CD34+ Fibrocytes May Over-arch the Orbit and Thyroid in Patients with Graves’ Disease and Ophthalmopathy

Abstract

Purpose: : The mechanisms that underlie inflammation and tissue remodeling in Graves’ disease (GD) and thyroid-associated ophthalmopathy (TAO) are not well understood. Moreover, the connection between thyroid and orbit in GD has not yet been identified. Fibrocytes (FC) are bone marrow-derived stem cells involved in tissue remodeling. Phenotypic characteristics of orbital fibroblasts (OF) from TAO patients include expression of CD34, Co1l, TSHR, and IGF-1R suggesting that a subpopulation may be derived from FC. We characterized thyroid fibroblasts (TF) from patients with GD to determine if they might resemble OF.

Methods: : TF from donors with GD were cultured and analyzed by flow cytometry and immunohistochemistry (IHC) for CD34, CD90, Col1, TSHR, IGF-1R, and alpha smooth muscle actin (αSMA). Some cultures were treated with TGF-β (5 ng/mL) for 7 days and assessed for differentiation to myofibroblasts.

Results: : Flow cytometry analysis revealed that a subset of TF from patients with GD co-expressed CD34/Col1/THSR and CD34/Col1/IGF1-R . These findings were confirmed by IHC. TF underwent differentiation into myofibroblasts as was evidenced by upregulated αSMA expression in response to TGF-β.

Conclusions: : A subset of GD-derived TF co-express CD34, Col1, THSR, and IGF1-R suggesting that they 1) resemble OF from patients with TAO and 2) derive from FC. TF from these patients can differentiate into myofibroblasts with upregulated αSMA expression in response to TGF-β. These findings suggest that recruitment of FC to the TAO orbit and GD thyroid may underlie the shared manifestations of GD in the two anatomically distant tissues. Investigation of local factors which target FC trafficking and differentiation may lead to the development of specific therapies.

Keywords: autoimmune disease • flow cytometry • immunohistochemistry