Heparan sulfate modulates Vcam1-dependent adhesion. (A-D) Expression of niche-related molecules in Mx1⁺ cells. (A) Real-time polymerase chain reaction for Vcam1, Cxcl12, Angpt1, and Scf1. (B) Cxcl12 protein level quantification in CD45⁻ Ter119⁻ Mx1⁺ stromal cells from control and mutant Ext1 mice. (C) Vcam1 protein level quantification and (D) representative histogram of Vcam1 protein levels in CD45⁻ Ter119⁻ Mx1⁺ stromal cells from control and mutant Ext1 mice. (E-H) Functional evaluation of Vcam1 in Mx1⁺ cells. (E) Overview of the experimental design. (F) Number of circulating progenitors measured by CFU-C assay in PB of control and mutant mice injected with G-CSF and Vcam1 neutralizing antibody. (G) Total PB reconstitution, 16 weeks after transplantation, in recipient mice transfused with 150 μL PB from control or mutant mice mobilized with G-CSF and Vcam1 neutralizing antibody or isotype control. CD45.1 BM cells were transplanted for radioprotection in equal numbers in control and mutant mice. (H) Quantification of PB circulating progenitor cells measured by CFU assay from Ext1 control or mutant mice receiving Vcam1 neutralizing antibody or isotype control. Data are representative of at least 2 independent experiments; n = 5 to 8 mice per genotype per experiment. In mobilization experiments, PB was collected from at least 5 mice per experimental group. Data are represented as mean ± SD. *P < .05; **P < .01; ***P < .001.