Immunohistochemical features of expression and distribution of antibodies to thyroglobulin in the thyroid glands of newborn rats after prenatal exposure of dexamethasone

In clinical practice, synthetic glucocorticoids, such as dexamethasone, are used to accelerate fetal maturation in pregnant women at risk of preterm birth. Increasing the concentration of cortisol in humans and other mammals often causes structural and functional changes in fetal tissues, preparing it for childbirth and extrauterine life, but they can have long-term consequences in the structural organization of organs postnatally. Despite the large number of studies on the effect of glucocorticoids on the fetus, there are almost no data on the prenatal effect of dexamethasone on the processes of synthesis and resorption of thyroglobulin by thyroid thyrocytes in the postnatal period of life. Therefore, the aim of the study was to determine the immunohistochemical features of expression and distribution of antibodies to thyroglobulin in the thyroid glands of newborn rats in normal and after prenatal exposure to dexamethasone. The study material was the thyroid gland of Wistar rats aged 1 to 7 days of postnatal development (54 animals): I group - intact animals (norm); ІІ group - control, animals which were injected with 0.9% NaCl solution at a dose of 0.05 ml to each fetus on the 18th day of dated pregnancy; III group - experimental animals, which were administered a solution of dexamethasone at a dilution of 1:40 at a dose of 0.05 ml to each fetus on the 18th day of the date of pregnancy operatively during laparotomy, by intrauterine, transdermal subcutaneous injection into the interscapular area (Ukrainian patent №112288). Thyroglobulin Antibody (2H11) monoclonal antibodies: sc-51708 from Santa Cruz Biotechnology, Inc. were used for immunohistochemical study. Photo documentation of the studied objects was performed using a “Primo Star” microscope (Carl Zeiss, Germany) using an AxioCam camera using the Zeiss Zen program (2011). Analysis of micropreparations of thyroid glands of intact and control rats showed invariance of thyroglobulin synthesis and its accumulation, which was expressed by sufficient immunohistochemical expression of antibodies to thyroglobulin (ТgAb+). Prenatal administration of dexamethasone leads to intensification of the processes of morphological development of hormone-producing structures (follicles and follicular epithelium), production, resorption and iodination of thyroglobulin. This is evidenced by immunohistochemical studies found in 1-3 days of the neonatal period. It should be noted that on the 7th day of life the newborn was found intense changes in the structure of the parenchyma of the thyroid gland of animals of the experimental group: increased relative percentage of follicle cavity due to increased number of large and medium, some follicles had no resorption vacuoles which was accompanied by a slowdown in the excretion of hormones into the bloodstream and led to overstretching of the follicles and, as a consequence, to the flattening of the thyroid epithelium. Intrauterine administration of dexamethasone leads to prenatal acceleration of structure formation, folliculogenesis and enhancement of hormone-producing function, which is confirmed by the peculiarities of immunohistochemical expression of TgAb. By the end of the neonatal period in rats prenatally exposed to dexamethasone, the thyroid gland is depleted of compensatory-reactive internal reserves, which is morphologically and immunohistochemically manifested by signs of hypofunction and hypertrophy. Thus, detected in the thyroid glands of animals prenatally exposed to dexamethasone, aberration of cytoplasmic expression of ТgAb+, intensification of colloidal expression of ТgAb+, flattening of thyroid epithelium, and the absence of resorption vacuoles are signs of impaired hormone-forming function, which is the morphological basis for the development of hypofunctional states and requires further study.

On the Regulatory Capabilities of Thyroid Mast Cells in Thiamazole Model of Hypothyroidism and Infrared Laser Exposure

The regulatory effect of mast cells on the state of thyroid gland in hypothyroidism and laser therapy remains unclear. Aim: to study the secretory processes of mast cells in relationship with the indicators of functional activity of thyroid gland. Materials and methods. Experimental groups: (55 rats) 1) intact rats, 2) hypothyroidism (thiamazole 25mg/kg) 3) hypothyroidism and 0.5W laser exposure, 4) hypothyroidism and 2.0W laser exposure. Histological samples of the thyroid gland were removed on the 1, 7, and 30 days. Histological sections were stained with toluidine blue. Morphometric data analysis included descriptive statistics and non-parametric tests (Mann Whitney, Spearman correlation coefficient). Results. The increase in the granular saturation of mast cells and the average histochemical coefficient was observed in the hypothyroidism group, the degranulation index increased by day 30. After 0.5 W laser exposure, there was a decrease in the granular content in mast cells and an increase in the degranulation index; the granular saturation increased by day 30. After 2.0 W laser exposure, the content of granules in mast cells decreased on day 1, and on days 7 and 30 it was higher than in the hypothyroidism group; the degranulation index decreased by day 30. The correlation was revealed between the indicators of granule accumulation in a mast cell, the index of mast cell degranulation, the thyroid epithelium height, and relative vascular area. Conclusions. The synthesis processes prevailed over secretion for mastocytes in thiamazole hypothyroidism. 0.5 W laser exposure was more effective for stimulation of the secretory processes in mast cells compared to 2.0 W exposure. The secretory activity of mast cells was associated with the functional activity of thyroid gland, which confirms their regulatory role in tissue repair after thiamazole induced hypothyroidism modeling.

