Dimethyl Fumarate Restores Functional Vitamin-D3 Tolerogenic Dendritic Cells differentiated from Multiple Sclerosis Patients

Multiple Sclerosis (MS) is a chronic disease characterised by dysregulated self-reactive immune responses damaging neurons’ myelin sheath, causing disability. The primary therapeutic option, immunosuppressants, inhibit pathogenic anti-myelin responses but depresses the entire immune system. Antigen-specific autologous tolerogenic dendritic cell (tolDC) therapies offer an approach to restore tolerance to auto-antigens without causing generalised immunosuppression. However, immune dysregulation in MS could impact the phenotype and functionality of the starting material for cell therapy. In this study, we defined the immune signature of CD14+ monocytes, mature dendritic cells (mDCs) and Vitamin D3 tolDCs (VitD3-tolDCs) isolated from MS patients and healthy donors (HD). By using a multi-omic approach, we identified a shift in these cell types toward a proinflammatory profile dominated by alterations in the AhR pathway and increased NFkB signalling. Moreover, tolDCs isolated from MS patients showed reduced tolerogenic properties compared to those from HD, which were fully restored through AhR agonism and NFkB downregulation through in vivo or in vitro supplementation with Dimethyl Fumarate (DMF). Remarkably, a combined therapy of DMF and VitD3-tolDC was more efficient to reduce the clinical score of experimental autoimmune encephalomyelitis mice than monotherapies. In summary, we demonstrate that DMF restores the functionality of VitD3-tolDCs derived from MS patients. Moreover, a combined therapy with DMF and VitD3-tolDCs could offer enhanced therapeutic potential in treating MS.