MATRIX, HORMONES, AND DIFFERENTIATION IN MAMMALIAN CELLS

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The long-term objectives are to establish model systems and culture conditions by which to analyze the mechanisms of regulation of growth and/or differentiation of normal and neoplastic epithelial cells. The model systems being developed are prostatic epithelial cells and of normal hepatocytes. The approach is based on the hypothesis that the growth and differentiation of epithelial cells are effected by complex cellular interactions present in tissues and which can be analyzed and simulate in culture conditions. The cellular interaction on which we are focused is the epithelial-mesenchymal relationship which can be stimulated by utilization of basement membranes, a form of extracellular matrix, and of specific hormones and growth factors, the mixture of which is designed for each specific cell type. Our intent is to continue the development of appropriate substrate and defined medium conditions by which to permit the maintenance in culture of normal prostatic epithelial cells and of normal hepatocytes in either a state of growth or a state of maximal expression of their tissue-specific functions. To date, we have developed methods for the isolation of tissue-specific forms of extracellular matrix which can be utilized as substrates for cells in culture. Cells plated onto these matrix substrates have shown enhanced attachment and plating efficiencies and growth or differentiative responses more similar to their in vivo responses. In combination with this approach, we are utilizing the methodologies of Sato and his associates to develop "defined media", serum-free, hormonally supplemented media designed for specific cell types. We are finding that the types of matrix and the composition of the defined media vary not only with the cell type but also with the physiological response of the cells. Thus, the matrix and defined medium needed for growth of a particular cell type is distinct from that needed for the maintenance of the cell in maximal differentiation. We hope to complete the chaacterization of these culture conditions and the characterization of the cultures of cells maintained under each of these conditions permitting us ultimately to vary in a systematic way the conditions in an analysis of growth regulation and regulation of differentiation.