Bone marrow–derived cells differentiate into portal vein endothelium. Following transplantation of BM or HSCs (KSL), recipient liver was examined for donor-derived CD31⁺/VWF⁺ cells. (A) Hematoxylin and eosin stain of recipient liver tissue showing the lumen of a portal vein (L). (B) Y-chromosome–positive (red) male donor cell in the nucleus of a cell in the intima of a portal vein 8 months after KSL transplantation detected by Y-PAINT/FISH with DAPI (blue) nuclear staining. (C) X-gal detection of LacZ expression in a ROSA26 donor-derived cell (blue) in a portal vein. (D-F) A portal vein from a GFP⁺ KSL transplant recipient demonstrating the expression of CD31 (red, D) and GFP (green, E). (F) Merged image. (G-I) A portal vein from a GFP⁺ KSL recipient demonstrating the expression of VWF (red, G) and GFP (green, H). (I) Merged image. (J) Confocal microscopy images of a donor-derived GFP⁺, CD31⁺, DAPI⁺ cell in a portal vein; (K) a GFP⁺, VWF⁺, DAPI⁺ cell in a portal vein. (B,J-K, 500 KSL cells per recipient; C, 10⁶ BM cells per recipient; D-F,G-I, 2000 KSL cells per recipient. Scale bars: A, D-I, 20 μm; B-C, 10 μm; J-K, 5 μm; L indicates portal vein lumen.)