Proliferation of human smooth muscle cells promoted by lipoprotein(a).

Elevated blood concentrations of lipoprotein(a) [Lp(a)] and its constituent, apolipoprotein(a) [apo(a)], constitute a major risk factor for atherosclerosis, but their physiological activities remain obscure. Lp(a) and purified apo(a) stimulated the growth of human smooth muscle cells in culture. This effect resulted from inhibition of plasminogen activation, and consequently the activation by plasmin of latent transforming growth factor-beta, which is an inhibitor of smooth muscle cell growth. Because smooth muscle proliferation is one of the hallmarks of atherosclerotic lesions, these results point to a plausible mechanism for the atherogenic activity of Lp(a).