A rat model of corneal reinnervation using nerve grafts and transfers from the contralateral face

Abstract

Purpose : Loss of corneal sensation causes neurotrophic keratopathy, resulting in corneal scarring and vision loss. In clinical studies, surgically reinnervating the cornea using normal nerves from the contralateral face restores corneal sensation and may improve ocular surface health. Investigating how reinnervation with foreign nerves influences the corneal epithelium requires an animal model in which tissue can be harvested and analyzed.

Methods : Thy1-GFP+ rats, which express green fluorescent protein in axons, were used to monitor corneal denervation and reinnervation. Corneal denervation was accomplished using stereotactic electrocautery of the ophthalmic branch (V1) of trigeminal nerve (CN V). Corneal reinnervation was performed on the denervated right eye using two nerve grafts coapted to the contralateral infraorbital nerve and tunneled into the denervated cornea. The cornea was harvested four weeks after denervation, and nerve density was determined using NeuronJ software. In a separate group of animals, the cornea was retrograde labeled with 4% Fluorogold to determine the location and number of neurons reinnervating the cornea. Reinnervated corneas were compared with uninjured and non-reinnervated controls.

Results : Corneal reinnervation resulted in a significant increase in corneal axon density (Figure 1). Denervated corneas demonstrated minimal reinnervation after 4 weeks (2301 μm/mm² ± 1347) and significantly less than reinnervated (62872 μm/mm² ± 12400; p < 0.0001) and uninjured controls (46165 μm/mm² ± 3965). Retrograde-labeling of the left uninjured cornea labeled 219 ± 36 neurons in the left (ipsilateral) trigeminal ganglion (TG) innervating the cornea, with no labeled neurons in the right (contralateral) TG. In contrast, labeling of reinnervated (left) cornea demonstrated few labeled neurons in the left (ipsilateral) TG (1 ± 1), with a significant number of labeled sensory neurons in the right (contralateral) TG (206 ± 82), suggesting axons reinnervating the cornea derived from the contralateral face.

Conclusions : The described rat model of corneal reinnervation can be used to investigate how reinnervation of the cornea using foreign donor nerves influences corneal epithelial health, including epithelial healing and gene expression.

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.

 

Figure 1. Axons in the uninjured cornea (A) are absent four weeks after injury (B). Significant axon reinnervation is present after neurotisation (C).