Extracellular vesicles (EVs) are a heterogeneous population involved in intercellular communication. Little attention has been paid to a peculiar EV type with the appearance of a multivesicular body: extracellular multivesicular body (EMVB), also termed matrix vesicle cluster/multivesicular cargo. The aim of this work is to assess the ultrastructural characteristics, participation, and tissue location of EMVBs in inflammation/repair and tumors (with physiopathological processes involving intense intercellular communication), for which representative specimens were used. The results showed several forms of EMVBs: a) mature EMVBs, made up of clusters of vesicles surrounded by a plasma membrane, b) pre-EMVBs, with protruding grouped vesicles under the cell membrane, and c) post-EMVBs, releasing their vesicles. In tissues with inflammation/repair, EMVBs were observed in vessel lumens, interstitial spaces of vessel walls (between endothelial cells, pericytes, and smooth muscle cells) and between inflammatory and stromal cells. In tumors, such as basal cell carcinoma, craniopharyngioma, syringocystoadenoma, fibrous histiocytoma, alveolar rhabdomyosarcoma, lymphomas, neuroblastoma, astrocytomas, meningiomas, and hydatiform mole, EMVBs were present in tumor gland lumens and between tumor cells. In conclusion, in numerous physiopathological processes, we contribute EMVB ultrastructural characteristics (including different forms of mature, pre- and post-EMVBs, suggesting a more efficient EV transport), location and relationship with different types of cells. Further studies are required to assess the role of EMVBs in these physiopathological conditions.
Keywords: Extracellular vesicles; extracellular matrix; inflammation/repair; intercellular communication; tumors.