New Scientist: To see if young blood could also help ageing bones, Benjamin Alman at the Hospital for Sick Children in Toronto, Canada, surgically joined the circulatory systems of mice of various ages. Fractured shin bones of old mice healed faster and better when the rodents were joined to young mice than to mice their own age.

http://www.newscientist.com/article/mg22630222.300-young-blood-helps-repair-fractured-bones-of-ageing-mice.html#.VXhBaM9Vikp