To assess biological aging in brain cells of MS patients and controls, we first sought to compare epigenetic clocks that have been previously used in brain samples, that is, the multi-tissue Horvath’s clock and the brain-restricted Cortical clock, in our study samples composed of bulk NAWM (n = 46), sorted neuronal (n = 54), and glial nuclei (n = 66) from post-mortem brain material (Table 1). This evidence concerns the gene CLOCK and myeloid sarcoma.