Figure 1

Erythropoietin induces proliferation of quiescent BM VSELs. Panel A. BrdU incorporation into VSELs after EPO treatment. (a) The percentage of VSELs that incorporated BrdU into newly synthesized DNA. After treatment with 10 doses of EPO at 25 U/dose, ~20% of VSELs are BrdU⁺, in contrast to the control group (~2% of VSELs are BrdU⁺). (b) Incorporation of BrdU was measured by FACS. Representative FACS analysis of six experiments is shown. Panel B. Analysis of VSELs for the presence of erythroid markers. Cells were fixed and stained with 7AAD to show only events exhibiting DNA content, gate P1 (not shown). Gate P2 includes small, agranular cells. Gate P3 includes Sca-1⁺/Lin^- cells, which are visualized on the next dot plot as CD45-negative cells (VSELs) and CD45-positive cells (HSPCs). Erythroblast markers CD 71 and Ter-119 are not expressed on VSELs (right, lower panel) in contrast to control cells, where some of the cells express CD71 and Ter-119 among the population from the P2 gate (left, lower panel). One representative dot plot analysis out of three is shown.