The cell biological properties of collagen, gelatin and collagen hydrolysate (<15 000 Da) were studied using murine keratinocytes. Keratinocyte culture experiments demonstrated that only collagen had significant effects on cell attachment and proliferation, but the results of cells cultured on gelatin and collagen hydrolysate showed the rates of adhesion and proliferation were similar to those of cells cultured on plastic as a control. It is concluded that collagen has better physiological effects than those of gelatin and collagen hydrolysate as skin-care cosmetic materials.

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Scanning electron microscopy (SEM) observation showed that fully differentiated spherical adipocytes were embraced by a network of collagens and fibroblastic preadipocytes. The properties of both the collagen networks and the preadipocytes allow the adipocytes to be interconnected, forming a fat-cell cluster, which can anchor to the bottom of a culture dish. In this network structure, collagen fibrils and fibrillar bundles were closely arranged and stratified. We found that immunostained collagens appeared to form extracellular network structures, which can be observed by SEM. The extracellular network of fibronectin was the first to develop among the extracellular matrix (ECM) components, though it became degraded with the progress of adipocyte differentiation. The type I collagen network was the last to develop and remained well organized through the late stage of adipocyte differentiation. The extracellular networks of type III, V, and VI collagen developed by the mid-stage and remained in the late stage of adipocyte differentiation. The network structures of type IV collagen and laminin became degraded during the differentiation process and localized at the surface of spherical cells. In addition to these basement membrane components, types III, V, and VI collagens also showed pericellular spherical staining patterns. These results demonstrated that the constitution and distribution of the ECM are altered during adipocyte differentiation, suggesting that the organization of each ECM component into a suitable structure is a requirement for the differentiation and maintenance of unilocular adipocytes.

In order to determine the localization of extracellular matrix components in bovine term placenta, the tissue distributions of collagen types I to XI in the amnion, smooth chorion, villous chorion and villi were examined by indirect immunofluorescence microscopy. Collagen types I, III, V, and VI were found in the stroma of the smooth chorion, villous chorion and villi and in the compact layer of the amnion. Type II collagen, which was thought to be present only in cartilage, was found to be distributed in the epithelium of the amnion, stroma of the chorion and trophoblast of the villous chorion. Basement membrane components, type IV and VII collagens, were found to be located not only in the basement membrane but also in the epithelium and compact layer of the amnion. Additionally, type VI collagen was found to be located in the stroma of smooth chorion, and type VII collagen was found to be distributed in the trophoblast layer of the villous chorion. Types VIII, IX, X and XI collagens were found, for the first time, to be distributed in the trophoblast layer, amnion and chorionic epithelium as well as in the blood vessel walls of the chorion. Our results indicated that the compact layer of the amnion contained various types of collagen (I-IX) with various arrangements. However, the fibroblast layer of the amnion contained collagen types III, V and VI but type I collagen could not be observed. The blood vessel wall of the chorion contained all of the types of collagen examined in this study.

To clarify the role of fibronectin (FN) during the early period of feather development, reconstituted skin consisting of intact epithelium and isolated mesenchymal cells from embryonal chick skin was used. In early feather development, FN was localized around mesenchymal cells of the dermal condensation. Isolated mesenchymal cells had associated with FN on their surfaces. FN on the cell surface dissociated following EDTA treatment, and EDTA-treated cells re-associated with exogenous FN. The intact epithelium also bound to exogenous FN at the placode. When FN-associated or FN-reassociated mesenchymal cells were used, the reconstituted skin formed feather rudiments only at the positions where the epithelial placode existed originally, and the locality of tenascin transferred from the placode to the mesenchyme during the period of feather bud formation. However, in reconstituted skin using FN-dissociated mesenchymal cells, feather rudiments did not form. Additionally, the epithelial placodes disappeared, and tenascin was distributed uniformly on the surface of the epithelium and not localized in the mesenchyme. These findings suggest that FN associated on the surfaces of mesenchymal cells maintains the functions of mesenchymal cells as dermal condensation and mediates epithelial-mesenchymal interactions during the early period of feather development. The results also suggest that reconstituted skin is a useful tool for functional studies on the extracellular matrix.