypothesized that LA removes not only lipoproteins, but also extracellular vesicles (EVs). To test this hypothesis, we performed a prospective study in 22 patients undergoing LA for hyper-Lp(a) and ASCVD. Different EVs subtypes were measured before and directly after LA, and after 7 days. We used calibrated flow cytometry to detect total particle concentration (diameter >  ~ 100 nm), total lipoproteins concentration (diameter > 200 nm, RI > 1.51), total EV concentration (diameter > 200 nm, RI < 1.41), concentrations of EVs derived from erythrocytes (CD235a+; diameter > 200 nm, RI < 1.41), leukocytes (CD45+; diameter > 200 nm, RI < 1.41) and platelets (CD61+, PEVs; diameter > 200 nm, RI < 1.41). LA reduced the concentrations of all investigated EVs subtypes and lipoproteins. Lp(a) concentration was lowered by 64.5% [(58% - 71%); p < 0.001]. Plasma concentrations of EVs > 200 nm in diameter derived from platelets (CD61 +), leukocytes (CD45+) and erythrocytes (CD235a+) decreased after single LA procedure by 42.7% [(12.8-54.7); p = 0.005], 42.6% [(29.7-54.1); p = 0.030] and 26.7% [(1.0-62.7); p = 0.018], respectively, compared to baseline. All EV subtypes returned to the baseline concentrations in blood plasma after 7 days. To conclude, LA removes not only Lp(a), but also cell-derived EVs, which may contribute to LA beneficial effects.

Small extracellular vesicles from pregnant women with maternal supraphysiological hypercholesterolemia impair endothelial cell function in vitro

Maternal physiological hypercholesterolemia (MPH, maternal total cholesterol (TC) levels at term of pregnancy ≤280 mg/dl) occurs to assure fetal development. Maternal supraphysiological hypercholesterolemia (MSPH, TC levels >280 mg/dl) is a pathological condition associated with maternal, placental, and fetal endothelial dysfunction and early neonatal atherosclerosis development. Small extracellular vesicles (sEVs) are delivered to the extracellular space by different cells, where they modulate cell functions by transporting active signaling molecules, including proteins and miRNA.

AIM

To determine whether sEVs from MSPH women could alter the function of endothelial cells (angiogenesis, endothelial activation and nitric oxide synthesis capacity).

METHODS

This study included 24 Chilean women (12 MPH and 12 MSPH). sEVs were isolated from maternal plasma and characterized by sEV markers (CD9, Alix and HSP70), nanoparticle tracking analysis, transmission electron microscopy, and protein and cholesterol content. The endothelial cell line HMEC-1 was used to determine the uptake of labeled sEVs and the effects of sEVs on cell viability, endothelial tube formation, endothelial cell activation, and endothelial nitric oxide expression and function.

RESULTS

In MSPH women, the plasma concentration of sEVs was increased compared to that in MPH women. MSPH-sEVs were highly taken up by HMEC-1 cells and reduced angiogenic capacity and the expression and activity of eNOS without changing cell viability or endothelial activation.

CONCLUSION

sEVs from MSPH women impair angiogenesis and nitric oxide synthesis in endothelial cells, which could contribute to MSPH-associated endothelial dysfunction.

Understanding the extracellular vesicle surface for clinical molecular biology

Extracellular vesicles (EVs) are lipid-membrane enclosed nanoparticles that play significant roles in health and disease. EVs are abundant in body fluids and carry an array of molecules (proteins, lipids, nucleic acids and glycans) that reflect the identity and activity of their cell-of-origin. While the advent of high throughput omics technologies has allowed in-depth characterisation of EV compositions, how these molecular species are spatially distributed within EV structures is not well appreciated. This is particularly true of the EV surface where a plethora of molecules are reported to be both integral and peripherally associated to the EV membrane. This coronal layer or 'atmosphere' that surrounds the EV membrane contributes to a large, highly interactive and dynamic surface area that is responsible for facilitating EV interactions with the extracellular environment. The EV coronal layer harbours surface molecules that reflect the identity of parent cells, which is likely a highly valuable property in the context of diagnostic liquid biopsies. In this review, we describe the current understanding of the mechanical, electrostatic and molecular properties of the EV surface that offer significant biomarker potential and contribute to a highly dynamic interactome.

