Reducing TGF‐β1 cooperated with StemRegenin 1 promoted the expansion ex vivo of cord blood CD34(+) cells by inhibiting AhR signalling

OBJECTIVE: As an inhibitor of the AhR signalling pathway, StemRegenin 1 (SR1) not only promotes the expansion of CD34(+) cells but also increases CD34(−) cell numbers. These CD34(−) cells influenced the ex vivo expansion of CD34(+) cells. In this work, the effects of periodically removing CD34(−) cells combined with SR1 addition on the ex vivo expansion and biological functions of HSCs were investigated. MATERIALS AND METHODS: CD34(−) cells were removed periodically with SR1 addition to investigate cell subpopulations, cell expansion, biological functions, expanded cell division mode and supernatant TGF‐β1 contents. RESULTS: After 10‐day culture, the expansion of CD34(+) cells in the CD34(−) cell removal plus SR1 group was significantly higher than that in the control group and the SR1 group. Moreover, periodically removing CD34(−) cells with SR1 addition improved the biological function of expanded CD34(+) cells and significantly increased the percentage of self‐renewal symmetric division of CD34(+) cells. In addition, the concentration of total TGF‐β1 and activated TGF‐β1 in the supernatant was significantly lower than those in the control group and the SR1 group. RT‐qPCR results showed that the periodic removal of CD34(−) cells with cooperation from SR1 further reduced the expression of AhR‐related genes. CONCLUSIONS: Periodic removal of CD34(−) cells plus cooperation with SR1 improved the expansion of CD34(+) cells, maintained better biological function of expanded CD34(+) cells and reduced the TGF‐β1 contents by downregulating AhR signalling.