Citation

Background: Multiple sclerosis (MS), an inflammatory disease of the central nervous system (CNS), leads to demyelination, neuronal injury, and loss of white matter, yet still can’t be cured. Exosomes are doublelayered membrane vesicles of 30–200 nm in size, which can easily penetrate the blood–brain barrier
(BBB). Exosomes derived from umbilical cord mesenchymal stem cells exosomes (UMSC-exos) has been shown to treat experimental autoimmune encephalomyelitis (EAE) through the action of antiinflammatory and immunomodulatory, but its clinical translation has been hampered by their
inefficacious accumulation in CNS. Therefore, we developed a TAxI-peptide-chimeric UMSC-exos termed TAxI-exos for CNS-specific accumulation and curative effect in EAE. Methods: We used an EAE model in vivo, and actived T cells and BV-2 cells models in vitro. After two immunizations to establish the EAE model, UMSC-exos, TAxI-exos or DiR labeled exosomes were administered to EAE mice EAE mice for one dose (150μg) before the peak at day 15. On day 30, the mice were sacrificed to collect spinal cords, spleens, and blood for analysis of demyelination, inflammation, microglia, the proportions of T-cell subsets, and the expression of inflammatory cytokines. In vitro, for immune mechanism analyses, PBMCs and splenocytes isolated from healthy C57BL/6 mice, were
activated and incubated with 0.15mg/mL UMSC-exos or TAxI-exos. Activated BV-2 cells were used to explore the targeting-ability and polarization-regulating ability of UMSC-exos and TAxI-exos. Results: As expected, TAxI-exos had significant curative effects in EAE mice compared with UMSC-exos
via an enhanced targeting-ability. The treatment alleviated inflammation, facilitated microglial cell polarization from M1 to M2, reduced the proportions of T-cell subsets, increased the expression levels of IL-4, IL-10, TGF-β, and IDO-1, and decreased the levels of IL-2, IL-6, IL-17A, IFN-γ, and TNF-α.
Conclusions: TAxI-exos have a great CNS-targeting ability and suppress pathological processes in EAE mice, which have a great potential therapeutic utility for MS and other CNS diseases.