Mouse model of Graves’ orbitopathy induced by the immunization with TSHR A and IGF-1R α subunit gene

Purpose: The study aimed to establish a mouse model of Graves’ disease (GD) with Graves’ orbitopathy (GO; GD + GO) that can represent the clinical disease characteristics. Methods: A eukaryotic expression plasmid of insulin-like growth factor 1 receptor (IGF-1R) α subunit (pcDNA3.1/IGF-1Rα) and a thyrotropin receptor (TSHR) A subunit plasmid (pcDNA3.1/TSHR-289) were injected in female BALB/c mice followed by immediate electroporation to induce a GD + GO model. Grouping was performed according to the frequency of injection (2- to 4-week intervals) and type of injected plasmids: T: pcDNA3.1/TSHR-289(+), I: pcDNA3.1/IGF-1Rα(+), or co-injection T + I: pcDNA3.1/TSHR-289(+) and pcDNA3.1/IGF-1Rα(+). Serum TSH, T4, TSAb, TSBAb, body weight, and blood glucose levels were evaluated. Thyroid TcO imaging and retrobulbar magnetic resonance imaging (MRI) were performed, and bilateral eye muscle volumes were measured. Immunohistochemistry and hematoxylin–eosin staining were performed on the relevant tissues, and semi-quantitative analysis was performed. Results: A total of 60% of mice (3/5, one mouse died) in the T group developed GD + GO. In the T + I group, 83.3% of mice (5/6) developed GD + GO. Mice in the I group did not develop GD. Compared with the control group, serum T4, TSAb, and TSBAb of the mice in the GD + GO model groups were increased to varying degrees (P < 0.05), and serum TSH and body weight were significantly lower compared to the control group (P < 0.05). The thyroid uptake capacity of TcO and the volume of eye muscle of mice in the GD + GO group were significantly higher compared to the control group (P < 0.05). The thyroid and retrobulbar muscles of these mice showed varying inflammatory infiltration and interstitial muscle edema. The severity of GD + GO in the co-injection group was not related to injection frequency; however, GD and ocular signs in co-injection mice were more severe compared to the T group. Conclusions: We successfully induced a GD + GO mouse model by a repeated co-injection of pcDNA3.1/IGF-1Rα and pcDNA3.1/TSHR-289 plasmids. Injection of pcDNA3.1/IGF-1Rα alone failed to induce GD. Co-injection of two plasmids induced more severe GD + GO than pcDNA3.1/TSHR-289(+) alone.