Proceedings: In vitro studies of the normal human mammary gland.

In vitro techniques can be used to analyze human mammary gland physiology. In organ culture, human breast tissue survived intact for up to 16 days in defined medium without supplemental serum or hormones. The alveolar epithelial cells showed a significant level of DNA synthesis and mitosis which could be further augmented by insulin or prolactin. Ultrastructural studies of organ cultures verified that the tissue was healthy. There was some morphologic evidence of protein synthesis but specific signs of milk protein synthesis were lacking. Adding the combination of insulin, hydrocortisone, and prolactin did not result in convincing morphologic evidence or milk synthesis. These findings are at variance with extensive studies of other investigators on the mouse mammary gland. Primary cell cultures were made from pieces of the large collecting ducts after their dissection from the mammary gland. After treatment with trypsin-EDTA, the epithelial cells were separated from the underlying connective tissue and plated out in petri dishes or flasks. Cell shape, growth pattern, and ultrastructural features were most consistent with an epithelial origin. Proliferation occurred at a high level in medium containing 10% fetal calf serum. Hormones had no further effect on proliferation and only a minimal effect on ultrastructural appearance. The ease of propagating these cells should encourage their use in other studies of mammary cell behavior.