FRI533 A Novel Cre-loxP Based Mouse Model For Graves' Disease

Disclosure: D. Kim: None. Y. Bao: None. M. Kang: None. Y. Cho: None. Y. Kim: None. Y. Hwang: None. C. Ku: None. E. Lee: None. Objectives: Over years, various approaches have been used to model human Graves’ disease in mice, including transfected fibroblasts, and plasmid or adenoviral immunizations with the extracellular A subunit of the human thyrotropin receptor (hTSHRa). However, these models require a lot of effort for multiple dosing over several months and the results are very heterogeneous, limiting their use as a platform for the development of new therapeutics. Thus, we developed a novel Cre-loxP based mouse model for Graves' disease. Methods: To overcome the limitation of existing animal models, we made ESC-derived KI mouse expressing hTSHRa that will act as an antigen in a conditional manner by inserting the CAG-loxP-STOP-loxP-hTSHRa cassette into the mouse Rosa26 locus. TAT-Cre, a recombinant cell-permeant fusion cre-recombinase protein, was used for site-specific recombination to avoid leaky expression which may induce immune tolerance. Various concentrations of TAT-Cre were tested to avoid neutralization and produce adequate hyperthyroidism. Serum TSHR Ab and T4 levels were measured. Immunohistochemical examinations of the thyroid gland and orbits were performed. Results: Treatment with TAT-Cre within the range of 250-750U produced the most efficient TSHR Ab and significantly increased T4. Four weeks after TAT-Cre 500U administration, TSHR Ab levels were already significantly produced in all mice and T4 levels started to increase. At 8 and 12 weeks, TSHR Ab levels were produced at a very high levels in all mice and T4 levels were increased to a very high levels in over 80% of mice. After 3 months, MRI images did not show any significant protrusion. However, there was an enlargement in the volume of the orbital muscles. We also found thyroid enlargement and hypertrophy, orbital macrophage infiltration and fibrosis in Immunohistochemical examinations. Conclusions: A new mouse model for Graves' disease was successfully established by using the Cre-loxP system. After being optimized for orbitopathy induction, this model can be used as a platform for the development of novel therapeutics. Presentation: Friday, June 16, 2023