[An exploration of induction methodology and experimental duration of Graves disease animal model]

To compare the efficacy of Graves disease animal models induced by thyroid stimulating hormone receptor (TSHR) plasmid DNA (pcDNA3.1-TSHR) and by TSHR A subunit recombinant adenovirus (Ad-TSHR289), and to investigate the influence of duration for preparing animal model induced by Ad-TSHR289 on Graves hyperthyroidism and its related indices.

The plasmid group and the adenovirus group were set up respectively. The plasmid group: 21 female BALB/c mice were randomly divided into model group (n = 12) and control group (n = 9). The model group were injected intradermally with pcDNA3.1-TSHR 50 µg, once every 3 weeks, totally 3 times. Then 4 weeks after the last immunization, the mice were euthanized to obtain blood for testing TSHR antibody (TRAb), total T(4), and thyroid tissue for histological examination. The controls were injected with the same dose of pcDNA3.1 in the same way. The adenovirus group: 52 female BALB/c mice were divided into 10-week model group (n = 8), 14-week model group (n = 10) and 18-week model group (n = 8), and the respective controls (n = 8, n = 10, n = 8) were set up. All model groups were injected intramuscularly with Ad-TSHR289, three times at three weekly intervals. Then the mice were euthanized at 4, 8 and 12 weeks to test TRAb, total T(4) level and to observe the change of thyroid histology. The controls were treated with the same dose of Ad-lacz in the same way. Another 8 mice were scheduled to test the dynamic variation of TRAb before and after the 3 times immunization.

In the plasmid model group, only two of 12 mice developed weak antibody responses against TSHR, and no elevated total T(4) level and no hyperplasia changes of thyroid were observed. In the 10-week model group, all mice had high level TRAb [(807.65 ± 136.33) U/L], Six-eighths mice had hyperthyroidism exhibited hyperplasia changes. In the 14-week model group, the TRAb level [(650.12 ± 192.88) U/L] and the incidence of hyperthyroidism (3/10) were lower than those in 10-week group. Histologically, the degree of thyroid hyperplasia lightened to a small extent, but its positive rate did not decline. In the 18-week model group, only 2 of 8 mice displayed slightly elevated TRAb level, and no mice showed increased total T(4) level. Additionally, thyroid tissues of 2 mice were mildly abnormal. Compared with the model groups at different time, the change of antibody levels of the mice for TRAb dynamic observation exhibited the similar trend.

Being good at repeatability and high incidence of hyperthyroidism, the animal model of Graves disease induced by Ad-TSHR289 is still an ideal research tool presently. The duration of model can be maintained 18 weeks, and 10 weeks is the best period to sustain characteristic of Graves disease.