The hormone involved in social bonding also enables old muscles to rejuvenate.

Wendy Cousin, Irina Conboy and their colleagues at the University of California, Berkeley, injected the hormone oxytocin into old mice, and found that after an injury the muscles in these animals had similar regeneration levels to muscles in young mice. The hormone improves repair by activating a signalling pathway in muscle stem cells — thereby boosting the cells' proliferation. Moreover, mice engineered to lack oxytocin showed decreased muscle repair and greater loss of muscle tissue compared with normal mice of the same age.

Oxytocin could be used as a drug to prevent or slow down muscle ageing, the authors say.

Nature Commun. 5, 4082 (2014)