MACROPHAGE PRODUCTS INHIBIT HUMAN AORTIC SMOOTH-MUSCLE CELL-PROLIFERATION AND ALTER 1-ALPHA(I) PROCOLLAGEN EXPRESSION

While the role of the foam cell in early atherogenesis has been well c haracterized, much less is known about the interaction between infiltr ating macrophages and medial smooth muscle cells (SMC) in chronic athe rosclerosis. Our purpose was to determine the effects of soluble macro phage mediators on normal human aortic SMC proliferation and matrix ex pression. Human aortic SMC in subconfluent culture were exposed to sup ernatants from activated lipopolysaccharide (LPS) and nonactivated mac rophages. SMC proliferation and type-1 procollagen expression were det ermined. Both activated and nonactivated macrophage supernatants exhib ited a potent growth inhibitory effect which became apparent at 48 hou rs. While nonactivated macrophage supernatant had no effect on procoll agen expression, activated supernatant inhibited its expression. (33%; p < 0.05) These findings are consistent with the loss of medial SMC a nd matrix proteins associated with chronic atherosclerosis.