MORPHOLOGICAL CHANGES OF THE THYMUS DURING THE HEALING OF BURN WOUNDS

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Currently, an urgent problem in the functional morphology of the thymus remains to find out which shifts in the structure of this organ are the morphological substrate of its pathology, which develops when exposed to various extreme factors on a living organism (Babaeizadeh S., Heydarnezhad S., 2016; Li L, Shang L., Gao J., Liu C., 2020). Detection of micro- and ultrastructural damage in the thymus at various periods after exposure to factors such as, for example, hyperthermia, ionizing and ultraviolet radiation, stress, etc., is necessary to understand the fundamental foundations of changes occurring in the organ under their influence, and to develop ways to correct them.Despite the apparent study of this issue, it should be noted that the specific structure that would play a leading role in the restructuring processes of the body in question in extreme conditions for it has not yet been definitively established. The significance of such data for modern clinical medicine is difficult to overestimate, because the thymus is a kind of "heart" for a number of human organ systems – immune, nervous and endocrine.The purpose of the study is to study the morphometric features of the thymus during regeneration processes with various protocols for the management of burn wounds. To perform the experiment , the following tasks are set:To identify quantitative changes in the proportion of the area of the cortical and medulla of the thymus in the dynamics of post–burn regeneration and to establish a correlation between changes in the number of mast cells - degranulating and without degranulation – To evaluate the quantitative value of mast cells in the process of wound healing after burn injury, the experiment was performed on 36 white male rats of the Wistar line weighing 165-210 g at the Research Institute of Experimental Biology and Medicine of the Voronezh State Medical University named after N.N. Burdenko. The animals were divided into 3 groups:Group 1 (n=12) - control (6 sexually mature and 6 immature individuals)Group 2 (n=12) - spontaneous healing (6 mature and 6 immature individuals)Group 3 (n=12) - with the use of ointment (6 mature and 6 immature individuals) containing silver sulfadiazine as the active substance.Sample preparation of histological material was carried out, and paraffin blocks were made. Sections of the thymus with a thickness of 4 microns were also made for staining with hematoxylin and eosin and Giemsa solution and subsequent microscopy. The morphometric stage of the study included:counting of mast cells in 25 visual fields with division into functional types (with and without signs of degranulation)area of cortical and medulla – 10 fields of view, the results are presented in % relative to the total area.As a result of the conducted research on the basis of the data obtained , the following patterns were deduced:In all experimental groups, there was an increase in the number of mast cells over time by the 14th day of withdrawal from the experiment compared with the control group, moreover, the percentage of degranulated mast cells also increased in relation to their total number; In all the studied individuals, a quantitative change in the proportion of morphofunctional zones of the thymus was observed by the 14th day of withdrawal from the experiment compared with the control group – the area of the medulla gradually increased and the area of the cortical substance decreased, which is characteristic of accidental thymus involution.Based on the results obtained, it can be assumed that a significant increase in the number of degranulated mast cells contributed to the release and accumulation in the organ of a large number of various BAS (histamine, serotonin, cytokines, etc.). Since many of these biogenic amines have an inhibitory effect on the proliferation and differentiation of T-lymphocytes in the cortical substance, especially in the subcapsular zone (for example, histamine), this served as the basis for further conclusion that the mass cell death of T-lymphocytes, characteristic of accidental involution, occurs precisely as a result of excessive accumulation of data substances. The development of cellular apoptosis leads to hypoplasia, which is well expressed in the cortical substance – there is a significant decrease in its area; the area of the medulla may presumably increase due to increased migration of T-lymphocytes into the subcapsular zone.

About the authors

Maria Yuirevna Soboleva

Email: soboleva.doc1@yandex.ru
ORCID iD: 0000-0001-7508-9327
Russian Federation, 10, Studencheskaya str., Voronezh, 394036, Russia

Natalia Timofeevna Alexeeva

Email: alexeevant@list.ru
ORCID iD: 0000-0003-1510-8543
Russian Federation, 10, Studencheskaya str., Voronezh, 394036, Russia

Daria Romanovna Krivoruchko

Email: darkism@yandex.ru
ORCID iD: 0009-0007-5227-8847
Russian Federation, 10, Studencheskaya str., Voronezh, 394036, Russia

Olga Alexandrovna Kuznetsova

Author for correspondence.
Email: olpheya2004@yandex.ru
ORCID iD: 0009-0004-8880-5627
Russian Federation, 10, Studencheskaya str., Voronezh, 394036, Russia

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