Stochastic outgrowth of CD34⁺CD90⁺ cells in CFC assays. (A) Number of divisions of CFSE-stained CD34⁺CD90⁺ cells after 24-hour culture in CFC medium. CFSE staining was determined flow cytometrically, and the number of divisions as well as the frequency of divided cells were calculated relative to the parental population. (B) Size and composition of CD34⁺CD90⁺-derived colonies after 11 days of culture. Phenotypes and cell numbers were determined flow cytometrically. Tables in the center indicate the frequency of colonies containing phenotypically defined stages of differentiation defined above. (C) Simulation of the change in the clonal repertoire (blue line) and number of CD34⁺CD90⁺ cells in colonies over time (red line). (D) Correlation of the size of CD34⁺CD90⁺-containing colonies with the actual number of CD34⁺CD90⁺ cells within each colony. (E) Number of CD34⁺CD90⁺ cells within colonies. (F) Visualization of the change in the clonal repertoire and CD34⁺CD90⁺ clone size in colonies based on the simulation. (G) Actual size of the clonal repertoire and CD34⁺CD90⁺ clone size from the CFC assay in panel C. The dot size is proportional to the number of cells in the colony.