Epithelial-stromal interactions in the mouse and human mammary gland in vivo.

This review deals with the development and hormonal responses of mouse and human mammary glands. A major focus of the review is the role of mesenchymal-epithelial interactions in embryonic mammary development and the role of stromal-epithelial interactions in mammary gland biology. Finally, we present a new model for studying growth, differentiation and hormonal response in human breast epithelium grown in vivo in nude mouse hosts. This new model involves the construction of tissue recombinants composed of human or mouse mammary fibroblasts plus human breast epithelium in polymerized collagen gels. In the model, mouse mammary fibroblasts and human breast fibroblasts appear to support the normal differentiation and growth of human breast epithelium equally. This observation raises the possibility of using mouse mammary fibroblasts from various mutant mice to assess the role of specific paracrine-acting gene products in human mammary gland biology and carcinogenesis.