Abstract
Purpose :
Herpes simplex virus type-1 (HSV-1) causes a potentially blinding corneal inflammatory disease called herpes stromal keratitis (HSK) that manifests as edema, opacity, neovascularization and hypoesthesia of the cornea. Mouse corneas are heavily innervated by sensory nerves, with few if any sympathetic nerves. Mice with primary HSK completely lose corneal sensory nerves leading to severe, diffuse inflammation that is maintained by subsequent hyperinnervation with sympathetic nerves derived from the superior cervical ganglion. In humans HSK is usually recurrent disease and ranges from focal areas of corneal opacity and vascularization to diffuse inflammation. Recurrent HSK in mice tends to be focal and transient in C57BL/6(B6) mice, but severe and diffuse in NIH mice. Our goal was to characterize corneal nerve changes associated with recurrent HSK in these two mouse strains.
Methods :
B6 and NIH mice were infected with HSV-1 McKrae and treated with anti-HSV-1 antibody to prevent primary HSK. Recurrent HSK was induced by UV-B corneal irradiation 30 days after primary infection. Whole mounts of irradiated and non-irradiated corneas of infected mice, or irradiated corneas of non-infected were stained with fluorescent antibodies to β III tubulin (all nerves), tyrosine hydroxylase (sympathetic nerves), and substance P (sensory nerves). Z-stacks spanning entire cornea thickness were acquired by confocal microscopy and nerve plexus density was quantified using FIJI software. ANOVA was used for statistical analysis.
Results :
UV-B irradiation did not alter sensory innervation of non-infected corneas. Infected corneas of NIH mice showed mild loss of sensory nerve plexus prior to irradiation, but diffuse loss of sensory nerves and sympathetic hyperinnervation of the corneal stroma after irradiation. Infected corneas of B6 mice did not exhibit a significant reduction in the sensory nerve plexus prior to irradiation, but showed focal areas of sensory nerve loss with coincident sympathetic innervation after irradiation.
Conclusions :
Loss of corneal sensory nerves and innervation by sympathetic nerves are closely associated with recurrent HSK in mice. Moreover, the degree of sensory nerve loss and sympathetic innervation appear to correlate with the severity of recurrent HSK. We are currently investigating the correlation between focal nerve changes and leukocytic infiltration in recurrent HSK in B6 mice.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.