Extracellular Vesicles in Atherosclerosis Research

The methodologies described in this chapter inform on how to incorporate extracellular vesicles (EV) in model systems to investigate their role in the initiation and progression of the atherosclerotic plaque. The section will cover application of EV in coagulation and thrombus formation, monocytic migration, and adhesion to endothelial monolayers. These methodologies can be used with EV isolated from any cell type and under any conditions.

Extracellular Vesicles in Diagnosing Chronic Coronary Syndromes the Bumpy Road to Clinical Implementation

Coronary artery disease (CAD), comprising both acute coronary syndromes (ACS) and chronic coronary syndromes (CCS), remains one of the most important killers throughout the entire world. ACS is often quickly diagnosed by either deviation on an electrocardiogram or elevated levels of troponin, but CCS appears to be more complicated. The most used noninvasive strategies to diagnose CCS are coronary computed tomography and perfusion imaging. Although both show reasonable accuracy (80–90%), these modalities are becoming more and more subject of debate due to costs, radiation and increasing inappropriate use in low-risk patients. A reliable, blood-based biomarker is not available for CCS but would be of great clinical importance. Extracellular vesicles (EVs) are lipid-bilayer membrane vesicles containing bioactive contents e.g., proteins, lipids and nucleic acids. EVs are often referred to as the “liquid biopsy” since their contents reflect changes in the condition of the cell they originate from. Although EVs are studied extensively for their role as biomarkers in the cardiovascular field during the last decade, they are still not incorporated into clinical practice in this field. This review provides an overview on EV biomarkers in CCS and discusses the clinical and technological aspects important for successful clinical application of EVs.

Extracellular vesicles in cardiovascular disease

Cardiovascular disease remains the leading cause of morbidity and mortality globally. Extracellular vesicles (EVs), a group of heterogeneous nanosized cell-derived vesicles, have attracted great interest as liquid biopsy material for biomarker discovery in a variety of diseases including cardiovascular disease. Because EVs inherit bioactive components from parent cells and are able to transfer their contents to recipient cells, EVs hold great promise as potential cell-free therapeutics and drug delivery systems. However, the development of EV-based diagnostics, therapeutics or drug delivery systems has been challenging due to the heterogenicity of EVs in biogenesis, size and cellular origin, the lack of standardized isolation and purification methods as well as the low production yield. In this review, we will provide an overview of the recent advances in EV-based biomarker discovery, highlight the potential usefulness of EVs and EV mimetics for therapeutic treatment and drug delivery in cardiovascular disease. In view of the fast development in this field, we will also discuss the challenges of current methodologies for isolation, purification and fabrication of EVs and potential alternatives.

Cross-Talk between Lipoproteins and Inflammation: The Role of Microvesicles

Atherothrombosis is the principal underlying cause of cardiovascular disease (CVD). Microvesicles (MV) are small blebs originated by an outward budding at the cell plasma membranes, which are released in normal conditions. However, MV release is increased in pathophysiologic conditions such as CVD. Low density lipoprotein (LDL) and MV contribute to atherothrombosis onset and progression by promoting inflammation and leukocyte recruitment to injured endothelium, as well as by increasing thrombosis and plaque vulnerability. Moreover, (oxidized)LDL induces MV release and vice-versa, perpetuating endothelium injury leading to CVD progression. Therefore, MV and lipoproteins exhibit common features, which should be considered in the interpretation of their respective roles in the pathophysiology of CVD. Understanding the pathways implicated in this process will aid in developing novel therapeutic approaches against atherothrombosis.

