Histological Changes in Autografts of Adipose Tissue in Rats in the Middle Postoperative Period

Autotransplantation of adipose tissue is a widely used technique in aesthetic and reconstructive surgery for correcting atrophic changes and scar deformities. Adipose tissue is a biologically active substance and its function goes far beyond fat deposition. Objective. To identify histological changes in autografts of adipose tissue and surrounding tissues in rats after various methods of fat treatment 30 days after surgical interventions. Materials and methods. The animals were divided into five groups, with six individuals in each group. Group 1 consisted of intact animals (no exposure); Group 2 served as the control (saline solution); Group 3 included animals with a subdermal implantation of fat, previously extracted from a skin incision in the groin area, through a 1 mm diameter incision. In Group 4, fat crushed with a scalpel was injected under the skin with a syringe once. In Group 5, animals were implanted with fat crushed using a shredder nozzle in a Luer Lock syringe. Four implantations were performed with a volume of 0.05 ml. The sections were stained using the Mallory method, hematoxylin and eosin, methylene blue. The Mann-Whitney U test was used to assess statistically significant differences. Results. Morphometric parameters of the dermis showed an increase in its thickness, mainly of the mesh layer, as well as, physiologically significant increase in the proportion of microcirculatory vessels in the skin of animals in the experimental groups. The number of sebaceous gland profiles was slightly higher in the experimental groups compared to the control groups (p < 0.05). The thickness of the fat autograft was significantly greater in Group 3 (p < 0.001), where a large fat fragment was implanted, however, in this group, almost all rats had pathological reactions in the form of leukocyte (primary lymphocytic) infiltrations and varying degrees of necrosis. Infiltrations containing lymphocytes and fibroblast-like cells were also observed in animals of groups 4 and 5, but were significantly less pronounced than in Group 3. In Group 5, relatively large fat fragments surrounded by lymphocytic infiltrates were detected in the skin of only two rats, in other animals, fat fragments of microscopic size were found, which, as a rule, were integrated with the adipose tissue of the transplant site. Conclusions. The introduction of autologous fat can not only lead to its gradual degradation, but also can stimulate the formation of adipose tissue in the area of administration. The components of the fat graft (lipids) become part of the newly formed adipose tissue. This process is more effective when the size of the injected graft particles is smaller.