Older mice who are surgically joined with young mice in order to share a common bloodstream get stronger and healthier, making parabiosis one of the hottest topics in age research. Researchers now report that MANF (mesencephalic astrocyte-derived neurotrophic factor) is one of the factors responsible for rejuvenating the transfused older mice. Researchers also show the naturally occurring, evolutionarily conserved repair mechanism protects against liver damage in aging mice and extends lifespan in flies.