VEGFR3-positive vessel markers in skull bone marrow and channels. (A) Schematic representation of the skull sample preparation, processing, and imaging after clearing using TESOS. The black dotted line indicates the location of the imaging sample. (B) Representative images of coronal sections from parietal bones of 2-mo-old mice stained with antibodies against VEGFR3 (red) and Col1a1 (white), with a stitched section thickness of 650 µm. The white boxes indicate the magnified regions, shown in B1 and B2. (B1 and B2) Magnified images of the sagittal suture region and the skull at the border region with multiple SPCs. The sagittal suture is outlined by a purple line, with a connected vessel between the bone marrow and the inner skull bone indicated by a purple arrowhead. Scale bars: 500 and 200 µm (inset). (C) Enlarged images of the bone marrow channels from the region, indicated by white boxes in B2. A zoomed-in view of the channels connecting the bone marrow, marked by purple arrowheads. (D) Magnified images of channels connecting to the periosteum. The purple boxes highlight further magnified areas displayed on the left. Purple arrowheads indicate the surface openings, which are the exit points of the channels on the skull surface. Scale bars: 100 and 30 µm (inset). All data are represented with n ≥ 3 mice per experiment.