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УДК 542.934:612.42:612.428:612.67
Бекенева К.А.
Студент 5 курса НГУ, г. Новосибирск, РФ Быстрова В.И.
Студент 5 курса НГУ, г. Новосибирск, РФ Веременко А.С.
Студент 4 курса НГУ, г. Новосибирск, РФ Николайчук К.М.
Студент 5 курса НГУ, г. Новосибирск, РФ Левченко И.Д.
Студент 4 курса НГУ, г. Новосибирск, РФ Кузнецова В.А.
Студент 5 курса НГУ, г. Новосибирск, РФ Научный руководитель: Горчаков В.Н., д.м.н, проф., НГУ, НИИКЭЛ - филиал ИЦиГ СО РАН
г. Новосибирск, РФ
СТРУКТУРНО-ФУНКЦИОНАЛЬНАЯ ОРГАНИЗАЦИЯ РАЗНЫХ ЛИМФАТИЧЕСКИХ РЕГИОНОВ В ПОЖИЛОМ ВОЗРАСТЕ
Аннотация
Основной задачей данной работы было изучить морфологические характеристики лимфатических узлов, подвергшихся старческим преобразованиям и расположенными в разных анатомо-топографических регионах. Исследование выполнено при помощи анализа полученных гистологических срезов лимфоузлов на световом микроскопе. Возрастные различия морфологических характеристик связаны с функцией дренируемых органов лимфоузлами разной анатомо-топографической локализации. Регионарные лимфатические узлы в процессе старения приобретают специфические изменения в морфологии. Так лимфоузлы брыжеечного региона отличаются наименьшей величиной индекса К\М, площадью межъузелковой части коры, Т-зоны, минимальным соотношением В- и Т-зон и большой площадью мозгового вещества. Лимфоузлы, принадлежащие трахеобронхиальному лимфатическому региону, отличаются высоким значением индекса К\М, большой Т-зоной и низким значением соотношения лимфоидных узелков с герминативным центром и без него. Паховые лимфоузлы после старения разросшеюся паракортикальную область большой площади, увеличенные лимфатические синусы, при этом соотношения лимфоидных узелков с герминативным центром и без него также увеличивается. Старческие преобразования приводят к изменению размера функциональных зон лимфоузлов, что отражается в структурно-функциональной специфике лимфатических узлов разной анатомо-топографической локализации.
Ключевые слова
Лимфатический регион, лимфоузлы, геронтология.
Bekeneva K.A.
5th-year student of NSU Novosibirsk, Russia Bystrova V.I.
5th-year student of NSU Novosibirsk, Russia Veremenko A.S.
4th-year student of NSU Novosibirsk, Russia Nikolaychuk K.M.
5th-year student of NSU Novosibirsk, Russia Levchenko I.D.
4th-year student of NSU Novosibirsk, Russia Kuznetsova V.A.
5th-year student of NSU Novosibirsk, Russia Scientific supervisor: Gorchakov V.N., MD, Prof., NSU, RICEL - Branch of IC&G SB RAS
Novosibirsk, Russia
STRUCTURAL AND FUNCTIONAL ORGANIZATION OF DIFFERENT LYMPHATIC REGIONS IN OLD AGE
Annotation
The main objective of this work was to study the morphological characteristics of lymph nodes that have undergone senile transformations and are located in different anatomical and topographic regions. The study was performed by analyzing the obtained histological sections of lymph nodes on a light microscope. Age-related differences in morphological characteristics are associated with the function of drained organs by lymph nodes of different anatomical and topographic localization. Regional lymph nodes in the process of aging acquire specific changes in morphology. Thus, the lymph nodes of the mesenteric region are distinguished by the smallest value of the K \ M index, the area of the interstitial part of the cortex, the T-zone, the minimum ratio of B- and T-zones and a large area of the medulla. The lymph nodes belonging to the tracheobronchial lymphatic region are distinguished by a high value of the K\M index, a large T-zone and a low value of the ratio of lymphoid nodules with and without a germinal center. Inguinal lymph nodes after aging.
Keywords
Lymphatic region, lymph nodes, gerontology
Introduction
The problem of aging and the issue of health and quality of life of elderly people remains relevant today because of the morphological changes characteristic of them from different organs and systems of the body, including the lymphatic system [1, 2, 3]. This actualizes the need to study the morphology of the lymphatic (lymphoid) system as a life support system in different periods of life, associated with the need to increase nonspecific resistance.
