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Smith TJ. Fibrocyte Participation in Thyroid-Associated Ophthalmopathy Suggests New Approaches to Therapy. Ophthalmic Plast Reconstr Surg 2023; 39:S9-S18. [PMID: 38054981 PMCID: PMC10703002 DOI: 10.1097/iop.0000000000002509] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/07/2023]
Abstract
PURPOSE Review the historical context of research and changing therapeutic landscape of thyroid-associated ophthalmopathy (TAO) by focusing on the relationship between TAO, CD34+ fibrocytes, thyrotropin receptor (TSHR), and insulin-like growth factor-I receptor (IGF-IR). METHODS A literature review using search terms, including fibrocytes, IGF-IR, TSHR, TAO, and thyroid eye disease. RESULTS The mechanisms involved in TAO have been partially identified. Substantial progress has been made over several decades, including 1) recognizing the interplay between the professional immune system and orbital tissues; 2) TSHR and IGF-IR act interdependently in mediating the pathogenesis of TAO; 3) Multiple cytokines and specific immune cells are involved in activating and remodeling orbital tissue; 4) Recognition of these mechanisms is allowing the development of target therapies such as teprotumumab, a monoclonal antibody IGF-IR inhibitor approved by the US Food and drug administration for treatment of TAO; and 5) It appears that teprotumumab acts on the systemic immune system peripheral to the orbit. CONCLUSION Additional molecules targeting IGF-IR and other plausible disease mechanisms are currently under development. This activity in the TAO therapeutic space portends even greater improvements in patient care.
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Affiliation(s)
- Terry J. Smith
- Department of Ophthalmology and Visual Sciences, Kellogg Eye Center and Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, MI 48105
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2
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Zhang P, Zhu H. Cytokines in Thyroid-Associated Ophthalmopathy. J Immunol Res 2022; 2022:2528046. [PMID: 36419958 PMCID: PMC9678454 DOI: 10.1155/2022/2528046] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2022] [Revised: 11/01/2022] [Accepted: 11/03/2022] [Indexed: 09/07/2023] Open
Abstract
Thyroid-associated ophthalmopathy (TAO), also known as thyroid eye disease (TED) or Graves' orbitopathy (GO), is a complex autoimmune condition causing visual impairment, disfigurement, and harm to patients' physical and mental health. The pathogenesis of TAO has not been fully elucidated, and the mainstream view is that coantigens shared by the thyroid and orbit trigger remodeling of extraocular muscles and orbital connective tissues through an inflammatory response. In recent years, cytokines and the immune responses they mediate have been crucial in disease progression, and currently, common evidence has shown that drugs targeting cytokines, such as tocilizumab, infliximab, and adalimumab, may be novel targets for therapy. In this review, we summarize the research development of different cytokines in TAO pathogenesis in the hope of discovering new therapeutic targets.
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Affiliation(s)
- Pengbo Zhang
- Department of Ophthalmology, Xinhua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai 200092, China
| | - Huang Zhu
- Department of Ophthalmology, Xinhua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai 200092, China
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Proctor ES, Smith TJ. Bone marrow fibrocytes: villain or white knight in thyroid-associated ophthalmopathy? Curr Opin Endocrinol Diabetes Obes 2022; 29:441-448. [PMID: 35950703 DOI: 10.1097/med.0000000000000765] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
PURPOSE OF REVIEW We attempt to provide an historical perspective on progress made in understanding the pathogenesis of thyroid-associated ophthalmopathy (TAO), focusing on the roles of orbital fibroblasts (OF) in the diseased orbit (termed GD-OF) and how these cells differ from those residing in the healthy orbit. GD-OF comprise both residential OF and those apparently derived from CD34 + fibrocytes. RECENT FINDINGS CD34 + fibrocytes of the monocyte lineage putatively traffic to the TAO orbit from bone marrow. We believe that these fibroblastic cell populations dictate the activity and severity of TAO. Their impact on disease may be moderated by Slit2, a neuron axon guidance repellent synthesized by and released from residential CD34 - OF. Approximately 50% of patients with GD develop clinically meaningful TAO. Relatively few require systemic medical and surgical therapies, while milder disease can be managed with conservative, local care. Determining the intrinsic properties of GD-OF and their expression of Slit2 may explain why some patients with GD develop severe, vision-threatening TAO while others virtually escape any of its manifestations. Such insights should allow for improved and better-tolerated therapies. SUMMARY Identifying unique characteristics of fibrocytes and GD-OF subsets reveals their apparent roles in tissue activation, inflammation, and remodeling associated with TAO. Better understanding of these cells, their origins, behavior, and factors modulating their activities remains necessary for the development of more targeted, effective, and safe treatments.
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Affiliation(s)
- Erin S Proctor
- Department of Ophthalmology and Visual Sciences, Kellogg Eye Center, and Division of Metabolism, Endocrinology and Diabetes, Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, Michigan, USA
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Fernando R, Smith TJ. Teprotumumab Divergently Alters Fibrocyte Gene Expression: Implications for Thyroid-associated Ophthalmopathy. J Clin Endocrinol Metab 2022; 107:e4037-e4047. [PMID: 35809263 PMCID: PMC9516078 DOI: 10.1210/clinem/dgac415] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/11/2022] [Indexed: 11/19/2022]
Abstract
CONTEXT Teprotumumab, an IGF-I receptor (IGF-IR) inhibitor, is effective in thyroid-associated ophthalmopathy (TAO). The drug can modulate induction by TSH of IL-6 and IL-8 in CD34+ fibrocytes and their putative derivatives, CD34+ orbital fibroblasts (CD34+ OF). Fibrocytes express multiple thyroid autoantigens and cytokines implicated in TAO, which are downregulated by Slit2. Inflammation and disordered hyaluronan (HA) accumulation occur in TAO. Whether teprotumumab alters these processes directly in fibrocytes/CD34+ OF remains uncertain. OBJECTIVE Determine teprotumumab effects on expression/synthesis of several TAO-relevant molecules in fibrocytes and GD-OF. DESIGN/SETTING/PARTICIPANTS Patients with TAO and healthy donors were recruited from an academic endocrine and oculoplastic practice. MAIN OUTCOME MEASURES Real-time PCR, specific immunoassays. RESULTS Teprotumumab attenuates basal and TSH-inducible autoimmune regulator protein, thyroglobulin, sodium iodide symporter, thyroperoxidase, IL-10, and B-cell activating factor levels in fibrocytes. It downregulates IL-23p19 expression/induction while enhancing IL-12p35, intracellular and secreted IL-1 receptor antagonists, and Slit2. These effects are mirrored by linsitinib. HA production is marginally enhanced by teprotumumab, the consequence of enhanced HAS2 expression. CONCLUSION Teprotumumab affects specific gene expression in fibrocytes and GD-OF in a target-specific, nonmonolithic manner, whereas IGF-IR control of these cells appears complex. The current results suggest that the drug may act on cytokine expression and HA production systemically and locally, within the TAO orbit. These findings extend our insights into the mechanisms through which IGF-IR inhibition might elicit clinical responses in TAO, including a potential role of Slit2 in attenuating inflammation and tissue remodeling.
