Smooth muscle cells were grown from explants of the tunica media of fetal and adult human aorta. Collagen was isolated after incubation with [ 14 C]glycine and was characterized by ion-exchange chromatography. All cells investigated synthesized two types of collagen: Type I (chain composition [al(I)] 2 a2) and type III (chain composition [al(III)] 3 ). The collagen made by cells from adult donors contained approximately 70% type I and 30% type III collagen. This corresponds to the collagen composition in the original tissue. No age-related change in the type I/type III ratio was found with cells from donors between 9 and 67 years of age. On the other hand, the type III portion of the collagen made by fetal cells was markedly less (about 15 -20% of total collagen).
Tissue specimens from human fibrotic liver obtained by needle biopsy were cultured. Two cell types emerged from the tissue explants. From their morphology and biosynthetic products they resembled smooth muscle cells and endothelial cells from blood vessel walls. In the "endothelial" cells, factor VIII-associated protein was demonstrated by indirect immunofluorescence. Synthesis of collagen types I and 111, basement membrane collagen types IV and V, and fibronectin by both cell types was observed by immunofluorescence microscopy. Homogeneous cultures of "smooth muscle cells" were observed in subcultures. After incubation with ["C]glycine, collagen was isolated and characterized by CM cellulose chromatography, and consisted mainly of types I and III. These data suggest involvement of mesenchymal cells in hepatic fibrosis; they presumably originate from blood vessel or sinusoidal walls.
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