CELL-INTERACTIONS BETWEEN EPITHELIAL AND MESENCHYMAL COMPONENTS IN PRIMARY SHEETS OF FETAL RAT LUNG-CELLS, AND EFFECTS OF 3-METHYLCHOLANTHRENE TREATMENT

Cell rearrangement of epithelial and mesenchymal components was analyzed in primary cell sheets derived from whole lungs from fetal rats and maintained in tissue culture for 3-175 days without being subcultured. A limited reconstruction of original lung tissue from the dissociated cells was observed in these primary cell sheets. From the initial monolayer spread, ciliated columnar epithelial coverage appeared on fibroblast sheets after .apprx. 2 wk maintenance. Cystic formations also developed within the fibroblast layers. Histotypic collagen fibril formation appeared in the fibroblast layers and resulted in the development of multilayered collagenous connective tissue in vitro. Epithelial elements survived as a form of surface coverage during maintenance of the sheets and as cystic structures in the collagenous layers. Treatment with the carcinogen 3-methylcholanthrene induced severe proliferation of epithelial elements in the cell sheets. These proliferative changes included rapid extension of epithelial surface coverage, stratification of immature cells and squamous cell metaplasia.