Fig 1: Human IPSC-derived skin organoid microvessels possess arterial endothelial cell identity. Representative images of arterial [SRY-box transcription factor 17 (SOX17; A and B) and neuropilin (NRP1; E and F)] and venous [chicken ovalbumin upstream promoter-transcription factor II (COUP-TFII; C and D) and NRP2 (G and H)] endothelial markers from pre– and early hair-forming organoids (days 44 to 54; A, C, E, and G) and late hair-bearing organoids (days 73 to 112; B, D, F, and H) are shown. Immunohistochemical profiling was performed on skin organoids (SKOs) collected from three independent experiments. Robust expression of SOX17 and NRP1, in conjunction with the absence of COUP-TFII and NRP2, supports an arterial endothelial identity of the SKO microvasculature. No difference was observed in the abundance or degree of SOX17 and NRP1 endothelial positivity between early and late organoids. A–H:n = 7 early SKOs; n = 13 late SKOs. Scale bar = 50 μm (A–H). Original magnification, ×400 (A–H). α-SMA, α-smooth muscle actin.