A first characterization of placenta-derived extracellular vesicles in patients with multiple sclerosis.

Background: Multiple sclerosis (MS) is a chronic autoimmune inflammatory disease of the central nervous system (CNS), mainly affecting women. During pregnancy, an anti-inflammatory state is established, and disease activity is reduced. This peculiar immunomodulation is believed to be mediated by factors released by placenta, such as extracellular vesicles (pEVs). Studies show that pEVs from healthy donors (HC) could inhibit activity and proliferation of autoreactive T cells. Objectives: The aim of this work is to characterize for the first time to our knowledge pEVs from women with MS and evaluate their effects on activated CD14+ monocytes, CD4+ T cells and regulatory T cells (T-regs). Methods: Total pEV from 15 women with MS and 17 HC were isolated by ultracentrifugation and quantified by Nanoparticle Tracking Analysis. 37 surface markers were characterized by flow cytometry using the human MACSPlex Exosome Kit. CD14+ monocytes, T-regs and CD4+ T cells were separated from donor buffy coats. The expression level of pro and anti-inflammatory cytokines in CD14+ monocytes activated with LPS and conditioned with pEVs was evaluated by real-time PCR. CD4+ T cells were activated via CD3-CD28 and their proliferation activity was assessed by BrdU Cell Proliferation Assay after co-culture with T-regs conditioned with pEVs. Results: Several surface markers were differentially expressed between pEVs from decidua and trophoblast, but not between pEVs from MS women and HC, except for CD133 and CD45. Although not statistically significant, the conditioning with MS-pEVs resulted in a modest decrease in the expression level of pro-inflammatory cytokines in CD14+ monocytes and in the proliferation rate of CD4+ T cells co-cultured with T-regs. Conclusions: This study provides the first preliminary characterization of human pEVs from women with MS and sets the stage for the clarification of molecular mechanisms behind the pregnancy-related improvement of MS disease activity.