Microparticles: biomarkers and beyond

Abstract

Membrane microparticles are submicron fragments of membrane shed into extracellular space from cells under conditions of stress/injury. They may be distinguished from other classes of extracellular vesicles (i.e. exosomes) on the basis of size, content and mechanism of formation. Microparticles are found in plasma and other biological fluids from healthy individuals and their levels are altered in various diseases, including diabetes, chronic kidney disease, pre-eclampsia and hypertension among others. Accordingly, they have been considered biomarkers of vascular injury and pro-thrombotic or pro-inflammatory conditions. In addition to this, emerging evidence suggests that microparticles are not simply a consequence of disease, but that they themselves may contribute to pathological processes. Thus microparticles appear to serve as both markers and mediators of pathology. The present review examines the evidence for microparticles as both biomarkers of, and contributors to, the progression of disease. Approaches for the detection of microparticles are summarized and novel concepts relating to the formation of microparticles and their biological effects are examined.

Extracellular Vesicles in Renal Diseases

“…1 Cytoskeletal reorganizations and alterations in the phospholipid symmetry are likely important parts of the blebbing process, which may differ among cells. 28,29 Under normal conditions, aminophospholipids are found solely on the inner part of the plasma membrane.…”

“…10 In contrast, microparticles (MPs), ranging from 100 to 1000 nm, are thought to be the product of exocytic budding (Figure 1). 1 The term EVs in this review is used for both vesicle types. Unfortunately, there is currently no consensus regarding the nomenclature of secreted membraneenclosed vesicles.…”

“…3,4 EVs were initially thought as artifacts or cell dust, 5 but there is accumulating evidence for their important role as messengers for cell signaling and communication in normal and disease states. 1,2,6,7 They may function in the transfer of proteins, lipids, and nucleic acids and represent a novel type of biomarker. 8 EVs represent a heterogeneous group of vesicles deriving from activated cells or generated during apoptosis from nearly all mammalian cells.…”

“…Because they carry markers of the parent cell, specific EV subpopulations, such as vesicles deriving from endothelial cells, immune cells, or kidney-specific cells, like podocytes, can be determined. 1,9,13 Analysis of urinary extracellular vesicles (uEVs) may serve as a logical and novel diagnostic approach for the nephrologist, because these vesicles can derive from the kidney and urinary tract. Noninvasive biomarkers are clearly needed in the field of nephrology, particularly for different clinical renal syndromes, including AKI and glomerular and tubular diseases.…”

“…8 EVs represent a heterogeneous group of vesicles deriving from activated cells or generated during apoptosis from nearly all mammalian cells. 1,9,10 Smaller vesicles or exosomes, 30-100 nm in size, are released from intracellular multivesicular bodies (MVBs). 10 In contrast, microparticles (MPs), ranging from 100 to 1000 nm, are thought to be the product of exocytic budding (Figure 1).…”