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Affiliation(s)
- Roshini Fernando
- Department of Ophthalmology and Visual Sciences, Kellogg Eye Center, Ann Arbor, MI 48105, USA
- Division of Metabolism, Endocrinology and Diabetes, Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, MI 48105, USA
| | - Terry J Smith
- Correspondence: Terry J. Smith, MD, Department of Ophthalmology and Visual Sciences, Kellogg Eye Center, Brehm Tower, 1000 Wall St, Ann Arbor, MI 48105, USA.
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Morshed SA, Ma R, Latif R, Davies TF. Mechanisms in Graves Eye Disease: Apoptosis as the End Point of Insulin-Like Growth Factor 1 Receptor Inhibition. Thyroid 2022; 32:429-439. [PMID: 34927457 PMCID: PMC9048181 DOI: 10.1089/thy.2021.0176] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Background: Graves' eye disease, also called Graves' orbitopathy (GO), is a potentially debilitating autoimmune disease associated with retro-orbital inflammation and tissue expansion, involving both fibroblasts and adipocytes, resulting in periorbital edema, worsening proptosis, and muscle dysfunction with diplopia and may ultimately threaten sight. Accumulating evidence has indicated that autoantibodies to the thyrotropin receptor (TSHR), which induce the hyperthyroidism of Graves' disease, also help mediate the pathogenesis of the eye disease in susceptible individuals through TSHR expression on retro-orbital cells. Since it has long been known that the effects of insulin-like growth factor 1 (IGF-1) and thyrotropin are additive, recent clinical trials with a human monoclonal IGF-1 receptor blocking antibody (teprotumumab; IGF-1R-B-monoclonal antibody [mAb]) have demonstrated its ability to induce significant reductions in proptosis, diplopia, and clinical activity scores in patients with GO. However, the molecular mechanisms by which such an antibody achieves this result is unclear. Methods: We have used Li-Cor In-Cell Western, Western blot, and immunohistochemistry to define levels of different proteins in mouse and human fibroblast cells. Proteomic array was also used to define pathway signaling molecules. Using CCK-8 and BrdU cell proliferation ELISA, we have analyzed proliferative response of these cells to different antibodies. Results: We now show that a stimulating TSHR antibody was able to induce phosphorylation of the IGF-1R and initiate both TSHR and IGF-1R signaling in mouse and human fibroblasts. IGF-1R-B-mAb (1H7) inhibited all major IGF-1R signaling cascades and also reduced TSHR signaling. This resulted in the antibody-induced suppression of autophagy as shown by inhibition of multiple autophagy-related proteins (Beclin1, LC3a, LC3b, p62, and ULK1) and the induction of cell death by apoptosis as evidenced by activation of cleaved caspase 3, FADD, and caspase 8. Furthermore, this IGF-1R-blocking mAb suppressed serum-induced perkin and pink mitophagic proteins. Conclusions: Our observations clearly indicated that stimulating TSHR antibodies were able to enhance IGF-1R activity and contribute to retro-orbital cellular proliferation and inflammation. In contrast, an IGF-1R-B-mAb was capable of suppressing IGF-1R signaling leading to retro-orbital fibroblast/adipocyte death through the cell-extrinsic pathway of apoptosis. This is likely the major mechanism involved in proptosis reduction in patients with Graves' eye disease treated by IGF-1R inhibition.
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Affiliation(s)
- Syed A. Morshed
- Thyroid Research Unit, Icahn School of Medicine at Mount Sinai, New York, New York, USA
- James J. Peters VA Medical Center, New York, New York, USA
- Address correspondence to: Syed A. Morshed, MD, PhD, Thyroid Research Unit, Icahn School of Medicine at Mount Sinai, Box 1055, 1 Gustave L Levy Place, New York, NY 10029, USA
| | - Risheng Ma
- Thyroid Research Unit, Icahn School of Medicine at Mount Sinai, New York, New York, USA
- James J. Peters VA Medical Center, New York, New York, USA
| | - Rauf Latif
- Thyroid Research Unit, Icahn School of Medicine at Mount Sinai, New York, New York, USA
- James J. Peters VA Medical Center, New York, New York, USA
| | - Terry F. Davies
- Thyroid Research Unit, Icahn School of Medicine at Mount Sinai, New York, New York, USA
- James J. Peters VA Medical Center, New York, New York, USA
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Abstract
PURPOSE Our understanding of thyroid-associated ophthalmopathy (TAO, A.K.A Graves' orbitopathy, thyroid eye disease) has advanced substantially, since one of us (TJS) wrote the 2010 update on TAO, appearing in this journal. METHODS PubMed was searched for relevant articles. RESULTS Recent insights have resulted from important studies conducted by many different laboratory groups around the World. A clearer understanding of autoimmune diseases in general and TAO specifically emerged from the use of improved research methodologies. Several key concepts have matured over the past decade. Among them, those arising from the refinement of mouse models of TAO, early stage investigation into restoring immune tolerance in Graves' disease, and a hard-won acknowledgement that the insulin-like growth factor-I receptor (IGF-IR) might play a critical role in the development of TAO, stand out as important. The therapeutic inhibition of IGF-IR has blossomed into an effective and safe medical treatment. Teprotumumab, a β-arrestin biased agonist monoclonal antibody inhibitor of IGF-IR has been studied in two multicenter, double-masked, placebo-controlled clinical trials demonstrated both effectiveness and a promising safety profile in moderate-to-severe, active TAO. Those studies led to the approval by the US FDA of teprotumumab, currently marketed as Tepezza for TAO. We have also learned far more about the putative role that CD34+ fibrocytes and their derivatives, CD34+ orbital fibroblasts, play in TAO. CONCLUSION The past decade has been filled with substantial scientific advances that should provide the necessary springboard for continually accelerating discovery over the next 10 years and beyond.
