Alterations of Murine Subbasal Corneal Nerves after Environmental Dry Eye Stress

Abstract

Purpose : To investigate the morphological changes in the subbasal corneal nerve (SCN) plexus in wild type mice after exposure to environmental dry eye stress (EDES) using in vivo confocal microscopy (IVCM).

Methods : Twenty-two eyes of eleven eight-week-old wild type (Balb/c) male mice were examined. The mice were exposed to an air fan inside a small compartment 5 hours a day for 3 days (EDES) (Fig. 1). Aqueous tear secretion and corneal epithelial damage were assessed. The corneal subbasal nerves were investigated by laser-scanning IVCM. Density, tortuosity, and reflectivity of SCNs, and dendritic cell (DCs) densities were evaluated using a semi-automated NeuronJ software (Fig. 2).

Results : EDES significantly decreased the aqueous tear secretion quantity (p=0.0019) and significantly increased the corneal fluorescein (p=0.005) and lissamine green staining scores (p=0003). The SCN density showed a significant decrease after EDES exposure (before 2813 ± 762, after 1906 ± 896 pixel/frame, p = 0.0071). The tortuosity and the reflectivity grades did not show statistically significant differences after EDES exposure (tortuosity p = 0.307, reflectivity p=0.758). On the other hand, the mean DC density showed a significant increase after EDES exposure (before 12.62 ± 5.94 cells/mm², after 15.93 ± 5.30 cells/mm², p = 0.026).

Conclusions : Even short term exposure to EDES induced alterations in the SCN plexus morphology including decreased subbasal corneal nerve density and increased amount of DCs in mice. EDES mouse model is a promising experimental model to study the ocular surface and corneal nerve changes associated with dry eye disease.

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.

 

Representative photograph of the environmental dry eye stress mice model

 

Representative images of corneal subbasal nerves in 8-week-old male WT mice.
Two observers evaluated the CSN images with semi-automatically independent of each other. A, Representative IVCM images of WT mice exposed to environmental dry eye stress. B, Representative IVCM images of WT mice before environmental dry eye stress. Traced nerve fibers seen in purple and white arrow indicating the measurement differences between two observers