Introduction: Human hematopoietic stem cells (HSCs) have been clinically used for transplantation and gene and cellular therapy for more than 4 decades. However, this use is limited because of the challenges in the ex vivo culturing of HSCs. The major hurdle is to amplify these cells without losing their self-renewing property.
Methods: In our study, we tested 3',4'-dimethoxyflavone (3'4'-DMF) and valproic acid (VPA) on the ex vivo expansion of HSCs under both normoxic (20% O2) and hypoxic (1% O2) conditions. 3'4'-DMF is a widely used anticancer drug that acts as a competitive antagonist of the aryl hydrocarbon receptor. VPA is a potent inhibitor of histone deacetylase and is used in the treatment of neurologic disorders.
Results: Culturing HSCs (from mobilized peripheral blood) under normoxia, with 3'4'-DMF and VPA, highly preserved the CD34 positivity (3'4'-DMF, 22.1%, VPA, 20.3%) after 1 week and strongly enhanced the CD34(+) cells (3'4'-DMF, 27.8 fold; VPA, 34.1 fold) compared with the control cultures (11.6% and 14.4 fold). Addition of 3'4'-DMF and VPA also resulted in more primary colonies and replating efficiency compared with control cultures. Although no significant effect was observed on the enhancement of CD34(+) cells under hypoxia, the number of primary colonies was significantly higher than the control cultures.
Conclusions: Based on these findings, this study presents, for the first time, in vitro evidence for a new and relevant effect of 3'4'-DMF on human HSCs. In addition, the results suggest a potential clinical use of 3'4'-DMF and VPA in HSC therapy.