APOE and Wilson disease: Lipid-laden cells were observed by oil red O staining in the septa and alveolar lumina in the ApoE−/− WD mice at 12 weeks (Fig. 1N), whereas scattered lipid-filled cells were observed in the ApoE−/− WD mice at 4 and 24 weeks (Fig. 1M and O) or the ApoE−/− ND littermates at 24 weeks.