Studies suggest that zombie cells do not die as they build up in the body they promote aging; and the conditions that come with it like osteoporosis and Alzheimer’s disease. Researchers are studying drugs that can kill zombie cells and possibly treat the problems they bring.
Basically the goal is to fight aging itself, which hopefully will in turn delay the appearance of age-related disease and disabilities as a group, says geriatrics specialist Dr. James Kirkland of the Mayo Clinic in Rochester, Minnesota. That’s in contrast to playing a “whack-a-mole game” of treating one disease only to see another spring up, he said.
The research was doing chiefly in mice. Earlier this year, the first test in people was publishing and provided some tantalizing results. Zombie cells are actually called senescent cells. They start out normal but then encounter a stress, like damage to their DNA or viral infection. At that point, a cell can choose to die or become a zombie, basically entering a state of suspended animation.
Eliminating zombie cells
The problem is that zombie cells release chemicals that can harm nearby normal cells. That’s where the trouble starts. What kind of trouble? In mouse studies, drugs that eliminate zombie cells so-called senolytics—have been shown to improve an impressive list of conditions, such as cataracts, diabetes, osteoporosis, Alzheimer’s disease, enlargement of the heart, kidney problems, clogged arteries and age-related loss of muscle.
Mouse studies have also shown a more direct tie between zombie cells and aging. When drugs targeting those cells were given to aged mice, the animals showed better walking speed, grip strength and endurance on a treadmill. Even when the treatment was applied to very old mice, the equivalent of people ages 75 to 90, it extended lifespan by an average of 36 percent.
Researchers have also shown that transplanting zombie cells into young mice basically made them act older: their maximum walking speed slowed down, and their muscle strength and endurance decreased. Tests showed the implanted cells converted other cells to zombie status.
Idiopathic pulmonary fibrosis
Kirkland and colleagues this year published the first study of a zombie-cell treatment in people. It involved 14 patients with idiopathic pulmonary fibrosis, a generally fatal disease that scars the lining of the lungs. Risk rises with age, and the lungs of patients show evidence of zombie cells.
In the preliminary experiment, after three weeks of treatment, patients improved on some measures of physical fitness, like walking speed. Other measures did not show improvement. This April 2019 microscope photo provided by the Niedernhofer Lab of the Institute on the Biology of Aging and Metabolism at the University of Minnesota shows senescent human fibroblast cells in Minneapolis, Minn.
DNA or viral infection
“Zombie” cells start out normal but then encounter a stress, like damage to their DNA or viral infection. At that point, a cell can choose to die or become a zombie, which means they stop going through their normal cycle of activities. The problem is that they then start secreting substances that can harm nearby normal cells. (Matthew Yousefzadeh, Mariah Witt/University of Minnesota via AP)
Overall, the results are encouraging and “it really raises enthusiasm to proceed with the more rigorous studies,” said Dr. Gregory Cosgrove, chief medical officer of the Pulmonary Fibrosis Foundation, who played no role in the study. The field of zombie cells is still young. But Kirkland estimates at least a dozen companies have formed or have launched efforts to pursue treatments. He holds shares in one.