Fig 1: Generation and characterization of induced bone marrow organoids (iBMOs) from human iPSCs. A Schematic illustration of the workflow for iBMO induction under matrix-free, self-organizing culture conditions. Aggregated embryoid bodies were induced toward mesoderm with BMP4 and VEGF, followed by floating culture to promote vascularization and hematopoietic stem/progenitor cell (HSPC) colonization. B Bright-field images of iBMOs exhibiting a coral-like morphology during culture, consistently observed across two independent iPSC lines. Scale bars, 200 μm. See also Fig. S1B. C Hematoxylin and eosin staining of day-14 iBMOs demonstrating organized tissue architecture with vascular-like structures. Data were obtained from four independent differentiations (n = 12). Scale bars, 50 μm. D Immunofluorescence staining of iBMOs for VE-cadherin (CD144; endothelial marker), CD271 (NGFR; stromal marker), UEA-I (endothelial marker), and CD71 (erythroid marker), revealing the spatial organization of vascular and hematopoietic compartments. Nuclei are counterstained with DAPI. Data were obtained from two independent differentiations (n = 4 for left, n = 3 for right). Scale bar, 20 μm. E Three-dimensional reconstruction of whole-mount, CUBIC-cleared iBMOs showing mesenchymal stromal populations (CD271, CD90) and HSPCs (CD34). Data were obtained from two independent differentiations (n = 2). Scale bars, 40 μm. F Transmission electron microscopy (TEM) analysis of iBMOs. Samples were obtained from two independent differentiations, with each sample pooled from a single well of a 6-well plate. Left: Pseudo-colored image showing stromal cells (green) with prominent nucleoli (Nu) and endothelial cells (magenta). Center: Stromal cells exhibiting tight junctions (TJ), mitochondria (M), lysosomes (Ly), and extracellular vesicles (EV). Right: Macrophage-like cells with phagocytic vacuoles (asterisks), pseudopodia (arrows), and characteristic nuclear morphology (N). Scale bars, 10 μm (left), 1 μm (center), 5 μm (right)