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Affiliation(s)
- E J Neag
- Department of Ophthalmology and Visual Sciences, Kellogg Eye Center, Brehm Tower, 1000 Wall Street, Ann Arbor, MI, 48105, USA
- Department of Internal Medicine, Division of Metabolism, Endocrinology, and Diabetes, University of Michigan Medical School, Ann Arbor, MI, 48105, USA
- Michigan State University College of Osteopathic Medicine, East Lansing, MI, USA
| | - T J Smith
- Department of Ophthalmology and Visual Sciences, Kellogg Eye Center, Brehm Tower, 1000 Wall Street, Ann Arbor, MI, 48105, USA.
- Department of Internal Medicine, Division of Metabolism, Endocrinology, and Diabetes, University of Michigan Medical School, Ann Arbor, MI, 48105, USA.
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Kang J, Li Y, Zhao Z, Zhang H. Differentiation between thyroid-associated orbitopathy and Graves' disease by iTRAQ-based quantitative proteomic analysis. FEBS Open Bio 2021; 11:1930-1940. [PMID: 33934566 PMCID: PMC8255837 DOI: 10.1002/2211-5463.13172] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2021] [Revised: 03/17/2021] [Indexed: 11/12/2022] Open
Abstract
Graves' ophthalmopathy, also known as thyroid-associated orbitopathy (TAO), is the most common inflammatory eye disease in adults. The most common etiology for TAO is Graves' disease (GD); however, proteomic research focusing on differences between GD and TAO is limited. This study aimed to identify differentially expressed proteins between thyroid-associated orbitopathy (TAO) and GD. Furthermore, we sought to explore the pathogenesis of TAO and elucidate the differentiation process via specific markers. Serum samples of three patients with TAO, GD, and healthy controls, respectively, were collected. These samples were measured using the iTRAQ technique coupled with mass spectrometry. Differentially expressed proteins in TAO and GD were identified by proteomics; 3172 quantified proteins were identified. Compared with TAO, we identified 110 differential proteins (27 proteins were upregulated and 83 were downregulated). In addition, these differentially expressed proteins were closely associated with cellular processes, metabolic processes, macromolecular complexes, signal transduction, and the immune system. The corresponding functions were protein, calcium ion, and nucleic acid binding. Among the differential proteins, MYH11, P4HB, and C4A were markedly upregulated in TAO patients and have been reported to participate in apoptosis, autophagy, the inflammatory response, and the immune system. A protein-protein interaction network analysis was performed. Proteomics demonstrated valuable large-scale protein-related information for expounding the pathogenic mechanism underlying TAO. This research provides new insights and potential targets for studying GD with TAO.
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Affiliation(s)
- Jianshu Kang
- Department of Ophthalmology, The Second People's Hospital of Yunnan Province, The Fourth Affiliated Hospital of Kunming Medical University, China.,Yunnan Eye Institute, Kunming, China.,Key Laboratory of Yunnan Province for the Prevention and Treatment of Ophthalmologya, Kunming, China.,Yunnan Eye Disease Clinical Medical Center, Kunming, China.,Yunnan Eye Disease Clinical Medical Research Center, Kunming, China
| | - Yunqin Li
- Department of Ophthalmology, The Second People's Hospital of Yunnan Province, The Fourth Affiliated Hospital of Kunming Medical University, China.,Yunnan Eye Institute, Kunming, China.,Key Laboratory of Yunnan Province for the Prevention and Treatment of Ophthalmologya, Kunming, China.,Yunnan Eye Disease Clinical Medical Center, Kunming, China.,Yunnan Eye Disease Clinical Medical Research Center, Kunming, China
| | - Zhijian Zhao
- Department of Ophthalmology, The Second People's Hospital of Yunnan Province, The Fourth Affiliated Hospital of Kunming Medical University, China.,Yunnan Eye Institute, Kunming, China.,Key Laboratory of Yunnan Province for the Prevention and Treatment of Ophthalmologya, Kunming, China.,Yunnan Eye Disease Clinical Medical Center, Kunming, China.,Yunnan Eye Disease Clinical Medical Research Center, Kunming, China
| | - Hong Zhang
- Department of Ophthalmology, The Second People's Hospital of Yunnan Province, The Fourth Affiliated Hospital of Kunming Medical University, China.,Yunnan Eye Institute, Kunming, China.,Key Laboratory of Yunnan Province for the Prevention and Treatment of Ophthalmologya, Kunming, China.,Yunnan Eye Disease Clinical Medical Center, Kunming, China.,Yunnan Eye Disease Clinical Medical Research Center, Kunming, China
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8
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Smith TJ. Potential Roles of CD34+ Fibrocytes Masquerading as Orbital Fibroblasts in Thyroid-Associated Ophthalmopathy. J Clin Endocrinol Metab 2019; 104:581-594. [PMID: 30445529 PMCID: PMC6320239 DOI: 10.1210/jc.2018-01493] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/09/2018] [Accepted: 09/10/2018] [Indexed: 12/19/2022]
Abstract
CONTEXT Orbital tissues in thyroid-associated ophthalmopathy exhibit particular reactivity and undergo characteristic remodeling. Mechanisms underlying these changes have remained largely unexplained. Studies have characterized orbital connective tissues and derivative fibroblasts to gain insights into local manifestations of a systemic autoimmune syndrome. EVIDENCE ACQUISITION A systematic search of PubMed was undertaken for studies related to thyroid-associated ophthalmopathy (TAO), orbital fibroblasts, and fibrocytes involved in pathogenesis. EVIDENCE SYNTHESIS Orbital tissues display marked cellular heterogeneity. Fibroblast subsets, putatively derived from multiple precursors, inhabit the orbit in TAO. Among them are cells displaying the CD34+CXC chemokine receptor 4+collagen I+ phenotype, identifying them as fibrocytes, derived from the monocyte lineage. Their unique presence in the TAO orbit helps