Abstract
Purpose: :
Current understanding of dry eye disease (DED) pathogenesis is based mostly on acute DED models. However, the mechanisms underlying the chronic phase of the disease are poorly understood. In this study, we investigated whether autoimmune mechanisms are involved in the chronic phase of DED.
Methods: :
Chronic DED was induced by exposing C57BL/6 mice to a controlled environmental chamber (CEC) and scopolamine injection for the first 14 days, followed by maintaining them in a normal (non-desiccated) environment for more than 3 months. Transcript levels of IL-1β and IL-23 in the cornea, as well as IFN-γ and IL-17 in the conjunctiva, were analyzed by real-time PCR. Cells from the draining lymph nodes (LN) and spleen were examined for memory (CD44hiCD62L-CD4+) and naïve (CD44-/lowCD62L+CD4+) T cell subsets by flow cytometry. T cells from normal or chronic DED mice were adoptively transferred to syngeneic normal mice which were then placed in the CEC (without scopolamine injection). IL-17 protein level in draining lymph nodes was detected by ELISA.
Results: :
After the initial 14 days of disease induction, DED-associated corneal epitheliopathy persisted through Day 126 with a disease score of 4.6±0.3, despite no exposure of the mice to any desiccating challenge. Real-time PCR revealed significantly increased expression of IL-23 in the cornea (p<0.01) and IL-17 in the conjunctiva (p<0.05) after 3 months of DED. The draining LNs and spleen of chronic DED mice showed increased frequency of memory CD44hiCD62L-CD4+ T cells. After CEC challenge, mice receiving chronic DED-T cells exhibited both a faster onset and a more severe clinical disease compared to mice receiving normal T cells. Furthermore, the chronic DED-T cell transferred group showed significantly increased expression of IL-17 in the conjunctiva (2.3-fold, p<0.05) and draining LNs (4.0-fold, p<0.05) compared to the normal T cell-transferred group.
Conclusions: :
These data demonstrate for the first time that memory T cells sustain DED in the long-term, leading to chronic (autoimmune) inflammation even in the absence of desiccating stress.
Keywords: autoimmune disease • cornea: basic science • inflammation