Activation of Lipid Mediator Formation Due to Lipoprotein Apheresis

Lipoprotein apheresis reliably reduces low-density lipoprotein (LDL) cholesterol in patients with atherosclerotic disease and therapy-refractory hypercholesterolemia or elevated lipoprotein (a) (Lp(a)). Besides lowering lipoproteins and triglycerides, apheresis also decreases levels of essential omega-6 and omega-3 polyunsaturated fatty acids (n-6 and n-3 PUFAs) in blood plasma. In contrast, heparin-induced extracorporeal low-density lipoprotein precipitation (HELP) lipid apheresis might increase the formation of potentially pro-inflammatory and pro-thrombotic lipid mediators derived from n-6 and n-3 PUFAs. The study presented here analyzed lipid mediator profiles in the plasma of patients with hyperlipidemia treated by one of three different apheresis methods, either HELP, direct absorption (DA), or membrane filtration (MDF), in a direct pre- and post-apheresis comparison. Using gas chromatography and liquid chromatography tandem mass spectrometry (LC-MS/MS) we were able to analyze fatty acid composition and the formation of lipid mediators called oxylipins. Our data illustrate—particularly in HELP-treated patients—significant decreases of essential omega-6 and omega-3 polyunsaturated fatty acids in blood plasma but significant increases of PUFA-derived lipoxygenase-, as well as cyclooxygenase- and cytochrome P450-derived lipid mediators. Given that n-3 PUFAs in particular are presumed to be cardioprotective and n-3 PUFA-derived lipid mediators might limit inflammatory reactions, these data indicate that n-3 PUFA supplementation in the context of lipid apheresis treatment might have additional benefits through apheresis-triggered protective n-3 PUFA-derived lipid mediators.

Extracellular vesicles: biomarkers and regulators of vascular function during extracorporeal circulation

Extracellular vesicles (EVs) are generated at increased rates from parenchymal and circulating blood cells during exposure of the circulation to abnormal flow conditions and foreign materials associated with extracorporeal circuits (ExCors). This review describes types of EVs produced in different ExCors and extracorporeal life support (ECLS) systems including cardiopulmonary bypass circuits, extracorporeal membrane oxygenation (ECMO), extracorporeal carbon dioxide removal (ECCO₂R), apheresis, dialysis and ventricular assist devices. Roles of EVs not only as biomarkers of adverse events during ExCor/ECLS use, but also as mediators of vascular dysfunction are explored. Manipulation of the number or subtypes of circulating EVs may prove a means of improving vascular function for individuals requiring ExCor/ECLS support. Strategies for therapeutic manipulation of EVs during ExCor/ECLS use are discussed such as accelerating their clearance, preventing their genesis or pharmacologic options to reduce or select which and how many EVs circulate. Strategies to reduce or select for specific types of EVs may prove beneficial in preventing or treating other EV-related diseases such as cancer.

Molecular interactions at the surface of extracellular vesicles

Extracellular vesicles such as exosomes, microvesicles, apoptotic bodies, and large oncosomes have been shown to participate in a wide variety of biological processes and are currently under intense investigation in many different fields of biomedicine. One of the key features of extracellular vesicles is that they have relatively large surface compared to their volume. Some extracellular vesicle surface molecules are shared with those of the plasma membrane of the releasing cell, while other molecules are characteristic for extracellular vesicular surfaces. Besides proteins, lipids, glycans, and nucleic acids are also players of extracellular vesicle surface interactions. Being secreted and present in high number in biological samples, collectively extracellular vesicles represent a uniquely large interactive surface area which can establish contacts both with cells and with molecules in the extracellular microenvironment. Here, we provide a brief overview of known components of the extracellular vesicle surface interactome and highlight some already established roles of the extracellular vesicle surface interactions in different biological processes in health and disease.

The Impact of Vascular Disease Treatment on Platelet-Derived Microvesicles

Platelet-derived microvesicles (pMVs) are small, heterogeneous vesicles released from platelet membranes as a result of activation. These microvesicles possess a wide range of properties, including prothrombotic, proatherogenic, proinflammatory, immunomodulatory, and even anticoagulant activity. The elevated release of these microvesicles has been observed in various metabolic, inflammatory, thrombotic, and vascular diseases, including ischemic heart disease, stroke, hypertension, diabetes, and connective tissue disease. Modulation of both pMV generation and the expression of their surface molecules may have beneficial clinical implications and could become a novel therapeutic target. However, mechanisms by which pharmacological agents can modify pMV formation are elusive. The purpose of this review is to discuss the effects of drugs routinely used in primary and secondary prevention of vascular disease on the release of pMV and expression of their surface procoagulant and proinflammatory molecules.

