Abstract
Purpose: :
Thrombospondin-1 (TSP-1) is one of the activators of TGF-β1. The purpose of this study was to evaluate the effects of desiccating ocular surface stress on conjunctival intraepithelial lymphocytes (IEL) in TSP-1 knock-out (TSP-1KO) mice.
Methods: :
Desiccating stress (DS) was induced by subcutaneous injection of scopolamine and exposure to a drafty low humidity environment in TSP-1KO and wild-type (WT) mice, aged 12 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. Conjunctival goblet cell density was counted in periodic acid Schiff (PAS) stained sections. Immunohistochemistry was used to identify and count cells that were positive (+) for CD4 and CD8α in conjunctival tissue. TGF-β1 bioactivity was assessed using a reporter assay utilizing mink lung epithelial cells transfected with a plasminogen activator inhibitor promoter-luciferase construct (MLEC PAI/L) via a luminescence based assay.
Results: :
Non-stressed TSP-1KO mice showed higher numbers of CD4+ T cells in conjunctiva compared to NS-WT. TSP-1KO after DS had an opposite response than WT: they showed an increase in PAS+ cells, a decrease in conjunctival CD4+ cell infiltration and an increased CD4+ and CD8α+ cell density in the lacrimal glands when compared to NS TSP-1KO mice. Bioactive TGF-β1 levels in tears were progressively decreased in TSP-1KO mice after DS.
Conclusions: :
TSP1-KO mice had lower TGF-β1 bioactive levels in tears with DS. This was accompanied by an increased number of GC and a parallel decrease in CD4+ T cells, suggesting that TGF- β1 is critical to the immune phenotype in dry eye.
Keywords: autoimmune disease • lacrimal gland • cell-cell communication