Application of new therapies in Graves' disease and thyroid-associated ophthalmopathy: animal models and translation to human clinical trials

Wnt signalling inhibits adipogenesis in orbital fibroblasts from patients with Graves' orbitopathy

BACKGROUND/AIMS

To investigate the role of Wnt signalling in adipogenesis using an in vitro model of Graves' orbitopathy (GO).

METHODS

Orbital fat was obtained from patients with GO and non-GO participants for primary orbital fibroblast (OF) culture. Expression levels of Wnt5a, Wnt10b, β-catenin, phospho-β-catenin and cyclin D1 were compared between GO and non-GO OFs. These expression levels were also determined during adipogenesis of GO and non-GO OFs. The effects of a stimulator and inhibitor of Wnt signalling on adipogenesis of GO and non-GO OFs were investigated.

RESULTS

Western blotting analysis showed significant reductions in β-catenin and cyclin D1 and significant enhancement of phospho-β-catenin in OFs from patients with GO, compared with OFs from non-GO participants (p<0.05). Expression of Wnt5a, Wnt10b, β-catenin and cyclin D1 in OFs was highest on day 0, and then gradually declined after induction of adipogenic differentiation. The expression levels of PPARγ, C/EBPα and C/EBPβ were reduced in Wnt stimulator-treated OFs in a dose-dependent manner. Oil red O staining confirmed that a stimulator of Wnt inhibited adipogenesis in GO OFs.

CONCLUSION

These results indicate that Wnt signalling inhibits adipogenesis in OFs from patients with GO and non-GO participants. Further studies are required to examine the potential of Wnt signalling as a target for therapeutic strategies.

Modeling Graves' Orbitopathy in Experimental Graves' Disease

Graves' orbitopathy (GO), also known as thyroid eye disease is an inflammatory disease of the orbital tissue of the eye that arises as a consequence of autoimmune thyroid disease. The central feature of the disease is the production of antibodies to the thyrotropin hormone receptor (TSHR) that modulate the function of the receptor leading to autoimmune hyperthyroidism and GO. Over the years, all viable preclinical models of Graves' disease have been incomplete and singularly failed to progress in the treatment of orbital complications. A new mouse model of GO based upon immunogenic presentation of human TSHR A-subunit plasmid by close field electroporation is shown to lead to induction of prolonged functional antibodies to TSHR resulting in chronic disease with subsequent progression to GO. The stable preclinical GO model exhibited pathologies reminiscent of human disease characterized by orbital remodeling by inflammation and adipogenesis. Inflammatory lesions characterized by CD3+ T cells and macrophages were localized in the orbital muscle tissue. This was accompanied by extensive adipogenesis of orbital fat in some immune animals. Surprisingly, other signs of orbital involvement were reminiscent of eyelid inflammation involving chemosis, with dilated and congested orbital blood vessels. More recently, the model is replicated in the author's independent laboratories. The pre-clinical model will provide the basis to study the pathogenic and regulatory roles of immune T and B cells and their subpopulations to understand the initiation, pathophysiology, and progression of GO.

Graves' Ophthalmopathy: VISA versus EUGOGO Classification, Assessment, and Management

Graves' ophthalmopathy (GO) is an autoimmune inflammatory disorder associated with thyroid disease which affects ocular and orbital tissues. GO follows a biphasic course in which an initial active phase of progression is followed by a subsequent partial regression and a static inactive phase. Although the majority of GO patients have a mild, self-limiting, and nonprogressive ocular involvement, about 3–7% of GO patients exhibit a severe sight-threatening form of the disease due to corneal exposure or compressive optic neuropathy. An appropriate assessment of both severity and activity of the disease warrants an adequate treatment. The VISA (vision, inflammation, strabismus, and appearance), and the European Group of Graves' Orbitopathy (EUGOGO) classifications are the two widely used grading systems conceived to assess the activity and severity of GO and guide the therapeutic decision making. A critical analysis of classification, assessment, and management systems is reported. A simplified “GO activity assessment checklist” for routine clinical practice is proposed. Current treatments are reviewed and management guidelines according to the severity and activity of the disease are provided. New treatment modalities such as specific monoclonal antibodies, TSH-R antagonists, and other immunomodulatory agents show a promising outcome for GO patients.

