Hayflick Limit

Synonyms

• Hayflick number

• irreversible replicative senescence

• mortality stage 1

Definition

The term Hayflick limit refers to the fact that the maximum number of cell divisions of a certain cell population is genetically fixed such that aging cells become non-dividing (senescent) at last. This replicative life span is probably defined by a ‘critical’ telomere length [telomerase [telomerase]]. Human fibroblasts for instance, divide in vitro 70 to 80 times, before multiplication reaches a plateau. Usually, the cells then increase in size, flatten in shape and enter an irreversible state of arrest, called senescence; senescence and immortalization. An exception appear to be human mammary epithelial cells that can escape mortality stage 1, exhibit eroding telomere sequences and ultimately generate the types of chromosomal abnormalities that are seen during early breast cancer development.