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An international team of scientists have identified for the first time a key factor responsible for declining muscle repair during aging, and discovered how to halt the process in mice with a common drug
An international team of scientists have identified for the first time a key factor responsible for declining muscle repair during ageing, and discovered how to halt the process in mice with a common drug. Although an early study, the findings provide clues as to how muscles lose mass with age, which can result in weakness that affects mobility and may cause falls.
The study, to be published in the journal Nature, involved researchers from King's College London, Harvard University and Massachusetts General Hospital.
The study looked at stem cells found inside muscle which are responsible for repairing injury to find out why the ability of muscles to regenerate declines with age. A dormant reservoir of stem cells is present inside every muscle, ready to be activated by exercise and injury to repair any damage. When needed, these cells divide into hundreds of new muscle fibres that repair the muscle. At the end of the repairing process some of these cells also replenish the pool of dormant stem cells so that the muscle retains the ability to repair itself again and again.
The researchers carried out a study on old mice and found the number of dormant stem cells present in the pool reduces with age, which could explain the decline in the muscle's ability to repair and regenerate as it gets older. When these old muscles were screened the team found high levels of FGF2, a protein that has the ability to stimulate cells to divide. While encouraging stem cells to divide and repair muscle is a normal and crucial process, they found that FGF2 could also awaken the dormant pool of stem cells even when they were not needed. The continued activation of dormant stem cells meant the pool was depleted over time, so when the muscle really needed stem cells to repair itself the muscle was unable to respond properly.
Following this finding, the researchers attempted to inhibit FGF2 in old muscles to prevent the stem cell pool from being kick-started into action unnecessarily. By administering a common FGF2 inhibitor drug they were able to inhibit the decline in the number of muscle stem cells in the mice.
Dr Albert Basson, Senior Lecturer at the King's College London Dental Institute, said: 'Preventing or reversing muscle wasting in old age in humans is still a way off, but this study has for the first time revealed a process which could be responsible for age-related muscle wasting, which is extremely exciting.
'The finding opens up the possibility that one day we could develop treatments to make old muscles young again. If we could do this, we may be able to enable people to live more mobile, independent lives as they age.'
Dr Andrew Brack, senior and corresponding author of the study from Harvard University, said: 'Analogous to the importance of recovery for athletes training for a sporting event, we now know that it is essential for adult stem cells to rest between bouts of expenditure. Preventing stem cell recuperation leads to their eventual demise.'
Kieran Jones, co-author of the study from King's, added: 'We do not yet know how or why levels of the protein FGF2 increase with age, triggering stem cells to be activated when they are not needed. This is something that needs to be explored.
'The next step is to analyse old muscle in humans to see if the same mechanism could be responsible for stem cell depletion in human muscle fibres, leading to loss of mass and wastage.'
The world needs to do more to prepare for the impact of a rapidly ageing population, the UN has warned - particularly in developing countries. Within 10 years the number of people aged over 60 will pass one billion, a report by the UN Population Fund said. The demographic shift will present huge challenges to countries' welfare, pension and healthcare systems. The UN agency also said more had to be done to tackle "abuse, neglect and violence against older persons". The number of older people worldwide is growing faster than any other age group. The report, Ageing in the 21st Century: A Celebration and a Challenge, estimates that one in nine people around the world are older than 60.
The elderly population is expected to swell by 200 million in the next decade to surpass one billion, and reach two billion by 2050. This rising proportion of older people is a consequence of success - improved nutrition, sanitation, healthcare, education and economic well-being are contributing factors, the report says. But the UN and a charity that also contributed to the report, HelpAge International, say the ageing population is being widely mismanaged. "In many developing countries with large populations of young people, the challenge is that governments have not put policies and practices in place to support their current older populations or made enough preparations for 2050," the agencies said in a joint statement.
'Cast out'
The report warns that the skills and experience of older people are being wasted, with many under-employed and vulnerable to discrimination. HelpAge said more countries needed to introduce pension schemes to ensure economic independence and reduce poverty in old age. It stressed that it was not enough to simply pass legislation - the new schemes needed to be funded properly. The UN report used India as an example, saying it needed to take urgent steps in this area. Almost two-thirds of India's population is under 30. But it also has 100 million elderly people - a figure that is expected to increase threefold by 2050. Traditionally, people in India live in large, extended families and elderly people have been well looked after. But the trend now is to have smaller, nuclear families and many of the country's elderly are finding themselves cast out, says the BBC's Sanjoy Majumder in Delhi.
There are more and more cases of physical and mental abuse, including neglect, suffered by the elderly at the hands of their families. It is slowly becoming a widespread social problem, particularly in urban areas, one which India still has not got to grips with, our correspondent says. By contrast, the UN report cited the case of Bolivia as an example of good practice in the developing world. All Bolivians over the age of 60 get a pension that is the equivalent of about $30 (£19) a month. Bolivia suffers from frequent flooding and landslides, and older people there have been organised into "Brigadas Blancas" - White Haired Brigades. They help with preparations for emergencies, and accessing humanitarian aid.
BBC News - UN warns over impact of rapidly ageing populations