explain the tissue reactivity and characteristic remodeling that occurs in the disease. Their unanticipated expression of several proteins traditionally thought to be thyroid gland specific, including the TSH receptor and thyroglobulin, may underlie orbital involvement in Graves disease. Although no currently available information unambiguously establishes that CD34+ orbital fibroblasts originate from circulating fibrocytes, inferences from animal models of lung disease suggest that they derive from bone marrow. Further studies are necessary to determine whether fibrocyte abundance and activity in the orbit determine the clinical behavior of TAO. CONCLUSION Evidence supports a role for fibrocytes in the pathogenesis of TAO. Recognition of their presence in the orbit now allows development of therapies specifically targeting these cells that ultimately could allow the restoration of immune tolerance within the orbit and perhaps systemically.
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Affiliation(s)
- Terry J Smith
- Department of Ophthalmology and Visual Sciences, Kellogg Eye Center, Ann Arbor, Michigan
- Division of Diabetes, Endocrinology, and Metabolism, Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, Michigan
- Correspondence and Reprint Requests: Terry J. Smith, MD, Department of Ophthalmology and Visual Sciences, University of Michigan Medical School, Kellogg Eye Center, Brehm Tower, 1000 Wall Street, Ann Arbor, Michigan 48105. E-mail:
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Fernando R, Grisolia ABD, Lu Y, Atkins S, Smith TJ. Slit2 Modulates the Inflammatory Phenotype of Orbit-Infiltrating Fibrocytes in Graves' Disease. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2018; 200:3942-3949. [PMID: 29752312 PMCID: PMC6070359 DOI: 10.4049/jimmunol.1800259] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/23/2018] [Accepted: 03/26/2018] [Indexed: 01/09/2023]
Abstract
Human CD34+ fibrocytes, circulating monocyte lineage progenitor cells, have recently been implicated in thyroid-associated ophthalmopathy (TAO), the ocular manifestation of Graves' disease (GD). Fibrocytes express constitutive MHC class II (MHC-2) and, surprisingly, thyroglobulin (Tg) and functional thyrotropin (TSH) receptor (TSHR). Underlying expression of these thyroid proteins is the autoimmune regulator protein (AIRE). Fibrocytes respond robustly to TSH and thyroid-stimulating Igs by generating extremely high levels of inflammatory cytokines, such as IL-6. In TAO, they appear to infiltrate the orbit, where they transition to CD34+ orbital fibroblasts (OF). There, they coexist with CD34- OF as a mixed fibroblast population (GD-OF). In contrast to fibrocytes, GD-OF express vanishingly low levels of MHC-2, Tg, TSHR, and AIRE. Further, the amplitude of IL-6 induction by TSH in GD-OF is substantially lower. The molecular basis for this divergence between fibrocytes and CD34+ OF remains uncertain. In this article, we report that Slit2, an axon guidance glycoprotein, is constitutively expressed by the CD34- OF subset of GD-OF. Culture conditioned medium (CM) generated by incubating with GD-OF and CD34- OF substantially reduces levels of MHC-2, Tg, TSHR, and AIRE in fibrocytes. Expression can be restored by specifically depleting CM of Slit2. The effects of CD34- OF CM are mimicked by recombinant human Slit2. TSH induces Slit2 levels in GD-OF by enhancing both Slit2 gene transcription and mRNA stability. These findings suggest that Slit2 represents a TSH-inducible factor within the TAO orbit that can modulate the inflammatory phenotype of CD34+ OF and therefore may determine the activity and severity of the disease.
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Affiliation(s)
- Roshini Fernando
- Department of Ophthalmology and Visual Sciences, Kellogg Eye Center, University of Michigan Medical School, Ann Arbor, MI 48105; and Division of Metabolism, Endocrinology, and Diabetes, Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, MI 48105
| | - Ana Beatriz Diniz Grisolia
- Department of Ophthalmology and Visual Sciences, Kellogg Eye Center, University of Michigan Medical School, Ann Arbor, MI 48105; and Division of Metabolism, Endocrinology, and Diabetes, Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, MI 48105
| | - Yan Lu
- Department of Ophthalmology and Visual Sciences, Kellogg Eye Center, University of Michigan Medical School, Ann Arbor, MI 48105; and Division of Metabolism, Endocrinology, and Diabetes, Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, MI 48105
| | - Stephen Atkins
- Department of Ophthalmology and Visual Sciences, Kellogg Eye Center, University of Michigan Medical School, Ann Arbor, MI 48105; and Division of Metabolism, Endocrinology, and Diabetes, Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, MI 48105
| | - Terry J Smith
- Department of Ophthalmology and Visual Sciences, Kellogg Eye Center, University of Michigan Medical School, Ann Arbor, MI 48105; and Division of Metabolism, Endocrinology, and Diabetes, Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, MI 48105
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Abstract
The fibrocyte, which was first described in 1994, is a type of circulating mesenchymal progenitor cell in the peripheral blood. Fibrocytes play important roles in chronic inflammation, wound healing, tissue remodeling, and fibrosis. Emerging evidence indicates that fibrocytes are involved in a wide variety of ocular disorders associated with inflammation and fibrosis. In this review, we summarize recent advances regarding the general characteristic profile of fibrocytes, molecular mechanisms underlying the fibrocyte recruitment to target tissues, their differentiation into fibroblasts, and the potential role of fibrocytes in ocular disease. Given the critical role of fibrocytes in ocular disorders, fibrocytes may serve as a promising pharmaceutical target in the development of novel therapeutic strategies to treat ocular inflammation and fibrosis.
