Changes in corneal nerve morphology and epithelial wound healing after prolonged ocular dryness induced by lacrimal gland ablation

Abstract

 

Purpose

 

To analyze the morphological changes of corneal nerves and corneal epithelial wound healing at different times (1-8 months) after surgical removal of the lacrimal gland in guinea-pigs.

 

Methods

 

The right exorbital lacrimal gland was surgically removed in anesthetized animals thereby inducing a chronic tear flow reduction (dry eye); 1, 2, 3, 4 and 8 months after surgery, eyes were fixed and cryoprotected. Whole-mount corneas were incubated with neuronal class III β-tubulin antibody and Alexa fluor 488. A set of corneas was incubated in ABC. Corneas of 6 non-operated guinea pigs served as control. Corneal epithelial wound healing was studied 1 and 6 months after surgery in 15 dry eyes and in 5 control eyes. Epithelium debridation was performed with a 2mm-diameter piece of paper soaked in n-heptanol. Lesions were stained with fluorescein and photographed regularly until complete closure. Images were analyzed with image processing software. Epithelial migration rate (EMR, in µm/h) and estimated time of healing (ETH, in hours) were calculated.

 

Results

 

Density and length of subbasal nerves decreased significantly after 1 month in dry eyes compared to control eyes. Subbasal nerves appeared less branched and the number of epithelial nerve terminals was significantly reduced. These effects were more prominent 2 months after induction of eye dryness. 4-8 months after tearing deficiency, density and length of subbasal corneal nerves had recovered values close to control, although nerve architecture was not fully normal. EMR was significantly decreased and ETH was significantly increased 1 and 6 months after surgery (Table 1), although at month 6th, ETH was partly recovered.

 

Conclusions

 

The changes in corneal subbasal nerve architecture 1-2 months after lacrimal gland removal suggest that nerve damage develops shortly after induction of reduced tearing, leading to a neurotrophic slowdown of epithelial wound healing. At longer times, regeneration of corneal nerves appears to restore in part the wound healing capabilities of the normal corneal epithelium.

 

 

Keywords: 565 innervation: sensation • 765 wound healing