HEART
April 24, 2009

You Can Mend a Broken Heart

Heart cells can regenerate, according to a study that used a an approach more common to archeology than biology.
An inventive new study by a team at the Karolinska Institute in Stockholm challenges the long-held belief that heart cells are incapable of regenerating and that our hearts, in effect, are made of exactly the same cells as they were at birth. The idea that heart cells may actually be able to renew themselves could be used down the road in developing new treatments for certain types of heart disease.

As suspected, the team found that some heart cells did contain Carbon 14, indicating that some cells had divided at one or more points during the person's lifetime.

To determine whether heart cells may actually renew themselves, researchers looked at the hearts of participants who were born prior to Cold War-era nuclear bomb testing — specifically, before 1955. Nuclear testing released the isotope Carbon 14 into the atmosphere, affecting virtually all living organisms. Since cells can use the isotope Carbon 14 to build DNA as they prepare to divide, all animals and plants were radioactively "labeled" with Carbon 14 during the 1950s. (In case you were wondering, 1963 brought the Limited Nuclear Test Ban Treaty which controlled the amount of Carbon 14 released in to the atmosphere.)

The logic of using this using this odd phenomenon was as follows: if the hearts of participants born before 1955 did not regenerate any cells at all, then these hearts should not have incorporated any Carbon 14 into their cells along the way. On the other hand, if hearts cells are capable of division, then one would expect to see some heart cells with Carbon 14 in their DNA.

As suspected, the team found that some heart cells did contain Carbon 14, indicating that some cells had divided at one or more points during the person's lifetime.

The researchers then determined how many cells might be turning over at any given age. They found that at age 20, a person's heart regenerates about 1% of its cells per year — by age 75, this number dwindles to only 0.4%. However, considering this trend, this means that the average 50 year old heart would contain about 45% new heart cells, while 55% would be cells that he or she was born with.

The researchers caution that the findings are preliminary and more research needs to be done before thinking about how to apply the results towards developing treatments for those with heart problems.

While noting that the study provides "really basic knowledge that doesn't solve any problem or help someone with a heart attack," Jonas Frisén, coauthor of the paper, remains optimistic about the study's implications. He adds that, "[t]he dream scenario would be after a heart attack, we have a drug to take to increase heart cells." The study's data, he says, "indicate that it is rational and realistic to think of such possibilities."
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