Proceedings of the National Academy of Sciences · 1982 · 261 citations · 30 references
Cell CultureCell ProliferationLow DensityCell GrowthCellular PhysiologyMammary Gland DevelopmentTissue DevelopmentMatrix BiologyMilk Sugar LactoseHealth SciencesMammary GlandCell BiologyRat LiverDevelopmental BiologyPhysiologyCell-matrix InteractionExtracellular Matrix BiologyBreast CancerTissue CultureMammary Gland BiologyMedicineCell DevelopmentLacrimal GlandExtracellular Matrix
Growth and differentiation of mammary epithelium are difficult to maintain in vitro because existing substrates are inadequate. The authors sought to create a primary culture system that preserves mammary epithelial growth and differentiation. They used an acellular matrix derived from whole rat mammary glands, which supports the cells for months. Cultures on this matrix produced 50× more alpha‑lactalbumin than on tissue‑culture dishes, retained lactose secretion for over 30 days, and demonstrated organ‑specific differentiation, with matrix‑surface cells showing higher lactalbumin, lectin binding, DNA synthesis, and continued proliferation until confluence.
The study of growth and differentiation of mammary epithelium has been hampered by the difficulty of maintaining these functions in vitro. We describe a system for the primary culture of rat mammary epithelium on an acellular matrix derived from whole rat mammary glands that maintains growth and differentiation for months. Cultures plated on this complex substratum produce 50 times the alpha-lactalbumin of those on tissue culture dishes and 5 times the alpha-lactalbumin of those on floating collagen gels as determined by radioimmunoassay. Unlike cultures grown on floating collagen gels, which rapidly lose the ability to secrete the milk sugar lactose, mammary cells on this matrix retain this ability for over 30 days in culture. The organ specificity of this mammary extracellular material is shown by the failure of extracellular matrix prepared from rat liver to support mammary differentiation. Within a given culture dish, cells on the surface of mammary extracellular matrix are more differentiated than those on the adjacent plastic. This is demonstrated by their increased alpha-lactalbumin content as shown by indirect immunofluorescence, and by their increased ability to bind fluorescein-conjugated peanut lectin. Cells on the surface of the matrix continue to synthesize DNA as determined by [3H]thymidine incorporation and autoradiography. Even when mammary epithelial cells are plated at low density, cell division continues until the matrix is covered with a confluent layer. We propose that the limited growth, differentiation, and survival of mammary cells in previously described in vitro systems may have been due to substrate that were inadequate to support these functions.
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