Heart weight/animal weight ratios are significantly increased in Apoe−/− mice compared to C57BL/6J (**, p<0,01 versus C57BL/6J) (Panel A). Hypercholesterolemic diet led to a strong increase of interstitial matrix collagen deposition in Apoe−/− compared to C57BL/6J under both normoxic and hypoxic condition (Panel B left). We analyzed 3 coronal area sections from each animal and the results are expressed using a semiquantitative score: 1 absent collagen, 2 mild collagen deposition, 3 severe collagen deposition. Panel B right is a representative image of absent (1), mild (2) and severe (3) collagen deposition. The number of apoptotic cells is significantly increased in Apoe−/− compared to C57BL/6J only under normoxic condition. We performed TUNEL staining on 3 coronal area sections from each animal and results are expressed as mean of number of apoptotic cells (*, p<0.05 versus C57BL/6J normoxia) (Panel C left). Panel C right is a representative image of positive TUNEL staining (1, arrow) and overlap with propidium iodide as a nuclei marker (2, arrow). Results presented are mean±SD of C57BL/6J normoxia n = 4; C57BL/6J hypoxia n = 5; Apoe−/− normoxia n = 6; Apoe−/− hypoxia n = 7.