November 29, 2010
Scientists Slow Aging Process In Mice
Harvard scientists believe they might be a step closer to reversing the aging process.
The researchers at Harvard Medical School developed an experimental treatment that turned weak and feeble old mice into healthy animals by regenerating their aged bodies.
An anti-aging therapy could have a dramatic impact on public health by reducing the burden of age-related health problems.
"What we saw in these animals was not a slowing down or stabilization of the ageing process. We saw a dramatic reversal "“ and that was unexpected," said Ronald DePinho, who led the study, which was published in the journal Nature.
"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 told the Guardian
Scientists know that the aging process is caused by highly reactive particles known as free radicals that are made naturally in the body and cause damage to cells, while smoking, ultraviolet light and other environmental factors also contribute to aging.
The Harvard group focused on a process known as telomere shortening. Most cells in the body contain 23 pairs of chromosomes, which carry our DNA.
Each chromosome has a protective cap known as telomere at the end. Each time a cell divides, the telomeres become shorter, until eventually they stop working and the cell dies or goes into a suspended state known as "senescence."
The scientists bred genetically manipulated mice that lacked an enzyme called telomerase that stops telomeres from getting shorter. Without the enzyme, the mice aged prematurely and suffered ailments, such as poor sense of smell, smaller brain size, infertility and damaged intestines and spleens.
However, when DePinho gave the mice injections to reactivate the enzymes, it repaired the damaged tissues and reversed the signs of aging.
"These were severely aged animals, but after a month of treatment they showed a substantial restoration, including the growth of new neurons in their brains," DePinho told The Guardian.
Raising telomerase levels in people might slow the aging process, but would increase the risk of cancer.
DePinho said the treatment might be safe in humans if they were given periodically and only to younger people who do not have tiny clumps of cancer cells already living in their bodies.
David Kipling, who studies aging at Cardiff University, told The Guardian: "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. 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."
Lynne Cox, a biochemist at Oxford University, told The Guardian the study was "extremely important" and "provides proof of principle that short-term treatment to restore telomerase in adults already showing age-related tissue degeneration can rejuvenate aged tissues and restore physiological function."
The Harvard researchers' mice developed cancer after the treatment. The team is now investigating whether it extends the lifespan of mice or enables them to live healthier into old age.
Tom Kirkwood, director of the Institute for Aging and Health at Newcastle University, told The Guardian: "The key question is what might this mean for human therapies against age-related diseases? 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."
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