Killing Worn-Out Cells to Stop Aging
Nov. 4, 2011
Weakened muscles and certain other signs of aging could be reversed or even prevented if a technique used in mice can be applied to humans, says a team of researchers at the Mayo Clinic in Rochester, Minnesota. The technique involves targeting worn-out cells, called senescent cells, for destruction. Senescence is the process of growing old.
Scientists have long known that all cells in the body divide during growth and development. But cells can divide only a limited number of times. Aging cells often die. Only about 5 to 15 percent of the cells in the body of a typical elderly adult become senescent. But these few cells have a dramatic effect on the body. In people, age-related changes include graying or loss of hair, weakened muscles, wrinkled skin, and hearing and vision problems. One way senescent cells produce such changes is by secreting a variety of harmful compounds that cause inflammation. In healthy individuals, inflammation is the body’s normal response to injury or infection. However, inappropriate or uncontrolled inflammation can damage healthy tissue. Scientists believe inflammation is an underlying cause of many age-related diseases in people, including arthritis, cataracts, and dementia.
Exercise can help elderly people maintain or improve physical fitness. © Chuck Savage, Corbis.
The Mayo scientists experimented with a strain of mice that were genetically engineered so their cells produced a molecule called caspase 8 as they aged. They then injected the mice with a drug that specifically targets the molecule and causes those cells that contain it to commit suicide. The drug has no effect on normal cells, so healthy tissues were spared and there were no side effects. The drug did not affect the life expectancy of the mice. This kind of genetic engineering cannot be used in people, but researchers hope to develop other ways of targeting human senescent to produce the same beneficial effects. However, such techniques are probably years away.
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