Analysis of kidney cells gives insight into aging process

Stuart Kim

For the first time ever, researchers have examined how kidney cells change at a molecular level with the passage of time, providing new evidence that different cell types age in a similar fashion.

“Our work suggests that there’s a common way for different tissues to get old,” said Stuart Kim, PhD, professor of developmental biology and genetics, who led the study published in today’s issue of Public Library of Science Biology.

Kim’s findings are contrary to a theory that each cell type follows a different pathway as it ages. If this were the case then the cells of an aging kidney would look quite different on the molecular level from, say, the cells of an aging liver.

But Kim’s research suggests that different cells in an animal peter out in the same way. If this were true, researchers would find the same molecular differences between old and young cells from different tissue types.

Indeed, Kim and his group compared which genes are active in kidney cells from 74 people, ranging in age from youth to elderly. They found 742 genes that become more active as the kidney ages and 243 genes that become less active.

They then did the same experiment using different types of kidney tissue, with one sample from the outer kidney, called the cortex, and the other from the inner kidney, called the medulla. Although these two tissues are both from the kidney, they are as different in function as cells from entirely different organs. The researchers found exactly the same genes varied in old and young samples from these two tissues.

Kim said future applications of this work could include helping screen kidneys used for transplant. In the study, the group found that the “molecular age” of a kidney matched how well that kidney filtered blood. One sample from an older person had the molecular appearance of a much younger kidney and it filtered blood like a more youthful organ.

This correlation could help identify healthy kidneys from people older than 60 whose organs would ordinarily be rejected for transplants. Older kidneys with a youthful molecular appearance might still function well enough to be transplanted. “We can look at the kidneys that are being thrown out and parse them into those that are physiologically young and physiologically old,” he said.