Corneal Sulfated Glycosaminoglycans and Their Effects on Trigeminal Nerve Growth Cone Behavior In Vitro: Roles for ECM in Cornea Innervation

Department of Comparative Biosciences, University of Illinois at Urbana-Champaign, College of Veterinary Medicine, 2001 South Lincoln Avenue, Urbana, IL, 61802, United States.
Investigative ophthalmology & visual science (Impact Factor: 3.66). 11/2012; 53(13). DOI: 10.1167/iovs.12-10832
Source: PubMed

ABSTRACT PURPOSE: Sensory trigeminal nerve growth cones innervate the cornea in a highly coordinated fashion. The purpose of this study was to determine if extracellular matrix glycosaminoglycans (ECM-GAGs), including keratan sulfate (KS), dermatan sulfate (DS) and chondroitin sulfate-A (CS-A) and -C (CS-C), polymerized in developing eyefronts, may provide guidance cues to nerves during cornea innervation. Methods: Immunostaining using anti-neuron-specific-β-tubulin and monoclonal antibodies for KS, DS, and CS-A/C was performed on eyefronts from embryonic day (E)9-14 and staining visualized by confocal microscopy. Effects of purified GAGs on trigeminal nerve growth cone behavior were tested using in vitro neuronal explant cultures. RESULTS: At E9-10, nerves exiting the pericorneal nerve ring grew as tight fascicles, advancing straight toward the corneal stroma. In contrast, upon entering the stroma, nerves bifurcated repeatedly as they extended anteriorly toward the epithelium. KS was localized in the path of trigeminal nerves, whereas DS and CS-A/C-rich areas were avoided by growth cones. When E10 trigeminal neurons were cultured on different substrates comprised of purified GAG molecules, their neurite growth cone behavior varied depending on GAG type, concentration and mode of presentation (immobilized vs. soluble). High concentrations of immobilized KS, DS, CS-A/C inhibited neurite growth to varying degrees. Neurites traversing lower, permissive concentrations of immobilized DS and CS-A/C displayed increased fasciculation and decreased branching, whereas KS caused decreased fasciculation and increased branching. Enzymatic digestion of sulfated GAGs canceled their effects on trigeminal neurons. CONCLUSIONS: Data herein suggest that GAGs may direct the movement of trigeminal nerve growth cones innervating the cornea.

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