Lacritin, a Novel Tear Glycoprotein, Stimulates Tear Production in Rabbits without Ocular Toxicity

Abstract

Dry eye is extremely common and debilitating disease. Current treatment options like artificial tears and cyclosporin are palliative and do not effectively address the underlying pathology of dry eye. Lacritin is a newly discovered glycoprotein that occurs naturally in human tears, produced solely by meibomian, lacrimal and salivary glands. Human recombinant lacritin stimulates tear secretion in cultured rat lacrimal acinar cells, leading us to hypothesize that topical application of lacritin will increase production of tears of normal composition. Bilateral tear production in New Zealand white rabbits was measured at 60, 120 and 240 min after a single topical administration of 50μl lacritin (1, 10, or 50 μg/ml). Tears were collected and slit lamp examination and ocular surface staining measured before and 240 min after treatment. Tear pH, protein and electrolyte concentrations were then measured. A 50 μg/ml lacritin dose increased tear production by 40% within 60 min and maintained for 240 min (p<0.05). With other doses, a significant increase (55% from baseline, p<0.05) was observed only at 240 min. No local irritant effects were noted by slit‐lamp examination. The composition (pH, Na2+ and K+) of tears was also not different from normal tears. In conclusion, lacritin is a novel, safe and effective candidate for dry eye therapy. Lacritin, being mitogenic, may also help restore the natural tear film.