Insulin-like growth factor 1 promotes the proliferation and adipogenesis of orbital adipose-derived stromal cells in thyroid-associated ophthalmopathy

Thyroid-associated ophthalmopathy (TAO) is characterised by increased volume of the orbital contents involving adipose tissue, but the factors responsible for stimulation of orbital adipogenesis remain uncertain. Previous studies have shown that insulin-like growth factor 1 (IGF-1) is increased in the orbital fatty connective tissues of patients with TAO. The present study was conducted to investigate the effects of IGF-1 on orbital adipose-derived stromal cells (OADSCs) derived from TAO patients and to identify the signalling mechanisms involved. Our results showed that IGF-1 significantly promoted the cell proliferation and lipid accumulation of TAO OADSCs. The mRNA expression of adipogenic markers (adiponectin, leptin, adipocyte fatty acid binding protein [AP2] and fatty acid synthase [FAS]) was increased in TAO cultures treated with IGF-1. Further research demonstrated that the protein levels of peroxisome proliferator-activated receptor-γ (PPARγ) were up-regulated when OADSCs were treated with IGF-1. We also found that the inhibition of either IGF-1 receptor (IGF-1R) or phosphoinositide 3-kinase (PI3K) activity decreased the levels of IGF-1-stimulated mRNA encoding adiponectin, leptin, AP2, and FAS, as well as PPARγ protein levels. Moreover, the expression of phosphorylated Akt (p-Akt) protein in TAO cells was up-regulated by IGF-1, while a specific PI3K inhibitor (LY294002) or an antibody of IGF-1R blocked this effect. These results indicate that IGF-1 is a pro-proliferative and pro-adipogenic factor in TAO OADSCs. IGF-1 enhances the adipogenesis of TAO OADSCs by up-regulation of PPARγ via the activation of the IGF-1R and PI3K pathways, suggesting that the blocking of IGF-1R or inhibition of PI3K signalling might be a potential novel therapeutic approach to TAO.

Decrease in proportion of CD19+ CD24(hi) CD27+ B cells and impairment of their suppressive function in Graves' disease

IL-10-producing B cells (B10 cells) have been shown to play a suppressive role in the peripheral blood of humans, with their numbers and function altered in several autoimmune diseases. However, the role of B10 cells in Graves' disease (GD) remains unknown. In this study, we demonstrated that B10 cells in human peripheral blood belonged to a CD24(hi)CD27(+) B cell subpopulation. The proportion of B10 cells along with the CD19(+)CD24(hi)CD27(+) B cell subset was significantly lower in new-onset patients compared with healthy individuals. In recovered patients, these proportions were restored to levels similar to those seen in healthy individuals. Additionally, we found that CD19(+)CD24(hi)CD27(+) B cells from healthy individuals inhibited proliferation and TNF-α production of CD4(+) T cells via an IL-10-independent pathway. They also inhibited IFN-γ production by CD4(+) T cells, through an IL-10-dependent pathway. In contrast, their suppressive function on CD4(+) T cell proliferation and cytokine production was impaired in new-onset and recovered patients compared with healthy individuals. Our study provides evidence that CD19(+)CD24(hi)CD27(+) B cells may possess the capacity to downregulate immune responses, partially by production of IL-10 in human peripheral blood. Impairment of their immunosuppressive function may contribute to GD pathogenesis and relapse.

Treatment of mild to moderate Graves' ophthalmopathy with sodium diclofenac: a pilot study

OBJECTIVE

To report the use of sodium diclofenac, an antagonist of PPAR-gamma and cyclooxigenase-2 (COX-2) inhibitor in the treatment of mild to moderate Graves' ophthalmopathy.

SUBJECTS AND METHODS

Thirteen patients with clinical activity score (CAS) 2 to 7 were treated during a period ranging from 3 to 12 months (mean 7.8 ± 3.4) with oral sodium diclofenac, 50 mg every 12 hours.

RESULTS

Extra-ocular muscle restriction and CAS improved significantly, p = 0.003 and = 0.004, respectively. Ocular pain and diplopia disappeared, except for one patient who reported improvement of these symptoms. No recurrence was found after interruption of treatment.

CONCLUSIONS

Treatment of moderate Graves' ophthalmopathy with oral sodium diclofenac is a good, safe and less expensive therapeutic option. Like others new treatment trials, findings must be confirmed in a greater number of patients in a controlled study.

