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Originally published In Press as doi:10.1167/iovs.09-3563 on April 30, 2009
 (Investigative Ophthalmology and Visual Science. 2009;50:4581-4587.)
© 2009 by The Association for Research in Vision and Ophthalmology, Inc.
doi:10.1167/iovs.09-3563
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Mucin-type O-glycans in Tears of Normal Subjects and Patients with Non-Sjögren’s Dry Eye

Ana Guzman-Aranguez, Flavio Mantelli, and Pablo Argüeso

From the Schepens Eye Research Institute and Department of Ophthalmology, Harvard Medical School, Boston, Massachusetts.

PURPOSE. O-linked carbohydrates (O-glycans) contribute to the hydrophilic character of mucins in mucosal tissues. This study was conducted to identify the repertoire of O-glycans in the tear film and the glycosyltransferases associated with their biosynthesis, in normal subjects and patients with non-Sjögren’s dry eye.

METHODS. Human tear fluid was collected from the inferior conjunctival fornix. O-glycans were released by hydrazinolysis, labeled with 2-aminobenzamide, and analyzed by fluorometric, high-performance liquid chromatography (HPLC) coupled with exoglycosidase digestions. O-glycan structures identified in tears were related to potential biosynthetic pathways in human conjunctival epithelium by using a glycogene microarray database. Lectin-binding analyses were performed with agglutinins from Arachis hypogaea, Maackia amurensis, and Sambucus nigra.

RESULTS. The O-glycan profile of human tears consisted primarily of core 1 (Galβ1-3GalNAc{alpha}1-Ser/Thr)–based structures. Mono-sialyl O-glycans represented approximately 66% of the glycan pool, with {alpha}2-6-sialyl core 1 being the predominant O-glycan structure in human tears (48%). Four families of glycosyltransferases potentially related to the biosynthesis of these structures were identified in human conjunctiva. These included 13 polypeptide-GalNAc-transferases (GALNT), the core 1 β-3-galactosyltransferase (T-synthase), three {alpha}2-6-sialyltransferases (ST6GalNAc), and two {alpha}2-3-sialyltransferases (ST3Gal). No significant differences in total amount of O-glycans were detected between tears of normal subjects and patients with dry eye, by HPLC and lectin blot. Likewise, no differences in glycosyltransferase expression were found by glycogene microarray.

CONCLUSIONS. This study identified the most common mucin-type O-glycans in human tears and their expected biosynthetic pathways in ocular surface epithelia. Patients with non-Sjögren’s dry eye showed no alterations in composition and amount of O-glycans in the tear fluid.






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