Disruption of TGF-β Signaling Improves Dry Eye Disease

Abstract

Purpose: : We hypothesize that transforming growth factor β (TGF-β) is critical to the immune phenotype observed in dry eye. The purpose of this study was to study the response to desiccating stress in the dominant-negative TGF-β type II receptor (CD4-DNTGFβRII) mice. These mice have a truncated TGF-β receptor type II in CD4+ T cells, rending them unresponsive to TGF-β.

Methods: : Desiccating stress (DS) was induced by subcutaneous injection of scopolamine and exposure to a drafty low humidity environment in CD4-DNTGFβRII and wild-type (WT) mice, aged 14 weeks, for 5 days. Non-stressed (NS) control mice were maintained in a separate room containing 50-75% relative humidity without exposure to forced air. Corneal smoothness was assessed by reflection of a ring light. Corneal barrier function was assessed using fluorescent Oregon-Green Dextran (OGD). Conjunctival goblet cell density was counted in periodic acid Schiff stained sections. Immunohistochemistry evaluated CD4 and CD8 T cell infiltration of the conjunctiva. T helper (Th)-1, 2 and 17 associated cytokines were evaluated in conjunctiva by real time PCR.

Results: : After desiccating stress, WT mice showed an increase in OGD staining, cornea irregularity, a decrease in PAS+ goblet cells and an increased T cell infiltration in the conjunctiva than NS WT mice. Non-stressed CD4-DNTGFβRII mice exhibited a spontaneous dry eye phenotype; however, desiccating stress improved their corneal barrier function and corneal surface irregularity, increased their number of conjunctival PAS+ cells, and lowered CD4+T cell infiltration in conjunctiva. In contrast to WT, CD4-DNTGFβRII mice were unable to generate a Th-17 and Th-1 response, and they failed to upregulate MMP-9, IL-23, IL-17A, RORγT, IFN-γ and T-bet mRNA transcripts in conjunctiva.

Conclusions: : Disruption of TGF-β signaling in CD4+ T cells causes paradoxical improvement of dry eye disease in mice subjected to desiccating stress.

Keywords: cornea: tears/tear film/dry eye • immunomodulation/immunoregulation • inflammation