An important role belongs to peripheral lymphoid organs - regional lymph nodes, which belong to the
protective barrier of the body and are responsible for the formation of an immune response to the external environment [1, 4]. Lymph Nodes occupy a special place in the lymphatic system, simultaneously carrying out drainage and immune function, and they are indicators of the state of the internal environment [5, 6, 7]. At the same time, the prognostic significance of assessing the state of the structural organization of regional lymph nodes in their relationship with drained organs remains one of the important directions in morphological studies of aging. It is important to take into account the belonging of lymph nodes to the somatic or visceral group, taking into account age [8] and to determine the territorial specifics of their changes in accordance with the concept of the lymphatic region [1]. This is important in prognostic terms for the characterization of adaptive reserves and the possibilities of age-related modification of peripheral lymphoid organs.
The latter consist in changing the size of lymph nodes, replacing lymphoid tissue with connective or fatty tissue, thickening the capsule and trabeculae, coarsening the reticular tissue, expanding the medulla and reducing the number of lymphoid nodules with a germinal center. Additionally, the lymphatic channel changes due to changes in the size of the lymphatic sinuses. In this regard, there is a problem of aging and maintaining the quality of life of the organism at the later stages of ontogenesis. This makes it relevant to study age-induced changes in the morphology of the lymphatic system as a life support system associated with endoecological safety and increased nonspecific resistance [9, 10].
Materials and methods
The work was performed on 45 white male Wistar rats aged 1-2 years. The selected age of the animals correlates with the senile period of human life (75 years), which is calculated using a coefficient of 1.7 [11]. All animals in the study had free access to water and received a standard diet. The object of the study was the inguinal, mesenteric, tracheobronchial lymph nodes. The choice of these lymph nodes is based on the principles of ecological lymphology [1]. The research work included the following methods.
The histological method was used to assess the dimension of lymph node compartments. The method is based on the production of histological preparations with their subsequent study by light microscopy (using microscopes Leica DM 750, Micmed-2 with a scanning prefix ScanMicro, combined with a computer) in accordance with the existing requirements for histological examination. The extracted lymph nodes were fixed in 10% neutral formalin for subsequent execution of the classical wiring scheme and pouring the material into paraffin. The final stages were the preparation of paraffin sections and their staining with histological dyes (hematoxylin and eosin, azur and eosin, trichromic dye according to C. Masson).
Statistical processing of the obtained results is carried out using Excel and StatPlus Pro, AnalystSoft Inc. The arithmetic mean is calculated with the determination of its standard (RMS) error. The Student's t-test was applied to assess the level of statistical significance of differences (p < 0.05) under the condition of a normal distribution or close to it.
The animal experiment was conducted in accordance with the principles of bioethics, the rules of laboratory practice (GLP, European Communities Council Directives of 24 November 1986, 86/609/EEC), set out at the Geneva Conference (1971), as well as in the documents "On the approval of the rules of laboratory practice", "On the humane treatment of experimental animals" (Ministry of Health USSR No. 775 of 12.08.1977), "International recommendations for conducting biomedical research using animals" (1985), guidelines for laboratory animals [12] and in accordance with the Order of the Ministry of Health of the Russian Federation No. 267 of 19.06.2003. Withdrawal from experience and painful manipulations on animals were performed under general ether anesthesia. The study was approved by the Ethics Committee of the Federal State Budgetary Institution "Scientific Research Institute of Clinical and Experimental Lymphology" (Protocol No. 126 of 11/30/2016).
Results and discussion
Lymph nodes, depending on belonging to a certain lymphatic region, have characteristic features and differences in structural and functional characteristics. In the process of aging, the lymph nodes of various topographic areas undergo a reorganization of the structure. The design features of visceral and somatic lymph nodes are determined by differently directed changes in the area of structural and functional zones. Due to this, lymph nodes determine the nature of lymphodynamics, the state of the extracellular matrix and the immune properties of the internal environment in their lymphatic region belonging to different organs [4, 13]. A common pattern is the involution of lymphoid tissue, an increase in connective tissue, a decrease in the area of secondary lymphoid nodules in comparison with young animals.
