Britannica Sources used in this answer

Why can established cell lines continue reproducing indefinitely?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

tissue culture Tissue culture often requires sterile working conditions and thus is typically performed in a laminar flow cabinet (or tissue culture hood), which circulates filtered air to reduce the risk of culture contamination.

Established cell lines are able to reproduce indefinitely because they have overcome the natural limitations on cell division, a process often referred to as escaping the Hayflick limit.1

In normal cells, telomeres—the protective DNA sequences at the ends of chromosomes—shorten with each round of replication. Once these telomeres reach a critically short length, the cell enters a state of senescence or dies. Established cell lines, however, typically achieve immortality through one of the following mechanisms:23

Activation of Telomerase: Many immortalized cells, particularly cancer cells, activate the enzyme telomerase. This enzyme adds repetitive nucleotide sequences to the ends of chromosomes, preventing further shortening and allowing the cells to divide indefinitely.23
Genetic Mutation: Some cell lines are derived from primary cells that have undergone mutations or chromosomal rearrangements. These genetic changes can result in the loss of growth-limiting factors, effectively bypassing the regulatory mechanisms that normally trigger cell aging and death.14

While these adaptations allow for indefinite replication, it is important to note that such cells often accumulate further mutations over time, which can alter their original characteristics.1