Figure 6. A schematic model of ex vivo CD34⁺CD90⁺ expansion from human PBSC HSPCs.

We propose the following model: Under culture conditions with stimulating cytokines, CD34⁺ HSPCs tend to differentiate and become CD34⁻ or CD34⁺CD90⁻ cells. Addition of epigenetic modifiers, such as the HDACi TSA to the culture media, results in expansion of CD34⁺CD90⁺ cells. The TSA-mediated HSPC expansion functions, at least in part, through transcription factor SALL4 (TF SALL4).