Genetic loss of Gas6 induces plaque stability in experimental atherosclerosis

The growth arrest-specific gene 6 (Gas6) plays a role in pro-atherogenic processes such as endothelial and leukocyte activation, smooth muscle cell migration and thrombosis, but its role in atherosclerosis remains uninvestigated. Here, we report that Gas6 is expressed in all stages of human and mouse atherosclerosis, in plaque endothelial cells, smooth muscle cells and macrophages. Gas6 expression is most abundant in lesions containing high amounts of macrophages, ie thin fibrous cap atheroma and ruptured plaque. Genetic loss of Gas6 does not affect the number and size of initial and advanced plaques in ApoE^-/- mice, but alters its plaque composition. Compared to Gas6^+/+: ApoE^-/- mice, initial and advanced plaques of Gas6^-/-: ApoE^-/- mice contained more smooth muscle cells and more collagen and developed smaller lipid cores, while the expression of TGFβ was increased. In addition, fewer macrophages were found in advanced plaques of Gas6^-/-: ApoE^-/- mice. Hence, loss of Gas6 promotes the formation of more stable atherosclerotic lesions by increasing plaque fibrosis and by attenuating plaque inflammation. These findings identify a role for Gas6 in plaque composition and stability.