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Juana Gallar, Laura Fernandez-Sanchez, Carolina Luna, Susana Quirce, Illes Kovacs, M.Carmen Acosta, Carlos Belmonte, Nicolas Cuenca; Corneal Nerve Morphology in an Experimental Model of Dry Eye in the Guinea Pig. Invest. Ophthalmol. Vis. Sci. 2011;52(14):3764.
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© ARVO (1962-2015); The Authors (2016-present)
Nerve impulse activity of corneal sensory nerves is altered at 4 weeks after lacrimal gland removal in the guinea pig (Kovacs et al, 2010;ARVO E-Abstract 3403). The aim of this study was to elucidate whether this altered sensitivity of sensory nerve fibers is accompanied by changes in corneal nerves morphology.
Corneas from six animals were used in this study. Four weeks after lacrimal gland removal, animals were sacrificed and the eyes were dissected, fixed in 4% paraformaldehyde and then cryoprotected in gradients of sucrose. Corneas were incubated in mouse monoclonal antibody against neuronal class III beta-tubulin (TuJ1, 1:500). After incubation with secondary antibody (Alexa fluor 488 anti-rabbit), whole-mount corneal epithelium and stroma were visualized with a confocal microscope (Leica TCS SP2).
In control corneas, TuJ1-positive nerve fibers were distributed homogeneously throughout the cornea. From stromal nerve bundles, most nerve fibers branched into several subbasal nerve fibers (leashes) travelling between the basal epithelium cells parallel from each other around 200µm. Subbasal nerve fibers then fold by 90º and continued towards the superficial corneal epithelial layer ending as asymmetrical clusters of free nerve terminals. At 4 weeks after dry eye, morphological appearance presented differences with control corneas. In the peripheral cornea, subbasal leashes were less abundant and less branched, presented a tortuous trajectory and ran for shorter distances than in control eyes, finally ending at the superficial layers of the epithelium as sparse free nerve endings. In the central cornea, leashes were scarce and very disorganized, although some pencillate small clusters, resembling TRPM8-positive cold thermoreceptors (Parra et al., Nat Med 2010;doi:10.1038/nm.2264) were present.
The present study provides comprehensive information of the architecture of nerves in the guinea pig cornea, not previously described in detail. Together to an altered sensitivity of corneal sensory nerves there are alterations of corneal nerve morphology, as reduction of leashes at the subbasal nerve plexus and tortuosity of nerve fibers, suggestive of early nerve degeneration developed in lacrimo-deficient animals.
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