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Affiliation(s)
- Feng Zhang
- Department of Ophthalmology, The Second Xiangya Hospital, Central South University, Changsha, 410011, Hunan Province, China.,Hunan Clinical Research Center of Ophthalmic Disease, Changsha, 410011, Hunan Province, China
| | - Ke Liu
- Department of Ophthalmology, The Second Xiangya Hospital, Central South University, Changsha, 410011, Hunan Province, China.,Hunan Clinical Research Center of Ophthalmic Disease, Changsha, 410011, Hunan Province, China
| | - Han Zhao
- Department of Ophthalmology, The Second Xiangya Hospital, Central South University, Changsha, 410011, Hunan Province, China.,Hunan Clinical Research Center of Ophthalmic Disease, Changsha, 410011, Hunan Province, China
| | - Yan He
- Department of Ophthalmology, The Second Xiangya Hospital, Central South University, Changsha, 410011, Hunan Province, China. .,Hunan Clinical Research Center of Ophthalmic Disease, Changsha, 410011, Hunan Province, China.
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11
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Dik WA, Virakul S, van Steensel L. Current perspectives on the role of orbital fibroblasts in the pathogenesis of Graves' ophthalmopathy. Exp Eye Res 2016; 142:83-91. [PMID: 26675405 DOI: 10.1016/j.exer.2015.02.007] [Citation(s) in RCA: 90] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2014] [Revised: 02/05/2015] [Accepted: 02/10/2015] [Indexed: 02/06/2023]
Abstract
Graves' ophthalmopathy (GO) is an extra-thyroidal complication of Graves' disease (GD; Graves' hyperthyroidism) characterized by orbital tissue inflammation, expansion, remodeling and fibrosis. Although the initiating trigger of GO is still indistinct, excessive orbital fibroblast activity is at the heart of its pathogenesis. Orbital fibroblasts are activated by cellular interactions with immune cells and the soluble factors they secrete. Orbital fibroblasts, especially from GO patients, express the thyrotropin receptor (TSH-receptor; TSHR), and activation of the orbital fibroblast population by stimulatory autoantibodies directed against the TSHR may provide an important link between GD and GO. Furthermore, stimulatory autoantibodies directed against the insulin-like growth factor-1 receptor have been proposed to contribute to orbital fibroblast activation in GO. Activated orbital fibroblasts produce inflammatory mediators thereby contributing to the orbital inflammatory process in GO. Moreover, orbital fibroblasts exhibit robust proliferative activity and extracellular matrix (especially hyaluronan) synthesizing capacity and can differentiate into adipocytes and myofibroblasts with disease progression, thereby contributing to tissue expansion/remodeling and fibrosis in GO. Orbital fibroblasts, especially those from GO patients, exhibit a hyper-responsive phenotype when compared to fibroblasts from other anatomical regions, which may further contribute to GO pathogenesis. Fibrocytes have been identified as additional source of orbital fibroblasts in GO, where they may contribute to orbital tissue inflammation, adipogenesis and remodeling/fibrosis. This review addresses our current view on the role that orbital fibroblasts fulfill in GO pathogenesis and both established as well as less established not fully crystallized concepts that need future studies will be discussed.
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Affiliation(s)
- Willem A Dik
- Department of Immunology, Laboratory Medical Immunology, Erasmus MC, University Medical Center Rotterdam, The Netherlands.
| | - Sita Virakul
- Department of Immunology, Laboratory Medical Immunology, Erasmus MC, University Medical Center Rotterdam, The Netherlands
| | - Leendert van Steensel
- Department of Immunology, Laboratory Medical Immunology, Erasmus MC, University Medical Center Rotterdam, The Netherlands
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12
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Slany A, Bileck A, Kreutz D, Mayer RL, Muqaku B, Gerner C. Contribution of Human Fibroblasts and Endothelial Cells to the Hallmarks of Inflammation as Determined by Proteome Profiling. Mol Cell Proteomics 2016; 15:1982-97. [PMID: 27025457 DOI: 10.1074/mcp.m116.058099] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2016] [Indexed: 12/20/2022] Open
Abstract
In order to systematically analyze proteins fulfilling effector functionalities during inflammation, here we present a comprehensive proteome study of inflammatory activated primary human endothelial cells and fibroblasts. Cells were stimulated with interleukin 1-β and fractionated in order to obtain secreted, cytoplasmic and nuclear protein fractions. Proteins were submitted to a data-dependent bottom up analytical platform using a QExactive orbitrap and the MaxQuant software for protein identification and label-free quantification. Results were further combined with similarly generated data previously obtained from the analysis of inflammatory activated peripheral blood mononuclear cells. Applying a false discovery rate of less than 0.01 at both, peptide and protein level, a total of 8370 protein groups assembled from 117,599 peptides was identified; mass spectrometry data have been made fully accessible via ProteomeXchange with identifier PXD003406 to PXD003417.Comparative proteome analysis allowed us to determine common and cell type-specific inflammation signatures comprising novel candidate marker molecules and related expression patterns of transcription factors. Cardinal features of inflammation such as interleukin 1-β processing and the interferon response differed substantially between the investigated cells. Furthermore, cells also exerted similar inflammation-related tasks; however, by making use of different sets of proteins. Hallmarks of inflammation thus emerged, including angiogenesis, extracellular matrix reorganization, adaptive and innate immune responses, oxidative stress response, cell proliferation and differentiation, cell adhesion and migration in addition to monosaccharide metabolic processes, representing both, common and cell type-specific responsibilities of cells during inflammation.
