We mark the passage of time linearly, with cake and presents on our birthdays each year. But, for better or worse, our bodies have their own plan. Rather than marching in lockstep along with the passage of time, different parts of our bodies age at different rates. Now a new study published in the journal Nature Aging is unraveling their schedules.
Researchers led by a team of data scientists from the Sanford Burnham Prebys Medical Discovery Institute in Southern California turned to data collected by the Genotype-Tissue Expression Project, which collects tissue samples from a variety of organs to investigate gene expression. But the researchers weren’t primarily interested in the genes. Instead, they wanted the imaging data (digital reams of photos of thinly sliced tissue) to examine the structural changes that occur as time passes.
The team used a deep-learning computer vision model they developed to scan more than 25,000 images of 40 types of normal tissue from nearly 1,000 donors between the ages of 21 and 70. They found our organs structurally age in three distinct patterns. The first are early aging systems, like our blood vessels. These tissues experienced accelerated aging from ages 30 to 39 that then tapered off. Late-aging organs, like the uterus and vagina, showed steady aging before accelerating around ages 50 to 59.
But most of the organs showed a different pattern, which the researchers termed “biphasic aging.” In these organs, which include everything in the digestive tract as well as the prostate and testes, they found two distinct peaks of accelerated structural aging. The timing of the peaks differed depending on the organ type, but in general, they seemed to occur when people are in their 30s and their 50s.
Once they had the basic patterns down, the researchers knew where (or when) to look for differences in the gene expression data. They found that aging peaks coincided with increased expression of genes involved in inflammation and decreased expression of genes related to energy production, cell growth, and cellular quality control. In other words, the structural difference they identified corresponded with the kinds of epigenetic differences you might expect.
And that’s not all. While the team found that organs in the same system seemed to experience the same aging patterns, they also found some degree of cross-coordination between the digestive and reproductive systems. For example, if someone experienced accelerated aging in their colon and esophagus, their prostate would likely show accelerated aging as well. Basically, these systems seem to be talking to one another (probably via hormones).
It would be nice if they filled us in, too.
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