Routine Screening Method for Microparticles in Platelet Transfusions

Platelet inventory management based on screening microparticle content in platelet concentrates is a new quality improvement initiative for hospital blood banks. Cells fragment off microparticles (MP) when they are stressed. Blood and blood components may contain cellular fragments from a variety of cells, most notably from activated platelets. When performing their roles as innate immune cells and major players in coagulation and hemostasis, platelets change shape and generate microparticles. With dynamic light scattering (DLS)-based microparticle detection, it is possible to differentiate activated (high microparticle) from non-activated (low microparticle) platelets in transfusions, and optimize the use of this scarce blood product. Previous research suggests that providing non-activated platelets for prophylactic use in hematology-oncology patients could reduce their risk of becoming refractory and improve patient care. The goal of this screening method is to routinely differentiate activated from non-activated platelets. The method described here outlines the steps to be performed for routine platelet inventory management in a hospital blood bank: obtaining a sample from a platelet transfusion, loading the sample into the capillary for DLS measurement, performing the DLS test to identify microparticles, and using the reported microparticle content to identify activated platelets.

Lowering Low-Density Lipoprotein Particles in Plasma Using Dextran Sulphate Co-Precipitates Procoagulant Extracellular Vesicles

Plasma extracellular vesicles (EVs) are lipid membrane vesicles involved in several biological processes including coagulation. Both coagulation and lipid metabolism are strongly associated with cardiovascular events. Lowering very-low- and low-density lipoprotein ((V)LDL) particles via dextran sulphate LDL apheresis also removes coagulation proteins. It remains unknown, however, how coagulation proteins are removed in apheresis. We hypothesize that plasma EVs that contain high levels of coagulation proteins are concomitantly removed with (V)LDL particles by dextran sulphate apheresis. For this, we precipitated (V)LDL particles from human plasma with dextran sulphate and analyzed the abundance of coagulation proteins and EVs in the precipitate. Coagulation pathway proteins, as demonstrated by proteomics and a bead-based immunoassay, were over-represented in the (V)LDL precipitate. In this precipitate, both bilayer EVs and monolayer (V)LDL particles were observed by electron microscopy. Separation of EVs from (V)LDL particles using density gradient centrifugation revealed that almost all coagulation proteins were present in the EVs and not in the (V)LDL particles. These EVs also showed a strong procoagulant activity. Our study suggests that dextran sulphate used in LDL apheresis may remove procoagulant EVs concomitantly with (V)LDL particles, leading to a loss of coagulation proteins from the blood.

Tunable resistive pulse sensing: potential applications in nanomedicine

An accurate characterization of nanomaterials used in clinical diagnosis and therapeutics is of paramount importance to realize the full potential of nanotechnology in medicine and to avoid unexpected and potentially harmful toxic effects due to these materials. A number of technical modalities are currently in use to study the physical, chemical and biological properties of nanomaterials but they all have advantages and disadvantages. In this review, we discuss the potential of a relative newcomer, tunable resistive pulse sensing, for the characterization of nanomaterials and its applications in nanodiagnostics.

The significance of platelet microparticles in patients with chronic hepatitis C and their association with antiviral treatment and smoking

Background

Platelet microparticles (PMPs) are platelet-derived membrane vesicles involved in cardiovascular diseases and atherosclerosis. Chronic hepatitis C (CHC) is associated with increased atherosclerosis, but the effect of therapy on its atherogenic potential has not been adequately studied.

Methods

We evaluated PMP levels before and after treatment with pegylated-interferon-alfa and ribavirin in 28 CHC patients compared with 20 non-alcoholic fatty liver disease (NAFLD) patients and 20 healthy volunteers (HV).

