Hayflick limit

As Hayflick Limit ( English Hayflick limit ) is in eukaryotes , the limited number of cell divisions called, which a cell can undergo before the programmed cell death is initiated because the telomeres reach a critical length.

It was named after Leonard Hayflick , who discovered this border in 1961. With his proof that normal human cells (unlike embryonic cells, for example ) divide around 52 times before cell aging finally sets in, he refuted the prevailing opinion, according to Alexis Carrel , that cells are fundamentally immortal. Hayflick observed the shortening of the telomeres caused by each mitosis , which naturally puts an end to further cell division. The amount of natural divisions, and thus the Hayflick limit, varies from species to species and is a major factor influencing life expectancy.

For the crucial experiment, he mixed male fibroblasts after 40 cell divisions with female fibroblasts after 10 cell divisions. After about 15 more cell divisions, he could only find female fibroblasts in the nutrient solution. This ruled out that only technical errors or contamination limited the cell division.

However, in every cell structure in the human body there are u. a. Stem cells , many of which are not restricted by the Hayflick limit. They make the enzyme telomerase or use other mechanisms to maintain the length of the telomeres. Telomerase is also active in tumor cells and is one of the prerequisites for these cells to divide in an uncontrolled manner.

Web links

New Scientist (2007): Cell immortality and cancer. (English)
Web of Stories - Leonard Hayflick (English)

Individual evidence

↑ Hayflick, L. & Moorhead, PS (1961): The serial cultivation of human diploid cell strains. In: Exp. Cell Res. 25: 585-621. PMID 13905658 doi : 10.1016 / 0014-4827 (61) 90192-6
↑ Hayflick, L. (1965): The limited in vitro lifetime of human diploid cell strains. In: Exp. Cell Res. 37 (3): 614-636. PMID 14315085 doi : 10.1016 / 0014-4827 (65) 90211-9
^ JW Shay, WE Wright: Hayflick, his limit, and cellular aging. In: Nature reviews. Molecular cell biology. Volume 1, number 1, 10 2000, pp. 72-76, doi : 10.1038 / 35036093 , PMID 11413492 (review).

[1] Hayflick, L. & Moorhead, PS (1961): The serial cultivation of human diploid cell strains. In: Exp. Cell Res. 25: 585-621. PMID 13905658 doi : 10.1016 / 0014-4827 (61) 90192-6

[2] Hayflick, L. (1965): The limited in vitro lifetime of human diploid cell strains. In: Exp. Cell Res. 37 (3): 614-636. PMID 14315085 doi : 10.1016 / 0014-4827 (65) 90211-9

[3] JW Shay, WE Wright: Hayflick, his limit, and cellular aging. In: Nature reviews. Molecular cell biology. Volume 1, number 1, 10 2000, pp. 72-76, doi : 10.1038 / 35036093 , PMID 11413492 (review).