Scientists say they have reversed age-related degeneration in mice, resulting in an improvement in the rodents' fertility and the growth of new brain tissue. But it could be some time before the technique might be used in humans.
Fountain of youth
Scientists at Harvard University's Dana-Farber Cancer Institute in Boston report they were able to reverse signs of aging in mice by tweaking a gene that protects cells from the harmful, cumulative effects associated with growing old.
The gene is involved in the production of structures at the tips of DNA chromosomes called telomeres.
Telomeres are like the plastic caps on the ends of shoe laces that keep them from becoming frayed. In the case of chromosomes, the telomeres protect the strands of DNA from environmental assaults such as chemical and radiation exposure.
But every time a cell divides, its telemeres shorten, eventually leading to DNA damage and aging.
In studies with mice, researchers switched off the telomerase gene and watched the rodents rapidly develop age-related impairments.
However, when they turned the genes back on on, the animals' declines reversed.
"Their fertility was restored. We also saw a big effect on the lining of the intestines and as well as in the brain, which was a little bit unexpected," says lead researcher Mariela Jaskelioff. "We actually saw a decrease in the size of the brains of these mice with premature aging. And we could reverse these by reactivating telomerase."
The mice in the study were at an age equivalent of an 80- or 90-year-old human. Researchers restored them to middle age by turning on the telomerase gene.
Despite the encouraging results, the genetic manipulation is not the secret to eternal youth for humans. Jaskelioff says the telomerase gene is involved in the growth of both normal and cancerous cells.
"The fear is that in humans, adult humans, we accumulate mutations all through our lifetimes," she says. "And if we were to reactivate telomerase in cells that have malignant mutations, then the propensity to develop cancer would probably be exacerbated."
However, according to Jaskelioff, it might be possible to stimulate the telomerase gene for short periods of time in people with a rare disorder which causes premature aging.
Scientists describe how they reversed aging in mice in an article published in the journal Nature Medicine.