Comparison of hematopoietic stem cell expansion methods reveals that aryl hydrocarbon receptor inhibition optimally expands CD90 engrafting cells

Expansion of human hematopoietic stem cells (HSCs) has potential to improve patient outcomes after transplantation. To optimize stem cell expansion, we used prospective sorting and transplant to show that all NOD scid gamma (NSG)- engraftment activity after culture is found within the CD34 CD90 population. Next, we compared three expansion methods: the aryl hydrocarbon receptor (AHR) antagonist, StemRegenin1 (SR1); a pyrimidoindole derivative (UM171); and histone deacetylase inhibitors (HDACi), for the ability to expand phenotypic and functional HSCs. While HDACi and UM171 generated the greatest number of CD34 CD90 cells during in vitro culture, SR1 was superior at increasing functional HSCs with SGengrafting capabilities. We further show that the reduced capacity of HDACi and UM171 to increase engraftment is due to upregulation of HSC markers on nonengrafting CD34 CD90- progenitor cells, a property not seen with SR1. These data suggest that compounds that block differentiation via AHR antagonism are optimal for expanding functional HSCs.