StemRegenin 1 is an aryl hydrocarbon receptor signaling antagonist (IC50: 127 nM in CD34+ cells).

In vitro: In a previous study, the unbiased screen with primary human HSCs identified the StemRegenin 1 (SR1), which could promote the ex-vivo expansion of CD34+ cells. In addition, the culture of HSCs with SR1 resulted in a 50-fold increase in cells expressing CD34. Moreover, the mechanistic studies showed that SR1 acted by antagonizing the AhR [1].

In vivo: In an animal study, 300 to 30,000 uncultured CB CD34+ cells were transplanted into NSG mice. Results showed that CB CD34+ cells cultured with SR1 led to significant increases in human engraftment in the peripheral blood at 1 week, compared with mice transplanted with 10,000 uncultured cells or the progeny of 10,000 control cells [1].