[Normal skin cells in vitro].
Major cells in skin are epidermal cells in epidermis and fibroblasts in dermis. These cells can be isolated as a relatively pure population from the tissues using proteases and chelating agents. In this review we describe the way of culture where these two kinds of cells express normal function as they do in vivo. 1) It is important to consider the polarity of epidermal cell membranes in the transport of nutrients and metabolites when the cells are to be cultured in a healthy state in a long period. Epidermals cells expressed their normal polarities when cultured on a porous thin film of collagen and bathed on both sides (apical and basal) in culture media. 2) It is important to consider the interactions of fibroblasts with collagen when normal morphology and physiology are expected to be expressed in the cell in culture. Collagen affected the morphology of the cell and profoundly decreased the rate of DNA synthesis. We present a hypothesis which explains the fibronectin-independent interaction of fibroblasts with collagen. 3) It is important to consider the interactions between fibroblasts and epidermal cells when normal physiology of the skin as a whole is expected to be expressed in vitro, because exchange of information between them control their metabolic activities and functions. In this review, two examples for this exchange are presented: cell growth and collagenolysis.