Stem Cells Tightly Regulate Dead Cell Clearance to Maintain Tissue Fitness

This document reports on the discovery that stem cells can temporarily take on the role of non-professional phagocytes to clear dying cells during the hair cycle, a process essential for maintaining tissue health. The study reveals that this phagocytic activity is tightly regulated by local lipids from apoptotic cells, which activate RXRα, and tissue-specific retinoids that activate RARγ, ensuring that stem cells can balance their primary function of cell replenishment with the clearance of dead cells. This mechanism provides a way for stem cells to maintain tissue integrity during normal conditions and has wider implications for understanding how non-motile stem or progenitor cells manage cell death in areas where the immune system is less active.