Pathomorphological and immunohistochemical characteristics of liver tissue in dynamics in experimental modeling of primary hypothyroidism

An experimental model of primary postoperative hypothyroidism was obtained on 92 white Wistar male rats. The duration of the experiment was 60 days. Animals were withdrawn from the experiment on the 7th, 14th, 21st, 28th, 35th, 45th and 60th days. The control group consisted of 23 rats. For histological examination, pieces of the liver were taken, followed by their fixation in 10% buffered neutral formalin. Micropreparations were prepared according to recognized standards. Histological sections were stained with hematoxylin-eosin, toluidine blue, picrofuchsin according to Van Gieson, Sudan-3. The immunohistochemical study was based on the peroxidase-antiperoxidase method using the apoptosis marker caspase-3 and the anti-apoptotic marker Bcl-2, as well as the marker of proliferative cell activity Ki67. Histologically, in the liver with postoperative hypothyroidism, there is venous hyperemia, stasis phenomena, followed by erythrocyte slugging, and diffuse edema. Hepatic cells are characterized by a pattern of predominant hydropic, balloon degeneration, as well as small droplet fatty degeneration. Characterized by foci of cytolysis, foci of coliquational necrosis of hepatocytes. There are signs of minimally active steatohepatitis. Foci of regeneration are found everywhere, the number of hepatocytes with hyperchromic enlarged nuclei increases. Reparative processes are noted. By the end of the experiment, areas of fibroblast proliferation appear, the first signs of the formation of connective tissue septa, stained bright red with picrofuchsin according to Van Gieson. The immunohistochemical method revealed an increase in the positive expression of caspase-3 on the 21-28th day of the experiment and a decrease in the expression of Bcl-2 starting from the 21st day, an increase in the index of proliferative activity according to the expression of Ki67 on the 28th day, with the beginning of its decrease by the end of the 45th day of the experiment.