Ultrastructure of adrenal glands endocrinocytes after thermal skin injury under conditions of correction with cryo-lyophilized xenograft skin substrate

According to WHO studies, burn injuries are one of the most common injuries in the world, and their number has increased significantly due to the military actions in Ukraine. The adrenal glands, which regulates metabolism and participates in the body's defense reactions, is sensitive to burn injuries, which leads to morphological changes in the organ. The aim of the study was to investigate the ultrastructural changes in endocrinocytes of the adrenal glands after experimental thermal skin injury under conditions of correction with cryo-lyophilized xenograft skin substrate. A second-degree burn was modeled by applying heated copper plates to the skin of the back of laboratory male rats, which accounted for 18-20 % of the body surface. For electron microscopic analysis on days 7th, 14th, and 21st of the experiment, pieces of the adrenal glands were taken. They were fixed in a glutaraldehyde solution, post-fixed in osmium tetraoxide, and processed according to standard procedures. Ultrathin sections were contrasted with uranyl acetate and lead citrate, and submicroscopic changes were studied using a PEM-125K electron microscope. On the 7th day after the burn with correction (using a cryo-lyophilized xenograft skin substrate), moderate changes in the ultrastructure of the nuclei and organelles of the endocrinocytes were found. Mitochondrial hyperplasia, changes in the shape of the nuclei and the presence of small clumps of heterochromatin in the karyoplasm were observed. On the 14th day, under the conditions of correction, there were signs of restoration of the cell ultrastructure, in particular, the structure of the nucleus and the membrane of the zona glomerulosa cells was restored, ribosomes and hypertrophied mitochondria with an electronically bright matrix appeared, as well as numerous lipid droplets. After 21 days, the ultrastructure of the cells of the zona glomerulosa was restored, and lipid droplets were evenly distributed in the cytoplasm. In the zona reticularis and adrenal medulla, changes in the submicroscopic organization of endocrinocytes were insignificant. We observed a uniform distribution of secretory granules in the cytoplasm of chromaffinocytes, mitochondrial recovery and unchanged ultrastructural organization of the organelles of the synthetic apparatus. Thus, the results of the study confirmed that the cryo-lyophilized xenograft skin substrate effectively promotes the restoration of the ultrastructure of adrenal endocrinocytes, reducing the degree of damage to cytoplasmic membranes, organelles of the synthetic apparatus of cells, endocrinocyte nuclei, especially activating the regeneration processes in the late stages after thermal skin injury.