Clonetics Corporation is a commercial supplier of human cell culture products for research and toxicity testing. Current products include smooth muscle cells of arterial, venous, and bronchial origin, as well as a serum-supplemented medium for their growth. The proposed research seeks to develop a chemically-defined serum-free medium for these cells. The amount of serum supplementation required will be minimal levels by optimization of the nutrient medium. The residual requirements for serum proteins will then be replaced with hormones, growth factors, attachment factors, carrier proteins and supplemental nutrients as needed for optimal growth in a defined medium. Proliferation of smooth muscle cells at inappropriate locations within the lumens of arteries plays a major role in the pathology of atherosclerosis. Recent research has shown that highly diverse chemical signals arising from several other cell types in response to dietary factors and minor vascular injury interact in complex ways to influence that growth. The availability of a highly-defined commercially-produced medium will greatly facilitate analysis of responses human vascular smooth muscle cells to the large numbers of different signaling molecules that are currently believed to exert regulatory effects on their proliferation. Because bronchial smooth muscle cells grow well in the serum-supplemented medium for vascular smooth muscle cells, we anticipate that they will also grow well in the defined medium that is to be developed, with no more than minor modifications in the formulation.