Detection and Measurement of Microparticles: An Evolving Research Tool for Vascular Biology

Abstract

Microparticles are small, membrane-bound vesicles that are generated from cells of different origin. It now appears that all circulating blood cells as well as endothelial cells release membranous fragments ~1 mum in size or smaller bearing at least some characteristics of the parent cell. Elevated levels of microparticles have been described in cardiovascular states, thrombotic conditions, and cancer. Various methods of detection for microparticles include flow cytometry, enzyme-linked immunoassays, and functional assays. Flow cytometry has several advantages including its ability to quantitate and identify microparticles of different cellular origin. However, the standardization of preanalytical and analytical variables for enumeration of microparticles remains a significant challenge. Newer approaches are being investigated, and an international collaboration is working on standardization of detection as well as quantitation of microparticles by flow cytometry. Although it has evolved as an important vascular biology research tool, microparticle detection needs further evaluation and refinement before it becomes truly useful as a clinical tool.

Role of extracellular membrane vesicles in the pathogenesis of various diseases, including cancer, renal diseases, atherosclerosis, and arthritis

“…In Trousseau's syndrome, widespread thromboembolism becomes the dominant feature of the patient's cancer-related illness, and often serves as the cause of death. 68 Osteoarthritis Osteoarthritis (OA) is a progressive disease of unknown etiology characterized by degeneration of articular cartilage, particularly in large, weight-bearing joints (namely the knee Bobryshev et al, 18 Chen et al, 15 Demer and Tintut, 22 Giachelli, 21 Hsu and Camacho, 4 Kim, 19 Li et al, 20 Reynolds et al, 17 Shao et al, 23 Tanimura Amabile et al, 29 Bakouboula et al, 27 Chironi et al, 28 Dvorak, 30 Enjeti et al, 33 Satta et al 32 …”

Altered profile of circulating microparticles in rheumatoid arthritis patients

“…Traditionally, MPs had been identified by annexin V-binding in their surface [16], but recent evidence has brought into question this methodology, since annexin V-negative MPs express specific surface markers [17,18] and have been reported to have clinical relevance [19]. Consequently, many authors have chosen different approaches to avoid annexin staining, such as MP total labelling [20] or no labelling [4].…”

Intramicroparticle nitrogen dioxide is a bubble nucleation site leading to decompression-induced neutrophil activation and vascular injury

“…MPs are defined as membrane lipid bilayer-enclosed vesicles with a diameter of 0.1-1.0 m. MPs are present in peripheral blood of healthy individuals, increase with traumatic and inflammatory disorders, and may serve as intercellular messengers because they can contain cytokines or other signaling proteins, mRNA, and microRNA (19). MPs are generated when cells undergo oxidative stress, apoptosis, or cell activation/calcium influx, and they are characterized by surface expression of antigenic markers from parent cells (8,9,14,25). As MPs bud from these cells, negatively charged phosphatidylserine residues are exposed, which often leads to secondary binding of annexin V. MPs can directly stimulate release of proinflammatory cytokines, and platelet-derived MPs stimulate leukocyte activation and aggregation (15,17,21).…”