In the structure of the lymph nodes of old animals, the proportion of connective tissue increases sharply, which is manifested by the thickening of the capsule and trabeculae of all groups of lymph nodes in varying degrees of severity. This is confirmed in other works [5, 6, 7]. A progressive series of changes in the area of the capsule of lymph nodes can be made as follows: inguinal (6.91 ± 0.38%), mesenteric (14.93 ± 0.14%), tracheobronchial (17.14 ± 0.30%). It is significant that the capsule in the visceral lymph nodes increases 2.2-2.4 times more than in the somatic lymph nodes.
Standardization of the area of lymph nodes revealed that the cortical substance occupies a certain proportion of the area, increasing sequentially in a row: mesenteric (58.88%), inguinal (64.24%) and tracheobronchial (74.08%) lymph nodes. The area of the medulla has the opposite tendency to the cortical, so the medulla in the tracheobronchial lymph node accounts for 25.9%, in the inguinal - 34.1%, and in the mesenteric - 40.96%.
At the same time, regardless of the topographic area where the lymph nodes are located, the latter are formed by cortical and cerebral substances. The ratio of cortical and medulla is determined by the K/M index, which has a different value for mesenteric (1.44 ± 0.03), inguinal (1.88 ± 0.06), tracheobronchial (2.86 ± 0.06) lymph nodes. The K/M index indicates a different degree of dominance of the cortical substance in lymph nodes of different localization, depending on the lymphatic region.
The cortical substance includes the interstitial part of the cortex, the paracortical region and lymphoid nodules, and the cerebral substance includes the cerebral cords and cerebral lymphatic sinuses. These structures determine the immune properties of lymph nodes, forming T- and B-dependent zones responsible for cellular and humoral immunity. The thymus-dependent zone (T-zone), which includes the interstitial part of the cortex and the paracortical region, forms a T-dependent immune response (the cellular link of the immune response) in the corresponding lymphatic region. The size of the T-zone progressively increases in the following series of lymph nodes: mesenteric (28.58 ± 2.15%), tracheobronchial (38.96± 2.48%), inguinal (46.20± 3.12%). In old animals, the interstitial part of the bark has a tendency to reduce its area. Thus, the smallest area of this compartment in the mesenteric lymph node is 5.98 ± 0.28%, intermediate in the inguinal lymph node is 8.10± 0.38% and the largest in the tracheobronchial lymph node is 14.52± 0.31%. However, the interstitial part of the cortex does not always undergo age-related involution. Thus, morphometry revealed that the interstitial part of the cortex increases 1.3 times in the inguinal, decreases 2.1 times in the mesenteric and remains at the same level in the tracheobronchial lymph node in comparison with young animals. The size of the paracortical region of old animals is comparable to young ones in the lymph nodes of different lymphatic regions. The paracortical region of old animals in the visceral group of lymph nodes accounts for about 22,63±1,06% - 24,44±2,24%. The size of this compartment in the inguinal lymph node is 36.87 ± 2.85%, which is 1.5 times larger than in the visceral group of lymph nodes. However, against the background of the unchanged size of the compartment, an uneven distribution of cells over the area is observed, which is manifested by a small cell density in the center of the structure and a large concentration of cells on its periphery. Such cellular redistribution is caused by the depletion of the paracortical region by lymphoid cells. The described changes in the T-zone cause an age-related decrease
in the effectiveness of the cellular link of immunity.
The thymus is an independent zone (B-zone), including lymphoid nodules and brain cords, responsible for the effectiveness of B-cell immunity (humoral link of the immune response). The B-zone occupies almost the same area in the inguinal (32.73± 2.14%) and tracheobronchial (34.84± 2.48%) lymph nodes and most of the mesenteric (44.85± 3.16%) lymph node of old animals. Lymphoid nodules with a germinative center in the process of ontogenesis decrease in area in the inguinal lymph node by 1.4 times, in mesenteric by 1.9 times and tracheobronchial by 2.3 times lymph nodes to the level of 4.79%-5.84%. These changes are reflected in the ratio of lymphoid nodules with and without a germinal center. This indicator consistently decreases in a number of lymph nodes: inguinal (1.10± 0.03), mesenteric (0.91± 0.03), tracheobronchial (0.69±0.03), as evidence of a decrease in proliferative activity, especially in the visceral lymph nodes. The brain cords of old animals in the inguinal node occupy about 21.62 ± 1.36% and the tracheobronchial lymph node - 22.11 ± 1.07%, which is comparable with the indicators for the lymph nodes of young animals. In the mesenteric lymph node, the area of the cerebral cords increases by 2 times in comparison with young animals and is about 34.8 ± 0.51%. The different representation of T- and B-domains determines their ratio depending on the localization of lymph nodes. For inguinal and tracheobronchial lymph nodes, the ratio of T-zone and B-zone zones is 1.41 ± 0.04 and 1.12± 0.04, respectively, and for mesenteric lymph node - 0.64 ± 0.02. The index of the ratio of T- and B-zones allows us to judge the predominant type of immune response: cellular - in the inguinal and tracheobronchial, humoral - in the mesenteric lymph nodes.
