Explant culture of human submandibular gland epithelial cells: evidence for ductal origin.

As an approach to investigating the disease cystic fibrosis, attempts were undertaken to culture from human submandibular glands epithelial cells with a potential for manifesting the cystic fibrosis genetic defect. To initiate the culture of submandibular gland epithelial cells, tissue fragments from glands were explanted as a function of both the composition of the serum-free growth medium and of the matrix utilized to coat the culture vessel growth surface. A morphologically homogeneous growth of submandibular gland epithelial cells, uncontaminated by fibroblasts, was obtained, once optimum culture conditions were defined. Light microscopic examination of these explant cultures in a transverse plane of section demonstrated variation in the outgrowth according to distance from the explant. At its outer margin, the outgrowth consisted of one or two layers of viable low cuboidal cells, and more centrally, it was multilayered. Mitotic figures were observed in the periphery of the outgrowth. In the region, a few cells removed from the periphery where the outgrowth consisted of about three to six cell layers, dilated intercellular spaces, indicative of secretion of fluid and ions into the spaces, separated the basal cuboidal cells. Overlying cells were increasingly flattened toward the culture surface and devoid of nuclei. Centrally, near the explant, the multilayer appeared completely involuted throughout. Ultrastructural examination in a transverse plane of the multilayered region with viable basal cells confirmed these observations showing wide spaces separating the cuboidal basal cells, keratinization of midstratum cells, and complete involution of the upper layer of ghost-like cells. These cells cultured from the submandibular gland reacted positively to immunochemical staining for keratin.