Figure 1.
Hypothetical tracing of the offspring of a single HSC during aging. In mice, the most primitive HSC are believed to cycle only once every ∼4 months.23 With each cell division, daughter cells lose developmental (long-term repopulating) potential, such that each daughter is less potent than its ancestor. Cell-cycle times decrease with developmental stage. In young mice, the pool of stem cells is small, but the potency of each stem cell is high. In aged mice, the pool of stem cells has expanded, but their functionality is restricted. Adapted from Van Zant et al24 and Jung et al.25
