The role of mechanical and humoral factors in growth regulation of vascular smooth muscle and cardiac myocytes.

Structural changes of the heart and blood vessels participate in the long-term regulation of the cardiovascular system. In hypertension and myocardial dysfunction, the adaptive process of cardiac and vascular remodeling may contribute to the pathophysiology and complications of these diseases. Recent investigations have enhanced our understanding of the cellular and molecular biology of vascular smooth muscle and cardiac myocyte growth. Mechanical and neurohormonal factors can independently stimulate hypertrophy-hyperplasia in vascular and cardiac myocytes. Increased pressure-stretch of cardiac myocyte and vascular smooth muscle cells can activate protooncogene expressions that may mediate the growth response. Vasoactive substances also regulate cardiovascular growth. In general, endogenous vasoconstrictors (eg, angiotensin, endothelin) act as growth promoters, and endogenous vasodilators (eg, nitric oxide, prostacyclin, atrial natriuretic peptide) act as growth inhibitors of vascular smooth muscle and, possibly, cardiac myocytes. Recent data have demonstrated that the vasoconstrictive agents, such as angiotensin, activate protooncogenes and autocrine growth factors that mediate vascular growth. Furthermore, the development of vascular hypertrophy versus hyperplasia is dependent on the relative activation of endogenous proliferative growth factor (eg, platelet-derived growth factor, basic fibroblast growth factor) versus antiproliferative factor (eg, transforming growth factor-beta) by the growth stimulus. Taken together, these data demonstrate that complex interactions of local mediators, which participate in the pathophysiology of cardiovascular diseases, control cardiovascular growth.