Implication of CD44 and RHAMM Hyaluronan Receptors in Human Ocular Surface Inflammation

Abstract

Purpose: : The purpose of this pilot study is to determine whether CD44 and RHAMM hyaluronan receptors are implicated in human ocular surface inflammation.

Methods: : Conjunctival epithelial samples from healthy donors (n = 14) and patients with active ocular surface inflammation (n = 26) were recovered by brush cytology from upper tarsal conjunctiva, as previously reported (Reinoso R. et al, IOVS 2011). This study followed the tenets of the Declaration of Helsinki. Patients were evaluated by an ophthalmologist (author M.C.), and classified in different groups according to the course of the disease (chronic or acute-recurrent), the etiology (immune-allergic, immune non-allergic or non-immune), and the inflammation intensity (mild/moderate or severe). CD44 and RHAMM proteins from healthy donors were studied by immunocytochemistry. Total messenger RNAs (mRNAs) from healthy donors and patients were isolated and its CD44 and RHAMM levels were measured using real-time RT-PCR. One-way ANOVA was performed to determine the statistical significance of differences.

Results: : CD44 and RHAMM proteins were immunodetected in all the analyzed samples. CD44 signal was predominantly membrane-associated. RHAMM expression pattern was predominantly cytoplasmic, with additional membrane and perinuclear distribution. This pattern was the same regardless of age or gender. CD44 mRNA levels were 100-250 times higher than those of RHAMM in all cases. CD44 mRNA levels were higher in healthy women than in healthy men (p = 0.019). No significant differences were detected in the CD44 levels among the previously described groups of patients and healthy donors. In contrast, RHAMM mRNA levels were significantly different among healthy controls and all groups with severe inflammation. We detected a three-fold increase in RHAMM levels in immune-allergic patients (p < 0.001), a 30% decrease in immune non-allergic causes (p = 0.025), and a 75% decrease in non-immune etiologies (p = 0.001).

Conclusions: : According to our results, RHAMM may be implicated in severe human ocular surface inflammation affecting, at least, upper tarsal conjunctiva. For those reasons, we conclude that RHAMM could potentially be used as clinical biomarker and/or therapeutic target of ocular surface inflammation.

Keywords: conjunctiva • cytology • inflammation