Abstract
Purpose :
Dry eye is a common manifestation of ocular graft versus host disease (GVHD). Multiple studies have reported elevated levels of inflammatory cytokines in the tears of GVHD patients. Mucins are glycosylated proteins that are crucial for ocular surface hydration. It is likely that an increase in inflammatory cytokines can cause changes in the mucins gene expression which can negatively impact the tear film. Therefore, the purpose of this study is to test the effect of proinflammatory cytokines (TNF-α, IL-6, IFN-γ) on mucins expression of human corneal and conjunctival epithelial cells.
Methods :
Human conjunctival and corneal epithelial cells were used. Conjunctival cells were grown in serum-free low calcium F12/DMEM medium, and then switched to serum-containing keratinocyte medium for stratification. Corneal epithelial cells were grown on transwell membrane inserts, in growth factor-supplemented complete keratinocyte medium. The experimental groups included exposing the conjunctival and corneal cells to a) IL-6 b) IFN-γ c) TNF-α for 24 hours. For each cytokine 5 different doses (30, 60, 125, 250, 500 pg/µL) were tested. After treatment for 24 hours, the cells were harvested for mRNA isolation using the RNeasy mini-kit (Qiagen), and RNA was reverse transcribed into cDNA (using Qiagen kit) for gene quantification of mucin 1, mucin 4, mucin 16 and mucin 19 using real time PCR. Statistical Analysis was done using two-way ANOVA and Bonferroni test.
Results :
The modulation of conjunctival and corneal epithelial cell mucins gene expression was both cytokine and mucin subtype-dependent. TNFα caused the most notable decrease in the gene expression of mucins in both corneal and conjunctival cells. IL-6 exposure caused a dose-dependent decrease in the gene expression of mucin 19. Lastly, IFN-γ exposure did not modulate the gene expression of any of the tested mucins either in the conjunctival or corneal epithelial cells.
Conclusions :
Proinflammatory cytokines can modulate the expression of ocular mucins in a cytokine and mucin subtype specific manner. Cytokine-mediated modulation of ocular mucins may be one of the likely mechanism contributing to the pathogenesis of GVHD associated dry eye.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.