Cells in the body usually do what they’re told. In response to cues, cells divide, grow, shrink or die as needed. But there are some cells that start to ignore the body’s order to expire: senescent cells. Sometimes called "zombie cells" for their undead lingering, senescent cells have triggered the body’s kill command, but instead of dying, they exist in a sort of suspended reality, unable to work properly but actively spewing out toxic chemicals.
Animal studies have implicated senescent cells in conditions of aging ranging from brain dysfunction to osteoporosis, but research on senescent cells and their contribution to poor health is still fairly new. The primary focus has been on senescent cells themselves and how removing them affects disease states. Now researchers are looking at the toxic proteins released by senescent cells, called the senescence-associated secretory phenotype, or SASP. They are examining the effect of those proteins in the environment around the cells (microenvironment) and as they circulate through the body.
In a recent study, Mayo Clinic researchers report that the SASP circulating in the human bloodstream might be a reliable marker for distinguishing who is at risk for age-related diseases as well as poor outcomes after surgery. The article published online June 18, 2020, in the journal JCI Insight. Led by the lab of Mayo researcher Nathan LeBrasseur, Ph.D., a collaboration of colleagues assembled to understand how the toxic factors from senescent cells may mirror biological age and, correspondingly, heightened risk for medical procedures.
“We first developed a panel of approximately 30 senescence biomarkers by examining the abundance of diverse proteins secreted by various types of human senescent cells,” says Dr. LeBrasseur. “We then assessed whether they were detectable in human blood samples.”
The researchers looked for those proteins in blood samples of Mayo Clinic Biobank participants. The 267 samples were evenly distributed in donor sex and age from 20–90.
“We show the circulating abundance of the majority of our biomarkers increased with advancing age,” says Dr. LeBrasseur.
Concentrations of 19 biomarkers were associated with chronological age, and, after adjustments for sex and body weight index, 17 remained. This, the authors write, showcases the importance of these factors on the body and how it ages. They conclude that as different types of senescent cells accumulate with age, they may contribute to a personalized and changing SASP within each person.
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