Ohki Saitoh

T helper type 17 immune response plays an indispensable role for development of iodine-induced autoimmune thyroiditis in nonobese diabetic-H2h4 mice.

T helper type 1(Th1)/Th2 paradigm has been expanded by discovery of a novel effector T cell (T(eff)) subset, Th17 cells, which produce a proinflammatory cytokine IL-17. Th17 cells have recently been shown to play a major role in numerous autoimmune diseases that had previously been thought to be Th1-dominant diseases. We here studied the significance of Th17 cells in iodine-induced autoimmune thyroiditis in nonobese diabetic-H2(h4) mice, a mouse model of Hashimotos thyroiditis in humans, which spontaneously develop antithyroglobulin autoantibodies and intrathyroidal lymphocyte infiltration when supplied with iodine in the drinking water. We observed increased numbers of Th1 and Th17 cells in spleen and accumulation of both types of T(eff) in the thyroid glands of iodine-fed wild-type mice, indicating that Th17 cells as well as Th1 cells constitute thyroid lesions. Furthermore, the incidence and severity of intrathyroidal lymphocyte infiltration, and the titers of antithyroglobulin autoantibodies were markedly reduced in iodine-treated IL-17(-/-) mice as compared with wild-type mice. Of interest, IL-17(+/-) mice showed an intermediate phenotype. Therefore, the present study, together with a previous report demonstrating the importance of Th1, not Th2, immune response for developing thyroiditis using mice deficient for interferon-gamma or IL-4, clearly indicates that both Th1 and Th17 cells are critical T(eff) subsets for the pathogenesis of spontaneous autoimmune thyroiditis in nonobese diabetic-H2(h4) mice.

Expression of Immunoregulatory Molecules by Thyrocytes Protects Nonobese Diabetic-H2h4 Mice from Developing Autoimmune Thyroiditis

One approach to prevent tissue destruction by autoimmune attack in organ-specific autoimmune diseases is to protect the target tissue from autoimmune reaction, regardless of its persistent activity. To provide proof-of-principle for the feasibility of this approach, the immunoregulatory molecules, TNF-related apoptosis-inducing ligand (TRAIL) and indoleamine 2, 3-dioxygenase, were expressed in the thyroid glands using adenovirus vector in nonobese diabetic-H2(h4) mice that spontaneously develop thyroiditis. Mice were anesthetized, and the thyroid glands were exposed by neck dissection, followed by in situ infection with adenovirus vector (5 x 10(10) particles per mouse) twice or thrice, starting 1 d or 4 wk before mice were supplied with sodium iodine (NaI) water. After 8 wk NaI provision, the extent of thyroiditis, serum titers of antithyroglobulin antibodies, and cytokine expression in the spleen were examined. In situ infection of adenovirus expressing TRAIL or indoleamine 2, 3-dioxygenase, but not green fluorescent protein, significantly suppressed thyroiditis scores. However, antithyroglobulin antibody titers and expression levels of cytokines (interferon-gamma and IL-4) in the spleen remained unaltered. Importantly, adenovirus infection 4 wk after NaI provision was also effective at suppressing thyroiditis. The suppressive effect of TRAIL appears to be mediated at least partly by accumulation of CD4(+)Foxp3(+) regulatory T cells into the thyroid glands. Thus, localized expression of immunoregulatory molecules efficiently protected the thyroid glands from autoimmune attack without changing the systemic autoimmunity in nonobese diabetic-H2(h4) mice. This kind of immunological intervention, although it does not suppress autoimmune reactivity, may have a potential for treating organ-specific autoimmune diseases.

Fibroblast-Mediated In Vivo and In Vitro Growth Promotion of Tumorigenic Rat Thyroid Carcinoma Cells but Not Normal Fisher Rat Thyroid Follicular Cells

BACKGROUND It is known that genetic abnormalities in oncogenes and/or tumor suppressor genes promote carcinogenesis. Numerous recent articles, however, have demonstrated that epithelial-stromal interaction also plays a critical role for initiation and progression of carcinoma cells. Furthermore, ionizing radiation induces alterations in the tissue microenvironments that promote carcinogenesis. There is little or no information on epithelial-stromal interaction in thyroid carcinoma cells. The objective of this study was to determine if epithelial-stromal interaction influenced the growth of thyroid carcinoma cells in vivo and in vitro and to determine if radiation had added or interacting effects. METHODS Normal Fisher rat thyroid follicular cells (FRTL5 cells) and tumorigenic rat thyroid carcinoma cells (FRTL-Tc cells) derived from FRTL5 cells were employed. The cells were injected into thyroids or subcutaneously into left flanks of rats alone or in combination with skin-derived fibroblasts. In groups of rats, fibroblasts were irradiated with 0.1 or 4 Gy x-ray 3 days before inoculation. In vitro growth of FRTL-Tc and FRTL-5 cells were evaluated using the fibroblast-conditioned medium and in a co-culture system with fibroblasts. RESULTS The in vivo experiments demonstrated that FRTL-Tc cells injected intrathyroidally grew faster than those injected subcutaneously, and that admixed fibroblasts enhanced growth of subcutaneous FRTL-Tc tumors, indicating that the intrathyroidal milieu, particularly in the presence of fibroblasts, confer growth-promoting advantage to thyroid carcinoma cells. This in vivo growth-promoting effect of fibroblasts on FRTL-Tc cells was duplicated in the in vitro experiments using the fibroblast-conditioned medium. Thus, our data demonstrate that this effect is mediated by soluble factor(s), is reversible, and is comparable to that of 10% fetal bovine serum. However, normal FRTL5 cells did not respond to the fibroblast-conditioned medium. Furthermore, high- and low-dose irradiation enhanced and suppressed, respectively, the in vivo fibroblast-mediated growth promotion. This effect was, however, not observed in the in vitro experiment with conditioned medium or even that allowing cell-cell contact. CONCLUSIONS The intrathyroidal stromal microenvironments, particularly fibroblasts, appear to enhance the growth of thyroid carcinomas through soluble factor(s), which is modulated differently by high- and low-dose irradiation. To our knowledge this is the first study to show epithelial-stromal interaction in thyroid carcinoma.