Large arteries allow the vascular system to be more than a simple route in which the blood circulates within the organism. The elastic fibers present in the wall endow these vessels with elasticity and are responsible for the smoothing of the blood pressure and flow, which are delivered discontinuously by the heart. This function is very important to ensure appropriate hemodynamics. Elastic fibers are composed of
elastin (90%) and
fibrillin-rich microfibrils (10%) which provide the vessels with elasticity and are also signals able to bind to relatively specific cell membrane receptors. Stimulation of the high affinity
elastin receptor by
elastin peptides or
tropoelastin--the
elastin precursor--triggers an increase in intracellular free
calcium in vascular cells, especially endothelial cells, associated with attachment, migration or proliferation. Similar effects of the stimulation of endothelial cells by microfibrils or
fibrillin-1 fragments, which bind to
integrins, have been demonstrated. This dual function--mechanical and in signaling--makes the elastic fibers an important actor of the development and ageing processes taking place in blood vessels. An alteration of the
elastin (Eln) or
fibrillin (Fbn) gene products leads to severe genetic pathologies of the cardiovascular system, such as
supravalvular aortic stenosis, or
Williams Beuren syndrome--in which
elastin deficiency induces aortic
stenoses--or
Marfan syndrome, in which on the contrary
fibrillin-1 deficiency promotes the appearance of
aortic aneurysms. Genetically-engineered mouse models of these pathologies (such as Eln+/- mice and Fbn-1+/mgΔ mice, Eln+/-Fbn-1+/- mice) have permitted a better understanding of the pathogenesis of these syndromes. In particular, it has been shown that
elastin and
fibrillin-1 roles can be complementary in some aspects, while they can be opposed in some other situations. For instance, the double heterozygosity in
elastin and
fibrillin-1 leads to increased arterial wall stress--compared to the level induced by one of these two deficiencies alone--while the decrease in diameter induced by Eln deficiency is partly compensated by an additional deficiency in Fbn-1. Also, it is now clear that early modifications of
elastin or
fibrillin-1 availability can alter the normal signaling action of these
proteins and lead to long term modifications of the vascular physiology and ageing processes.