Regional Conjunctival Differences in Glycocalyx Mucin Expression in Dry Eye and Normal Subjects

Purpose

To compare regional conjunctival expression of membrane-associated mucins (MAMs) MUC1, MUC4, and MUC16 in normal and dry eye (DE) subjects.

Methods

Adults with and without signs and symptoms of DE were recruited. Impression cytology was performed to collect MAMs from four bulbar and upper eyelid palpebral conjunctival regions of both eyes. After protein extraction, samples from both eyes of a single subject were pooled by region, and expression was analyzed using a capillary electrophoresis nano-immunoassay system. The chemiluminescence intensity of each antigen binding signal was calculated after normalization to the total protein amount. Statistical analyses were conducted using GraphPad Prime 9.

Results

Samples from thirteen to sixteen DE and seven to eleven normal subjects were analyzed. In normal samples, MUC1 expression from the nasal bulbar conjunctiva was significantly greater than superior (P = 0.004) and inferior (P = 0.005). In DE samples, MUC1 expression was highest superiorly. Significant differences in MUC4 and MUC16 expression were not seen in normal samples. MUC4 and MUC16 expression was upregulated superiorly (P < 0.0001) and inferiorly (P < 0.0001) in DE compared with those regions in normal samples.

Conclusions

Although MAMs form a hydrophilic barrier called the glycocalyx, each mucin may have unique functions that are currently unexplored. All MAMs were expressed in the upper palpebral conjunctiva. Increased MUC1 expression nasally in healthy subjects suggests a functional need for increased protection. When comparing DE with normal eyes, upregulation of MUC1 superiorly, and in both MUC4 and MUC16 both superiorly and inferiorly, may indicate a need to decrease eyelid friction during blinking, especially in DE.

Impact of Improper Approach to Identify Lid Wiper Epitheliopathy (LWE)

Purpose

Variability in the use of ophthalmic dyes to diagnose lid wiper epitheliopathy (LWE) has led to division in the literature and clinical practice. The principal aim of this study was to evaluate whether the use of a non-optimal methodology to identify LWE had a potential for false negatives; in which LWE was overlooked.

Patients and Methods

A total of 20 participants were initially categorized to not have LWE and were enrolled in this study. The protocol examined whether or not LWE would later be revealed through the use of optimized methodology. Semi-automated analysis was performed of images taken after two different drop instillations with varying post-dye viewing times for both lissamine green (LG) and sodium fluorescein (NaFl).

Results

There was a significant increase in area of staining revealed when an optimal methodology for LWE identification was used. Comparisons for every non-optimal condition were statistically significantly different against the optimal condition (all p<0.01). The use of a non-optimal methodology resulted in a 70% false-negative rate when using LG and a 95% false-negative rate when using NaFl.

Conclusion

The study demonstrated that using a double instillation of dye was statistically different from a single-dose, even with extended wait time for clinical observation. A single instillation did not offer adequate volume of dye for adequate lid margin uptake. A careful adherence to volume as well as a repeat administration is key to revealing the full area of LWE. A non-optimal approach to diagnose LWE can lead to false negatives.

Effect of topical rebamipide on goblet cells in the lid wiper of human conjunctiva

It has been demonstrated that topical administration of rebamipide, which is an antiulcer agent, increases the mucin level of the tear film and ameliorates ocular surface conditions such as lid wiper epitheliopathy. The aim of the present study was to analyze the changes in goblet cell number, cell proliferation, and epidermal growth factor receptor (EGFR) induced by topical rebamipide addition to the lid wiper of humans. A total of 30 eyelid tissue samples were obtained during involutional entropion surgeries, fixed in paraformaldehyde, embedded in paraffin and divided into two groups: Rebamipide or non-rebamipide. The tissues in the rebamipide group were obtained from patients who had a medical history of topical rebamipide use prior to surgery. The number of goblet cells was counted under light microscopy. A total of 22 eyelid tissue samples were further examined using immunohistochemistry with anti-Ki-67 and anti-EGFR antibodies to evaluate cell proliferation and EGFR expression, respectively. Histologically, the lid wiper and palpebral conjunctiva were clearly identified in the tissues. The number of goblet cells was significantly higher in the rebamipide group compared with the non-rebamipide group (P=0.0367). There was no significant difference in lid wiper cell proliferation between the rebamipide and non-rebamipide groups. Immunohistochemistry revealed that EGFR levels in the lid wiper epithelial cells were significantly higher in the rebamipide group compared with the non-rebamipide group (P=0.0237). These results suggest that topical rebamipide application increases the number of goblet cells in the lid wiper, which in turn upregulates the expression of EGFR. These findings may be clinically relevant and provide a therapeutic basis for the treatment of ocular disease such as dry eye and lid wiper epitheliopathy.

Topical rebamipide improves lid wiper epitheliopathy

Administration of topical rebamipide increases the mucin level of tear film and improves the ocular surface in short break-up time type of dry eye. Lid wiper epitheliopathy (LWE) is a disorder of the marginal conjunctiva of the upper eyelid with dry eye symptoms. LWE may be related to mechanical forces during blinking resulting in inflammation of the ocular surface. Rebamipide also has various anti-inflammatory effects. In this report, we tried treatment with topical rebamipide for two cases of LWE. One case had been treated with sodium hyaluronate ophthalmic solution and diquafosol sodium eye drops by other doctors for several weeks. The other case was not previously treated. In both cases, fluorescein staining of the cornea and lid margin was remarkably improved, ocular symptoms decreased, and tear film break-up times increased with rebamipide eye drops four times daily for 2-3 weeks. Topical rebamipide was effective for corneal and conjunctival disorders in LWE. This drug may provide a novel approach to the treatment of LWE.