As we age, the ability of our tissues to maintain homeostasis and to repair themselves declines, eventually leading to organ degeneration and failure. Aging of muscle tissue is characterized by deficient muscle regeneration after injury and by altered muscle function and associated atrophy, known as sarcopenia. Some previous work suggests that the age-related decline in regenerative capacity of skeletal muscle can be reversed by exposing tissue from an older animal to the circulatory system of a younger animal, but the circulatory components underlying the reversal have not been identified. Now, researchers from the University of California, Berkeley, led by Irene M. Conboy, report that oxytocin can improve muscle regeneration in older mice. They show that plasma oxytocin concentration and the number of oxytocin receptors in muscle stem cells both decline with age in mice. Furthermore, administration of oxytocin to old mice restores muscle regeneration by improving the function of muscle stem cells. Conboy's team suggests that regulation of oxytocin levels could be helpful in preventing age-related declines in muscle tissue maintenance and repair, although the amount of oxytocin required to maintain healthy tissues is not yet known.

Credit: Michael Dwyer/Alamy

The researchers evaluated the effects of oxytocin in both young and old mice. First, they injected mice subcutaneously with oxytocin and assessed healing after muscle injury. Oxytocin administration improved muscle healing in old mice but had no effect in young mice (Nat. Commun. 5, 4082; 2014). Next, they used an oxytocin antagonist to inhibit oxytocin signaling in young mice and found that blocking the effects of oxytocin markedly compromised muscle regeneration. Finally, they examined muscle development and function in knockout mice that lacked the gene encoding oxytocin. When these mice were young, their muscle mass and regenerative ability were similar to those of wild-type mice, indicating that the lack of oxytocin did not affect muscle development. But when the knockout mice reached adulthood, they showed signs of premature aging and sarcopenia.

Taken together, the results indicate that oxytocin supports muscle maintenance and repair and that age-related reductions in oxytocin contribute to sarcopenia. These findings suggest that treatment strategies involving the manipulation of oxytocin could be beneficial in combating muscle deterioration in the elderly. “Aging is a natural process,” Conboy states in a press release, “but I believe that we can meaningfully intervene with age-imposed organ degeneration, thereby slowing down the rate at which we become progressively unhealthy.”