Plate and collagen-gel cultures of normal canine mammary epithelial cells.

Plate and collagen gel (floating or embedded) cultures were made to study the cell morphology and growth characteristics of canine mammary epithelial cells in vitro. Hiratsuka's method was satisfactory for the separation of the epithelial cells from the fibroblasts in explants of canine mammary tissue. In the plate culture method, epithelial cells migrated out from the explants to form colonies. The characteristic features of epithelial colonies in this culture system were polygonal cells situated in the centre, elliptical cells in the outer region and large spindle-shaped cells, thought to be myoepithelial cells, at the periphery. These epithelial cells showed a pavement-like appearance and were positive for antikeratin antibody. On floating gels, the cells changed their shape dramatically from flattened to rounded when the gel was released from the glass dish. Cells embedded in collagen gels grew to form duct-like structures.