[Primary culture in chemically defined medium of human fetal mammary epithelial cells within reconstituted matrix]

A serum-free primary culture system has been developed which allows for three-dimensional growth and differentiation of normal human fetal mammary epithelial cells within an extracellular matrix preparation. Human fetal mammary epithelial cells were isolated from the mammary glands of human female fetuses, 17 to 39 weeks-old. The "organoids" were embedded within a reconstituted basement membrane matrix prepared from the Engelbreth-Holm-Swarm (EHS) sarcoma according to the method of Hahm and Ip. "Organoids" were grown in either serum-free medium or in medium with fetal calf serum (FCS). The "organoid" proliferated over a 2 to 3 weeks culture period and remained viable for 1 or 2 months within the basement membrane matrix in serum free medium. Several types of colonies were observed; including alveolar-like budding clusters obtained from cultures of mammary gland from fetuses of over 20 weeks age, units with ductule-like projections and stellate-type colonies. Cell proliferation was dependent on the culture medium (with FCS no proliferation was obtained) and on the substratum (without matrix, significantly less growth and development occurred). These types of colonies are obtained when a glandular differentiation of cells budding from the malpighian epithelium is observed. Light microscopic and transmission electron microscopic studies were undertaken at the time of culture. This unique system using normal fetal mammary epithelial cells thus provides a model in which the regulation of human mammary development can be investigated.