Determination of the Procoagulant Activity of Extracellular Vesicle (EV) Using EV-Activated Clotting Time (EV-ACT)

Summary

This protocol investigates the use of extracellular vesicle (EV)-rich plasma as an indicator of the coagulative ability of EV. EV-rich plasma is obtained through a process of differential centrifugation and subsequent recalcification.

Abstract

The role of extracellular vesicles (EV) in various diseases is gaining increased attention, particularly due to their potent procoagulant activity. However, there is an urgent need for a bedside test to assess the procoagulant activity of EV in clinical settings. This study proposes the use of thrombin activation time of EV-rich plasma as a measure of EV's procoagulant activity. Standardized procedures were employed to obtain sodium-citrated whole blood, followed by differential centrifugation to obtain EV-rich plasma. The EV-rich plasma and calcium chloride were added to the test cup, and the changes in viscoelasticity were monitored in real-time using an analyzer. The natural coagulation time of EV-rich plasma, referred to as EV-ACT, was determined. The results revealed a significant increase in EV-ACT when EV was removed from plasma obtained from healthy volunteers, while it significantly decreased when EV was enriched. Furthermore, EV-ACT was considerably shortened in human samples from preeclampsia, hip fracture, and lung cancer, indicating elevated levels of plasma EV and promotion of blood hypercoagulation. With its simple and rapid procedure, EV-ACT shows promise as a bedside test for evaluating coagulation function in patients with high plasma EV levels.

Introduction

Thrombosis, which is caused by hypercoagulability, plays a significant role in various diseases, including brain trauma¹, pre-eclampsia², tumors³, and fracture patients⁴. The mechanism underlying hypercoagulability is complex, and recent emphasis has been placed on the role of extracellular vesicles (EV) in coagulation disorders. EVs are vesicle-like bodies with a bilayer structure that detach from the cell membrane, ranging in diameter from 10 nm to 1000 nm. They are associated with a variety of disease processes, particularly coagulation disorders⁵....

Protocol

The collection of human samples was approved by the Medical Ethics Committee of Tianjin Medical University General Hospital. The collection of human venous blood strictly followed the guideline issued by the National Health Commission of China, namely WS/T 661-2020 Guideline for Collection of Venous Blood Specimens. Briefly, blood was collected from healthy individuals with informed consent from the anterior brachial area vein, and the samples were mixed using 3.2% sodium citrate anticoagulant in a ratio of 1:9. When onl.......

Discussion

In this study, the preparation of EV-rich plasma was described, and the method's rationality was verified using flow cytometry. Subsequently, the recalcified plasma samples were analyzed for ACT time using a clot analyzer based on viscoelasticity principles²⁴. As shown in Figure 3A, the concentration of EVs obtained through ultracentrifugation was found to shorten the EV-ACT time, while the supernatant after ultracentrifugation, which had reduced EV levels, exhibi.......

Materials

Name	Company	Catalog Number	Comments
AccuCount Ultra Rainbow Fluorescent Particles	3.8 microm; Spherotech, Lake Forest, IL, USA		For quantitative detection of MP
Calcium chloride	Werfen (china)	0020006800	20 mM
Century Clot analyzer	Tianjin Century Yikang Medical Technology Development Co., Ltd		The principle is to measure plasma viscosity by viscoelastic method
Disposable probe and test cup	Tianjin Century Yikang Medical Technology Development Co., Ltd
LSR Fortessa flow cytometer	BD, USA		Used to detect MP
Megamix polystyrene beads	Biocytex, Marseille, France	7801	The Megamix consists of a mixture of microbeads of selected diameters: 0.5 µm, 0.9 µm and 3 µm.