Figure 3.

Higher expression of CD150 identifies resilient LT-HSCs

(A) Flow cytometric index-sort data were used to determine the CD150 expression level of LT-HSCs at the time of isolation. Cells that did not survive at day 1 and day 7 were compared with those that survived out to day 7, with the latter population of cells correlating with higher CD150 expression. A boxplot shows the median with interquartile range. Vertical lines represent outermost quartiles. Black dots, if present, are extreme outliers. Unpaired t test: ^∗p < 0.05, ^∗∗p < 0.01, ^∗∗∗p < 0.001.

(B) Prospectively sorted CD150^high LT-HSCs show 4.2-fold higher survival than CD150^mid LT-HSCs (n = 480, 5 independent experiments). Paired two-tailed t test.

(C) Hibernating HSCs in serum-free and serum-supplemented conditions were transplanted, and their CD150 levels retrospectively assessed. Cells able to repopulate a recipient (black) did not differ in initial CD150 expression levels compared with cells unable to repopulate (gray).

(D) HSCs with high or low expression of CD150 were determined using index-sorting data from freshly isolated HSCs that were cultured for 7 days in serum-free medium supplemented with 20 ng/mL IL-11 and 300 ng/mL SCF. Three biological replicates were analyzed, and in each case the top third and bottom third of CD150 expressers were analyzed as CD150^high and CD150^low, respectively. Daily cell counts were performed to assess cell division kinetics. Entry into cell cycle and the second division were not significantly altered between CD150^high and CD150^low LT-HSCs.

(E) Using the same experimental data from Figure 3D, colony sizes from single LT-HSCs were measured on day 10 and clone sizes from single LT-HSCs with high expression of CD150 were significantly reduced compared with those with low CD150 expression (bars show mean with SD. Sidak's multiple comparison test: ^∗∗p < 0.01).