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A. Morimoto-Tochigi, T. Nakajima, A. Fujii, T. R. Shearer, M. Azuma; Functions of Primate Lacritin: Enhanced Secretion of Tear Proteins From Lacrimal Acinar Cells and Promotion of Corneal Epithelial Cell Adhesion. Invest. Ophthalmol. Vis. Sci. 2010;51(13):4178.
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© ARVO (1962-2015); The Authors (2016-present)
Lacritin, an extracellular glycoprotein, is highly expressed in human and monkey lacrimal glands. Recombinant lacritin showed mitogenic activity in corneal epithelial cells and enhanced protein secretion from rat acinar cells. These data suggest that lacritin might be an important factor in maintaining ocular surfaces, but its function in primates is unclear. Thus, the purpose of the present study was to investigate the function of primate lacritin in acinar cells from lacrimal gland and towards epithelial cells from cornea.
Tear fluid was collected from monkeys, and lacritin was purified by cationic exchange and gel filtration chromatography. Acinar cells were isolated from monkey lacrimal gland and cultured under conditions previously reported. Secreated proteins were detected by immunoblotting. Human corneal epithelial cells (HCE-T cells) were incubated with or without lacritin on extracellular matrix-coated plates. Attached cells were counted using a commercial kit.
Purified lacritin from monkey tears migrated on SDS-PAGE gels as a 21 kDa band, confirmed by immunoblotting. Purity of lacritin was more than 98%. Purified lacritin induced secretion of the tear proteins lactoferrin and lipocalin from cultured monkey acinar cells in a dose dependent manner. Lacritin also promoted attachment of HCE-T cells to extracellular matrix in a dose dependent manner.
Tear lacritin enhanced secretion of tear proteins from acinar cells and promoted cell adhesion between corneal epithelial cells and extracellular matrix. The present results and the presence of lacritin in monkey and human tears suggest that lacritin may be an important factor for maintaining the ocular surface in human.
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