Project Summary/Abstract Multiple sclerosis (MS) is an autoimmune demyelinating disease of the central nervous system (CNS) that is most commonly characterized by discreet periods of measurable and sustained reduction in neurologic function followed by remission. Available interventions target inflammatory injury by interfering with inflammatory immune functions but typically do not stimulate myelin repair or restore neurologic function. Targeted approaches that promote remyelination in MS would have a substantial impact on its management: demyelination interrupts metabolic support to axons normally provided by oligodendrocytes (OGs). As a result, denuded axons often degenerate, thereby worsening disability in MS patients. Although recent studies into the diverse role of glia in CNS pathologies have identified unique transcriptomes expressed during injury and recovery, OG responses to antibody-mediated demyelination/remyelination remain unclear. This proposal incorporates an innovative and cross-disciplinary approach to dissect OG responses during failed myelin repair. We have developed unique ex vivo and in vitro assays using disease-specific myelin binding recombinant antibodies (rAbs) first cloned from MS patient cerebrospinal fluid that recapitulate some of the barriers to remyelination in MS. In contrast to other demyelination/remyelination models, our patient-based remyelination model blocks remyelination during the transition of OGs from the early myelinating to actively myelinating stage, not during OPC differentiation. Experiments described in this application are designed to disentangle factors intrinsic & extrinsic to OGs that contribute to rAb-induced remyelination failure by thoroughly delineating OG-rAb responses using live cell imaging, immunohistochemistry, transgenic mice, innovative myelination assays, and next generation RNA sequencing modalities. To maximize the translational relevance of results generated in this model, biomarkers of remyelination blockade will be identified and interrogated in MS lesions. Thus, by utilizing sequential experimental and translational approaches, this proposal will identify how specific interactions between B cell humoral autoimmunity and OGs contribute to remyelination failure in human disease. Initially, we will test how MS rAbs affect oligodendrocytes directly by observing their effect on OG differentiation, ability to elaborate new myelin, and signaling pathways transduced by rAbs. We will then identify how oligodendroglial gene expression is influenced by rAbs during differentiation and myelinogenesis experimentally and evaluate candidate biomarkers for remyelination blockade in human MS plaques. These studies will not only expand scientific understanding of MS neuroimmunology, they will also illuminate factors contributing to remyelination that may be harnessed for the treatment of MS and other CNS demyelinating diseases.