Nuclear parameters and chromatin remodeling in epithelial cells and lymphocytes from the palpebral conjunctiva of dogs with keratoconjunctivitis sicca.

Objective: To study parameters related to nuclear morphology and chromatin remodeling in epithelial cells and lymphocytes from the inferior palpebral conjunctiva of dogs with and without keratoconjunctivitis sicca (KCS).

Animals Studied: Thirty-two dogs (64 eyes) were included in the study. Based on the tear production measured by Schirmer tear test 1, the dogs were distributed into control and KCS groups.

Procedures: Epithelial cells and lymphocytes were collected by conjunctival brush cytology, fixed on glass slides, and subjected to the Feulgen reaction, a topochemical method specific for DNA/chromatin. Feulgen-stained cells were studied by microscopy and video image analysis to establish nuclear size (area and perimeter) and shape (relative nuclear roundness factor = RNRF), DNA content (ploidy), and compaction and texture of chromatin.

Results: Conjunctival samples in the KCS group showed infiltration of inflammatory and immune cells. Micronuclei, snake-like chromatin, aberrant chromosomes, and goblet cells were not detected. Compared with the controls, cells on the conjunctival surface of dogs with KCS showed altered nuclei. Conjunctival epithelial cells were more affected by KCS (changes in nuclear size, shape, DNA content, and chromatin compaction) than lymphocytes (changes in chromatin compaction, only). Significant chromatin decompaction was observed in both conjunctival epithelial cells and lymphocytes.

Conclusions: Our results show that KCS promotes chromatin remodeling in epithelial cells and lymphocytes on the conjunctival surface of dogs. The changes described in this study are different from those reported for conjunctival cell nuclei of human KCS patients.