Evidence of oncogene-induced senescence in thyroid carcinogenesis

Oncogene-induced senescence (OIS) is a growth arrest triggered by the enforced expression of cancer-promoting genes and acts as a barrier against malignant transformation in vivo. In this study, by a combination of in vitro and in vivo approaches, we investigate the role of OIS in tumours originating from the thyroid epithelium. We found that expression of different thyroid tumour-associated oncogenes in primary human thyrocytes triggers senescence, as demonstrated by the presence of OIS hallmarks: changes in cell morphology, accumulation of SA-β-Gal and senescence-associated heterochromatic foci, and upregulation of transcription of the cyclin-dependent kinase inhibitors p16INK4a and p21CIP1. Furthermore, immunohistochemical analysis of a panel of thyroid tumours characterised by different aggressiveness showed that the expression of OIS markers such as p16INK4a, p21CIP1 and IGFBP7 is upregulated at early stages, and lost during thyroid tumour progression. Taken together, our results suggest a role of OIS in thyroid carcinogenesis.

Expression of Galectin-1 and Galectin-3 in Human Fetal Thyroid Gland

High levels of expression of galectin-1 and galectin-3, the β-galactoside-binding proteins, have been recently described in malignant thyroid tumors but not in adenomas nor in normal thyroid tissue. However, there are no data about the expression of these galectins during fetal thyroid development. In this study we analyzed immunohistochemically the presence of galectin-1 and galectin-3 in human fetal thyroid glands (16–37 weeks of gestation). Weak to moderate cytoplasmic staining for galectin-1 was observed in follicular cells of all fetal thyroids. Galectin-3 could not be detected in thyroid follicular cells of any fetal thyroid investigated. Both galectins were detected in stromal tissue, but staining for galectin-1 was more intense. The absence of galectin-3 in thyroid cells during fetal development suggests that galectin-3 is expressed de novo during malignant transformation of thyroid epithelium, and that galectin-1 could be considered an oncofetal antigen. The results obtained indicated potential roles for galectin-1 and galectin-3 during the investigated period of human fetal thyroid gland development. Both galectins might participate in developmental processes regarding stromal fetal thyroid tissue organization, whereas galectin-1 might have a function in thyroid epithelium maturation.

Galectin-3: A promising marker of thyroid malignancy

Background: Galectin-3 is an endogenous beta-galactoside binding lectin implicated in neoplastic transformation and tumor progression. High levels of this lectin have recently been found in malignant thyroid tumors, but not in normal or benign thyroid tissue, suggesting galectin-3 as a promising presurgical marker of thyroid malignancy. Methods: We analyzed immunohistochemically galectin-3 expression in thyroid tissue using a monoclonal antibody. The total of 108 tissue specimens included 55 cases of thyroid carcinoma (30 papillary, 15 follicular, and 10 anaplastic type), 15 samples of follicular adenoma, 15 samples of normal thyroid tissue, and 23 thyroid tissue specimens from human fetuses (16 to 37 weeks of intrauterine life). Results: The results showed galectin-3 expression in 20/30 papillary carcinomas, 11/15 follicular carcinomas, 10/10 anaplastic carcinomas, and 4/15 follicular adenomas. Thyroid follicular cells in normal adult and fetal tissue were negative. Conclusions: These results further confirm that galectin-3 expression is a feature of malignant thyroid cells, and that immunohistochemical detection of galectin-3 could be useful in thyroid carcinoma diagnostics. The absence of galectin-3 in thyroid cells during fetal development suggests that galectin-3 is expressed de novo during malignant transformation of thyroid epithelium, thus it should not be considered an oncofetal antigen.