Morphofunctional and molecular bases of pineal gland aging

Abstract

Together with the hypophysis and hypothalamus, the epiphysis (pineal gland, PG) is one of the highest centers of the endocrine system of the body [1]. The aging rate of the neuroimmunoendocrine system and age related pathology development are connected with involution of the PG, which, in turn, is determined to a greater degree by a decrease in its functional activity and to a lesser degree, by morphological and molecular changes [2,3]. Morphological Changes in the PG with AgingThe study of autopsy samples of the PGs obtained from 2700 subjects aged from several months to 90 years can be used as the initial point for the analysis of pub lished data on age related changes in the PG. It was shown that PG weight increases from 80-100 to 150 160 mg in the age interval 10-50 years [4]. PG weight is inversely proportional to sexual activity; therefore, this index is higher in pubertal and post menopausal peri ods than in the period of sexual maturity. The increase in the gland weight during aging was related to an increase in the volume of fibrous tissue and the number of cysts without a significant decrease in the number of pinealocytes in an organ's parenchyma. Changes in the connective tissue composition have been observed: the number of collagen fibers is increased, and the number of argyrophilic fibers is decreased [5].According to the computed tomography data, the volume of the PG characterizing its functional activity decreased at the age interval from 21 to 60 and then sta bilized [6]. These data are in good correlation with the study [7], which shows that there are no pronounced differences in PG structures at a young and elderly age.Sequential changes in three prevaling types of PG structure (cellular, trabecular, and alveolar) occur [8].The cellular type of structure of the PG is typical of a young age. PG is represented by a continuous field of pinealocytes.The trabecular type of the PG, glandular tissue with differently directed stromal septum, is typical of mid dle aged subjects. Replacement of the trabecular type by the alveolar type of PG structure is typical of elderly subjects. Trabeculae subdivide PG in alveolar structure into circular or polygonal lobules separated by stromal rings.In addition, one can see age related changes in the vessels of the PG. After birth, PG vessels are located among pinealocytes. Expansion of argyrophilic stroma around the vessels that takes place with age is the reason of the transition from a cellular to trabecular type of structure of the PG. A dense network of vessels enlaces the parenchymal lobules of the PG determining its alve olar structure. In subjects over 60 years of age, one can see the appearance of outgrowths of the reticular frame of connective tissue in the development of sclerosing processes in the PG. The blood circulation in the PG is decreased as compared to subjects aged 40-45 years. Age related decrease in trophism in the PG results in involution changes in its cells, pinealocytes.Accumulation of lipofuscin and lipid inclusions, as well as fragmentati...

Histomorphometric examination of the pineal gland in foals and adult horses

“…In adult horses, on the other hand, the trabecular septa and such branches were not conspicuous, but a loose connective tissue was discernible (Figures 2A and 2B). Redondo et al (22) The total number of pinealocytes in the human pineal gland decreases by 18% by aging (18). The data we obtained in horses did not immediately support this conclusion.…”

“…Presence of calcareous concentrations has been reported in gerbil (26) and even in young horses (6). Increase in deposition of calcium and lipofuscin pigment is often considered as the functional state of the gland, not directly related to aging (18). In the present study, we did not observe any calcareous concentrations either in foals or adult horses.…”

“…In the pineal gland, some pinealocytes had a nucleus with double DNA content and their frequency is higher in elderly (18). In our search of literature, we did not come across with reports on the presence of dikaryotic pinealocytes.…”

“…The human pineal gland is morphologically classified into three categories: cellular, trabecular, and alveolar (18). In the dog and cat, such a classification has not been reported (2,3).…”

“…Such a large nucleus might indicate presence of a large number of cells with an increased DNA content (29). It is well known that the pineal gland is significantly influenced by aging process (18), and the nuclear size of pineolocytes is one of the parameters investigated (11,13,15). A study by Gusek and Meier (13) claims that the nuclear size of the pinealocytes is larger in younger ages although the pineolocyte cell size is similar between the younger men (30 to 40-years-old) and elderly (13).…”