Plasticity and stringency: rethinking stem cell division modes

Asymmetric cell division (ACD) has been extensively studied in various stem cell systems as a fundamental mechanism that ensures the balance between stem cell self-renewal and differentiation. ACD allows one daughter cell to retain stem cell identity while the other commits to differentiation, thereby maintaining tissue homeostasis over time. Stem cells also undergo symmetric cell division, in which both daughter cells adopt either stem or differentiated fates. What are the outcomes of each cell division mode, and how strictly are these modes executed across different stem cell systems? There have been technical challenges of visualizing stem cell division in vivo due to the structural complexity of tissues and the rarity and ambiguous identity of genuine stem cells. Despite these difficulties, recent technical advancements have revealed how these cells operate within their native environments. This review summarizes key studies that elucidate distinct division modes and their functional outcomes across various stem cell systems.