Abstract
The stearoyl-CoA desaturase (SCD) family of enzymes catalyzes monounsaturated fatty acid synthesis by inserting a cis double bond at the Δ9 position of saturated fatty acids. Disruption of these enzymes has been reported to induce a severe dry skin phenotype. Since lipid abnormalities in the meibomian glands have been associated with dry eye, we analyzed selected eye tissues contributing to tear volume and composition in genetically SCD-1-deficient mice (SCD-1 KO), including the lacrimal glands and conjunctiva. Previous histopathological analysis had revealed atrophy and loss of meibomian glands; taken together with the increased goblet cell and MUC5AC expression in the conjunctiva reported here, these findings suggest that the tear volume and mucin levels secreted are enhanced in the absence of lipid secretion as a compensatory mechanism. The expression of lipid metabolism genes in lacrimal glands was decreased in SCD1 KO mice. Thus, these results provide new pathophysiological mechanisms to pursue with regard to meibomian gland dysfunction. In addition, lack of SCD-1 causes a compensatory increase in the tear volume and mucin levels associated with changes in expression of lipid metabolism genes. These results may be useful as a new concept for dry eye treatment strategies.
Highlights
Meibomian gland dysfunction (MGD) is a chronic or pervasive abnormality of the meibomian glands, in which qualitative and quantitative changes to glandular secretions occur in association with obstruction of the gland ducts[1,2,3,4]
The immunohistochemical results indicated that stearoyl-CoA desaturase (SCD)-1 was localized in the cytoplasm of acinar cells in wild-type mice, but was not detectable in ductal cell of wild type and lacrimal gland (LG) of SCD-1 KO mouse (Fig. 1A)
Western blot analysis revealed that SCD-1 expression was absent in SCD-1 KO mice in contrast to LG from wt mice, which expressed an immunopositive band (Fig. 1B)
Summary
Meibomian gland dysfunction (MGD) is a chronic or pervasive abnormality of the meibomian glands, in which qualitative and quantitative changes to glandular secretions occur in association with obstruction of the gland ducts[1,2,3,4]. These obstructions may cause changes in tear layer function, ocular discomfort, severe inflammation of the ocular surface, or epithelial disorders[5]. In this study, we aimed to ascertain the effect of meibomian gland abnormality on dry eye by analyzing tears and ocular tissue in SCD-1 KO mice
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