Abstract
Purpose: :
Deficiency in thrombospondin-1 (TSP1), a major activator of latent TGF-β results in lacrimal gland inflammation and correlates with an ocular surface disease like dry eye detectable in these mice. We determined if inflammation includes the presence of a Th17 population associated with many autoimmune diseases
Methods: :
Age-matched wild-type (WT) C57BL/6 mice and TSP1null mice (2-6 mo.) were used to harvest lacrimal glands (LG). Flow cytometric analysis of CD4, CD8 and IL-17 expressing cells from single cell suspensions prepared from LG or spleen (Spc) was performed. Protein extracts of the LGs and culture supernatants from the stimulated splenocytes (anti-CD3 antibodies or OVA-pulsed antigen presenting cells - WT vs. TSP-1null) were tested for IL-17 by ELISA. Entire eyeballs with lids harvested from 4-5 mo. old mice were analyzed by histologic examination (H&E) and enumeration of mucin filled conjunctival goblet cells. The expression of inflammatory molecules (TNF , MCP-1, MIP-2) in corneas was determined by real-time PCR.
Results: :
Lacrimal gland extracts derived from 3-4 and 6 mo. old TSP-1null mice contained significantly increased levels of IL-17 as compared to WT controls. Flow cytometric analysis of cells from the LGs of 6 mo. old mice indicated significantly increased numbers of CD4+ cells in TSP-1null as compared to WT controls, while no significant difference was noted in CD8+ population. A significantly higher proportion of CD4+ T cells in TSP-1null LGs expressed IL-17 compared to those in WT controls. Similar increase in IL-17 expressing population was detectable in the Spc derived from 2 mo. old TSP-1null, but not in WT, mice. The histologic exam of the cornea in TSP-1null mice (4-5 mo.) revealed deteriorated corneal epithelium and edema. Real-time PCR analysis indicated significantly increased expression of dry eye associated inflammatory molecules TNF, MCP-1 and MIP-2 in TSP-1null corneas compared to control WT corneas. The ocular surface inflammation correlated with the lacrimal gland inflammation. Furthermore, significantly increased numbers of mucin-filled goblet cells were detected in 4-5 mo. old TSP-1null conjunctiva as compared to that of WT mice. The inflammatory changes were accompanied by a significant decline in the number of Foxp3+ Treg in 6 mo. old TSP-1null mice as compared to age-matched WT controls.
Conclusions: :
. Lacrimal gland inflammation in TSP-1null mice resembles chronic inflammation detected in autoimmune diseases characterized by the presence of Th17 cells and accompanied by decline in peripheral Treg population. The lacrimal gland inflammation further correlates with the ocular surface inflammation.
Keywords: lacrimal gland • inflammation • cornea: tears/tear film/dry eye