However, many investigations utilizing immunostaining methods have demonstrated that various cell types, such as astrocytes, microglia, neurons, and ECs, in the AD brain exhibit elevated concentrations of senescence‐linked proteins, such as cell cycle inhibitors p16, p53, and p21 [205, 207, 213, 218, 219, 220, 221, 222, 223]. This evidence concerns the gene CDKN1A and Alzheimer disease.