A 3-Dimensional Hydrogel Model of Multiple Sclerosis Brain Lesions Reveals Insights into Re-Myelination

Re-myelination failure is one of the major causes of permanent disability in multiple sclerosis (MS), an inflammatory demyelinating disorder of the central nervous system (CNS). There is an urgent need for in vitro experimental models mimicking MS brain lesions to elucidate the mechanistic underpinnings of myelin repair process. Here, we report the development of a hyaluronic acid-based, 3-dimensional (3D) model, which mimics the tissue stiffness of active and chronic MS brain lesions. Utilizing this model, we elucidated the effects of tissue stiffness and inflammation on neural progenitor cell (NPCs) differentiation to myelinating oligodendrocytes. We cultured murine NPCs in 3D hydrogels and investigated cell clustering, viability, proliferation, and maturation using RNA analysis and immunohistochemistry. Our data suggest that increased matrix stiffness favors enhanced cell cluster formation. Softer matrices showed increased expression of myelin basic protein (MBP), hexaribonucleotide binding protein-3 (NeuN), and Ki67. However, the presence of pro-inflammatory cytokines in hydrogels mimicking progressive MS resulted in decreased cell cluster formation and decreased expression of MBP, NeuN, and Ki67 RNA transcripts. Taken together, our results suggest that both inflammation and tissue stiffness negatively impact NPC proliferation and maturation. However, inflammation has a larger effect on NPC differentiation and on re-myelination.