Figure 7.

Hibernation conditions keep the majority of human HSCs as single cells

(A) Single human HSCs (CD34⁺CD38⁻CD90⁺CD45RA⁻CD19⁻CD49f⁺) from umbilical cord blood were sorted into individual wells and cultured in the presence of IL-11 with or without SCF. In parallel, human HSCs were bulk-cultured for 7 days in the absence of SCF and transplanted at three different cell doses (22, 110, and 218) into immunodeficient recipients and monitored for engraftment.

(B) Survival of HSCs in the presence or absence of SCF over 7 days, where absence results in 1.5-fold reduced survival compared with SCF-supplemented cultures (fresh n = 192; post-hibernation, n = 672; 5 independent experiments)

(C) The proportion of cells divided at 5–7 days in culture with and without the addition of SCF is displayed. Significantly more cells divide in the presence of SCF with the majority of cells in hibernation conditions remaining as single cells (fresh, three independent experiments, post-hibernation, five independent experiments). Bars show mean with SEM.

(D) The graphs show the percentage of human cell engraftment (%CD45⁺⁺) in PB from transplanted mice at 12 and 20 weeks post-transplantation (cell dose 22, n = 5; 110, n = 4; 218, n = 3). The threshold for events considered as positive was >0.01% with a minimum of 30 analyzed events. Non-engrafted mice shown below the dashed line. CD45⁺⁺ indicates cells positive for two distinct CD45 antibodies. Bars show mean with SEM.