Inflammatory microglia correlate with impaired oligodendrocyte maturation in multiple sclerosis

We hypothesized more CD163⁺ microglia and BCAS1⁺ oligodendrocytes in remyelinated and active non-foamy lesions from ERDs and more iNOS⁺ microglia with fewer BCAS1⁺ oligodendrocytes in active foamy lesions from PRDs. For CD163⁺ microglia, however, no differences were observed between MS lesions and MS donor groups. In line with our hypothesis, we found that INOS⁺ microglia were significantly increased in PRDs compared to ERDs within remyelinated lesions. MS lesions, more late-stage BCAS1⁺ oligodendrocytes were detected in active lesions with non-foamy or foamy microglia in comparison with remyelinated lesions. Although no differences were found for early-stage BCAS1⁺ oligodendrocytes between MS lesions, we did find significantly more early-stage BCAS1⁺ oligodendrocytes in PRDs vs ERDs in remyelinated lesions. Interestingly, a positive correlation was identified between iNOS⁺ microglia and the presence of early-stage BCAS1⁺ oligodendrocytes. These findings suggest that impaired maturation of early-stage BCAS1⁺ oligodendrocytes, encountering inflammatory microglia, may underlie remyelination deficits and unsuccessful lesion repair in MS.