The present invention provides screening methods that use organisms or cells that lack function in one or both elastin genes. These methods are useful in identifying drugs for the prevention and treatment of obstructive vascular diseases, such as atherosclerosis, vascular restenosis and transplant arteriopathy. Further, the invention provides pharmaceutical compositions containing elastin-based compositions that are particularly potent regulators of proliferation, differentiation, and migration of smooth muscle cells in vitro and in vivo. These pharmaceutical compositions and related methods are useful in the prevention and treatment of disorders characterized by diminished capacity to regulate smooth muscle cell function.