Scientists have identified a pea-sized part of the brain they say may hold the key to extending human lifespans.
Researchers found it was “possible to slow and even reverse various aspects of ageing throughout the body” by replenishing adult stem cells that control how quickly the body grows old.
The small bundle of neurons that appears to keep a tight rein on ageing is called the hypothalamus and is located at the base of the brain.
Dongsheng Cai, from the Albert Einstein College of Medicine in New York, led the new study in which tests were carried out on lab mice to pinpoint this area.
The research, published in the journal Nature, showed that as the number of these cells declines naturally over time, or if their function is disrupted, the body’s organs and metabolic processes age faster and death occurs earlier.
“Our research shows that the number of hypothalamic neural stem cells naturally declines over the life of the animal, and this decline accelerates ageing,” said Professor Cai. “But we also found that the effects of this loss are not irreversible.”
Ageing could be held back by replenishing these stem cells “or the molecules they produce,” he added.
The scientists believe that humans are likely to respond to the influence of hypothalamus stem cells in just the same way as the mice.
The hypothalamus acts like a computer’s central processing unit (CPU), regulating a wide range of biological functions in the body and linking nerves and hormones.
One of its most important jobs is to maintain homeostasis – keeping different parts of the body working in a constantly stable, balanced way.
Among the many body functions it influences are temperature control, appetite, blood pressure, heart rate, sleep cycles, sex drive, and digestion. It operates via a complex array of hormones.
The crucial hypothalamus stem cells are “mother cells” that mature to produce new neurons.
Professor Cai’s team of researchers looked at what happened to the cells as healthy mice got older.
They found that 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. Mice in captivity live a maximum of only about two to three years.
“By old age – about two years of age in mice – most of those cells were gone,” said Professor Cai. When the stem cells in middle aged mice were selectively disrupted artificially, it led to “greatly accelerated ageing”, he said.
The professor added: “Those mice with disrupted stem cells died earlier than normal.”
The next step was to inject hypothalamus stem cells into the brains of mice whose own supply of the cells had been destroyed, as well as “normal” old mice.
In both groups of animals, various measurements including tissue analysis and assessments of muscle endurance, coordination, social behaviour and mental ability showed that ageing was either slowed or reversed.
The anti-ageing effects were traced to molecules called microRNAs (miRNAs) released by the stem cells.
These small snippets of genetic material play a key role in regulating gene activity. By pairing up with “messenger” RNA molecules, which carry genetic code instructions to protein-building machinery in cells, they can effectively switch off certain genes.
When miRNA was extracted from hypothalamus stem cells and injected into the cerebrospinal fluid of mice, ageing was once again significantly slowed.
As a first step towards new anti-ageing treatments, the scientists are now trying to identify specific populations of anti-ageing microRNAs and possibly other secretions from hypothalamus stem cells that may play a role.
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