Limited capacity to replicate is a defining characteristic of most normal cells and culminates in senescence, an arrested state in which the cell remains viable (1). Senescent cells are not stimulated to divide by serum or passage in culture, and senescence invokes a specific cell cycle profile that differs from most damage-induced arrest processes or contact inhibition (2). An enlarged cell size, expression of pH-dependent beta-galactosidase activity (3), and an altered pattern of gene expression (4,5) further characterize senescent cells. 复制能力的有限性是大多数正常细胞一个典型特征，最终以衰老结束，一种细胞仍然存活的阻滞状态(1)。衰老细胞不接受培养过程中血清或传代的刺激而分化，而且衰老能够引起特定的细胞周期属性，不同于大多数损伤诱导的阻滞或接触抑制(2)。增大的细胞体积，pH-依赖的β-半乳糖苷酶活性表达(3)，基因表达模式的改变(4,5)进一步表征了衰老细胞。