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Affiliation(s)
- Astrid Slany
- From the ‡Department of Analytical Chemistry, Faculty of Chemistry, University of Vienna, Austria
| | - Andrea Bileck
- From the ‡Department of Analytical Chemistry, Faculty of Chemistry, University of Vienna, Austria
| | - Dominique Kreutz
- From the ‡Department of Analytical Chemistry, Faculty of Chemistry, University of Vienna, Austria
| | - Rupert L Mayer
- From the ‡Department of Analytical Chemistry, Faculty of Chemistry, University of Vienna, Austria
| | - Besnik Muqaku
- From the ‡Department of Analytical Chemistry, Faculty of Chemistry, University of Vienna, Austria
| | - Christopher Gerner
- From the ‡Department of Analytical Chemistry, Faculty of Chemistry, University of Vienna, Austria
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Wong KH, Rong SS, Chong KKL, Young AL, Pang CP, Chen LJ. Genetic Associations of Interleukin-related Genes with Graves' Ophthalmopathy: a Systematic Review and Meta-analysis. Sci Rep 2015; 5:16672. [PMID: 26578206 PMCID: PMC4649612 DOI: 10.1038/srep16672] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2015] [Accepted: 10/07/2015] [Indexed: 12/23/2022] Open
Abstract
Graves’ ophthalmopathy (GO) is the commonest extra-thyroidal manifestation of Graves’ disease (GD). Associations between interleukin-related (IL) gene polymorphisms and GO have been reported in different populations. We aim to confirm such associations by conducting a meta-analysis. Totally 382 publications were retrieved in MEDLINE and EMBASE up to 25/2/2015. After removing the duplicates and assessing the studies, we retrieved 16 studies that met the selection criteria for meta-analysis, involving 12 polymorphisms in 8 IL-related genes, and 1650 GO cases and 2909 GD controls. The summary odds ratio (OR) and 95% confidence intervals (CI) were estimated. We found one polymorphism in IL1A (rs1800587, c.-889C>T) showing a suggestive association with GO in the meta-analysis (allelic model [T vs. C]: OR = 1.62, 95% CI: 1.00–2.62, P = 0.050, I2 = 53.7%; recessive model [TT vs. TC + CC]: OR = 2.39, 95% CI: 1.07–5.37, P = 0.039, I2 = 23.6%; heterozygous model [TC vs. CC]: OR = 1.52, 95% CI: 1.04–2.22, P = 0.034, I2 = 37.0%). No association with GO was detected for the other 7 genes (IL1B, IL1RA, IL4, IL6, IL12B, IL13 and IL23R). Our results thus indicate that IL1A is likely to be a genetic biomarker for GO. Further studies with larger sample sizes are warranted to confirm the associations of IL1A and other IL-related genes with GO.
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Affiliation(s)
- Kah Hie Wong
- Department of Ophthalmology and Visual Sciences, The Chinese University of Hong Kong, Hong Kong, China
| | - Shi Song Rong
- Department of Ophthalmology and Visual Sciences, The Chinese University of Hong Kong, Hong Kong, China
| | - Kelvin K L Chong
- Department of Ophthalmology and Visual Sciences, The Chinese University of Hong Kong, Hong Kong, China.,Department of Ophthalmology and Visual Sciences, Prince of Wales Hospital, Hong Kong, China
| | - Alvin L Young
- Department of Ophthalmology and Visual Sciences, The Chinese University of Hong Kong, Hong Kong, China.,Department of Ophthalmology and Visual Sciences, Prince of Wales Hospital, Hong Kong, China
| | - Chi Pui Pang
- Department of Ophthalmology and Visual Sciences, The Chinese University of Hong Kong, Hong Kong, China
| | - Li Jia Chen
- Department of Ophthalmology and Visual Sciences, The Chinese University of Hong Kong, Hong Kong, China.,Department of Ophthalmology and Visual Sciences, Prince of Wales Hospital, Hong Kong, China
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Abstract
Thyroid-associated ophthalmopathy (TAO) is a vexing and undertreated ocular component of Graves disease in which orbital tissues undergo extensive remodelling. My colleagues and I have introduced the concept that fibrocytes expressing the haematopoietic cell antigen CD34 (CD34(+) fibrocytes), which are precursor cells of bone-marrow-derived monocyte lineage, express the TSH receptor (TSHR). These cells also produce several other proteins whose expression was traditionally thought to be restricted to the thyroid gland. TSHR-expressing fibrocytes in which the receptor is activated by its ligand generate extremely high levels of several inflammatory cytokines. Acting in concert with TSHR, the insulin-like growth factor 1 receptor (IGF-1R) expressed by orbital fibroblasts and fibrocytes seems to be necessary for TSHR-dependent cytokine production, as anti-IGF-1R blocking antibodies attenuate these proinflammatory actions of TSH. Furthermore, circulating fibrocytes are highly abundant in patients with TAO and seem to infiltrate orbital connective tissues, where they might transition to CD34(+) fibroblasts. My research group has postulated that the infiltration of fibrocytes into the orbit, their unique biosynthetic repertoire and their proinflammatory and profibrotic phenotype account for the characteristic properties exhibited by orbital connective tissues that underlie susceptibility to TAO. These insights, which have emerged in the past few years, might be of use in therapeutically targeting pathogenic orbit-infiltrating fibrocytes selectively by utilizing novel biologic agents that interfere with TSHR and IGF-1R signalling.
