[Exosomes derived from PMN-MDSCs preconditioned by hypoxia attenuate arthropathy of collagen-induced arthritis mice].

Objective To investigate the role of the exosomes (EX) derived from polymorphonuclear myeloid-derived suppressor cells (PMN-MDSCs) preconditioned by hypoxia in the treatment of the collagen-induced arthritis (CIA) mouse model. Methods CIA mouse model was induced by bovine type II collagen(Col2) and Freund's adjuvant. PMN-MDSCs were isolated from CIA mouse spleen by magnetic beads. PMN-MDSC-derived exosomes (PMN-MDSC-EXs) were extracted from the supernatant of PMN-MDSCs under normal (210 mL/L O2) and hypoxia (10 mL/L O2) conditions. PMN-MDSC-EXs were identified by transmission electron microscopy and flow cytometry. The surface-specific markers of PMN-MDSC-EXs were detected by Western blotting, including CD9, CD63, heat shock protein 70 (HSP70), and calnexin. PMN-MDSC-EXs were added to the CD4+ T cell proliferation system in vitro to detect immunosuppressive ability. PMN-MDSC-EXs were injected into the CIA mouse model through the tail vein. The clinic scores of joints were recorded every three days, and the joint structures were observed by HE staining. The levels of total IgG, Col2 antibody, interferon γ (IFN-γ), interleukin 17 (IL-17) in the serum were detected by ELISA. The content of miR-29a-3p and miR-93-5p in PMN-MDSC-EXs under normal and hypoxia conditions was detected by real-time quantitative PCR. Results PMN-MDSCs were successfully isolated from the spleens of CIA mice and PMN-MDSC-EXs was prepared under normal and hypoxia conditions. Compared with normal PMN-MDSC-EXs, hypoxia-treated PMN-MDSC-EXs could inhibit the proliferation of CD4+ T cells more effectively. The swelling degree of toes, clinical scores, and joint damage in the group of hypoxia-treated PMN-MDSC-EXs were significantly reduced. The levels of total IgG, Col2 antibody, IFN-γ and IL-17 in the serum decreased after the treatment with hypoxia-treated PMN-MDSC-EXs. The content of miR-29a-3p and miR-93-5p in hypoxia-treated PMN-MDSC-EXs was much higher than that in normal PMN-MDSC-EXs. Conclusion Under hypoxia condition, the immunosuppressive ability of PMN-MDSC-EXs is stronger, which can alleviate the arthropathy of CIA mice more effectively.