Expression of thyroid stimulating hormone β splice variant in thyroid of mouse with autoimmune thyroiditis

Abstract

Objective To investigate the expression of marrow-derived thyroid stimulating hormone β（TSHβ） splice variant in thyroid of mouse with autoimmune thyroiditis induced by thyroglobulin （Tg） immunization, and to analyze whether TSHβ splice variant participated in the pathological process of autoimmune thyroiditis. Methods Using random number table, forty-eight mice（24 females and 24 males） Of 7 to 8 weeks old with body mass 20 to 25 g were randomly divided into 4 groups（12 females and 12 males in each group） based on body weight and gender. The control group： fed with deionized water; the Tg-treated group（TG） ： fed with deionized water, and immunized subcutaneously with 0.1 mg Tg at 8 weeks old, boost immunized twice at 11 and 15 weeks old, respectively; the high iodine-treated group （HI）： fed with deionized water containing 0.05% sodium iodide （NaI）;the Tg combined with HI group （TG ＋ HI ： fed with deionized water containing 0.05% NaI, and immunized the same way as the TG group did. Peripheral blood was collected after 8 weeks treatment, which was used for determination of total tetraiodothyronine （TT4）, free tetraiothyronine（FT4）, total triiodothyronine （TT3） and free triiodothyronine （FT3） with chemiluminescence immunoassay （CIA）; thyroid glands were collected to examine the expression of TSHβ splice variant with SYBR Green fluorescent quantitative real-time PCR, and frozen sections were HE stained for observation of histopathological changes of thyroid cells under light microscopy. Results Under naked eyes, the thyroid gland enlarged significantly, and looked dark red in HI and TG ＋ HIgroups. Under an optical microscope, thyroid follicular epithelial cells presented cuboidal, with abundant cytoplasm, presented abundant glial in follicular cavity, without lymphocyte infiltration in the control group; in TG group, the thyroid follicular epithelial cells presented cuboidal, with some single scattered lymphoeytes; in HI group, colloid volume expansion appeared in thyroid follicles, thyroid follicular epithelial cells presented low Cuboidal or flat, with few single scattered lymphocytes; in TG ＋ HI group, most colloid accumulative large follicles presented in thyroid, thyroid follicular epithelial cells presented flat, some destructive thyroid follicular structure and infiltrating lymphocytes appeared. The differences of FT3 TT4, FT4 and TSHβ splice variant between groups were statistically signitlcant（F = 4.00, 12.54, 31.92, 214.29, all P 〈 0.05）. Compared to the control group, the serum TT3（nmol/L： 0,92 ± 0.07 vs. 1.30 ± 0.33, t = - 2.24）, TT4（nmol/L： 1.30 ± 0.33 vs. 95.60 ±14.10, t = - 3.02）, FT4（pmol/L： 54.07± 3.67 vs. 154.80 ± 0.01, t = - 54.87） and the thyroids＇ TSHβ（ × 10-3. 4.11 ± 0.32 vs. 8.38 ± 0.22, t = - 19.11） were higher in TG group（all P 〈 0.05） ; the serum TT4（nmol/L： 67.75± 11.91 vs. 45.50 ± 3.85, t = 3.55, P 〈 0.05） was lower in HI group; the serum FT4（pmol/L： 54.07 ± 3.67 vs. 139.46 ±30.00, t = - 5.65） and the thyroids＇ TSHβ splice variant（ ×10-3：4.11 ± 0.32 vs. 5.33± 1.47, t =- 5.95） were higher in TG ＋ HIgroup （all P 〈 0.05）. Conclusions High iodine has aggravated thyroiditis of BALB/c mice induced by Tg immunization; the level of thyroid TSHβ in mice with autoimmune thyroiditis is higher; all of these results indicated that TSHβ is involved in the pathogenesis of autoimmune thyroiditis. Key words: Mouse ; Thyroglobulin; High iodine; Autoimmune thyroiditis; Thyroid-stimulating hormone β splice variant; Gene expression