Fig. 3. CCR2 receptor-ligand interactions promote HSPC chemotaxis toward ECs.

(A) Chemotaxis ratio of murine HSPCs through 5-μm pores toward CCR2L chemokine gradients (200 ng/ml). Chemotaxis assays were performed in the presence of CXCL12 (200 ng/ml). Chemotaxis of HSPCs toward (B) BM ECs or (C) CXCL12/CCR2L gradients after CCR2i. (D) Flow cytometric analysis of HSPC subpopulation-specific migration toward ECs after CCR2i. (E) Relative gene expression of all CCR2L in BM ECs harboring individual gene KO by CRISPR-Cas9 after HSPC EV uptake (WT, dotted line), demonstrating compensatory up-regulation of residual CCR2L after EV exposure. (F) Chemotaxis ratio of HSPCs toward WT ECs or ECs transduced with an IκBα dominant-negative mutant. Chemotaxis ratio of Ccr2^gfp/gfp HSPCs compared to WT HSPCs toward (G) BM ECs or (H) chemokine gradients. (I) GFP and surface CXCR4 expression across subpopulations in Ccr2^gfp/gfp marrows. *P < 0.05, **P < 0.01, and ***P < 0.001. Triangle points denote statistically significant outliers.