Results

Twenty-four (86%) CHC patients achieved sustained virological response (SVR). PMP levels were determined at baseline in CHC, NAFLD patients, and HV, and at end-of-treatment (EOT) and 24 weeks post-treatment (SVR24) in CHC patients. PMP levels at baseline were higher in CHC than NAFLD patients (P<0.001) and HV (P=0.007). Higher PMPs at baseline were observed in smokers than non-smokers with CHC (P=0.006). Among smokers from all groups, PMPs at baseline were higher in CHC than NAFLD patients (P=0.001) and HV (P=0.024). In CHC patients, PMPs declined from baseline to both EOT (P=0.035) and SVR24 (P=0.006). Only CHC patients with SVR had a significant decline in PMPs from baseline to SVR24 (P=0.018). PMPs at ΕΟΤ and SVR24 in all CHC patients were similar to PMPs in NAFLD patients and HV.

Conclusions

PMP levels are increased in CHC patients, particularly smokers, which further supports the atherosclerotic potential of CHC and suggests a potentially synergistic effect of smoking and CHC on the atherosclerotic process. Since PMP levels in CHC patients with SVR were similar to NAFLD patients and HV, the atherosclerotic potential of CHC seems to be abolished by effective antiviral treatment.

Extracellular vesicles as mediators of vascular inflammation in kidney disease

Vascular inflammation is a common cause of renal impairment and a major cause of morbidity and mortality of patients with kidney disease. Current studies consistently show an increase of extracellular vesicles (EVs) in acute vasculitis and in patients with atherosclerosis. Recent research has elucidated mechanisms that mediate vascular wall leukocyte accumulation and differentiation. This review addresses the role of EVs in this process. Part one of this review addresses functional roles of EVs in renal vasculitis. Most published data address anti-neutrophil cytoplasmic antibody (ANCA) associated vasculitis and indicate that the number of EVs, mostly of platelet origin, is increased in active disease. EVs generated from neutrophils by activation by ANCA can contribute to vessel damage. While EVs are also elevated in other types of autoimmune vasculitis with renal involvement such as systemic lupus erythematodes, functional consequences beyond intravascular thrombosis remain to be established. In typical hemolytic uremic syndrome secondary to infection with shiga toxin producing Escherichia coli, EV numbers are elevated and contribute to toxin distribution into the vascular wall. Part two addresses mechanisms how EVs modulate vascular inflammation in atherosclerosis, a process that is aggravated in uremia. Elevated numbers of circulating endothelial EVs were associated with atherosclerotic complications in a number of studies in patients with and without kidney disease. Uremic endothelial EVs are defective in induction of vascular relaxation. Neutrophil adhesion and transmigration and intravascular thrombus formation are critically modulated by EVs, a process that is amenable to therapeutic interventions. EVs can enhance monocyte adhesion to the endothelium and modulate macrophage differentiation and cytokine production with major influence on the local inflammatory milieu in the plaque. They significantly influence lipid phagocytosis and antigen presentation by mononuclear phagocytes. Finally, platelet, erythrocyte and monocyte EVs cooperate in shaping adaptive T cell immunity. Future research is needed to define changes in uremic EVs and their differential effects on inflammatory leukocytes in the vessel wall.

Release and cellular origin of extracellular vesicles during circulation of whole blood over adsorbent polymers for lipid apheresis

