The overall objective of this proposal is to understand the role of orbital fibroblasts in the pathogenesis of thyroid-associated ophthalmopathy (TAO), the ocular manifestation of Graves'disease (GD). In its most severe forms, TAO can threaten sight. There are currently no specific and effective therapies for TAO. Thus devising new treatments for TAO represents an important unmet need. Central components of TAO are localized inflammation and abnormal deposition of hyaluronan (HA). Cytokines produced by infiltrating T cells and orbital fibroblasts are thought to drive the pathogenesis of TAO. HA is synthesized by a family of three hyaluronan synthase (HAS) isoforms. Short chain HA, a product of multiple HAS isoforms, is highly inflammatory. CD34+ fibrocytes are circulating bone marrow derived hematopoietic stem cells. They express the chemokine receptor, CXCR4 and migrate to tissue injury in response to CXCL12. We have found that TAO orbital tissue comprises two discrete cell populations, including CD34+ and CD34- fibroblasts. Moreover, fibrocytes are recruited uniquely to the TAO orbit where they appear to give rise to CD34+ fibroblasts. In contrast, healthy orbital tissue contains only CD34- fibroblasts. Unexpectedly we found that fibrocytes and orbit-infiltrating CD34+ fibroblasts express thyrotropin receptor (TSHR), the central autoantigen in GD. When activated by GD-specific thyroid stimulating immunoglobulins (TSI) or with TSH, fibrocytes express high levels of inflammatory cytokines that are implicated in the pathogenesis of TAO. We have generated a new conceptual model of TAO based on two testable hypotheses. Hypothesis 1: recruitment of fibrocytes to the TAO orbit accounts for the two divergent populations of CD34+ and CD34- fibroblasts. CD34+ fibroblasts derive from fibrocyte precursors. They express TSHR and respond to TSH and TSI, accounting for the cytokines that drive TAO. On the other hand, CD34- fibroblasts over-express CXCL12 in TAO and thus orchestrate CD34+ fibrocyte recruitment to the orbit. Hypothesis 2: TAO orbit-infiltrating CD34+ fibroblasts uniquely express HAS1 enzyme and produce excessive highly inflammatory short-chain HA. To test these hypotheses, we now propose the following specific aims.
Specific Aim 1 : determine the mechanisms underlying TSHR-mediated cytokine production in fibrocytes and in orbit-infiltrating CD34+ fibroblasts and determine the mechanism for CXCL12 over-expression in TAO orbital tissue that may underlie fibrocyte recruitment.
Specific Aim 2 : define the mechanisms involved in the unique anatomic-site and disease-specific expression and induction by IL-1? of HAS1 and the production of short-chain HA by TAO orbital fibroblasts. Our results, we believe, support a new and potentially paradigm-shifting model for TAO. The proposed studies represent logical extensions of our preliminary findings. They should directly impact the field of TAO by defining potentially attractive therapeutic targets which can be tested in vitro and can be translated into clinical trials involving patients with this vexing disease.

Public Health Relevance

The central objective of this application is to identify the mechanisms involved in the activation of fibroblasts from the orbital tissues surrounding the eye. These cells we believe are recruited from the bone marrow and mediate the inflammation and tissue expansion found in patients with Graves'disease and its ocular manifestation, thyroid-associated ophthalmopathy. We believe that by understanding the pathways involved in activating these cells we will be able to design effective therapy for this disease. There are currently no safe and effective therapies for this condition and thus the application addresses a major unmet need.

Agency
National Institute of Health (NIH)
Institute
National Eye Institute (NEI)
Type
Research Project (R01)
Project #
5R01EY008976-19
Application #
8327707
Study Section
Anterior Eye Disease Study Section (AED)
Program Officer
Araj, Houmam H
Project Start
1992-12-01
Project End
2016-08-31
Budget Start
2012-09-01
Budget End
2013-08-31
Support Year
19
Fiscal Year
2012
Total Cost
$388,750
Indirect Cost
$138,750
Name
University of Michigan Ann Arbor
Department
Ophthalmology
Type
Schools of Medicine
DUNS #
073133571
City
Ann Arbor
State
MI
Country
United States
Zip Code
48109
Lee, Brian J; Atkins, Stephen; Ginter, Anna et al. (2015) Increased CD40+ Fibrocytes in Patients With Idiopathic Orbital Inflammation. Ophthal Plast Reconstr Surg 31:202-6
Chen, Hong; Mester, T√ľnde; Raychaudhuri, Nupur et al. (2014) Teprotumumab, an IGF-1R blocking monoclonal antibody inhibits TSH and IGF-1 action in fibrocytes. J Clin Endocrinol Metab 99:E1635-40
Smith, Terry J (2014) Advances in understanding autoimmune pituitary disease: standardized methods for autoantibody detection. J Clin Endocrinol Metab 99:1589-92
Wang, Yao; Smith, Terry J (2014) Current concepts in the molecular pathogenesis of thyroid-associated ophthalmopathy. Invest Ophthalmol Vis Sci 55:1735-48
Li, Bin; Smith, Terry J (2014) Regulation of IL-1 receptor antagonist by TSH in fibrocytes and orbital fibroblasts. J Clin Endocrinol Metab 99:E625-33
Li, Bin; Smith, Terry J (2014) PI3K/AKT pathway mediates induction of IL-1RA by TSH in fibrocytes: modulation by PTEN. J Clin Endocrinol Metab 99:3363-72
Fernando, Roshini; Lu, Ying; Atkins, Stephen J et al. (2014) Expression of thyrotropin receptor, thyroglobulin, sodium-iodide symporter, and thyroperoxidase by fibrocytes depends on AIRE. J Clin Endocrinol Metab 99:E1236-44
McCoy, Allison N; Kim, Denise S; Gillespie, Erin F et al. (2014) Rituximab (Rituxan) therapy for severe thyroid-associated ophthalmopathy diminishes IGF-1R(+) T cells. J Clin Endocrinol Metab 99:E1294-9
Fernando, Roshini; Vonberg, Andrew; Atkins, Stephen J et al. (2014) Human fibrocytes express multiple antigens associated with autoimmune endocrine diseases. J Clin Endocrinol Metab 99:E796-803
Rajaii, Fatemeh; McCoy, Allison N; Smith, Terry J (2014) Cytokines are both villains and potential therapeutic targets in thyroid-associated ophthalmopathy: From bench to bedside. Expert Rev Ophthalmol 9:227-234

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