Separately, it is worth considering the lymph node transport system responsible for drainage and detaxification function. The lymphatic drainage system in the lymph node is formed by subcapsular, cortical and cerebral lymphatic sinuses. The structures described together form a certain degree of development of the sinus system of lymph nodes, depending on their topographic localization. At a young age, the inguinal lymph node is characterized by the predominance of the paracortical zone with a developed sinus system, for the tracheobronchial lymph node, the predominance of the B-zone with a minimum area of sinuses, and for the mesenteric lymph node, the uniform development of T- and B-zones with a wide sinus system.
Age-related changes affect the lymph node transport system. With age, there is an increase in the area of the total sinus system in the inguinal (1.8 times), a decrease in the tracheobronchial (1.2 times) and mesenteric (1.9 times) lymph nodes in comparison with young animals. The sinus system in the lymph nodes of old animals reaches about 9.04%-14.29%, differing little between groups of lymph nodes. At the same time, in terms of the size of the occupied area, the cerebral lymphatic sinus prevails in the inguinal lymph node (12.5 ± 0.51%), which is 2 times more than in the mesenteric (6.16± 0.38%) and 3.3 times more than in the tracheobronchial (3.79± 0.40%) lymph node. Such transformations lead to changes in water and immune homeostasis to varying degrees in the corresponding lymphatic regions.
The design features of visceral and somatic lymph nodes are determined by regional signs of aging, causing their difference among themselves.
The mesenteric lymph node of old animals is characterized by a minimum value of the cortical-cerebral index, the area of the interstitial part of the cortex, the T-zone, a low ratio of T- and B-zones and a large size of the medulla from other groups of lymph nodes. The structure of the mesenteric lymph node is dominated by the B-zone (cerebral cords) and the sinus system.
The tracheobronchial lymph node of old animals is characterized by a high value of the cortical-cerebral index, a high proportion of the connective tissue component, a large area of the interstitial part of the cortex and a low ratio of lymphoid nodules with and without a germinal center. The anatomical and functional variant of the tracheobronchial lymph node at the late stages of ontogenesis is characterized by the predominance of the T-zone (the interstitial part of the cortex) in the presence of narrow lymphatic sinuses.
The inguinal lymph node of old animals is characterized by a large area of the paracortical region, the
cerebral lymphatic sinus, the ratio of lymphoid nodules with and without a germinal center. The morphological variant of the inguinal lymph node at the late stages of ontogenesis is characterized by relatively developed Tand B-zones (due to the paracortical region and lymphoid nodules, respectively) with wide lymphatic sinuses. Conclusions
However, with age, regional changes occur in the lymphatic bed, having an involutional character and manifested by microanatomic transformations. Senile reorganization of lymph nodes changes the size of the main functional compartments, which determines the anatomical and functional variant of regional specialization of lymph nodes. Mesenteric lymph node is characterized by a minimum value of the cortical-cerebral index, the area of the interstitial part of the cortex, the T-zone, a low ratio of T- and B-zones and a large size of the medulla. The tracheobronchial lymph node is characterized by a high value of the cortical-cerebral index, a large area of the interstitial part of the cortex (T-zone) and a low value of the ratio of lymphoid nodules with and without a germinal center. The inguinal lymph node is characterized by a larger area of the paracortical region, the cerebral lymphatic sinus, the ratio of lymphoid nodules with and without a germinal center. The age-related difference in the structural organization of lymph nodes reflects the characteristics of drained different organs in accordance with the concept of the lymphatic region.
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© Бекенева К.А., Быстрова В.И., Веременко А.С., Николайчук К.М., Левченко И.Д., Кузнецова В.А., 2023
