APOE and atherosclerosis: To determine whether a reduction in Tβ4 levels, as occurs during atherosclerosis, may contribute towards the modulation of VSMC state, we investigated the phenotype of Tβ4-null male mice (Tβ4-/Y) in a model of hypercholesterolaemia, by crossing onto the ApoE-/- background [22] and feeding a HFD (21.4 % fat; 0.2 % cholesterol) for up to 12 weeks.