Harvard Stem Cell Institute in Boston's scientists have shown that mixing blood from young people with the one from elderly might help reverse effects of aging, in a new study.
Lead researcher Amy Wagers discovered that the blood of the young animals seemed to rejuvenate ageing blood stem cells in the bone marrows of the older mice.
It also revitalised so-called "niche" cells in the bone marrow, which nourish, support and stimulate blood stem cells.
Although old mice make more blood stem cells and more niche cells than young mice, many are faulty.
"The reason the old animals have too many is probably an attempt to compensate for these flaws," New Scientist quoted Wagers as saying.
Old mice also make too many myeloid blood cells, which contribute to inflammation and the development of cancer, and too few lymphoid blood cells, which orchestrate tissue repair.
However, in the new study, these age-related changes were reversed and the mice made fewer myeloid cells and more lymphoid cells.
The research team concluded that young mice's blood flowed into the older animals, prompting youth-giving changes.
They said that as-yet-unidentified components in the young mice's blood passed into the older animals and prompted these youth-giving changes.
The findings appear in journal Nature.