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Almudena Íñigo-Portugués, Giovanna Exposito, Juana Gallar, Carlos Belmonte, Victor Meseguer; REMODELING OF CORNEAL COLD SENSORY NERVE FIBERS IN THE ADULT LIVING MOUSE. Invest. Ophthalmol. Vis. Sci. 2017;58(8):1021. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
To define the time course and magnitude of remodeling of corneal cold sensory nerve fibers of adult mice in vivo.
Mice expressing EYFP under the control of TRPM8 regulatory sequences (TRPM8-EYFP mouse) were anesthetized with an intraperitoneal injection of xylazine (16 mg/kg) followed by inhalation of isoflurane (1.5 %). In TRPM8-EYFP mice, only cold-sensitive fibers (roughly 20 percent of the total) display a green fluorescence, thus allowing their morphological identification. TRPM8+ sub-basal nerve leashes and intraepithelial terminals were imaged at 5x and 25x magnification by means of a confocal microscope and reconstructed in 3D using Imaris 8.2 software. Individual corneal leashes and intraepithelial terminals were monitored in the same animal at different time points over a week (day 0, day 2 and day 7). The total length of individual leashes was measured, and the length change rate calculated. The number of nerve terminals given by each sub-basal nerve fiber was also counted.
Points of penetration of a single stromal nerve into basal lamina to form a sub-basal leash were not homogeneously distributed throughout the cornea, being more abundant in its periphery than in the center. Five out of 7 leashes containing TRPM8 axons, measured in 3 mice, increased their total length at a rate of 34.56 ± 14.10 µm/day. Contrarily, total length decreased in another 2 leashes at a rate of -55.38 ± 34.60 µm/day. Additionally, the number, location and shape of nerve terminals given by the leashes changed with time (figure 1).
Corneal nerve fibers in the living animal experience dynamic configuration changes involving increases and decreases of leashes’ total length and redistribution of their terminal endings, reflecting a continuous remodeling of corneal epithelium innervation.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
Remodeling of TRPM8+ leashes and intraepithelial terminals in living mice. (A) Confocal micrograph of a subbasal leash and its nerve terminals in 3-D taken at day 0, and (B) at day 7. Asterisk indicates the reference point in the subepithelial plexus used in both images. Rendering in 3-D at day 0 (C) and day 7 (D) of the same sub-basal leash (red) and nerve terminals (in gray). Scale bar: 70 mm
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