Abstract
Purpose::
This study quantifies the level of neuron specific fluorescence in the corneas of transgenic mice expressing yellow fluorescent protein (YFP) driven by the thy1 promoter and examines the viability of using thy1-YFP mice as a model for studying nerve regeneration in vivo.
Methods::
The structure of corneal innervation in thy1-YFP mice visible with reporter gene fluorescence was compared to that visible with traditional immunofluorescence techniques. The percentage of corneal nerves with YFP fluorescence in wholemounted corneas and trigeminal neuron cultures was determined. Regeneration of fluorescent corneal neuronal processes after wounding was monitored in vivo.
Results::
In the mouse cornea, neuron specific immunostaining determined that nerves enter the stroma in several bundles which then extend throughout the entire cornea. These stromal nerve bundles formed a sub-basal plexus beneath the corneal epithelium. Fine nerves from this plexus traveled superficially to the ocular surface. Neuron specific expression of YFP allowed visualization of nearly all large nerve bundles of the stroma but only some of the many finer nerves of the sub-basal plexus and surface. In the sub-basal nerve plexus, 46% of total neuronal processes exhibited YFP neurofluorescence. In vitro, 22% of cultured trigeminal neurons exhibited YFP neurofluorescence. After corneal nerve transection, nerve processes distal to the site of injury degenerated while those proximal to the site regenerated in a pattern different from original nerve architecture.
Conclusions::
Thy1-YFP mice display neurofluorescence and provide a novel model for monitoring the patterning, injury, and growth of corneal nerves in vivo.
Keywords: cornea: basic science • innervation: sensation • wound healing