| Objective:As we all know in addition to pituitary, immune system can produce TSH. Scientists recently found a set of resident intrathyroidal bone marrow-derived hematopoietic cells which can express a novel TSHP splice variant. The TSHP splice variant gene was expressed in the pituitary, bone marrow and the thyroid. Spleen is an important immune organ which expresses TSHβ, we need to confirm it is native TSHP or TSHβsplice variant. We detected the expression of TSHP splice variant in different organs on autoimmune thyroiditis induced by iodine excess and thyroglobulin in NOD mice, to explore the function of TSHP splice variant in infection-or inflammatory-related thyroid disorders.Methods:Twenty Non-obese diabetic mice,7-8 weeks old, female, were randomly divided randomly into four groups:control group (C):drank deionized water; iodine excess group (HI):drank 0.05% NaI water; TG group (TG):drank deionized water, immunized with 0.1mg TG to each mouse by subcutaneously injection at 8 weeks old and enhanced at 11 and 15 weeks old; iodine excess+TG group (HI+TG):drank 0.05% NaI water, TG immunization was the same as TG group. Then collected blood samples, RIA and ELISA were used respectively to detect T4 and TSH level in serum.For observing distribution of TSHP positive cells, TSHβimmunofluorescence staining was used on pituitary, and spleen. The expression of TSHP splice variant mRNA were detected by real time PCR in different organs and the amplified gene of spleen was sequenced. SYBR Green real-time PCR was used to detect the levels of TSHP splice variant genes in different organs.Results:TG group had a higher level of T4 and TSH compared to C group. The level of T4 and TSH in C group were separately (36.43±3.87) nmol/L and (5.55±0.28) ng/mL, while the level of T4 and TSH in TG group were(69.70±16.45)nmol/L(P<0.05) and (8.44±0.71)ng/mL (P<0.01).The level of T4 in HI group and HI+TG group had no significant different compared to C group. But HI group and HI+TG group had higher level of TSH than C group, were (6.98±0.27)ng/mL (P<0.05) and (9.12±0.36)ng/mL(P<0.01) separately.In spleen, majority of TSHβ+ cells were localized in the marginal zones, few of which localized in germinal center. In pituitary, there were large number of TSHβ+ cells.RT-PCR showed that TSHP splice variant was not only expressed in the pituitary, bone marrow and thyroid but also in the spleen. Native TSHP was only expressed in pituitary. In TG group, expression of TSHP splice variant in bone marrow (0.026±0.010) (P<0.05) increased compared to C group (0.014±0.007), while pituitary and thyroid had no higher expression of TSHβsplice variant than C group. Native TSHβin pituitary had no significant different either. In HI group, expression of TSHP splice variant in bone marrow did not changed significantly, but expression of TSHP splice variant in pituitary(0.038±0.010)(P<0.01) and thyroid(0.036±0.007)(P<0.05) were higher than C group(0.017±0.003). Native TSHP in pituitary was higher (0.013±0.003) (P<0.01). In HI+TG group only the expression of native TSHP in pituitary increased (0.015±0.004) (P<0.01). TSHp splice variant expression in spleen had no significant result.Conclusions:Spleen as an important immune organ in NOD mice can express TSHP splice variant. Increased level of TSH in TG group had something to do with the expression of bone marrow TSHP splice variant. Its production and secretion may not be subject to the negative feedback regulation of circulating T4. In TG group, pituitary expression of native TSHβmRNA meet the HPT axis feedback theory, but the regulation of expression of TSHβsplice variant in pituitary needs further research. Expression of TSHP splice variant of thyroid in HI group and TG group was different, suggesting that excess iodine-induced EAT is a cellular immune-based inflammation, the inflammatory response and tissue damage are more serious than the TG immunity, leading to more bone marrow cells that express TSHP splice variant migrate to the thyroid.
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