It's an exciting time to be an elderly mouse. Researchers believe that by removing senescent cells (cells with a persistent damage response), which naturally accumulate with age, senior rodents can regrow hair, run faster, and improve organ function. This strategy may bring us one step closer to the "fountain of youth," but it's important to be cautious, says researcher of aging Dr. Peter de Keizer (photo) of the Erasmus University Medical Center in the Netherlands. In an Opinion piece published December 29, 2016 in Trends in Molecule Medicine, he discusses the milestones the field still needs to hit before translation to humans is ready for discussion. The piece is titled “The Fountain of Youth by Targeting Senescent Cells?" The removal of senescent cells, first discovered in the 1960s, received renewed interest in the 2010s as a therapeutic option to combat some aspects of aging. Researchers noticed that these permanently arrested cells accumulate in mature tissue and that some of them secrete factors that are harmful to tissue function and impair their neighboring cells. To explain what causes this noise in the system, Dr. de Keizer proposes a "senescence-stem lock model" in which the chronic secretion of pro-inflammatory factors by these senescent cells keeps neighboring cells in a permanent stem-like state and thereby prevents proper tissue renewal. "When bringing in a defective car for repairs it is insufficient to remove the rust and broken parts; you also want to replace these," says Dr. de Keizer "A perfect anti-senescence therapy would not only clear senescent cells, but also kick-start tissue rejuvenation by stimulating differentiation of nearby stem cells.