Altered vascular remodeling in fibulin-5-deficient mice reveals a role of fibulin-5 in smooth muscle cell proliferation and migration

Fibulin (fbln)-5 is an elastin-binding protein required for assembly and organization of elastic fibers. To examine the potential role of fbln-5 in vascular remodeling and neointima formation, we induced vascular injury by carotid artery ligation in fbln-5^-/- mice. Mutant mice displayed an exaggerated vascular remodeling response that was accompanied by severe neointima formation with thickened adventitia. These abnormalities were not observed in elastin^+/- mice that exhibited a comparable reduction of vessel extensibility to fbln-5^-/- mice. Thus, the severe remodeling response could not be attributed to altered extensibility of the vessel wall alone. Vascular smooth muscle cells cultured from fbln-5^-/- mice displayed enhanced proliferative and migratory responses to mitogenic stimulation relative to wild-type cells, and these responses were inhibited by overexpression of fbln-5. These findings demonstrate the importance of the elastic laminae in vascular injury, and reveal an unexpected role of fbln-5 as an inhibitor of vascular smooth muscle cell proliferation and migration.