Transduction of human liver EC repopulated mice by huCD105-LV. Rag2^−/−yc^−/− mice were repopulated with human liver ECs. Two weeks after reconstitution, mice were injected once with 2 × 10⁶ transducing units huCD105-LV. (A) Six to 8 days after vector injection, liver sections were stained for human CD31 (upper panel) or F4/80 (lower panel). Nuclei were stained with DAPI. GFP expression was observed by direct fluorescence. GFP/CD31 double-positive clusters of repopulated human liver ECs are indicated by arrows. Scale bars: 29.63 µm (upper panel) and 27.12 µm (lower panel). No GFP positive cells were detected after administration of huCD105-LV to mice without human liver endothelium (supplemental Figure 8). (B) Because individual human LSECs cannot be identified within the tightly connected clusters in the mouse liver, the amount of GFP-positive cells in the CD31-positive clusters was divided in quintiles of 0%, 25%, 50%, 75%, or 100% GFP expression. The relative quantities of these quintiles are plotted.