Fig. 1

Illustration of the discrepancy between the colony-forming efficiency and survival of CD264^+/− populations of hBMSCs. The two populations were generated by fluorescence-activated cell sorting based on the expression of CD264, a marker of cellular aging. a In vitro survival and colony-forming efficiency was resolved at the single-cell level by inoculating multi-well plates via limiting dilution. In wells inoculated with single cells, culture-matched CD264⁻ and CD264⁺ populations had a comparable percentage of surviving cells after a week of culture, as measured by cell attachment; however, fewer of the aging CD264⁺ cells formed colonies > 10 cells during the same period. b In vivo survival of the two populations was evaluated by bioluminescence imaging for a month after the cells were implanted subcutaneously on the dorsum of immunodeficient mice. Prior to implantation, hBMSCs were transduced with a luciferase, sorted into CD264⁻ and CD264⁺ populations, and attached to ceramic scaffolds. For each sorted population, colony-forming efficiency was measured 2 weeks after the cells were plated at clonogenic levels into 10-cm culture dishes. The luminescence half-life was similar for culture-matched CD264⁻ and CD264⁺ populations despite a lower efficiency for CD264⁺ cells to form colonies > 50 cells. CFU, colony-forming unit; hBMSCs, human bone marrow mesenchymal stem cells; Luc, luciferase