Published online Feb 26, 2024. doi: 10.4252/wjsc.v16.i2.163
Peer-review started: October 18, 2023
First decision: December 2, 2023
Revised: December 14, 2023
Accepted: January 12, 2024
Article in press: January 12, 2024
Published online: February 26, 2024
Processing time: 130 Days and 18.6 Hours
In vitro expansion to increase numbers of hematopoietic stem cells (HSCs) in cord blood could improve clinical efficacy of this vital resource. Nicotinamide (NAM) can promote HSC expansion ex vivo, but its effect on hematopoietic stem and progenitor cells (HSPCs, CD34+CD38) and functional subtypes of HSCs – short-term repopulating HSCs (ST-HSCs, CD34+CD38CD45RACD49f+) and long-term repopulating HSCs (LT-HSCs, CD34+CD38CD45RACD49f+CD90+) is not yet known. As a sirtuin 1 (SIRT1) inhibitor, NAM participates in regulating cell ad
To evaluate the effects and underlying mechanisms of action of different concentrations of NAM on HSC proliferation and differentiation.
CD34+ cells were purified from umbilical cord blood using MacsCD34 beads, and cultured for 10–12 d in a serum-free medium supplemented with cytokines, with different concentrations of NAM added according to experimental requirements. Flow cytometry was used to detect phenotype, cell cycle distribution, and apop
Compared with the control group, the proportion and expansion folds of HSPCs (CD34+CD38) incubated with 5 mmol/L or 10 mmol/L NAM were significantly increased (all P < 0.05). The ST-HSCs ratio and fold expansion of the 5 mmol/L NAM group were significantly higher than those of the control and 10 mmol/L NAM groups (all P < 0.001), whereas the LT-HSCs ratio and fold expansion of the 10 mmol/L NAM group were significantly higher than those of the other two groups (all P < 0.05). When the NAM concentration was > 10 mmol/L, cell viability significantly decreased. In addition, compared with the 5 mmol/L NAM group, the proportion of apoptotic cells in the 10 mmol/L NAM group increased and the proportion of cells in S and G2 phase decreased. Compared with the 5 mmol/L NAM group, the HSCs incubated with 10 mmol/L NAM exhibited significantly inhibited SIRT1 ex
Low concentrations (5 mmol/L) of NAM can better regulate the balance between proliferation and differentiation, thereby promoting expansion of HSCs. These findings allow adjustment of NAM concentrations according to ex
Core tip: This study reveals the dominant subgroups of hematopoietic stem cells (HSCs) and molecular mechanisms underlying the effects of different nicotinamide (NAM) concentrations. Activation or inhibition of sirtuin 1 (SIRT1) is determined by the concentration of NAM. High concentrations inhibit SIRT1 but are not conducive to self-renewal of HSCs, whereas low concentrations balance HSC proliferation and differentiation by regulating the SIRT1–HIF1A pathway and reactive oxygen species production, effectively promoting in vitro expansion of the stem cells. These findings could allow adjustment of NAM concentrations according to expansion needs and may help predict small molecules that synergistically promote expansion with NAM.