Treating the thyroid in the presence of Graves' ophthalmopathy

The etiology of Graves' orbitopathy (GO) remains enigmatic. Optimal therapeutic choices for the hyperthyroidism associated with Graves' disease (GD) in the presence of GO remain controversial. Whether antithyroid drugs (ATDs), radioiodine (RAI), or thyroidectomy should be favored in such patients remains debated. Pre-therapy variables such as ethnicity, sex, age, thyroid function, level of TSH-receptor antibodies and smoking behavior influence response to therapy. Among the most important management goals are restoring euthyroidism and abstaining from smoking. On average, ATDs and thyroidectomy - independent of extent - do not influence the natural course of GO. RAI can cause de novo development or progression of GO, which is largely preventable with oral steroid prophylaxis. In patients with mild GO, the thyroid treatment is largely independent of GO. Moderate to severe GO should be treated promptly. Deciding whether, in the latter, GD is better treated with ATDs, RAI, or surgery, is based more on expert opinion than on evidence. It is clear that in the individual patient a number of factors, not addressed in any trial, influence the final choice of therapy for GD, including concern of developing or negatively affecting pre-existing GO. Evidently, there is room for improving therapy of GO. Progress using novel drugs such as rituximab, which might potentially influence positively both GD and GO, are impatiently awaited.

Orbital fibrosis in a mouse model of Graves' disease induced by genetic immunization of thyrotropin receptor cDNA

The TSH receptor (TSHR) is the critical target for antibody production in Graves' disease (GD). Insulin-like growth factor 1 receptor (IGF1R) has been proposed as a second autoantigen in complications of GD such as orbitopathy. We attempted to induce orbital tissue remodeling in mice undergoing immunizations with plasmids encoding TSHR and IGF1R delivered by in vivo skeletal muscle electroporation, a procedure known to give a sustained, long-term antibody response. Female BALB/c mice were challenged with TSHR A-subunit or IGF1Rα subunit plasmid by injection and electroporation. Mice challenged with TSHR A-subunit plasmid resulted in high frequency (75%) of hyperthyroidism and thyroid-stimulating antibodies. But strikingly, immunization with TSHR A-subunit plasmid also elicited antibody to IGF1Rα subunit. Mice challenged in the same manner with IGF1Rα subunit plasmid produced strong antibody responses to IGF1R, but did not undergo any changes in phenotype. Simultaneous challenge by double antigen immunization with the two plasmids in distant anatomical sites reduced the incidence of hyperthyroidism, potentially as a consequence of antigenic competition. Thyroid glands from the TSHR A-subunit plasmid-challenged group were enlarged with patchy microscopic infiltrates. Histological analysis of the orbital tissues demonstrated moderate connective tissue fibrosis and deposition of Masson's trichrome staining material. Our findings imply that immunization with TSHR A-subunit plasmid leads to generation of IGF1R antibodies, which together with thyroid-stimulating antibodies may precipitate remodeling of orbital tissue, raising our understanding of its close association with GD.

Targeted biological therapies for Graves' disease and thyroid-associated ophthalmopathy. Focus on B-cell depletion with Rituximab

Based on experience from the treatment of other autoimmune diseases and because of the limitations imposed by existing therapeutic options for Graves' disease (GD) and thyroid-associated ophthalmopathy (TAO), rituximab (RTX) was recently proposed as a novel therapy option. Here, we summarize the rationale for using RTX; give an overview of the possible mechanisms of action; and give an account of its effects and side-effects when used in GD and TAO. Scant evidence, originating from only a few methodologically inhomogeneous studies, suggests that RTX may prolong remission for hyperthyroidism over that seen with antithyroid drugs, at least in mild GD. Furthermore, in patients with TAO, who are unresponsive to conventional immunosuppressive therapy, RTX seems efficacious. As we wait for larger-scale randomized studies, RTX, should be considered experimental and reserved for patients who do not respond favourably to conventional therapy. It is the first in what is likely to be a series of new and emerging treatments specifically targeting relevant components of the immune system. Further studies will hopefully lead to improved and better tailored, individualized therapy for GD and especially TAO.

Disease association of the CD103 polymorphisms in Taiwan Chinese Graves' ophthalmopathy patients

OBJECTIVE

To evaluate whether variations in the CD103 gene could be associated with Graves' ophthalmopathy (GO) in patients with Graves' disease.

DESIGN

Case-control study.

PARTICIPANTS

A total of 484 Chinese patients with Graves' disease in Taiwan, including 203 patients with GO and 281 patients without GO, were enrolled.

METHODS

Five single nucleotide polymorphisms (SNPs) in CD103 were genotyped using an assay-on-demand allelic discrimination assay and detection system according to the manufacturer's instructions.

MAIN OUTCOME MEASURES

Association of SNPs in CD103 with the development of GO.