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Affiliation(s)
- Terry J Smith
- Department of Ophthalmology and Visual Sciences, Room 7112, Brehm Tower, Kellogg Eye Center, University of Michigan Medical School, 1000 Wall Street, Ann Arbor, MI 48105, USA
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Li B, Smith TJ. PI3K/AKT pathway mediates induction of IL-1RA by TSH in fibrocytes: modulation by PTEN. J Clin Endocrinol Metab 2014; 99:3363-72. [PMID: 24840811 PMCID: PMC4154109 DOI: 10.1210/jc.2014-1257] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
CONTEXT TSH provokes expression of inflammatory genes in CD34(+) fibrocytes. These cells appear to infiltrate the orbit in Graves' disease (GD), where they putatively become the CD34(+) orbital fibroblast subset (GD-OF). This may have importance in solving the pathogenesis of thyroid-associated ophthalmopathy. The IL-1 family is targeted by TSH in fibrocytes and OFs by inducing secreted IL-1 receptor antagonist (IL-1RA) and intracellular IL-1RA in a cell-specific pattern. Phosphoinositide 3-kinase (PI3K) mediates several TSH actions in thyroid. This pathway is modulated by phosphatase and tensin homolog deleted on chromosome 10 (PTEN). Vanishingly little is known currently about TSHR signaling to IL-1RA expression in nonthyroidal cells. Furthermore, factors modulating TSH action in these cells are largely unexplored. OBJECTIVES To characterize intermediate signaling between TSHR and IL-1RA in fibrocytes and GD-OFs and to begin to identify the proximate regulators of TSHR signaling in nonepithelial, extrathyroidal cells as a strategy for developing therapies for thyroid-associated ophthalmopathy. DESIGN/SETTING/PARTICIPANTS Fibrocytes and GD-OFs were collected and analyzed from healthy individuals and those with GD in an academic clinical practice. MAIN OUTCOME MEASURES Real-time PCR, Western blot analysis, cell transfections, and chromatin immunoprecipitation analysis. RESULTS TSH induces IL-1RA in fibrocytes and GD-OFs by activating the PI3K/AKT pathway. Interrupting either PI3K or AKT with small molecule inhibitors or by knocking down their expression with targeting small interfering RNA attenuates the actions of TSH. OFs exhibit greater basal PTEN activity and lower constitutive AKT phosphorylation than do fibrocytes. Patterns of PTEN induction diverge in the two cell types. CONCLUSIONS The current findings identify the PI3K/AKT pathway as critical to the induction by TSH of IL-1RA in fibrocytes and GD-OFs. Furthermore, PTEN modulates the amplitude of the induction. In GD-OFs, relatively high basal PTEN levels prevent secreted IL-1RA expression or release. Knocking down PTEN allows GD-OFs to exhibit a pattern of IL-1RA expression resembling fibrocytes.
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Affiliation(s)
- Bin Li
- Departments of Ophthalmology and Visual Sciences (B.L., T.J.S.) and Internal Medicine (T.J.S.), Division of Metabolism, Endocrinology, and Diabetes, University of Michigan Medical School, Ann Arbor, Michigan 48105
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Chng CL, Lai OF, Chew CSM, Peh YP, Fook-Chong SMC, Seah LL, Khoo DHC. Hypoxia increases adipogenesis and affects adipocytokine production in orbital fibroblasts-a possible explanation of the link between smoking and Graves' ophthalmopathy. Int J Ophthalmol 2014; 7:403-7. [PMID: 24967181 DOI: 10.3980/j.issn.2222-3959.2014.03.03] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2014] [Accepted: 02/25/2014] [Indexed: 11/02/2022] Open
Abstract
AIM To assess the effects of hypoxia on human orbital fibroblasts (OF) on adipogenesis and adipocytokine production. METHODS Human OF were derived from tissues obtained from patients with Graves' ophthalmopathy (GO) and from patients without known thyroid diseases undergoing blepharoplasty. The OF were cultured separately under normoxic and hypoxic conditions. Comparisons of adipocytokine concentrations using multiplex ELISA and lipid accumulation in the cells using Oil Red O staining were subsequently performed. RESULTS There was increased adipogenesis in OF from GO subject when exposed to hypoxic culture conditions. This was not observed in OF from normal controls. Hypoxia led to an increase in leptin and a decrease in MCP-1 secretion in OF cultures. CONCLUSION Hypoxia induces adipogenesis in OF and may represent a mechanism by which smoking contributes to deterioration of GO. We also found novel changes to leptin and MCP-1 production in OF cultures exposed to hypoxia suggesting important roles of these cytokines in the disease process.
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Affiliation(s)
- Chiaw Ling Chng
- Department of Endocrinology, Singapore General Hospital, Level 3, the Academia, 20 College Road 169856, Singapore
| | - Oi Fah Lai
- Department of Clinical Research, Academia Discovery Tower Level 9 Research Office 2, 20 College Road 169856, Singapore
| | - Charmaine Sze-Min Chew
- Department of Clinical Research, Academia Discovery Tower Level 9 Research Office 2, 20 College Road 169856, Singapore
| | - Yu Pei Peh
- Department of Clinical Research, Academia Discovery Tower Level 9 Research Office 2, 20 College Road 169856, Singapore
| | | | - Lay Leng Seah
- Oculoplastic/Aesthetic Eyeplastic Service, Singapore National Eye Centre, 11 Third Hospital Avenue 168751, Singapore
| | - Daphne Hsu-Chin Khoo
- Department of Endocrinology, Singapore General Hospital, Level 3, the Academia, 20 College Road 169856, Singapore
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Fernando R, Vonberg A, Atkins SJ, Pietropaolo S, Pietropaolo M, Smith TJ. Human fibrocytes express multiple antigens associated with autoimmune endocrine diseases. J Clin Endocrinol Metab 2014; 99:E796-803. [PMID: 24517144 PMCID: PMC4010713 DOI: 10.1210/jc.2013-3072] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
CONTEXT Factors common to multiple autoimmune diseases have been sought vigorously. Graves' disease (GD) and type 1 diabetes mellitus (T1DM) involve end-organ remodeling. Fibrocytes participate in inflammatory diseases and were recently shown to express thyroid-specific proteins such as the thyrotropin receptor and thyroglobulin. OBJECTIVE The objective of the study was to determine whether a broader repertoire of autoantigen expression, such as proteins associated with T1DM, can be ascribed to fibrocytes. DESIGN, SETTING, AND PARTICIPANTS Fibrocytes and fibroblasts were collected and analyzed from healthy individuals and those with autoimmune diseases in an academic clinical practice. MAIN OUTCOME MEASURES Real-time PCR, Western blot analysis, gene promoter analysis, cell transfections, and flow cytometric cell sorting were performed. RESULTS Islet cell antigen ICA512 (IA-2) and islet cell autoantigen of 69 kDa (ICA69), two islet-specific proteins implicated in T1DM, are expressed by fibrocytes from healthy donors and those with T1DM, GD, and multiple sclerosis. Both transcripts are detected by PCR, the proteins are resolved on Western blots, and both gene promoters are active in fibrocytes. Levels of ICA69 are substantially higher than those of IA-2 in fibrocytes. ICA69 localizes to CD34(+) GD orbital fibroblasts putatively derived from fibrocytes, whereas higher levels of IA-2 are found in CD34(-) fibroblasts. CONCLUSIONS In addition to autoantigens implicated in thyroid autoimmunity, fibrocytes and derivative fibroblasts express multiple autoantigens associated with T1DM. This expression results from active gene promoters and abundant steady-state mRNA encoding ICA69 and IA-2. These latest findings demonstrate that fibrocytes express antigens relevant to multiple forms of endocrine autoimmunity. They suggest the potential for these cells playing a direct role in immune reactivity directed at the thyroid and pancreatic islets.
