A vital pea-sized component of the brain may be the key to holding back ageing and extending the human lifespan, research suggests.
The hypothalamus, a small bundle of neurons at the base of the brain, governs how quickly the body ages.
Tests on laboratory mice pinpointed ageing control to a tiny population of adult stem cells within the brain region.
The cells appear to keep a tight rein on ageing.
As their numbers decline naturally with time or if their function is disrupted, the body's organs and metabolic processes age faster and death occurs earlier.
Humans are likely to respond to the influence of hypothalamus stem cells in just the same way, scientists believe.
Lead investigator Professor Dongsheng Cai, of Albert Einstein College of Medicine in New York City, said: "Our research shows that the number of hypothalamic neural stem cells naturally declines over the life of the animal and this decline accelerates ageing.
"But we also found that the effects of this loss are not irreversible. By replenishing these stem cells or the molecules they produce, it's possible to slow and even reverse various aspects of ageing throughout the body."
The hypothalamus acts like a computer's central processor, regulating a wide range of biological functions in the body.
One of its most important jobs is to maintain homeostasis - keeping different parts of the body working in a stable, balanced way.
Among the many body functions it influences via a complex array of hormones are temperature control, appetite, blood pressure, heart rate, sleep cycles, sex drive and digestion.
The crucial hypothalamus stem cells are "mother cells" that mature to produce new neurons.
Prof Cai's team of researchers, whose findings are reported in the journal Nature, looked at what happened to the cells as healthy mice got older.
They found the number of hypothalamus stem cells began to diminish when the animals reached about 10 months, several months before the usual signs of ageing normally start to appear.
When the stem cells in middle-aged mice were selectively disrupted artificially, it led to "greatly accelerated ageing".
The next step was to inject hypothalamus stem cells into the brains of mice whose supply of the cells had been destroyed, as well as "normal" old mice.
In both groups of animals, various measurements showed ageing was either slowed or reversed.
