Abstract: Objective To verify the function of exosomes from 293T cells over-expressing membrane-localized IL-3 in vitro, so as to lay a foundation for in vivo function verification in animal models of Alzheimer′s disease. Methods Using the patented structure of the group, a recombinant IL-3 lentiviral vector was constructed and virus-infected 293T cells were packaged. Stable cell strain over-expressing IL-3 was screened. The membrane localization of IL-3 was verified by flow cytometry and immuno-fluorescence. Il-3-exosomes were purified by ultra filtration centrifugation, the exosmic morphology was observed by transmission electron microscope, the size distribution and concentration of exosomes were detected by nano-flow analysis, and the expression of IL-3 and exosome related marker proteins were detected by Western blot. The effect of BV-2 on the phagocytosis of Aβ amyloid was detected by immuno-fluorescence. Results Through vector construction, virus infection, screening and verification of puromycin, 293T cell strain with stable over-expression membrane-anchored IL-3 was obtained. The purified exosomes were collected and the structures of double-layer membrane vesicles with a diameter of 50-100 nm were observed under transmission electron microscope. Western blot results proved the presence of CD63, ALIX, TSG101 and other exosome marker proteins and these molecules were rich in IL-3 as compared with the control, that suggested the successful purification of IL-3-exosomes. The results of immuno-fluorescence assay showed that IL-3-exosomes promoted the phagocytosis of Aβ amyloid by BV-2 cells in vitro. Conclusions The gene modified 293T cell exosomes membrane-anchored expression of IL-3 can play a role of both IL-3 and exosomes in vitro, which promote the phagocytosis of microglia, there for provides a new idea for the clinical treatment of Alzheimer′s disease.

Key words: interleukin-3(IL-3), exosome, mouse brain microglial cell line(BV-2), Alzheimer′s disease