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Affiliation(s)
- Roshini Fernando
- Department of Ophthalmology and Visual Sciences (R.F., S.J.A., T.J.S.), Kellogg Eye Center and Division of Metabolism, Endocrinology, and Diabetes (A.V., S.P., M.P., T.J.S.), Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, Michigan 48105
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Abstract
CONTEXT The IL-1 family plays important roles in normal physiology and mediates inflammation. The actions of IL-1 are modulated by multiple IL-1 receptor antagonists (IL-1RA), including intracellular and secreted forms. IL-1 has been implicated in autoimmunity, such as that occurring in Graves' disease (GD) and its inflammatory orbital manifestation, thyroid-associated ophthalmopathy (TAO). We have previously reported that CD34(+) fibrocytes, monocyte-lineage bone marrow-derived cells, express functional TSH receptor, the central antigen in GD. When activated by TSH, they produce IL-6, IL-8, and TNF-α. Moreover, they infiltrate the orbit in TAO in which they transition into CD34(+) fibroblasts and comprise a population of orbital fibroblasts (OFs). Little is known currently about any relationship between TSH, TSH receptor, and the IL-1 pathway. OBJECTIVE The objective of the study was to determine whether TSH regulates IL-1RA in fibrocytes and OFs. DESIGN/SETTING/PARTICIPANTS Fibrocytes and OFs were collected and analyzed from healthy individuals and those with GD in an academic clinical practice. MAIN OUTCOME MEASURES Real-time PCR, Western blot analysis, reporter gene assays, and cell transfections were performed. RESULTS TSH induces the expression of IL-1RA in fibrocytes and GD-OFs. The patterns of induction diverge quantitatively and qualitatively in the two cell types. This results from relatively small effects on gene transcription-related events but a greater influence on secreted IL-1RA and intracellular IL-1RA mRNA stabilities. These actions of TSH are dependent on the intermediate induction of IL-1α and IL-1β. CONCLUSIONS Our findings for the first time directly link activities of the TSH and IL-1 pathways. Furthermore, they identify novel molecular interactions that could be targeted as therapy for TAO.
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Affiliation(s)
- Bin Li
- Department of Ophthalmology and Visual Sciences (B.L., T.J.S.) and Department of Internal Medicine (T.J.S.), Division of Metabolism, Endocrinology, and Diabetes, University of Michigan Medical School, Ann Arbor, Michigan 48105
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Wang Y, Smith TJ. Current concepts in the molecular pathogenesis of thyroid-associated ophthalmopathy. Invest Ophthalmol Vis Sci 2014; 55:1735-48. [PMID: 24651704 DOI: 10.1167/iovs.14-14002] [Citation(s) in RCA: 155] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Graves' disease (GD) is a common autoimmune condition. At its core, stimulatory autoantibodies are directed at the thyroid-stimulating hormone receptor (TSHR), resulting in dysregulated thyroid gland activity and growth. Closely associated with GD is the ocular condition known as thyroid-associated ophthalmopathy (TAO). The pathogenesis of TAO remains enigmatic as do the connections between the thyroid and orbit. This review highlights the putative molecular mechanisms involved in TAO and suggests how these insights provide future directions for identifying therapeutic targets. Genetic, epigenetic, and environmental factors have been suggested as contributory to the development of GD and TAO. Thyroid-stimulating hormone receptor and insulin-like growth factor receptor (IGF-1R) are expressed at higher levels in the orbital connective tissue from individuals with TAO than in healthy tissues. Together, they form a functional complex and appear to promote signaling relevant to GD and TAO. Orbital fibroblasts display an array of cell surface receptors and generate a host of inflammatory molecules that may participate in T and B cell infiltration. Recently, a population of orbital fibroblasts has been putatively traced to bone marrow-derived progenitor cells, known as fibrocytes, as they express CD45, CD34, CXCR4, collagen I, functional TSHR, and thyroglobulin (Tg). Fibrocytes become more numerous in GD and we believe traffic to the orbit in TAO. Numerous attempts at developing complete animal models of GD have been largely unsuccessful, because they lack fidelity with the ocular manifestations seen in TAO. Better understanding of the pathogenesis of TAO and development of improved animal models should greatly accelerate the identification of medical therapy for this vexing medical problem.
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Affiliation(s)
- Yao Wang
- Department of Ophthalmology and Visual Sciences and Division of Metabolic and Endocrine Disease, Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, Michigan
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