Effects of tear substitutes on conjunctival epithelium of mice

The effects of the administration of three tear substitutes on normal conjunctival epithelium of the mouse, with particular regard to goblet cells, were studied.

Three-month-old Swiss CD 1 mice were divided into four groups of 7 animals each. Group 1 was untreated (control). The other animals were treated with the instillation of 5 drops/day for 10 days as follows: group 2, 0.2% sodium hyaluronate (SH); group 3, 0.5% hydroxypropylmethylcellulose (HPMC); group 4, 0.9% NaCl. The entire conjunctiva was processed for light and electron microscopy. A morphometric study was performed to evaluate: the number and size of goblet cells and the number, size and optical density of mucin granules. Furthermore, Alcian blue/periodic acid-Schiff (AB/PAS) staining for goblet cells was carried out.

The SH-treated group showed that the area and number of goblet cells were similar to the untreated group; the mucin granules were reduced in number and optical density but increased in size. The HPMC-treated group showed a reduced area of goblet cells with reduced optical density of mucin granules. The saline-treated group showed that goblet cells were reduced in area and number; mucin granules showed a reduction in number and optical density and an increased size. The AB/PAS stain showed that each treatment was able to induce a treatment-specific modification of the staining characteristics of goblet cells.

Our results strongly suggest that tear substitutes can induce treatment-specific modifications of the conjunctival epithelium with particular regard to goblet cell structure and ultrastructure.