Expression of the P2Y₂ receptor on the rat ocular surface during a 1-year rearing period

P2Y2 receptors are expressed on ocular surface tissues. Diquafosol ophthalmic solution (DIQUAS(®) ophthalmic solution 3 %; Santen Pharmaceutical Co., Ltd.) acts on these receptors and promotes the secretion of water and mucin. It has been shown to be an efficient dry eye treatment. If P2Y2 receptor expression on the ocular surface decreases with age, the effect of diquafosol may be reduced in elderly persons. In this study, we investigated the changes in P2Y2 receptor expression on the rat ocular surface over an extended period of time.

P2Y2 receptor expression in the conjunctiva, cornea, meibomian gland and lacrimal glands of male and female Sprague-Dawley rats was examined from 5 weeks until 53 weeks of age using immunostaining and quantitative-PCR.

In the immunohistological examinations, P2Y2 receptor expression was observed in the conjunctival epithelium containing goblet cells, corneal epithelium, meibomian gland ductal epithelium and lacrimal gland ductal epithelium. However, its expression was not significantly different between each age group or between sexes. Regarding P2Y2 receptor mRNA expression, there was an age-related increase in the bulbar conjunctiva. In particular, a significant increase was observed in the 53-week-old age group as compared to the 5-week-old female age group. However, age-related changes in expression were not observed in the cornea or meibomian gland in males or females.

We observed no significant age-related decrease was observed for P2Y2 receptor protein and mRNA expression on rat ocular surface tissues.