This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pathology
[{'content': 'Atherosclerosis initiation by fibroblast plaque is mediated by injury to - \nSelect and explain. \nA. Smooth muscle, B. Media, C. Adventitia, D. Endothelium', 'role': 'user'}, {'content': 'Answer: D \nExplanation: The most acceptable hypothesis for the pathogenesis of atherosclerosis is "the response to injury hypothesis".\nAccording to this hypothesis, atherosclerosis is a chronic inflammatory response of the arterial wall initiated by injury to endothelium.\n\nPathogenesis of atherosclerosis \nFollowing stages occurs in the pathogenesis of Atherosclerosis\n\n1. Endothelial injury\n\nEarliest stages of the development of atherosclerosis are mediated by the inflammatory cascade.\nInflammation mediated injury to endothelium is the cornerstone in the development of atherosclerosis.\nAfter the injury, the endothelium is activated and there is increased expression of adhesion molecule-VCAM-1 and there is increased permeability to endothelium.\nTNF is the major cytokine to induce this expression.\n\n2. Migration of leukocytes\n\nWhen VCAM-1 is expressed on endothelium, leukocytes adhere to the endothelium.\nLeukocytes then cross the endothelial barrier and begin to accumulate in subendothelial intimal space.\nMacrophages engulf LDL cholesterol and form foam cells -> formation of the earliest lesion, i.e. fatty streak.\nMacrophages also form oxygen free radicals that cause oxidation of LDL to yield oxidized LDL (modified LDL).\n\n3. Smooth muscle cell migration and proliferation\n\nInflammatory cells in subendothelial intimal space secrete cytokines, mainly PDGF, TGF-α and FGF which cause migration of smooth muscle cells from media to subendothelial intimal space as well as their proliferation.\n\n4. Maturation of plague\n\nSmooth muscle cells synthesize extracellular matrix (especially collagen) and convert a fatty streak into a mature fibro-fatty atheroma, and contribute to the progressive growth of atherosclerotic lesions.', 'role': 'assistant'}]