Scientists think that different parts of our bodies are aging at different rates, with a new discovery showing that breast tissue may be one area of the female body that can age the fastest. Why is this, and how could this lead to better cancer diagnosis?
You will no doubt be familiar with the term “biological clock.” Strip it of the sexist connotations and the basic idea is a good one: examining the body and using its different processes, changes in chemical composition and tissue, to determine the life and age of the parts that make us whole.
One new way of looking at age that scientists have discovered is a change to the chemical markings on our DNA. As we get older, our every gene goes through a process of either losing or gaining quantities of the chemical methyl. The process changes the rate of gene expression, or how often a gene synthesizes vital things like new proteins. Those familiar with this aspect of biology will know this process as epigenetics, and it is this process that researchers at the University of California have used to begin estimating how fast or slow our different organs might be aging.
Testing Tissue: How Scientists Created a New Method of Determining Age
Professor Steve Horvath and his team examined what are known as methylation patterns in 7,844 healthy tissue samples taken from, in total, 51 different tissue types. Those tissues were of varying ages, taken from fetuses right through to adults of 101 years old.
Of course, because tissue function differs, not all those methylation patterns could be compared. So, the team had to find the methylation patterns that appeared to be shared by all the tissue samples. They found that there were about 353 shared patterns. With that as a measure, the team then set about creating an algorithm to discover the age of the tissues. There are of course other methods of identifying the aging-rate of tissue, but after validating the algorithm, the team found that reading methylation patterns allowed them to identify a person’s age with 96% accuracy with only a 3.6 year margin of error. The next best method gives only 53% accuracy.
The study demonstrated what is a remarkable uniformity to how fast body tissue ages, something that of itself has scientific interest. Yet the algorithm Horvath and team used also found that there were some marked differences between specific body tissues — and here’s where the usefulness of this kind of process really becomes obvious.
Different Parts of us Are Aging Differently
The team found that according to the methylation patterns in tissue samples from women aged about 46, healthy breast tissue might be as much as three years older than their so-called real age. On the other hand, heart tissue samples taken from both women and men showed that on average heart tissue might be as much as nine years younger than the person’s true age. Why might this be?
The researchers think that breast tissue is frequently exposed to a cocktail of hormones, which is a known factor for aging, whereas the heart is given the benefit of being renewed by stem cells. That age difference in itself is of scientific value because it offers a tantalizing glimpse at the specific factors that can contribute to certain parts of the body aging faster or being saved from aging and, in the long run, points to stem cells being a way to slow aging and perhaps ward off age-related disease –obviously, that’s only a theory. But there are some more immediate implications that arise as a result of this method.
Cancer is Getting Old. Really Old.
The scientists discovered that, per their test, the cancerous tissue ages fast. Very fast.
Calculating an average from tissue taken from 20 different cancers from 20 different organs across the body, cancerous tissue was found to be 36 years older than healthy tissue.
The researchers theorize that the reason breast cancer might be so prevalent is because breast tissue ages faster, perhaps as a result of hormone exposure. This might of course be true of the more prevalent cancers in men, such as prostate cancer. Of course, further research will be needed to establish this particular link.
Even so, if DNA methylation stands up as a measure of aging, it could be used as a new way for diagnosing a whole host of cancers through tissue biopsy, hopefully leading to better detection rates. As the process also works for dating blood, New Scientist notes the method may also have applications in the field of forensic medicine.
Rather than replacing the old methods of testing the age of body tissue, the researchers hope that the DNA methylation test will be used to compliment existing methods.
In terms of wider applications, the method is one more step to so-called “epigenetic interventions” that could allow scientists to slow the body’s aging processes. For those with a particular risk of certain cancers or diseases, scientists one day hope to be able to use stem cells — which this research showed has no DNA methylation age as they are effectively “new born” cells — to reverse aging and prevent disease.
This relies on the notion of there being a concrete link between stopping the body clock and preventing cancer and disease. This will be the subject of Horvath and team’s next set of studies, whereby they hope to discern how prominent a role DNA methylation plays in aging and whether this body clock is present and in what form in other animals.
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