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It’s easy enough for anyone to reel off a list of the symptoms of age: sprinkles of gray hair, wrinkles, aches and pains lurking in joints and limbs, an increased susceptibility to illness in myriad forms.
What actually causes each of those things is a much tougher question to answer. But over the last decade or so, scientists and researchers have started to chip away in earnest at the drivers of aging at the body’s most fundamental levels. “As I look back over the advances made in cancer research over the last 20 years, I believe the next 20 years will bring much more knowledge on the causes of aging,” says Jan van Deursen, who researches aging on the cellular level at the Mayo Clinic in Rochester, Minnesota.
There seems to be no single culprit in the process, but rather an array: genes that begin to function differently after a lifetime of accumulated damage, changes in how cells communicate with one another, shifts in metabolism that promote obesity and diabetes, how cells die (or don’t). As damage from one or more of these processes accumulates, our bodies show it in numerous ways: weight gain, disease, reduced mental acuity and function, fading eyesight, inflammation.
As the interplay between impaired cellular function and its effects on the body are better understood, scientists hope these insights will lead to strategies, therapies and pharmaceuticals to not only improve quality of life, but perhaps even prolong life.
“The natural human life span is around 30 years, which we’ve extended by decades,” van Deursen notes. “There’s no evolutionary reason for this life span extension; it’s because we’ve made improvements to our lifestyles and environments. The systems in the human body were not meant to last for so long, and so, like driving a car around for too many miles, the parts start to break down and function incorrectly.”
Van Deursen’s specific area of interest concerns senescent cells, or cells that have become damaged enough to stop dividing yet do not die. Though long thought to be benign and dormant (if unusual), it turns out that senescent cells play an important role in aging.
Senescence is triggered by stress and disease, and is thought to be one of the body’s antitumor mechanisms. While damaged, senescent cells send out signals for the immune system to come and clear them out. But this doesn’t always happen, so senescent cells accumulate slowly but steadily in tissues around the body throughout life.
Yet, it’s been discovered, these cells are far from inert: Senescence induces cells to produce a variety of chemical signals that cause neighboring cells to also malfunction. Further, they accumulate faster in areas of the body already weakened by other stress or physical damage, such as in arteries clogged by plaques.
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