Phenotype and differentiation potential of a novel rat tracheal epithelial cell line.

In this report we described the establishment and characterization of a continuous rat tracheal epithelial (RTE) cell line spontaneously derived from secondary RTE cell cultures. Designated SPOC1, this cell line is nontumorigenic and maintains a diploid karyotype with specific, nonrandom chromosomal alterations involving chromosomes 1, 3, and 6. SPOC1 cells demonstrate decreased requirements for peptide growth factors, compared with primary RTE cells. Upon inoculation into denuded rat tracheas, which are then implanted into syngeneic hosts, SPOC1 cells initially form a stratified squamous epithelium, which becomes less stratified with time and forms glandlike invaginations into the surrounding lamina propria. No evidence of ciliated cell differentiation is detected. The epithelium formed by SPOC1 cells in tracheal grafts reacts with antibodies specific for keratin 14, 13, and 19 (but not keratin 18) at both early and late time points, although the localization of antibody staining changes as the epithelium becomes less stratified with time. The suprabasal epithelial cells become positive for alcian blue-periodic acid-Schiff staining at later time points. The near-normal karyotype and differentiation potential of SPOC1 cells make this cell line a unique window into early changes occurring during immortalization of airway epithelial cells and will allow studies of relationships between differentiation state and neoplastic transformation

Mucin Production by SPOC1 Cells - An Immortalized Rat Tracheal Epithelial Cell Line

An airway epithelial mucous goblet cell line would be useful towards understanding mechanisms underlying the common problem of respiratory mucus hypersecretion. SPOC1 is a novel rat tracheal epithelial (RTE) cell line that developed cytologie features suggestive of mucous goblet cells when grown in tracheal grafts in vivo (Am. J. Respir. Cell Mol. Biol. 1995; 12:385-395). Our aims were to determine whether SPOC1 cells were capable of mucin synthesis and to directly compare mucin production by SPOC1 cells and RTE cells. Towards this end, we validated the use of monoclonal antibody (mAb) RTE11 (Exp. Lung Res. 1992; 18:323-342) as an immunologie probe for rat airway secretory mucin. Our results strongly suggest that mAb RTE11 detects a carbohydrate antigen that is a sensitive and specific marker for rat tracheobronchial secretory mucin. SPOC1 cells in tracheal grafts in vivo contained granules with ultrastructural features similar to mucous granules in normal rat airway goblet cells and they were strongly stained by mAb RTE11. Retinoic acid (RA) and culture on porous supports are known to profoundly modify airway epithelial cell phenotype in vitro. Expression of several retinoid-responsive proteins was similar in cultured SPOC1 and primary RTE cells, but major differences in mucin production were noted. Primary RTE cells in vitro only made mucin when grown on porous supports in the presence of RA, whereas SPOC1 cells produced mucin when grown on plastic or glass surfaces and even in the absence of RA. Interestingly, RA enhanced mucin secretion by SPOC1 cells during the early plateau stage of culture but there were no differences due to RA late in the culture period. SPOC1 cells are capable of mucin production and will be a useful tool for studying select aspects of airway secretory cell differentiation and function