What are "zombie cells" and how do you get rid of them?

Zombie cells are cells that have stopped dividing but refuse to die. They accumulate as you age and continuously pump inflammatory substances into their surroundings. Those substances damage neighbouring healthy cells and tissues and have been linked to multiple age-related diseases, from joint problems to brain disorders.

Not all zombie cells are harmful. During embryonic development and in ordinary wound healing they actually play a useful role: they inhibit uncontrolled cell growth and help renew tissue. The problem only arises when they build up for too long and the immune system can no longer clear them in time. In people with chronic diabetic foot wounds you can see exactly that going wrong: senescent cells accumulate and inhibit the healing process that they would accelerate in a normal wound.

In mouse models of Alzheimer-like brain diseases, zombie cells were also found in brain support cells. Early intervention by removing those cells prevented tau accumulation, brain inflammation and neuron loss, and kept memory better intact. This has been demonstrated exclusively in animal research; whether it works in humans is still unknown.

Several strategies have now been investigated for the targeted removal of zombie cells, so-called senolytics. The drug navitoclax activates programmed cell death specifically in senescent cells; in mice it rejuvenated blood-forming tissue and muscle tissue. Researchers at Erasmus MC designed a peptide that prompts senescent cells to self-destruct without affecting healthy cells: mice looked healthier and their kidney function improved. Surprisingly, the common diabetes drug canagliflozin (an SGLT2 inhibitor) also turned out to reduce senescent cells in mice via the immune system, and even to extend lifespan in mice with premature ageing. Notably, ordinary insulin treatment did not have this effect, suggesting it involves more than just lowering blood sugar.

All of these findings come from animal and laboratory research. No proven senolytic treatment is yet available for humans. Researchers are working on measurement methods to identify zombie cells in human tissue, but these are not yet clinically available. The field is active and the results in animals are consistently positive, but the step towards a safe and effective treatment in humans has yet to be taken.