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Neoplastic canine keratinocytes derived from a spontaneous oral squamous cell carcinoma were maintained in culture for more than 45 passages. The presence of desmosomes and keratin filaments was demonstrated by electron microscopy and immunohistochemistry. The keratinocytes were grown in two different culture conditions to induce variations in the stage of differentiation, i.e., in submerged cultures and at the air-liquid interface. For comparison, normal canine keratinocytes were grown under the same conditions. Anisocytosis was present in neoplastic cultures grown submerged in medium. Grown at the air-liquid interface, neoplastic keratinocytes differentiated into a well-organized, multilayered stratified squamous epithelium analogous to normal keratinocytes. Rare areas of irregular growth and formation of whorls were detected. Expression of lectin binding sites and specific cell surface antigens of neoplastic and normal keratinocytes demonstrated marked similarities between the two cell lines. Neoplastic cells lacked certain surface antigens that are present on normal cells. Squamous cell carcinoma cells grew faster than normal canine keratinocytes as demonstrated by growth curve evaluation. Neoplastic keratinocytes responded to growth stimulation by epidermal growth factor and cholera toxin as do normal keratinocytes. Neoplastic cells grown in medium lacking these factors proliferated faster than growth factor stimulated normal keratinocytes.

Keratoconjunctivitis sicca was produced experimentally in 16 beagles by bilateral surgical removal of the lacrimal and nictitans glands; four dogs were not treated, and 12 received tear-replacement therapy on post-operative days 7 through 28. Keratoconjunctivitis sicca was verified by reduction in Schirmer tear test values by post-operative day 6, and there was no response on day 28 to tear-replacement therapy. Corneas of both normal and tear-deficient dogs had polygonal squamous epithelial cells of light and dark electron density by scanning electron microscopy. Light cells had more microvilli and microplicae than dark cells. Conjunctivae were similar to corneas, except for numerous goblet cells on the surface. Corneal dark-cell density and goblet cell density were not different between groups. Goblet cells most often occurred singly in normal dogs, while they were in clusters in tear-deficient dogs. A hypothesis that petrolatum/mineral oil ointment should provide more effective artificial tear replacement than hydroxymethylcellulose drops for tear-deficient dogs could not be confirmed by objective analysis of corneal dark-cell density or conjunctival goblet cell density.