Vascular injury causing endothelial cell dysfunction stimulates which processes leading to intimal thickening?

• A. Platelet aggregation and neutrophil recruitment; lipid deposition; medial thinning
• B. Macrophage phagocytosis and cholesterol efflux; luminal widening
• C. Endothelial regeneration and endothelial proliferation; elastin synthesis; adventitial expansion
• D. Smooth muscle cell recruitment and proliferation; matrix synthesis; intimal thickening

Answer: (D)

Endothelial injury leading to dysfunction sets off a proliferative response in vascular smooth muscle cells that moves from the media into the intima, where they proliferate and lay down extracellular matrix. This neointimal formation creates intimal thickening (neointimal hyperplasia) and narrows the vessel lumen. Growth factors released after injury, like PDGF and TGF-β, push smooth muscle cells from a contractile state to a synthetic, matrix-producing state, which is exactly what drives the thickening. While platelets and neutrophils participate in the early injury response, they’re not the main driver of the thickening you see in the intima. Lipid deposition with macrophage activity is more characteristic of atherogenesis, where plaques form, rather than the neointimal hyperplasia following endothelial dysfunction. Endothelial regeneration and elastin synthesis with adventitial expansion are not the primary mechanisms for this particular process.