Endothelial cells serve as a functionally significant source of VEGF-C in the BM. (A) Experimental setup for evaluating the effects of Vegfc deletion in ECs. Vegfc was deleted from ECs in 7- to 10-week-old Cdh5-CreERT2;Vegfcflox/flox mice by tamoxifen injections. (B) Representative confocal immunofluorescence images of femur sections from VciΔEC mice and their littermate controls stained for ECs (endomucin, green) and LepR+ perivascular cells (red), with quantifications (right) (n = 6 mice per group). Bar represents 50 μm. (C) Quantification of HSPC subsets per femur from Vcfl/fl and VciΔEC mice determined by CD48 and CD150 staining (n = 13-14). (D) Experimental outline of scRNA-seq analysis of LepR+ cells and VE-cadherin–positive ECs from WT, Vcfl/fl, and VciΔEC mice. (E) UMAP plot of integrated BM ECs and LepR+ cells isolated from WT, Vcfl/fl, and VciΔEC mice (left). UMAP plots showing the clustering of integrated BM ECs and LepR+ cells from WT, Vcfl/fl, and VciΔEC mice (right). (F) Dot plot showing selected differentially expression genes in SECs (SEC-1 and -2), AECs, and arteriolar ECs after endothelial Vegfc deletion in comparison with Vcfl/fl mice. (G) Relative Cxcl12 mRNA levels in isolated BM ECs from VciΔEC and littermate control mice analyzed by qPCR. (H) Comparison of relative cell counts in Lepr-1, -2, -3, -4, and -5 clusters from Vcfl/fl and VciΔEC mice. (I) Dot plot showing selected differentially expression genes in LepR+ cells (Lepr-1, -2, and -3) after endothelial Vegfc deletion in comparison with the Vcfl/fl mice. (J) Relative Pten mRNA levels in isolated BM LepR+ cells from VciΔEC and littermate control mice analyzed by qPCR. *P < .05; **P < .01. MPP, multipotential progenitor.