Figure 4.

Endothelial cells (EC), fibroblasts, and MSCs from organoid stroma support hematopoiesis with increased hematopoietic support from VEGFA + C–stimulated vasculature. A, Comparison of expression of key receptors, adhesion proteins, and growth factors and chemokines in ECs from bone marrow organoids (Org.) and human fetal bone marrow (FBM). B, Comparison of expression of growth factors and chemokines in MSCs from organoids and FBM. Size of dots represents percentage of expressing cells, and color density indicates level of expression. C, Total predicted ligand–receptor interactions across clusters as predicted by CellPhoneDB (V2.0), showing extensive autocrine and paracrine interactions across BM organoid. MK, megakaryocyte; prog., progenitor. D, Volcano plot showing significantly differentially expressed (DE) genes in ECs from VEGFA + C versus VEGFA-only organoids (801 significantly upregulated and 700 significantly downregulated genes, P < 0.05, log₂FC > 0.5 or −0.5). E, Violin plots showing key hematopoietic support factors and markers of bone marrow sinusoidal endothelium in ECs of VEGFA + C and VEGFA-only organoids. P values are indicated below x-axis labels, and mean value is indicated on violin plots. ***, P < 0.001; ****, P < 0.0001 for pairwise comparison Wilcox test applied (FDR). UMI, unique molecular identifier. F–H, Sankey plots comparing TGFβ1-mediated (F), CXCL12-mediated (G), and CD44-mediated (H) interactions in VEGFA + C versus VEGFA-stimulated organoids. Endo, endothelial; Ery, erythroid; Fibro, fibroblast; Mono, monocyte. I, Expression of interacting receptor–ligand pairs between organoid HSPCs and cognate partner in organoid or FBM ECs (endo) and MSCs/fibroblasts with percentage of expressing cells and level of expression shown. J, Hematopoietic cytokines/growth factors produced by bone marrow organoids, measured by Luminex assay. Each datapoint represents supernatant pooled from 16 separately generated organoids. See also Supplementary Figs. 4–7.