Whole blood lipid apheresis is clinically applied in patients with familial hypercholesterolemia to reduce low density lipoprotein and other apolipoprotein B 100 containing lipoproteins. Here, the hemocompatibility of two polyacrylate-coated polyacrylamide-based polymers for lipid apheresis by evaluating the adhesion of blood cells to the adsorbent polymers, their respective activation, as well as the release of microvesicles during circulation of whole blood over the polymers was studied. Characterization of the adsorbents by scanning electron microscopy, atomic force microscopy, and X-ray photoelectron spectroscopy revealed differences with respect to their surface morphology and their surface chemical composition. Despite these differences, equivalent amounts of leukocytes and platelets adhered to both polymers during circulation of whole blood over the adsorbent columns. The release of phosphatidylserine-exposing microvesicles, in contrast, increased significantly with increasing surface roughness and with the amount of polyacrylate groups at the adsorbent surface. The majority of microvesicles generated during blood-material contact were platelet-derived, and their release was associated with enhanced thrombin generation. Microvesicles were present in free and in cell-bound form, and 75% of all monocytes, but only 0.2% and 2.3% of red blood cells and platelets, respectively, were associated with microvesicles, pointing to a role of monocytes in the clearance of released microvesicles. Taken together, microvesicles are sensitive indicators for biomaterial-induced activation of blood cells in apheresis. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 636-646, 2017.

Lipoprotein apheresis: present and future uses

PURPOSE OF REVIEW

For the past 40 years, apheresis, in particular, lipoprotein apheresis, has been the therapy of choice to lower LDL-C for familial hypercholesterolemia patients with uncontrolled dyslipidemia and cardiovascular disease. With the advent of recent and future lipid-modifying agents and their ability to lower LDL-C, the question arises on what will be the future of lipoprotein apheresis.

RECENT FINDINGS

Lipoprotein apheresis lowers not only plasma levels of apolipoprotein B lipoproteins but also markers of vascular inflammation and blood rheology. Other vascular diseases, not necessarily associated with familial hypercholesterolemia, such as nephrotic syndrome and peripheral arterial disease have profited from lipoprotein apheresis therapy. In 2013, the Food and Drug Administration approved lipoprotein apheresis therapy for patients with focal segmental glomerulosclerosis. Since 2010, the German healthcare ministry has approved lipoprotein apheresis therapy for patients with an elevated lipoprotein(a) and ongoing cardiovascular disease irrespective of LDL-C levels.

SUMMARY

Recent and future lipid-modifying therapies will most likely reduce the practice of lipoprotein apheresis therapy for familial hypercholesterolemia patients. Future implications for lipoprotein apheresis will involve vascular diseases that are at present lacking clinically effective therapy, whereas acute and chronic reductions of lipids, vascular inflammation, and/or rheology may improve the clinical outcome.

Characterisation of adipocyte-derived extracellular vesicles released pre- and post-adipogenesis

Extracellular vesicles (EVs) are submicron vesicles released from many cell types, including adipocytes. EVs are implicated in the pathogenesis of obesity-driven cardiovascular disease, although the characteristics of adipocyte-derived EVs are not well described. We sought to define the characteristics of adipocyte-derived EVs before and after adipogenesis, hypothesising that adipogenesis would affect EV structure, molecular composition and function. Using 3T3-L1 cells, EVs were harvested at day 0 and day 15 of differentiation. EV and cell preparations were visualised by electron microscopy and EVs quantified by nanoparticle tracking analysis (NTA). EVs were then assessed for annexin V positivity using flow cytometry; lipid and phospholipid composition using 2D thin layer chromatography and gas chromatography; and vesicular protein content by an immuno-phenotyping assay. Pre-adipogenic cells are connected via a network of protrusions and EVs at both time points display classic EV morphology. EV concentration is elevated prior to adipogenesis, particularly in exosomes and small microvesicles. Parent cells contain higher proportions of phosphatidylserine (PS) and show higher annexin V binding. Both cells and EVs contain an increased proportion of arachidonic acid at day 0. PREF-1 was increased at day 0 whilst adiponectin was higher at day 15 indicating EV protein content reflects the stage of adipogenesis of the cell. Our data suggest that EV production is higher in cells before adipogenesis, particularly in vesicles <300 nm. Cells at this time point possess a greater proportion of PS (required for EV generation) whilst corresponding EVs are enriched in signalling fatty acids, such as arachidonic acid, and markers of adipogenesis, such as PREF-1 and PPARγ.

Applications of tunable resistive pulse sensing

This Review focusses on the recent surge in applied research using tunable resistive pulse sensing, a technique used to analyse submicron colloids in aqueous solutions on a particle-by-particle basis.