AUTOCRINE AND PARACRINE GROWTH MECHANISMS IN VASCULAR SMOOTH-MUSCLE

The number of growth factors shown to stimulate smooth muscle cell growth has steadily increased. Recent data have established important regulatory interactions among these different growth factors. Specifically, individual growth factors have been shown to regulate their own expression as well as the expression of other growth factors and their receptors. In addition, the importance of the extracellular matrix as both a reservoir and a facilitator of growth-factor action has been established for transforming growth factor-beta and fibroblast growth factor. Immobilization of growth factors by proteoglycans in the matrix establishes a tight spatial control of growth-factor activity that may have major significance in the formation and maintenance of tissue architecture. In this light, alterations in the vessel matrix induced by hypertension should have important effects on growth-factor activity and vascular growth.