THE INFLUENCE OF LASER RADIATION ON VEGF EXPRESSION IN THYROID TISSUE IN EXPERIMENTAL HYPOTHYROIDISM

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Introduction. Laser irradiation of thyroid is successfully used to correct hypothyroidism. The functional state of the organ, the production of thyroid hormones, the vascular bed area, blood flow may change depending on the applied laser exposure. The aim was to study the effect of infrared laser irradiation of average intensity on the expression of vascular endothelial growth factor (VEGF) in thyroid gland tissue. Material and methods. The experiment was conducted on 30 male rats, divided into 6 groups: 1) intact animals; 2) animal model of hypothyroidism; 3), 4) five-fold 970 nm laser irradiation of the intact rat thyroid with the total dose density of 112 J/cm2 and 450 J/cm2 ; 5), 6) five-fold 970 nm laser irradiation of the thyroid of rats with hypothyroidism with the total dose density of 112 J/cm2 and 450 J/cm2 Hypothyroidism was modeled with mercazolil at 25 mg/kg for 21 days [1]. The removal from the experiment was carried out 1 day after. Expression of VEGF was determined immunohistochemically using specific antibodies (Biorbyt, USA) and labeling system based on Biotin-streptavidin-peroxidase method. The results were analyzed using ImagеScope computer program, combined with “DMRXA” microscope (“Leica”, Germany). Results and discussion. The expression of VEGF after hypothyroidism simulation increased. We found the presence of the growth factor in endothelial cells, in basal membrane area, in perivascular and interlobular connective tissue. Laser irradiation of thyroid both in intact control and in animals with hypothyroidism model at the dose of 112 J/cm2 and 450 J/cm2 caused the increase of VEGF expression, while the changes were more pronounced in the group of animals with hypothyroidism. According to the literature, the activation of neoangiogenesis requires an increase in the level of growth factors and their receptors in the localization of the future vessel, which in turn contributes to increased vascular permeability, the interaction of proteolytic enzymes and other growth factors, the destruction of contacts between endothelial cells and basal membranes, cell migration [2]. Matrix metalloproteinases and plasma-dependent proteolysis are activated as a result of vascular wall fenestration, so creating preconditions for neoangiogenesis. We explained the increased expression of VEGF after hypothyroidism modeling by activation of compensatory angiogenic mechanisms, increasing the vascular bed area and blood flow to eliminate the deficit of thyroid hormones. We supposed the increase in VEGF expression a day after laser irradiation of thyroid with the total dose density of both 112 J/cm2 and 450 J/cm2 in the intact control group and in animals with hypothyroidism model was associated with laser stimulating effect on VEGF producing cells. Changes at high dose were more pronounced (from 4.44 r.u. to 8.89 and 22.22 r.u. in intact animals; from 8.89 r.u. to and 22.22 and 26.67 r.u. in animals with the hypothyroidism model). Conclusion. The obtained results could be used for further development of laser therapy methods for hypothyroidism in experiment.

About the authors

E S Golovneva

South Ural State Medical University, Chelyabinsk

I V Smelova

Multidisciplinary Center for Laser Medicine, Chelyabinsk

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