From the Jerusalem Post: "researchers have discovered that pregnancy has the remarkable ability to promote the regeneration in elderly mice of damaged livers and muscles. They have also managed to mimic the state of pregnancy using specific molecules that trigger the regeneration and growth of livers in older rodents. This basic new concept [could] eventually be relevant to other tissues and organs and lead to the ability to stimulate their regeneration in elderly, sick patients. ... [Earlier researchers] had connected young mice to other young mice by uniting their blood vessels; old mice to old mice; and young mice to old mice (this procedure is called parabiosis). ... pregnancy was a kind of parabiosis in which a mother is connected by blood vessels to its young fetus. ... The team studied mice and indeed found that damage to tissue in the foot muscle (and later liver) of an older but pregnant mouse was quickly repaired, as if it had been connected to a live young animal. ... pregnancy causes a switch from regeneration based on proliferation (an increase in the number of cells due to cell division) to regeneration caused by hypertrophy (the increase in the volume of an organ or tissue due to the enlargement of its component cells). Certain molecules given to aged mice induced hypertrophy in their livers, thus mimicking the state of pregnancy and lengthening their lifespan."