Preserved immature phenotype of hematopoietic progenitor cells after in vitro myeloid differentiation culture. HSPCs (LSK cells) were differentiated in vitro into the myeloid lineage for 7 days in the presence or absence of VPA and/or Li. (A) Effects of VPA + Li treatment on cell proliferation. The number of viable cells was scored with trypan blue exclusion. Shown is the mean ± SD (n = 5-7). (B) The proportion of cells that excludes PI after 7 days of differentiation culture. Shown is the mean ± SD (n = 5-7). The proportion of cells excluding PI was in agreement with the proportion of dead cells stained with trypan blue (data not shown). (C) Representative flow cytometric analysis of LSK expression on cells cultured for 7 days with or without VPA + Li. Cells in the graphs were pregated for viable (PI⁻) cells. An equal number of events were collected for each sample. (D) Absolute number of cells with preserved LSK phenotype, quantified on the basis of on FACS data, presented as number of LSK cell per well. Error bars represent SD of the mean (n = 3-7). (E) Percentage of cells with preserved blast-like morphology after 7-day differentiation culture. Shown is the mean ± SD (n = 3-6). (F) Representative cell morphology of cells cultured with or without VPA + Li. Cytospin preparations were stained with May-Grünwald-Giemsa and viewed under a light microscope (original magnification ×100). The differences between groups were evaluated by Welch t test, **P < .01 and ***P < .001.