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(1) Spontaneous model is better than induced model. However, at present, the only spontaneous model TSHR/NOD.H2h4 transgenic rabbits use instruments to produce TSAb, which takes a long period and costs a lot, so it is not convenient to be widely used.
(2) Reproducibility. At present, the GD model induced by plasmid expressing TSHR has low repeatability in many laboratories around the world.
(3) The incidence of 3)GD is high, which is convenient for observing the etiology and assisting the new treatment.
(4) GD can be induced in multi-strain rabbits. Both Shimojo and M12 models can only induce GD in susceptible strains. Based on the above four points, the GD model induced by adenovirus expressing TSHR A subunit is widely recognized and has the best repeatability at present.
Instruments used in rabbit experiments
3.1 Successful construction of GD model of rabbits and macaques
In this study, by injecting recombinant adenovirus expressing TSHR A subunit, the monkey model (injected 5 times) and the rabbit model (injected 3 times) all showed TRAb positive, thyroid hormone level increased and thyroid tissue proliferated significantly. In addition, the macaque model also showed typical clinical symptoms of GD, such as weight loss and resting heart rate increase, and the rabbit model also showed a significant decrease in weight gain per unit food intake.
It is worth noting that the incidence of GD in the macaque model increased gradually with the increase of injection times. At the end of the third immunization, the increase rate of TT4 in the macaque model was only 16. 7%, but at the end of the fifth immunization, the increase rate of TT4 in the macaque model reached 50%. Our unpublished data show that the increase rate of TT4 will continue to increase if immunization continues. This result indirectly proves that TSHR is the most powerful antigen to induce GD, and it also shows that it may be necessary to extend the immunization time and increase the immunization times in order to obtain a higher incidence of GD in rhesus monkeys.
3.2 the relationship between GD model and Treg cells
Treg cells are a subset of T lymphocytes characterized by immunosuppression, and as important immunoregulatory cells, they play a central role in the pathogenesis of autoimmune diseases.
Forkheadbox protein 3 (foxp3) is an important regulator of the development and function of Treg cells. In this study, the rabbit experimental instrument GD model and the macaque GD model both showed a significant decrease in the proportion of CD4+CD25 +Foxp3+ Treg cells, which was consistent with the previously reported CD clinical experiment results.
This phenomenon once again proves that Treg cells may be related to the pathogenesis of GD, and these two animal models are good tools for studying the relationship between Treg cells and GD and immunotherapy against Treg cells in the future.
3.3 Comparison of experimental instruments used in rabbits and GD models of rhesus monkeys
At the end of the modeling, three rabbits in the macaque modeling group had the above phenomenon (50%), while six rabbits in the rabbit modeling group had the above phenomenon (75%), which was consistent with the reported data. Therefore, the incidence of GD in rabbit model group is slightly higher than that in macaque group, but there is no significant statistical difference. However, under the same number of injections (three injections), the incidence of GD in the monkey model (16.7%) was significantly lower than that in the rabbit model (P< 0. 05).
This shows that the incidence of GD model in rabbits is higher under the same immunization time and times.
Compared with the rabbit GD model, the macaque GD model will have significant clinical manifestations similar to those of human GD patients, including significant weight loss and increased resting heart rate. In addition, comparing the data of TT4 and TRAb levels of rabbits and macaques, we can see that the TT4 and TRAb levels of rabbits are significantly higher than those of macaques, which may also be due to biochemical differences caused by different species, among which the data of macaques and humans are closer.
In this study, adenovirus expressing human TSHRA was used in rabbit and macaque models. In fact, at the amino acid level, the homology of human and rabbit experimental instruments TSHRs is about 87%, while the homology of human and rhesus monkeys TSHRs is as high as 97%. Studies have confirmed that the cross-reactivity of antibodies induced by human A subunit immunization is poor when TSHR is detected by flow cytometry in rabbits. From the level of modeling mechanism, GD and its complications, especially hyperthyroidism heart disease, are caused by the downstream reaction initiated by the combination of TSHR receptors distributed in target organs and autoantibodies. We have reason to speculate that the rhesus monkey GD model is more convincing in replicating human GD and its complications.
Instruments used in rabbit experiments
From the application of the model, the rabbit CD model has the advantages of short modeling time, low site requirements and low experimental cost, but it is still not limited to further study the pathogenesis of GD, especially the pathogenesis of complications. The macaque GD model is more similar to human GD patients in terms of pathogenesis, clinical manifestations, complications, and provides a practical and effective way and scheme for the study of GD complications. With the problems of expensive large animals, high feeding costs and difficulty in scale being gradually solved, its research prospects and application prospects will be extremely broad.
To sum up, the incidence of GD in rabbit experimental instrument model is slightly higher than that in macaque model, but after the detection of basic physiological and biochemical indexes and immune related indexes, GD macaque shows more similar manifestations and mechanisms to human GD patients. Therefore, we should choose an appropriate animal model according to the experimental needs and funding arrangements, so as to achieve the expected goal more reasonably.