Cytoskeleton of rat aortic smooth muscle cells. Normal conditions and experimental intimal thickening.

The organization of actin, vimentin, and desmin in smooth muscle cells of rat aortic media and intima under normal conditions and 15 or 75 days after endothelial injury has been studied by means of electron microscopy, indirect immunofluorescence, densitometric analysis of sodium dodecyl sulfate-polyacrylamide gels, isoelectric focusing, and bidimensional gels. In the normal aortic media, practically all smooth muscle cells contain vimentin, and about 50% of them contain, in addition, desmin; upon analysis of actin isotypes by bidimensional gels, smooth muscle cells show a predominance of alpha-actin, some beta-actin, and very little gamma-actin. Fifteen days after endothelial injury, cells that have migrated into the intima contain decreased amounts of actin and desmin and increased amounts of vimentin compared with normal medial smooth muscle cells. Moreover, beta-actin becomes the predominant actin isotype and significant amounts of gamma-actin appear, whereas alpha-actin decreases. Seventy-five days after endothelial injury, regenerated endothelial cells have repaired the injury. Intimal smooth muscle cells are less numerous than 15 days after injury, and the organization of their cytoskeletal elements has reverted almost to normal conditions. At both 15 and 75 days after endothelial injury, no significant changes of cytoskeletal elements are seen in the aortic media underlying intimal thickenings.