MS cerebral organoids seemed to grow faster compared to control organoids, associated with thicker cortical structures, suggesting dysregulation of the stem cell proliferation/differentiation capacity. Immunostainings showed a significant reduction of the cyclin-dependent kinase inhibitor p21 expression in MS samples, particularly in PPMS. Loss of p21 seems to induce a slight decrease of stem cell marker SOX2 as well as a significant increase of neuronal marker CTIP2 in MS samples, while no significant difference was observed for CTIP2-positive intermediate progenitors. A further analysis of DNA damage and senescence/apoptosis markers in neural population is currently being performed.