Article posted Thursday, July 2, 2015 11:35am

Siamese twins are born connected to one another, share the same blood supply, and age at about the same rate. But what would happen if scientists surgically attached a young individual to an older one such that they shared the same blood supply? This experiment was recently carried out in mice, with astounding results. Scientists surgically connected three-month-old and 18-month-old mice along their sides. After ensuring that the two blood supplies became one, the mice were allowed to continue their development for five weeks. The pairs of mice did well and could move around together. After five weeks, various analyses showed that the brains of older mice were revitalized. New synaptic junctions formed and new neurons arose, especially in the hippocampus, where memories are processed. Examination of hippocampi of the older mice of a pair showed that, at the end of five weeks, their structure more closely resembled that of a young mouse. Other studies of conjoined mice showed that after five weeks, muscle structure, strength, and endurance were enhanced in older mice. A protein growth factor, called GDF11, is abundant in the blood of young mice but exists at low levels in aging mice. However, in conjoined mice with a common blood supply, older mice may become rejuvenated by increased levels of GDF11. When GDF11 was isolated and injected into individual old mice, they too showed many signs of rejuvenation. These studies have shocked the scientific world, for they appear to be too good to be true. Even if the studies are verified in other labs, there is still the question of whether GDF11, or some other kind of rejuvenating molecule, will work in humans. Also, could such growth factors cause cancer? (Science, May 5, 2014; Stanford Univ. School of Medicine, 2014, “Infusion of young blood recharges brains of old mice, study finds,” May 14; Nature Medicine, May 4, 2014; Alz Forum, Zilkha Symposium on Alzheimer’s Disease and Related Disorders, May 5, 2014)