Abstract
Purpose :
It has previously been demonstrated that dry eye disease (DED) results in decreased corneal nerve density. The aim of the current study was to evaluate if DED results in alterations of neuropeptides (NPs) and neurotrophins in the cornea and trigeminal ganglia (TG).
Methods :
Adult 6-8-week-old C57BL/6N female mice were injected with 0.5mg of scopolamine hydrobromide and kept in a controlled environment chamber for 14 days and compared to control mice. Clinical evaluations included slit-lamp microscopy, tear secretion, corneal esthesiometry and challenge with [5M] saline. Nerve density was assessed by immunohistochemistry of corneal whole-mounts for βIII Tubulin and confocal microscopy. mRNA and proteins levels of 11 molecular targets of NPs and neurotrophins were assessed by qRT-PCR and ELISA for corneas and TG. A one-way ANOVA with Tukey’s multiple comparison was used to compare effects between groups.
Results :
DED mice demonstrated decreased tear secretion (p≤0.0001) and increased corneal fluorescein staining compared to controls (p≤0.0001). Decreased corneal nerve densitywas measured in DED (78.2±2.8mm/mm2) compared to controls (142.5±13.7; p≤0.0001).A significant increase in paw wipe response was observed with 10 μL of [5M] salinein DED compared to controls 38.6 vs. 17.2 (p≤0.0001). Corneal qRT-PCR revealed decreased neurotrophin expression in DED compared to controls, with 3.1-fold decrease in NGF, 2.4-fold decrease in BDNF and 2.9-fold decrease in NT3 (all p<0.0001), which was confirmed at the protein level by ELISA (all p<0.0001). In addition, there was an upregulation of corneal Substance P (3.4-fold) and CGRP (2.5-fold) in DED compared to controls (p<0.0001 for both). In interestingly, there was downregulation of VIP (2.5-fold), PACAP (3.3-fold), Neurotensin (5.0-fold), Somatostatin (2.0-fold) and NPY (5.0-fold) (all p<0.01). In contrast TG of DED mice demonstrated 4.5-fold upregulation of NGF and 6.3-fold increase in NT-4/5 vs controls (p<0.0001). However, within the TG, only Substance P and Somatostatin were increased in DED by 1.7-fold and 2.2-fold respectively (both <0.05).
Conclusions :
This study provides evidence of imbalance in corneal and TG neurotrophins and NPs in DED. A deeper understanding of the neurochemistry, trophic factors and nervous system may lead to improved treatments for DED.
This is a 2021 ARVO Annual Meeting abstract.