Intravenous administration of bone marrow-derived mesenchymal stem cells induces a switch from classical to atypical symptoms in experimental autoimmune encephalomyelitis

Potent immunosuppressive and regenerative properties of mesenchymal stem cells (MSCs) position them as a novel therapy for autoimmune diseases. This research examines the therapeutic effect of MSCs administration at different disease stages in experimental autoimmune encephalomyelitis (EAE). Classical and atypical scores of EAE, associated with Th1 and Th17 response, respectively, and also Treg lymphocytes, were evaluated. MSCs administration at the onset (EAE+MSC_onset) induced an important amelioration of the clinical signs and less lasting effect at the peak of EAE (EAE+MSC_peak). No effect was observed when MSCs were applied after EAE stabilization (EAE+MSC_late). Surprisingly, EAE atypical signs were detected in EAE+MSC_peak and EAE+MSC_late mice. However, no correlation was found in Th17/Th1 ratio. Interestingly, regardless of time administration, MSCs significantly reduced IL-6 and also T-bet, RORγT, and Foxp3 mRNA levels in brain samples of EAE mice. The downregulation of IL-6 could restore the well-functioning of the blood-brain barrier of EAE mice, correlated with a decreased number of brain infiltrating leukocytes. These results suggest that the inflammatory status is important to be considered for administering MSCs in autoimmune pathologies, leading to a further research to clarify the effect of MSCs for multiple sclerosis.