Original source: New Scientist
Your brain may be to blame for your ageing body. A small cluster of stem cells in the brain seems to help mice stay young, and injecting extra stem cells helps them live longer. One day anti-ageing drugs might be able to replicate the effect in people.
Ageing is a complicated process, involving DNA damage, chronic inflammation, and worn-out cells, but we don’t yet know which of these has the biggest impact on ageing. Dongsheng Cai at the Albert Einstein College of Medicine in New York has been investigating the role of the brain in ageing, since it controls most of our bodily functions.
His team previously found that the hypothalamus, which releases hormones that affect other organs, seems to affect how mice age. By interfering with a molecular pathway in the hypothalamus, the team extended the lifespan of mice by 20 per cent.
Cai’s team wondered whether stem cells here might influence ageing. Although stem cells in the hypothalamus create new neurons throughout life, the team noticed that mice start losing them in middle age – about 10 or 11 months old. By the time mice are 2 years old – around 70 in human years – the cells are basically all gone, says Cai.
Mice age faster if these stem cells are destroyed. “There was a decline in learning and memory, coordination, muscle mass, endurance and skin thickness,” says Cai. The mice died a few months earlier than untreated animals.
But injecting the hypothalamus with extra stem cells, taken from the brains of newborn mice, slowed down this premature ageing, and gave mice an extra two to four months of life (Nature, DOI: 10.1038/nature23282).
First the team had to modify the stem cells so that they kick-started an anti-inflammatory pathway in the mice, otherwise the cells died and the injections didn’t work. This suggests that it may be inflammation that usually causes the death of stem cells in the brain as we age.
The team found that the injected stem cells secreted a particularly large amount of microRNAs. These are small molecules that can affect the way genes work, and the types of microRNA in our blood are known to vary according to age. Cai isn’t sure how the stem cell microRNAs might be working, but they seem to reduce biological stress and inflammation, he says.
Cai thinks his team’s findings could one day lead to a treatment for ageing. Once the microRNAs have been identified, it might be possible to develop drugs that mimic their effects, he says.
This may have the potential to become a therapy in about 30 years, says Richard Faragher at the University of Brighton, UK, who says other teams are already working towards microRNA drug treatments. An alternative strategy would be to target inflammation more generally. “I can see us taking multiple approaches,” says Faragher.