Fig. 3.

Differences between quiescent and cycling stem cells in DNA repair and metabolism. The proliferation rate of a stem cell affects its exposure and responses to mechanisms of aging. Although quiescent stem cells are less susceptible to DNA damage, when it does occur they are more likely to utilize error-prone non-homologous end-joining (NHEJ) as a repair mechanism, whereas cycling stem cells are more likely to use homologous recombination (HR). Cycling stem cells also have higher metabolic demands than quiescent stem cells, including both higher rates of glycolysis and increased oxidative metabolism.