Analyze differentiation and maturation of glial cells and neurons in long-term cultured cerebral organoids derived from induced pluripotent stem cells of patients with multiple sclerosis (PwMS).

MS is an auto-immune disease characterized by inflammation, demyelination and neural degeneration. It has been shown that environmental and genetic factors contribute to the development of MS, however, the etiology of this condition is unknown. Our previous research showed that organoids from PwMS display an exhaustion of the neural progenitor pool and an increase in neurogenesis. Here, we studied differentiation of neurons into glutamate and GABAergic neurons as glutamate excitotoxicity has been proposed to lead to inflammation and neuronal injury in MS. We also investigated glial cell differentiation and maturation in astrocytes and oligodendrocytes to determine their role in MS pathogenesis.

We analyzed neural cell differentiation in neuronal and glial lineages along with myelination capacity by immunofluorescence in MS cerebral organoids compared to healthy control organoids, after 120 days in vitro.

A strong decrease of Olig2 expression in MS organoids was detected highlighting a lower number of oligodendrocyte lineage cells. Moreover, no colocalization of Olig2 and APC was observed in MS, while multiple double positive cells were detected in control organoids, showing a defect of oligodendrocytes maturation. In parallel, GFAP staining showed a decrease of GFAP expression in MS organoids compared to control. We then analyzed GABAergic and glutamatergic differentiation. A strong increase of glutamatergic marker vGlut1 and a decrease of GABAergic marker GAD67 was detected at d120 in MS organoids compared to control signifying an imbalance of excitatory and inhibitory neurons.