H2AX and Alzheimer disease: To validate our findings in hiPSC-derived astrocytes, we evaluated the presence of senescent astrocytes in AD brains, finding a notable presence of phosphorylated H2A.X+ cells in the frontal cortex of Braak V-VI AD patients, which represented the 15% of all cells in this brain area, with most of them (78%) being GFAP+ astrocytes.