A study of atheromatous plaques shows that the release of growth factors, including PDGF, FGF, and TNF-a leads to increased extracellular matrix production. As a result, the size of the plaques increases. Which of the following cells is most likely to release these growth factors in the plaques?

Growth factor release from activated platelets, macrophages, and vascular wall cells induces smooth muscle cell recruitment, medial smooth muscle migrate into the intima, proliferate, and synthesize extracellular matrix (ECM) in much the same way that fibroblasts fill in a wound. Endothelial cell injury initiates atherogenesis, but endothelial cells do not form a significant part of an atheroma. Platelets do not synthesize ECM. T cells secrete inflammatory cytokines that activate macrophages, endothelial cells, and smooth muscle cells.