Development of a Humanized Mouse Model for Studying adult Spinal Cord myelination, remyelination and Drug Efficacy

Oligodendrocytes are essential for central nervous system (CNS) function through their roles in myelination and neuronal support. Remyelination, the regeneration of myelin after damage, often fails in human demyelinating diseases, leading to progressive neurological dysfunction. While the biology of rodent oligodendroglia has been investigated in depth, species-specific differences have hindered the study of human oligodendrocyte progenitor cells maturation using current animal models. To address this gap, we developed a humanized oligodendroglia chimeric mouse model by transplanting human iPSC-derived O4+ oligodendroglial progenitors (hiOLs) into the developing spinal cord of myelin deficient-immunosuppressed mice followed by demyelination of the adult humanized spinal cord. This paradigm allows in vivo investigation of hiOL fate during their maturation and ageing, and the response of their settled progeny to demyelinating injury. Following transplantation during postnatal development, hiOLs proliferated, migrated, and differentiated into mature oligodendrocytes, initiating axonal myelination. A population of undifferentiated, proliferative adult human oligodendrocyte progenitors presisted, indicating a reservoir of these cells capable of responding to injury. Spinal cord focal demyelination via lysolecithin injection in the adult humanized spinal cord led to transient loss of human-derived mature oligodendrocytes and myelin, followed by myelin recovery together with endogenous cells. Treatment with the histamine receptor H3 antagonist, bavisant, a recently identified promyelinating compound, significantly enhanced hiOL maturation and myelin production, indicating promotion of their differentiation when administered post-demyelination. Electron microscopy showed an increased number of human-derived remyelinated axons together with decreased g-ratios in bavisant treated animals. This humanized spinal cord model of myelination/demyelination-remyelination faithfully recapitulates key aspects of human oligodendrocyte biology and CNS repair, providing a powerful tool to study human-specific myelination and remyelination mechanisms and screen for emerging remyelinating therapies. Its application in disease modeling and preclinical testing holds promise for advancing personalized treatments in demyelinating and neurodegenerative disorders.