The ratio of proliferation and apoptosis in connective tissue cells of the skin during the healing of mechanical injury in an experiment

AIM - to quantitatively characterize the ratio of proliferation and apoptotic death of dermal cells at the stages of healing of a mechanical skin wound. METHODS. An experimental single-center continuous controlled randomized unblinded study was conducted. Skin pieces from Wistar rats taken from the middle third of the thigh at different stages of healing after an incised wound were used. The animals were divided into 9 groups: Group 1 — intact individuals (n=3), the remaining groups corresponded to the periods of withdrawal from the experiment (n=3 in each group) at 12 hours, 24 hours, 2nd, 3rd, 6th, 10th, 15th and 25th days after the injury. Skin fragments were used to prepare preparations for histological and immunohistochemical studies. Antibodies to histone H3 phosphorylated at serine 10 (H3S10ph) were used to detect proliferation processes, and reactions with antibodies to p53 and caspase 3 were used to detect apoptosis. RESULTS. Cells immunopositive to phosphohistone H3, caspase 3 and p53 were found in the dermis of experimental animals of all groups. The proliferation index of connective tissue cells of the dermis was determined and the dynamics of expression of proapoptotic proteins in intact skin and in the perinecrotic area of ​​the wound during regeneration was analyzed. Based on the analysis of the obtained results, the balance of apoptosis and proliferation processes was assessed and an index reflecting their activity was proposed. It was shown that a higher proliferative-apoptotic index is determined during periods of prevalence of proliferation over death processes (in intact skin and at the final stages of regeneration), the lowest index values ​​​​were detected when apoptosis processes prevailed over proliferation (the phase of inflammation and necrosis). CONCLUSION. In this work, an immunohistochemical reaction with antibodies to phosphohistone H3 was used for the first time in the study of skin wound regeneration. The marker correctly identifies proliferating cells, and in combination with apoptosis markers, it allows determining the proliferative-apoptotic ratio at the stages of regeneration.