Regeneration (biology)

In biology, regeneration is the ability to restore lost or damaged tissues, organs or limbs. It is a common feature in less complex creatures, such as worms, but is very rarely observed to any major degree in higher animals. Nevertheless, even humans possess some degree of regeneration ability. Children under 6 years of age are capable of regenerating lost fingertips and the human liver retains its ability to regenerate throughout a person's lifetime. The natural regenerative ability can sometimes be slightly enhanced by physical tension applied to the tissue. The principle is used for techniques such as breast reconstruction and foreskin restoration.

Aside from being used to generally describe any number of specific healing processes, regeneration also is a specific method of healing that is noted for its ability to regrow lost limbs, severed nerve connections, and other wounds that mammals cannot heal. This is present in some animals such as the newt and hydra.

To realize this healing, cells neighboring the injury undergo a process called dedifferentiation where the cells revert to a more generalized stem-cell like state, then respecialize into a different type of cell that needs replacement.

This is not possible in mammals because there are specific factors still being explored that inhibit the expression of regeneration. In one test involving rats, blocking two of these factors led to greatly increased nerve cell healing in severed spinal chords. In another, injection of a solution of tissue taken from a newt's blastoma into a rat's wound duplicated many of the elements of dedifferentiation.

If the processes behind regeneration are fully understood, it is believed this would lead to better treatment for individuals with nerve injuries, broken backs, paralysis, and missing limbs.