Biology, Pathophysiological Role, and Clinical Implications of Exosomes: A Critical Appraisal

Abstract

Exosomes are membrane-enclosed entities of endocytic origin, which are generated during the fusion of multivesicular bodies (MVBs) and plasma membranes. Exosomes are released into the extracellular milieu or body fluids; this process was reported for mesenchymal, epithelial, endothelial, and different immune cells (B-cells and dendritic cells), and was reported to be correlated with normal physiological processes. The compositions and abundances of exosomes depend on their tissue origins and cell types. Exosomes range in size between 30 and 100 nm, and shuttle nucleic acids (DNA, messenger RNAs (mRNAs), microRNAs), proteins, and lipids between donor and target cells. Pathogenic microorganisms also secrete exosomes that modulate the host immune system and influence the fate of infections. Such immune-modulatory effect of exosomes can serve as a diagnostic biomarker of disease. On the other hand, the antigen-presenting and immune-stimulatory properties of exosomes enable them to trigger anti-tumor responses, and exosome release from cancerous cells suggests they contribute to the recruitment and reconstitution of components of tumor microenvironments. Furthermore, their modulation of physiological and pathological processes suggests they contribute to the developmental program, infections, and human diseases. Despite significant advances, our understanding of exosomes is far from complete, particularly regarding our understanding of the molecular mechanisms that subserve exosome formation, cargo packaging, and exosome release in different cellular backgrounds. The present study presents diverse biological aspects of exosomes, and highlights their diagnostic and therapeutic potentials.

Exosomes derived from M0, M1 and M2 macrophages exert distinct influences on the proliferation and differentiation of mesenchymal stem cells

“…They are crucial mediators in intercellular communication and participate in many biological activities (Zhang et al, 2019). Exosomes, which carry proteins, lipids, nucleic acids and other cargos, can be released into the extracellular milieu and internalized by target cells, in which they modulate cellular behaviors (Jan et al, 2019). The biocompatibility, stability and capacity to transport bioactive components and overcome biological barriers indicate the great potential of exosomes as suitable therapeutic agents (Liu & Su, 2019).…”

MicroRNA Profiling of Exosomes Derived from Red Blood Cell Units: Implications in Transfusion-Related Immunomodulation

“…They are the products of exocytosis; they contain DNA, coding or noncoding RNAs (ncRNAs), and protein fragments that are secreted by their parental cell and can be taken into the recipient cells. Exosomes are reported 2 BioMed Research International to carry out several physiological and pathophysiological functions during carcinogenesis and immunomodulation in both in vitro and in vivo conditions [12][13][14][15]. ncRNAs of the exosomes have been proved to play an important role in regulation of these procedures [14,15].…”

Exosomal miRNAs as Potential Diagnostic Biomarkers in Alzheimer’s Disease

“…Different types of cells like neurons, adipocytes and fibroblasts are able to release exosomes and, therefore, they can be found in many biofluids such as blood, urine, saliva and amniotic fluid [ 65 ]. Exosomes can be purified from biological fluids and cell cultures in vitro using a variety of strategies.…”