Figure 5. Endothelial cells in the BM niche supply miR-126 to CML LT-HSCs.

(a, b) Frequency of BM mononuclear cell subpopulations (n=5 independent samples) (a) and LT-HSCs (n=5) (b) in miR-126^flox/flox/Mx1-cre+ (Mx1+) and miR-126^flox/flox/Mx1-cre- (Mx1-) mice at 16 weeks after pIpC injection. (c–e) miR-126 expression in CML BM cells (n=4 independent samples) (c), WBC counts (d) and survival (e) of SCLtTA/BCR-ABL/miR-126^flox/flox/Mx1+ or Mx1- mice subjected to tetracycline withdrawal and pIpC injection (n=9). (f) CD45.2 CML LT-HSCs (400 cells/mouse) from BCR-ABL-induced and pIpC-injected SCLtTA/BCR-ABL/miR-126^flox/flox/Mx1+ or Mx1− mice were transplanted into CD45.1 congenic recipient mice (n=10 in each group). (g–j) miR-126 expression, as assessed by QPCR, in donor CML LT-HSCs (n=3 independent samples) (g), WBC counts (h), CML cell engraftment in PB (i) and survival (j) of recipient mice from f (n=10 each). (k) CD45.1/CD45.2 CML LT-HSCs (400 cells/mouse) from induced CML mice were transplanted into CD45.2 congenic miR-126^flox/flox/Tie2- (n=14), miR-126^flox/wt(het)/Tie2+ (n=10) and miR-126^flox/flox(hom)/Tie2+ recipient mice (n=8). (l–o) miR-126 expression, as assessed by QPCR, in ECs sorted from the recipient mice from k (n=3 independent samples) (l), WBC counts (m), CML cell engraftment in PB (n) and survival (o) of recipient mice from k. (p) CD45.2 CML LT-HSCs (400 cells/mouse) from BCR-ABL-induced and pIpC-injected SCLtTA/BCR-ABL/miR-126^flox/flox/Mx1+ or Mx1− mice were transplanted into CD45.2 miR-126^flox/wt/Tie2+ or Tie2- recipient mice (n=12 in each group), respectively. (q,r) WBC counts (q) and survival (r) of the recipient mice from p. Comparison between groups was performed by two-tailed, unpaired Student’s t-test. The log-rank test was used to assess significant differences between survival curves. P values ≤0.05 were considered significant. Results shown represent mean ± SEM. ^*p ≤ 0.05, ^**p < 0.01, ^***p < 0.001, ^****p < 0.0001.