Epidermal growth factor-mediated growth control of confluent mammary epithelial cells cultured on artificial basement membrane.

Local epithelial cell growth is involved in physiological and pathological processes such as development, morphogenesis and carcinogenesis. Cell growth is triggered by the binding of growth factors, such as epidermal growth factor (EGF) to their own receptors (i.e. EGFR). In confluent states, EGFRs are distributed on the basal-lateral side of polarized cells. Therefore, the delivery of EGF to EGFR is thought to be regulated by both tight junctions between the cells, as well as by the basement membrane to which the cells are attached. This research constructed a new culture device with which EGF can be delivered to either the basal-lateral or apical side of confluent epithelial cells that are cultured on an artificial Matrigel basement membrane. Cells in a confluent state started to regrow as a result of incubation with basal medium containing EGF, but not as a result of incubation with apical medium containing EGF. The rate of confluent epithelial cell regrowth depended on EGF concentrations supplied via the basement membrane. In contrast, cells in which tight junctions were disrupted by pre-treatment with EGTA displayed regrowth as a result of incubation with apical medium containing EGF. These results suggest that EGF signaling from the basal-lateral side is regulated by the basement membrane, while that from the apical side is blocked by the tight junctions. Thus, this culture model can be readily used to study the control of local growth of epithelial cells in physiological and pathological processes.