Aryl Hydrocarbon Receptor Antagonists Promote the Expansion of Human Hematopoietic Stem Cells

Stem Cell Expansion The ability to expand hematopoietic stem cells (HSCs) during ex-vivo culture has been an important goal for over 20 years. Using a high-throughput chemical screen, Boitano et al. (p. 1345 , published online 5 August; see the Perspective by Sauvageau and Humphries ) found that a purine derivative, StemRegenin1 (SR1), promoted the expansion of human HSCs. Treatment of HSCs with SR1 (which blocked the activity of the aryl hydrocarbon receptor) led to the expansion of CD34 + cells and a 12 to 17-fold increase in the number of HSCs that engraft immune deficient mice.