The cell division history of CD34+CD90+ cells during ex vivo culture. CFSE-labeled CD34+ cells were cultured in the presence of cytokines with or without 5azaD/TSA treatment for 9 days. The panel shows a representative (1 of 3 experiments) flow cytometric profile of CFSE fluorescence intensity after 5 days and 9 days of culture. The arrow indicates the fraction of cells that have not undergone cell division.