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Thyroid-associated ophthalmopathy (TAO) is a kind of clinically common and incurable ocular disease, and its incidence is at top place.The etiology and pathologic mechanism of TAO are still unknown because of shortness of replicative animal models and difficulty to acquire the ocular tissues in the early stage of the disease.To better understand the pathogenesis of TAO and investigate effective treatable measures, an appropriate animal model should be developed.
This study was to immunize female BALB/c mice with the recombinant plasmid of human thyroid-stimulating hormone receptor (TSHR) extracellular domain in cationic liposomes for the establishement of TAO models.
Thirty-two 6- to 8-week-old female BALB/c mice were randomly assigned to four groups according to computer random allocation.pcDNA3.1+ /hTSHR289 of 100 μg in an adjuvant cationic liposomes was injected via anterior tibialis muscle and peritoneal cavity separately in the recombinant plasmid injection group in 0, 3, 6 weeks, and pcDNA3.1 or cationic liposomes was injected in the liposomes injection group or the blank plasmid group in the same way, respectively, and normal saline solution was injected in the blank control group.Body weight of the mice was measued before and 1 month, 2, 3 and 4 months after initial injection.The manifestations were observed after modeling.The mice were sacrificed 17 weeks after initial injection, and the histopathology examination was carried out on the thyroid gland and orbital tissue.The heart blood was collected from the mice, and serum contents of total thyroxin 4 (TT4) and thyroid-stimulating hormone (TSH) were assayed by ELISA.
Protrusion, eyelid swell and keratitis occurred in 12 eyes of 6 mice in the recombinant plasmid injection group after immunization.A significant difference in the body weight of the mice was found among the blank control group, blank plasmid group, liposomes injection group and recombinant plasmid injection group (Fgroup=3.425, P=0.028), and the body weight was considerably reduced in the recombinant plasmid injection group in comparison with the blank control group, blank plasmid group, liposomes injection group (Ftime=0.838, P=0.023). The serum levels of TT4 were (7.75±1.00), (7.96±0.76), (6.76±1.10) and (4.43±2.88)μg/dl in the blank control group, liposomes injection group, blank plasmid group, and recombinant plasmid injection group, and those of TSH were (6.36±2.58), (4.83±3.96), (6.63±1.71) and (1.60±1.76)ng/ml, showing significant differences among the groups (F=7.150, P<0.001; F=5.521, P<0.01), and the serum levels of TT4 and TSH were remarkably lower in the recombinant plasmid injection group than those of the blank control group, liposomes injection group and blank plasmid group (all at P<0.05). Histopathology revealed the lymphocyte infiltration of thyroid gland in 6 mice and proliferation of orbital adipose tissue, infiltration of lymphocytes and mastocytes, deposition of hyaluronic acid as well as swell, breakage and inflammatory cell infiltration of extraocular muscle in 15 eyes of the recombinant plasmid injection group.
A murine model of TAO can be successfully induced by immunization with recombination plasmid pcDNA3.1+ /hTSHR289 and cationic liposomes.The histopathology characteristics and ocular findings of the animal models are similar to human TAO.