After scientists rejuvenated tissues in middle-aged mice, the prospect of medical therapies that can reverse the aging process has become a little closer.
Researchers in the US treated healthy animals with a form of gene therapy that refreshed older cells, making the animals more youthful according to biological markers that are used to measure the effects of aging.
The findings will fuel interest in radical new therapies that aim to slow or reverse the aging process as a means of tackling age-related diseases such as cancer, brittle bones and Alzheimer's.
A host of age-related diseases might benefit from this approach, according to a principal fellow and director at the US firm Genentech.
If the approach can be shown to combat certain health problems, it would constitute a new therapeutic approach with a significant impact on unmet medical needs at all stages of our life.
The scientists drew on previous work by Prof Yamanaka, who showed that a mixture of four molecules, known as Yamanaka factors, can reprogram adult cells into stem cells that are capable of forming almost any tissue in the body.
The US team led by Jasper and Prof Juan Carlos Izpisua Belmonte at the Salk Institute in California and the San Diego Altos Institute found that mice who received Yamanaka factors for several months resembled younger animals in many ways.
When the animals were 12 to 15 months old, the therapy was more effective than it was when they were 7 to 10 months old. The scientists saw little impact when older animals were treated for a month.
Yamanaka factors can turn fully reprogrammed cells into clumps of cancer, so researchers are cautious about using them in humans.
The latest study shows that partial reprogrammability may be possible, but there are still hurdles to overcome. Many scientists think that new drugs will be needed to reprogram cells safely and effectively, rather than using Yamanaka factors.
Will this ever find application in humans, said Dr Tamir Chandra, an expert in the biology of aging at the University of Edinburgh, who was not involved in the study.
In theory, biological age reversal or reduction could be possible. We need to understand the basic science behind it better at this early stage.
Yamanaka factors have the risk of inducing cancer, and unlike mice, humans carry many more mutations at older age, which might already be predisposition to developing into a cancer.
Research groups are working on timing, dosage and combinations of Yamanaka factors.
The loss of cell identity and age reversal can be different in their trajectory now that we know about the rejuvenation effects.
The first applications are likely to be in tissue that is easily accessible and can be modified outside the body.
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