Sentinel p16INK4a+ cells in the basement membrane form a reparative niche in the lung

Senescence marker revisitedSearching for cells that express the p16INK4a tumor suppressor, which is often used as a marker of senescence during aging, Reyes et al. identified a population of fibroblasts within the stem cell niche in the lungs of young mice. When lung epithelial cells were injured with a toxic compound, they appeared to increase secretion and stimulate airway stem cells to regenerate the epithelium. The findings raise questions about whether all p16INK4a-expressing cells are senescent, and if strategies to remove such cells (because senescent cells can be harmful) could interfere with prevously unappreciated beneficial effects. —LBR