Very long-chain lipids could help prevent dry eye disease

What is it about?

Many might think tears are merely water, but actually the tear film is composed of three basic layers: mucin, water, and lipids, the latter of which helps prevent water evaporation from the ocular surface and protects against infection. The tear lipids are mostly derived from the meibomian glands and are called meibum lipids. Very long-chain meibum lipids cause severe dry eye disease when they were shortened in mice— a result that could help develop new drugs for the disease.

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Why is it important?

Meibum lipids are mainly composed of cholesteryl esters and wax esters both having very long-chain carbons (20 to 34). But much about meibum remains unclear, such as the significance of its long chains and its role in preventing dry eye disease. We reported that a sufficient chain-length of meibum lipids is crucial for the prevention of dry eye disease, using mutant mice that cannot elongate fatty acids. The mutant mice exhibited increases in eye blink frequency and water evaporation from the ocular surface at younger ages. Aged mice frequently developed corneal opacity with vascular invasion, accompanied by the epidermalization of the cornea. It was surprising to us that the quality (length) of meibum lipids, without changes in their total amount, was important for the barrier function of tear film.

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