Unveiling the potential of extracellular and outer membrane vesicles in fish aquaculture: a comprehensive review.

Live eukaryotic cells produce extracellular vesicles (EVs) that play a crucial role in cell-to-cell communication and transport various cargoes, including proteins, nucleic acids, and lipids. Based on their biogenesis, size, content, and pathways, EVs are mainly categorized into exosomes, microvesicles, and apoptotic bodies. These EVs have been studied as promising biomarkers for disease diagnosis, stress responses, and indicators of immune-physiological health in prominent aquaculture fish species. In fish studies, EVs have been associated with sex determination and immune response regulation, whereas EV-mediated tissue regeneration and cell permeability have mainly been investigated using zebrafish or medaka models, including studies employing non-fish- or cell culture-derived EVs. On the other hand, outer membrane vesicles (OMVs), primarily produced by gram-negative bacteria, possess acellular properties and are being explored for vaccine development. Intraperitoneal injections of OMVs act as vaccines, providing protection against infectious diseases and mortality. OMVs also modulate immune responses through gene transcription and promote anti-pathogenic antibody production. However, OMVs, which are biologically active nanoparticles, demonstrated infection potential in cultured species. Moreover, hemolytic activity, biofilm formation to protect the parent cell, and cytopathic effect were also confirmed in fish pathogen OMVs. Despite limited research on EVs and OMVs in fish, their potential in aquaculture should not be overlooked. In this report, we discuss the content and mechanisms of eukaryotic and prokaryotic nanovesicles in fish, along with the properties mentioned above. Moreover, research gaps and the future prospects of these nanomaterials will open a new prospect for upcoming researchers to utilize EVs and OMVs in the aquaculture sector.