Targeting the aryl hydrocarbon receptor nuclear translocator complex with DMOG and Stemregenin 1 improves primitive hematopoietic stem cell expansion

Abstract

Culture conditions used for the expansion of hematopoietic stemand progenitor cells (HSCs andHPCs, collectively HSPCs) should ideally favor the self renewal of long-termHSCs. At 20% O2, the synthesis of HIF-1α is balanced by its hydroxylation and proteasomal degradation. This favors HSPC differentiation, but can be prevented by culturing CD34+cord blood cells in the presence of dimethyloxaloylglycine (DMOG). This differentiation may also be reduced by culturing the cells in the presence of Stemregenin 1, an antagonist of the aryl hydrocarbon receptor (AhR). The objective of this studywas to investigate howhypoxia,DMOG and Stemregenin 1might affect the expansion ofHSPCswith the aim of identifying optimal conditions for expansion in culture. It was found thatDMOG decreased proliferation but was effective in preserving the number of cells in the primitive hematopoietic subpopulations in vitro. The effect of DMOG was similar to hypoxia, although differenceswere observedwith regard to the side population and CD34+ sub-populations. Stemregenin 1 on the other hand increased the size of the primitive as well as the other HSC sub-populations. The use of Stemregenin 1 with DMOG increased the proportion of primitiveHSCs to 3.54% compared to 2.61% for Stemregenin 1 alone. In vivo engraftment studies confirmed these findings and showed that fewer cells (3710) are required for long-term engraftmentwhen HSCs are grown in Stemregenin 1 together with hypoxia than in Stemregenin 1 under conditions of normoxia (13430).