Membrane lipids define small extracellular vesicle subtypes secreted by mesenchymal stromal cells

Abstract

Therapeutic efficacy of the mesenchymal stromal cell (MSC), a multipotent progenitor cell, is attributed to small (50 to 200 nm) extracellular vesicles (EVs). The presence of a lipid membrane differentiates exosomes and EVs from other macromolecules. Analysis of this lipid membrane revealed three distinct small MSC EV subtypes each with a differential affinity for cholera toxin B chain (CTB), annexin V (AV), and shiga toxin B chain (ST) that binds GM1 ganglioside, phosphatidylserine, and globotriaosylceramide, respectively. Similar EV subtypes are also found in biologic fluids and are independent sources of disease biomarkers. Here, we compared and contrasted these three EV subtypes. All subtypes carry β-actin, but only CTB-binding EVs (CTB-EVs) are true exosomes, enriched with exosome proteins and derived from endosomes. No unique protein has been identified yet in AV-binding EVs (AV-EVs); ST-binding EVs (ST-EVs) carry RNA and a high level of extra domain A (EDA)-containing fibronectin. Based on the CTB, AV, and ST subcellular binding sites, the origins of CTB-, AV- and ST-EV biogenesis are the plasma membrane, cytoplasm, and nucleus, respectively. The differentiation of EV subtypes through membrane lipids underlies the importance of membrane lipids in defining EVs and implies an influence on EV biology and functions.

Effect of MSCs and MSC-Derived Extracellular Vesicles on Human Blood Coagulation

“…Another mechanism involves an exhibition of procoagulant lipids, particularly phosphatidylserine, on the cell surface [47,48]. It has been described that MSC-derived EVs can expose phosphatidylserine on their surface [49], which provides a catalytic surface for the formation of the tenase (factors VIIIa, IXa, and X) and prothrombinase (factors Va, Xa, and II) complexes of the coagulation cascade. Phosphatidylserine may additionally contribute to the transformation of TF from its inactive, encrypted form into a biologically active state [18,50].…”

Defining mesenchymal stromal cell (MSC)‐derived small extracellular vesicles for therapeutic applications

“…A comparison of sEV preparations and the producing cell is also instructive. Relative amounts of certain lipids are different in MSC‐sEV membranes versus the bulk cellular membranes of the parent MSCs [reviewed by [58]]. For example, the major plasma membrane phospholipids, cholesterol, sphingomyelin and phosphatidylcholine, are enriched in the sEV membrane.…”

Current Status of Mesenchymal Stem/Stromal Cells for Treatment of Neurological Diseases

“…MSC-derived Evs can be identified by their affinity to certain molecules. Thus, exosomes have an affinity to cholera toxin B, which binds to the GM1 ganglioside, while annexin V and shiga toxin B bind to phosphatidylserine and globotriaosylceramide, and their biogenesis is related to the cytoplasm and nucleus, respectively (Lai and Lim, 2019 ). The lipid composition of Evs can define their origins and activity.…”