Harvard Medical School researchers have found a way to reverse the aging process in mice, and are now looking to do the same for humans. 

Ronald DePinho, leader of the study and a scientist at Harvard Medical School, along with a group of Harvard researchers, have regenerated the bodies of elderly mice turning them into healthy, rejuvenated animals again. 

The aging process is not completely understood at this point, but what researchers do know is that free radicals, which are highly reactive particles created naturally within the body, damage cells which helps cause the aging process. Other known causes are ultraviolet light, smoking and other environmental factors. 

But now, DePinho and his fellow researchers at Harvard Medical School have discovered that an anti-aging therapy called telomere shortening has the potential to eliminate age-related issues like dementia and heart disease by rejuvenating old, worn out organs. 

The body typically contains cells that have 23 pairs of chromosomes, and at the end of each chromosome is a "protective cap" called a telomere. Telomeres are cut shorter every time a cell divides, causing the telomere to eventually stop working, fall into a suspended state called "senescence" or die. This process wears out cells and contributes to the aging process. 

To counter this process, DePinho and his team of researchers genetically manipulated mice, eliminating the enzyme telomerase within them. Telomerase is an enzyme that prevents telomeres from getting shorter. In lab tests, these mice aged prematurely and experienced tell-tale signs of growing older, such as loss of smell, infertility, smaller brain size, and damaged organs such as the intestines. But when given injections to reactivate telomerase, the signs of aging were reversed and tissues that were previously destroyed had been repaired. 

"What we saw in these animals was not a slowing down or stabilization of the aging process. We saw a dramatic reversal - and that was unexpected," said DePinho. "This could lead to strategies that enhance the regenerative potential of organs as individuals age and so increase their quality of life. Whether it serves to increase longevity is a question we are not yet in a position to answer."

DePinho noted that these severely aged mice showed signs of considerable restoration after only one month of treatment. Among the several restored organs in the body was the brain, which showed growth of new neurons. 

While this therapy is ideal for mice, it will be challenging to translate this type of treatment to humans because slowing the aging process this way could increase the risk of cancer in humans. Mice have the ability to create telomerase throughout the span of their lives, but telomerase eventually discontinues in humans in order to stop cells from overpopulating and possibly turning into cancerous cells. The constant production of telomerase in mice kept all of the Harvard mice from developing cancer after completing treatment. 

DePinho said that increasing the levels of telomerase in humans could possibly slow the aging process the same way it did in mice, but the heightened risk of cancer makes this therapy much too chancy for people yet. But he also pointed out that the treatment could be safe if it was administered periodically to young people who do not have living cancer cells. 

"The goal for human tissue 'rejuvenation' would be to remove senescent cells, or else compensate for the deleterious effects they have on tissues and organs," said David Kipling, a researcher at Cardiff University who studies aging. "Although this is a fascinating study, it must be remembered that mice are not little men, particularly with regard to their telomeres, and it remains unclear whether a similar telomerase reactivation in adult humans would lead to the removal of senescent cells."

DePinho and his fellow researchers a Harvard hope to continue working on this therapy in order to make it accessible to humans without causing severe side effects, such as cancer. If an appropriate therapy was created for humans, it could prolong the quality of life for elderly people and eliminate health problems that come with age such as stroke and dementia. 

"They key question is what might this mean for human therapies against age-related diseases?" said Tom Kirkwood, director of the Institute for Aging and Health at Newcastle University. "While there is some evidence that telomere erosion contributes to age-associated human pathology, it is surely not the only, or even dominant cause as it appears to be in mice engineered to lack telomerase. Furthermore, there is the ever-present anxiety that telomerase reactivation is a hallmark of most human cancers."

This study was published in Nature on November 28.