Telomere length changes in donor cells after transplantation of purified human CB cells into immune-deficient mice. (A) Schematic for transplantation, sorting, and STELA analysis is shown on the left panel. Lin⁻CD34⁺CD38⁻Rho⁻ cells were transplanted into mice, and differentiated cell types were sorted 6 weeks after transplantation. STELA analysis was then performed and telomere lengths were compared. Differences in telomere lengths between differentiated and progenitor cell types in CB-4 are shown as kilobases, in red, whereas telomere lengths (excluding outliers) are shown in blue. The number of cell divisions between differentiated and progenitor cells are represented by arrowheads, each representing 2.5 cell divisions (assuming ∼ 100 bp loss per cell division). (B) Graphs showing the difference between telomere lengths from progenitor to daughter cells before and after transplantation in CB-4 and CB-5. Note the large decrease in telomere length from the Lin⁻CD34⁺CD38⁻Rho⁻ to the CD34⁺CD38⁻ populations in both transplants with respect to pretransplantation telomere loss.