Structural Changes of Rats Skin under the Influence of Chronic Social Stress

One of the risk factors for the development of various diseases, including dermatological pathology, is chronic social stress. Long-term studies demonstrate that stress is accompanied by switching-on a set of all nonspecific reactions of the body (vascular, neuroendocrine, immune). The activation of sympathoadrenal and hypothalamo-pituitary systems under the influence of stress, accompanied by the release of neuromediators and neuropeptides, the activation of mast cells producing cytokines, chemokines, prostaglandins and leukotrienes, leads to the launch of a cascade of pathological processes. The result is the vascular tone change and modulation of the activity of antigen-presenting cells. As a consequence there appears a shift in the functioning of the skin immune system. It is known that stress can lead to a violation of skin reparation. However, little is known about the skin structure changes under the influence of chronic social stress. The aim of this work was to evaluate the morphological changes in rats' skin under the influence of chronic social stress. The study was performed on 20 male rats. The 1st group, control comprised 10rats. We modeled chronic social stress on animals of the 2nd group (n = 10) by the three-week social isolation and prolonged psycho-emotional impact. The stress was confirmed in an open field test, which was performed by all animals before and after modeling of chronic social stress. Morphological examination of the animals' skin with modeled chronic social stress demonstrated a change in all structural elements. The epidermis of the skin was thinned, in its composition 3-5 layers of keratinocytes were determined. Its thickness was almost 2 times lower compared to the control group. In most cases, the basal membrane and epidermo-dermal junction were smoothed, in several zones there was a lack of granular layer, the phenomena of local parakeratosis reflecting a violation of the keratinization process. Changes in the dermis were noted mainly in the superficial areas of the dermis. First of all, attention was drawn to the narrowing of the vessels of the superficial vascular plexus and the formation of moderate leukocyte infiltration around them. In addition, there was an increase in the total cell density in the papillate and reticular layers of the dermis, with the appearance of a significant number of eosinophils. Such a reactive state of the skin can be partly explained by a decrease in the severity of the epidermal barrier, as well as trophic disorders due to the vascular reaction accompanying chronic stress. It is important to note the change in hair follicles under chronic social stress. A statistically significant decrease in the diameter of the hair follicles was revealed in the skin after chronic stress. Analysis of the hair follicles diameter in animals of the first group showed a bimodal distribution of the trait with peaks in the range of 15-18 μm and 26-30 μm. This variability of hair follicle structure of the hair follicles is in line with conception about heterogeneity of follicles in terms of different phases of the hair follicle cycle. Most of follicles corresponded to the phases of early and mature anagen (growth phase) and reached the hypodermis. In contrast, we found a prevalence of small hair follicles with a diameter of 15-18 μm in rats of the 2nd group. It was located predominantly in the dermis. In addition, signs of reduction of hair follicles with activation of apoptosis and formation of catagenous strands were defined. Thus, chronic social stress led to remodeling of all skin structures that can lead to a decrease in its barrier function.