RESULTS

The CD103 SNP rs11652878 was associated with GO, which may decrease the risk of GO by 1.57-fold (P = 0.029). The Ht5-GCGCG haplotype, composed of 5 SNPs in the CD103 gene (rs1716, rs3744679, rs11652878, rs16953477, and rs9905739), were protective haplotypes (P = 0.010). Moreover, the heterozygous genotype (Ht5/non-Ht5) was correlated with a reduced risk of GO and high grades of goiter as compared with the non-Ht5/non-Ht5 genotype (P = 0.006 and P = 0.048, respectively). Logistic analysis confirmed the contribution of CD103 rs11652878 to the protection of GO.

CONCLUSIONS

These data suggest that patients with Graves' disease in the presence of the G allele of SNP rs11652878, especially Ht5-GCGCG, in CD103 are less susceptible toward the development of GO.

Update on the medical treatment of Graves' ophthalmopathy

PURPOSE

To review recent advances in the understanding of Graves' ophthalmopathy (GO) pathogenesis as well as discuss current and future medical management strategies.

DESIGN

Interpretive essay.

METHODS

Literature review and interpretation.

RESULTS

Medical treatment of GO has slowly evolved during the past few decades and has been hampered by a poor understanding of the disease at a cellular and molecular level. Current treatment recommendations and guidelines therefore focus on nonspecific immuno-suppression. Newer classes of treatment agents hold promise to more selectively target underlying cellular and molecular alterations in GO.

CONCLUSION

Cooperation between individual patients, physicians and between differing medical centers, together with a refined understanding of the pathogenesis of GO, will lead to newer more-effective treatments for the disease and improve patient quality of life.

Clonal relationships between thyroid-stimulating hormone receptor-stimulating antibodies illustrate the effect of hypermutation on antibody function

Graves' disease is characterized by production of agonist antibodies to the thyroid-stimulating hormone receptor (TSHR), but knowledge of the genetic and somatic events leading to their aberrant production is limited. We describe the genetic analysis of two monoclonal antibodies (mAbs) with thyroid-stimulating activity (TSAb) obtained from a single mouse with experimental Graves' disease. The mAbs were class switched, but used the same rearrangement of immunoglobulin heavy chain, variable region (IGHV) and immunoglobulin light chain, variable region (IGLV) germline genes, implying a clonal relationship and derivation from a single precursor B-cell clone. The IGHV-region genes of the two mAbs underwent high degrees of somatic hypermutation by sharing numerous mutations before diverging, while the IGLV genes evolved separately. Interestingly, the mutations were present in both the complementarity-determining regions (CDRs) and the framework regions. The cloned IGHV and IGLV genes were confirmed to have TSAb properties in experiments in which they were expressed as recombinant Fabs (rFabs). In other experiments, we swapped the IGLV genes with IGHV genes by constructing chimeric rFabs and showed that the chimeras retained TSAb activities, confirming the close functional relatedness of the V-region genes. Importantly, the IGLV genes in chimeric rFabs had a dominant stimulatory effect at low concentrations, while the IGHV genes had a dominant effect at higher concentrations. Our findings demonstrate that, in experimentally immunized mice, multiple pathogenic antibodies to TSHR can arise from a single clone by a series of somatic mutations in the V-region genes and may give an insight into how such antibodies develop spontaneously in autoimmune Graves' disease.

Toward better models of hyperthyroid Graves' disease

Graves' disease affects only humans. Although it is a treatable illness, medical therapy with antithyroid drugs is imperfect, showing high rates of recurrence. Furthermore, the etiology and treatment of the associated ophthalmopathy still represent problematic issues. Animal models could contribute to the solution of such problems by providing a better understanding of the underlying pathogenesis and could be used for evaluating novel therapeutic strategies. This article discusses the pursuit of a better experimental model for hyperthyroid Graves' disease and outlines how this research has clarified the immunology of the disease.

Treatment of Graves' hyperthyroidism: evidence-based and emerging modalities

Currently there are three well-established treatment options for hyperthyroid Graves' disease (GD): antithyroid drug therapy with thionamides (ATD), radioactive iodine treatment with (131)I, and thyroid surgery. This article reviews the current evidence so the reader can evaluate advantages and disadvantages of these treatment modalities. Surgery is rarely used, except for patients who have a large goiter or ophthalmopathy. Fewer than 50% of patients treated with ATD remain in long-term remission. Therefore, radioactive iodine is used increasingly. No data as yet support the routine use of biologic therapies (eg, rituximab). Prospective, randomized studies comparing available and any novel therapeutic options for GD are needed. The focus of these studies should include, but not be limited to, cost and quality of life.