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Mary Ann Stepp, Sonali Pal-Ghosh, Gauri Tadvalkar; Alterations in cornea sensory nerves with aging and in response to injury in mice lacking the heparan sulfate proteoglycan syndecan-1. Invest. Ophthalmol. Vis. Sci. 2017;58(8):2000.
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© ARVO (1962-2015); The Authors (2016-present)
To determine the impact of the loss of the heparan sulfate proteoglycan syndecan-1 (sdc1) on intraepithelial corneal nerves (ICNs) during homeostasis, aging, and in response to injury, we quantify nerve density and fiber thickness (fasciculation) in male and female wt and sdc1 null mice as a function of time after birth through 40w of age and in response to two types of injury: 1.5mm trephine and 1.5 mm debridement.
Whole flat mounted corneas of BALB/c mice (male and female) were stained using antibodies against βIII tubulin to study the density of the ICNs using Sholl’s analysis and axon thickness using Image J as a function of time after injury (3w-10 mo) and after trephine and debridement injury. A minimum of 5 corneas are used per time point. Additional studies were performed assessing cell proliferation and localization of the regeneration activated gene GAP43 and lysosomal marker LAMP1 within subbasal nerves (SBNs) and intraepithelial nerve terminals (INTs).
Sdc1 null mice are slower to innervate their corneas; by 8 w of age sdc null mice have reduced axon density compared to wt mice. Both wt and sdc1 null mice lose axon density and thickness with aging. GAP43 expression in the intraepithelial nerve terminals of unwounded mice indicates that the ICNs are constantly growing. Although sdc1 null ICNs reinnervate the cornea with equal efficiency as wt ICNs after injuries requiring cell migration and sheet movement, after trephine injuries that leave the epithelium intact, they take longer than wt mice to regenerate. Axon fragments accumulate within 6 hours in LAMP1+ lysosomes in the corneal epithelium after trephine injury.
The intraepithelial corneal nerves (ICNs) in mice express the regeneration associated gene GAP43 constituitively; within hours after 1.5 mm trephine crush wounds, fragments of axons colocalize within lysosomes. Mice lacking the syndecan-1 show differnces in axon density and thickness and response of axons to trephine injury compared to controls.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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