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G. F. Schaefer, K. Jäger, G. Wu, S. Sel, D. Worlitzsch, F. Garreis, L. Bräuer, F. Paulsen; Detection of MUC16 in the Lacrimal Apparatus and Regulation by Inflammatory Mediators at the Ocular Surface. Invest. Ophthalmol. Vis. Sci. 2007;48(13):2688.
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The aim of the present study was to determine the possible expression of the mucin MUC16 in the lacrimal apparatus and to evaluate its regulation by proinflammatory cytokines and bacterial components at the ocular surface.
Expression and distribution of MUC16 in main and accessory lacrimal glands, nasolacrimal ducts, conjunctival (HCjE) and corneal (HCE) epithelial cell lines was monitored by RT-PCR and immunohistochemistry. To determine regulation of MUC16 cultured HCjEs and HCEs were stimulated with different cytokines, bacterial components/supernatants and analyzed by real time PCR, immunodot-blot and immunohistochemistry.
The results indicate that MUC16 is expressed and detected in all tissues investigated. It is membrane-anchored in accessory lacrimal glands whereas in lacrimal gland acinar cells and columnar cells of the nasolacrimal ducts it is stored in intracytoplasmic vesicles without membrane-association. Cell culture experiments revealed that MUC16 is differentially regulated between HCjEs and HCEs after challenge with inflammatory mediators and suggest shedding of MUC16 into the tear film.
Shedding of MUC16 seems to be precisely regulated. It can be differentially increased and decreased suggesting a protective function of membrane anchored MUC16 and supporting the hypothesis that dysregulation of MUC16 at the ocular surface may be involved in dry eye pathology. Moreover, MUC16 is present in the whole lacrimal apparatus. Its distribution pattern suggests different physiological functions with regard to tear film physiology and tear outflow. Our results demonstrate also the existence of so far not recognized qualitative differences in the secretion product of main and accessory lacrimal glands.
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