Ex vivo astrocyte-to-oligodendrocyte conversion in human adult cortical tissue using transcription factor overexpression

Multiple sclerosis (MS) is an autoimmune and neurological disorder characterized by myelin disruption and neuronal degeneration. Currently approved therapies focus on symptom relief but do not promote central nervous system (CNS) repair. In contrast, astrocytes proliferate and repopulate MS-related lesions. Moreover, in active lesions, they hinder regenerative processes such as neural progenitor migration. Here, we propose astrocytes as a potential target for myelin repair in the human diseased brain. To achieve this aim, we investigated whether glial fibrillary acidic protein (GFAP)+ astrocytes can be transdifferentiated into oligodendrocyte lineage cells through forced overexpression of transcription factors both in vitro and ex vivo organotypic cultures of human adult cortex. Our results show that overexpression of OLIG2 and SOX10 in human induced pluripotent stem cell-derived astrocytes gives rise to oligodendrocyte progenitor cells 12 days post-induction, as shown by morphological changes and O4 marker expression. Importantly, transdifferentiation of GFAP-expressing endogenous astrocytes in human adult cortical tissue give rise to mature oligodendrocytes, as shown by expression of CC1, after only 12 days of overexpression of OLIG2 and SOX10. To our knowledge, this is the first study to assess direct astrocyte-to-oligodendrocyte reprogramming in a human platform preserving the native three-dimensional architecture of the brain. Further work will be required to determine whether the reprogrammed cells can myelinate axons and to evaluate the potential of this approach for structural and functional repair in the demyelinated human CNS.