SUMMARYThe collagen produced by differentiated cells cultured from human amniotic fluid was characterized in two ways. By chain composition and by 4-hydroxyproline: 3-hydroxyproline isomer ratio, the collagen synthesized by F-type (fibroblast) cells was indistinguishable from that made by cultured fetal dermal fibroblasts. The predominant cells in young amniotic fluid cultures, termed AF-type, produced collagen with a lower isomer ratio, resembling that of basement membrane collagen. The chain composition, as determined by chromatography on carboxymethyl cellulose, varied for different cultures of the AF-type, but the major pattern was consistent with that of basement membrane collagen. On the basis of these characteristics, F cells are of fibroblast origin, whereas most AF cells are of a different origin either endothelial or epithelial. Other evidence (Megaw et al., 1977) suggests an epithelial origin for AF cells.Studies using human amniotic fluid cell culture as an aid to prenatal diagnosis are increasing in complexity. We began to investigate collagen synthesized by these cell cultures because of the need for prenatal diagnosis of inherited diseases affecting collagen. Initial studies in this laboratory had shown increased solubility of collagen produced by cultured dermal fibroblasts from Marfan syndrome compared with controls (Priest et al., 1973), and the question arose whether this or other disorders of connective tissue could be diagnosed in cultured amniotic fluid cells. Therefore, further studies were performed on collagen laid down in the cell layer and extracted by acid or neutral salt, or on collagen released into culture medium by two types of fetal cells cultured from amniotic fluid, F (fibroblast) and AF (amniotic fluid) types (Hoehn et al., 1974).We report here that the F and AF cells, distinguished from each other originally on the basis of morphology and growth characteristics, also differ biochemically in the types of collagen formed in culture. We also report another biochemical difference (Megaw et al

The distribution and amount of fibronectin in both involved and uninvolved skin from scleroderma patients and controls were compared by indirect immunofluorescence. A marked increase in fibronectin was found in the deep dermis of involved scleroderma skin, while the subepidermal papillary regions of all specimens revealed little variation in fibronectin content. The distribution of the accumulated fibronectin appeared to parallel that of the accumulated collagen in the involved reticular dermis.Progressive systemic sclerosis (PSS or scleroderma) is a generalized connective tissue disorder characterized by the deposition of collagen in the skin and various internal organs (1). In the active indurative phase of scleroderma there is a significant increase in

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