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Daniel Kasprick, Phillip E Kish, Fatemeh Rajaii, Alfonso Saera-Vila, Alon Kahana; Retinoic Acid and T3 Induce CCL2 in Human Orbital Fibroblasts – A Model of Thyroid Eye Disease. Invest. Ophthalmol. Vis. Sci. 2016;57(12):5992.
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© ARVO (1962-2015); The Authors (2016-present)
Thyroid eye disease (TED) is a congestive orbitopathy characterized by enlargement and fibrosis of orbital muscle and fat, which causes a compartment syndrome leading to pain, diplopia, corneal exposure and potentially compressive optic neuropathy. TED can be associated with both hyper- and hypothyroid states, yet its pathogenesis remains poorly understood. Based on embryologic studies of orbital development, we hypothesized that orbital tissues respond to thyroid hormone (T3) and retinoic acid (RA) by expressing pro-inflammatory cytokines that lead to orbital targeting.
Fibroblasts from whole orbital fat obtained from patients undergoing blepharoplasty were grown to confluence in tissue culture and treated with T3, RA, or a combination of the two for 6 and 9 hours. Following microarray transcriptome analysis, studies focused on the cytokine CCL2 (a.k.a MCP1). qRT-PCR was used to quantify CCL2 expression, normalized to 18S gene expression using the delta-delta method, comparing treatments with RA, T3, RA+T3, and DMSO control.
CCL2 expression was induced in all three treatment groups compared with control. T3 alone induced the lowest level of CCL2 expression (avg 2.28x, 0.65 SEM), then RA alone (avg 3.6x, 0.79 SEM), and RA+T3 induced the highest CCL2 expression (avg 4.25x, SEM 1.2). Importantly, the range of CCL2 induction reflected the heterogeneity expected from this clinical disease process, with one sample inducing CCL2 expression 10.72 fold.
Our data suggest that on average CCL2 expression can be induced by a combination of RA and T3, with significant variability in expression level among patients. The variability may represent an underlying predisposition of certain individuals to develop TED, accounting for the observed disease heterogeneity. RA analogs have been used therapeutically for many years, and CCL2 itself is a potential therapeutic target, suggesting new approaches to this debilitating and disfiguring disease. Analysis of this pathway as a driver of TED is ongoing, and additional data will be presented.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
Figure 1. Relative expression levels of CCL 2 showing greatest induction of expression with combined RA+T3 treatment.
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