Administration of the immune response to spinal cord injury in zebrafish by extracellular vesicles secreted by activated monocyte-like cells

The immune response to spinal cord injury is realized by local and systemic inflammation, followed by repair and restoration of the function of damaged organs. The opportunity to control pro-inflammatory activity and stimulate regenerative processes is an important aspect of the research. Extracellular vesicles (EVs) secreted by activated monocyte-like cells may be a useful tool to drive the polarization of the immune response towards M1 or M2. The aim of the study was to investigate the systemic effects of extracellular vesicles, produced by activated monocyte-like cells of the THP-1 line, after spinal cord injury in zebrafish. It was shown that intracoelomic administration to Danio rerio fish with spinal cord injury of EVs secreted by THP-1 cells, activated by the tumor necrosis factor (TNF), led to a proinflammatory effect, manifested by an increase in the expression of il-6 and tnf-α genes in the brain tissue, and to a less pronounced change in activity in the tissues of the heart, liver and kidney. In the same time, EVs, secreted by unactivated THP-1 cells as well as activated by the phorbol-12- myristate-13-acetate (PMA), did not show any activity. Thus, it was demonstrated that extracellular vesicles secreted by activated monocyte-like cells have the potential to influence on the polarization of the immune response after simulated spinal cord injury in zebrafish.