Prolactin and epidermal growth factor regulation of the proliferation, morphogenesis, and functional differentiation of normal rat mammary epithelial cells in three dimensional primary culture

Abstract

The epithelial cell-specific effects of prolactin and epidermal growth factor (EGF) on the development of normal rat mammary epithelial cells (MEC) were evaluated using a three dimensional primary culture model developed in our laboratory. Non-milk-producing MEC were isolated as spherical end bud-like mammary epithelial organoids (MEO) from pubescent virgin female rats. The cultured MEO developed into elaborate multilobular and lobuloductal alveolar organoids composed of cytologically and functionally differentiated MEC. Prolactin (0.01-10 micrograms/ml) and EGF (1-100 ng/ml) were each required for induction of cell growth, extensive alveolar, as well as multilobular branching morphogenesis, and casein accumulation. MEO cultured without prolactin for 14 days remained sensitive to the mitogenic, morphogenic, and lactogenic effects of prolactin upon subsequent exposure. Similarly, cells cultured in the absence of EGF remained sensitive to the mitogenic and lactogenic effects of EGF, but were less responsive to its morphogenic effects when it was added on day 14 of a 21-day culture period. If exposure to prolactin was terminated after the first week, the magnitude of the mitogenic and lactogenic effects, but not the morphogenic response was decreased. Removal of EGF on day 7 also reduced the mitogenic response, but did not have any effect on the magnitude of the lactogenic or morphogenic responses. These studies demonstrate that physiologically relevant development of normal MEC can be induced in culture and that this model system can be used to study the mechanisms by which prolactin and EGF regulate the complex developmental pathways operative in the mammary gland.

Copper is taken up efficiently from albumin and α2-macroglobulin by cultured human cells by more than one mechanism

“…In culture, PMC42 cells differentiate into several cell types, with some showing characteristics of secretory cells (swollen endoplasmic reticulum and secretory vesicles) and others characteristics of myoepithelial cells (contractile fibers). As with primary cultures of the breast epithelium (13,14), PMC42 cells grown as monolayers as organoids on filters coated with extracellular matrix can be stimulated toward milk production by sequential treatment with estradiol and progesterone and then insulin, hydrocortisone, and prolactin (1,70,71). These treatments not only induce the secretion of lipid (characteristic of milk) but synthesis of the milk-specific protein ␤-casein.…”

Ontogenesis of prolactin receptors in the human fetus in early gestation. Implications for tissue differentiation and development.

“…Extension of PRLR immunoreactivity into subcortical mesenchyme is accompanied by tubular growth and cytodifferentiation and branching of the airways, processes that require the direct interaction between mesenchymal and epithelial cells (28). In light of recent findings demonstrating that PRL induces branching morphogenesis in the mammary gland (34), it is tempting to speculate that lactogenic hormones may modulate the interactions between pulmonary mesenchyme and the branching pulmonary epithelium to facilitate lung development and growth. The expression of PRLRs in the airway epithelium may also provide a mechanism by which lactogenic hormones may, in concert with glucocorticoids, facilitate the production of surfactant in the human fetal lung (35, 36).…”

Changes in ErbB2 (her-2/neu), ErbB3, and ErbB4 during Growth, Differentiation, and Apoptosis of Normal Rat Mammary Epithelial Cells

“…Mammary epithelial organ-like fragments (organoids) were isolated as previously described (Darcy et al 1995). Briefly, the digest was fractionated by centrifugation to remove floating adipocytes and the suspension sequentially filtered through 530-m and 60-m nitex filters to remove large tissue fragments and single cells, respectively.…”

“…Immunoblotting and immunoprecipitation studies were used to confirm the specificity of the ErbB-selective antibodies and the developmental expression of ErbB2 and ErbB3. A primary culture model system (Darcy et al 1995) and an inhibitor of the tyrosine kinase domain of the ErbB receptor family (Fry et al 1997) were used to examine changes in ErbB receptor expression during the in vitro development of MECs and to identify the effects that were ErbB receptor-dependent.…”