Orbital fibroblasts from patients with thyroid-associated ophthalmopathy overexpress CD40: CD154 hyperinduces IL-6, IL-8, and MCP-1

Fibroblast diversity represents an emerging concept critical to our understanding of tissue inflammation, repair, and remodeling. Orbital fibroblasts heterogeneously display Thy-1 and exhibit unique phenotypic attributes that may explain the susceptibility of the human orbit to thyroid-associated ophthalmopathy (TAO). In the present study the authors investigated the role of CD40 ligation on macrophage chemoattractant protein-1 (MCP-1), IL-6, and IL-8 expression in fibroblasts from patients with TAO.

Human orbital fibroblasts were cultured from tissues obtained with informed consent from patients with TAO and from patients undergoing surgery for other noninflammatory conditions. The fibroblasts were then examined by flow cytometry, microscopy, and cytokine assays.

The authors report that orbital fibroblasts from patients with TAO expressed elevated levels of CD40. Surface CD40 could be further upregulated by IFN-gamma in TAO and control fibroblasts. This upregulation was mediated through Jak2 and could be blocked by dexamethasone and AG490, a powerful and specific inhibitor of tyrosine kinase. Treatment with CD154, the ligand for CD40, upregulated the expression of IL-6, IL-8, and MCP-1 in TAO fibroblasts but failed to do so in control cultures. Thy-1(+) fibroblasts displayed higher CD40 levels than did their Thy-1(-) counterparts and were largely responsible for this cytokine production. IL-1beta also induced MCP-1, IL-6, and IL-8 more vigorously in TAO-derived fibroblasts.

Characterization of orbital fibroblasts and their differential expression of cytokines and receptors should prove invaluable in understanding the site-specific nature of TAO and the development of specific therapies.