Andrey M. Fedyuk

Background/Objectives: The objective of this study was to assess the efficacy of a cell-containing wound dressing based on fibroblasts in hydroxyethylcellulose (HEC) gel for the local treatment of deep partial-thickness and/or full-thickness skin burns in an animal model. Methods: The rats (male Wistar, n = 100) were subjected to a full-thickness thermal burn (16 cm²). Radical necrectomy was performed one day after the burn. Three days later, the rats were randomly assigned to one of four groups: group 1 (no treatment), group 2 (chloramphenicol and methyluracil ointment, a routine clinical treatment), group 3 (a gel without cells, mock treatment), and group 4 (a dermal fibroblast-impregnated HEC gel). The treatment lasted for five days. The wound-healing process was evaluated by planimetric, cytologic, histologic, and immunohistochemical methods. Results: The differences in the rate of wound healing and the characteristics of wound cytology were identified. In the group 4, a regenerative type of cytogram was revealed, characterized by a significantly increased number of fibroblastic cells in comparison to samples from non-treated and mock-treated animals. Biopsy samples of burn wounds from animals in the group 4l demonstrated the presence of mature granulation tissue and a large number of microvessels. The repair process was stimulated, as evidenced by the increased thickness of newly formed granulation tissue and epidermis in the wound zone, elevated cellularity, and enhanced re-epithelialization activity. The number of Ki-67-positive proliferating cells was significantly higher in group 4 than in the control groups). A small number of non-proliferating donor fibroblasts was observed in the wound area 3 days after the end of treatment. Conclusions: The cell product is an effective agent for promoting wound healing during the regenerative phase. The experiments demonstrated that a gel populated by dermal fibroblasts can stimulate reparative regeneration processes in deep partial- and full-thickness burn wounds.

BACKGROUND: Contemporary experimental models for spinal cord injury studies are mainly based on spinal cord injury in rats and mice. Modeling of experimental spinal cord injuries is generally performed from the dorsal approach, which excludes its injury as a result of compression by the fragments of the fractured vertebral body and significantly restricts the application of the results obtained from clinical practice. AIM: To develop and create contusional spinal cord injury model from the ventral approach with its subsequent comparison with the contusional spinal cord injury model from the dorsal approach. MATERIALS AND METHODS: The study examined 20 female Soviet Chinchilla rabbits weighing 3.5–4.5 kg. The rabbits were subjected to standardized spinal cord injuries from the ventral and dorsal approaches at the LII level. Somatosensory- and motor-evoked potentials, H-reflex, were recorded in all experimental animals before injury, immediately after, and 3 and 8 h after injury. Histological studies were also performed using qualitative and semiquantitative analyses of biopsy samples of damaged areas and assessing the number of dystrophic neurons over time. The results of neurophysiological and histological examinations of the spinal cord in cases of ventral and dorsal trauma were statistically processed. RESULTS: When modeling spinal cord injury from the ventral approach, in comparison with the model from the dorsal approach, more significant damage is detected. As a result of the injury factor, the dysfunction of both neurons at the traumatization level and peripheral neurons below the injury zone was revealed; however, as histological examinations have shown, in contrast to the dorsal approach, mild hemorrhage was observed in the ventral approach. CONCLUSIONS: The results obtained indicate a more significant and strict contusion mechanism of the spinal cord injury model from the ventral approach and the maximum proximity of the resulting model in a clinical situation. In the future, the experimental model of the contusional spinal cord injury in a laboratory animal can be used in chronic experiments.

BACKGROUND: Reconstruction of extensive defects to bone tissue is one of the important problems of orthopedics and traumatology. Especially in acuteis, the problem is associated with the restoration of bone tissue in conditions of its deficiency in pediatric patients. AIM: The aim of the study is to analyze modern methods of surgical treatment in children with extensive bone tissue injuries based on the published literature. MATERIALS AND METHODS: Our report presents a review of the literature of methods of surgical treatment of extensive bone defects. The literature search was carried out in several databases such as PubMed, ScienceDirect, E-library, GoogleScholar for the period from 2005 to 2020, using the keywords given below. As a result of the search, 105 foreign and 37 domestic sources were found. After exclusion, 56 articles were analyzed, all presented works were published in the last 15 years. RESULTS: The gold standard for replacing bone defects is still the use of autografts, including the use of technologies on a vascular pedicle. Various types of xenografts and allografts of bone tissue are increasingly being replaced by various kinds of synthetic implants. CONCLUSIONS: To date, there is no single generally accepted standard for the surgical treatment of extensive bone defects. The option of surgical treatment of extensive bone tissue defects using tissue-engineered bone implants with axial blood supply seems to be extremely interesting and promising.

Hemorrhage occurring during and after surgery still remains one of the biggest problems in medicine. Although a large number of hemostatic products have been created, there is no universal preparation; thus, the development of new materials is an urgent task. The aim of this research is to increase hemostatic properties of chitosan by introducing chitin nanofibrils (ChNF). The blood absorbance by ChNF-containing chitosan sponges and time-until-arrest of bleeding were studied. Non-woven materials containing 0.5% of ChNF and materials without chitin were obtained. The studies of ζ-potential showed that the material containing 0.5% ChNF had relatively a high positive charge, but efficiencies of both materials for hemorrhage arrest were comparable to those of commercial hemostatic products (Surgicel and TachoComb). To investigate the interaction between the materials and living organism, histological studies and optical microscopy studies were conducted after implantation of fibers. Despite bioinertness of fibers, implantation of non-woven materials led to formation of significant granulomas.

The crystal and supramolecular structure of the bacterial cellulose (BC) has been studied at different stages of cellobiohydrolase hydrolysis using various physical and microscopic methods. Enzymatic hydrolysis significantly affected the crystal and supramolecular structure of native BC, in which the 3D polymer network consisted of nanoribbons with a thickness T ≈ 8 nm and a width W ≈ 50 nm, and with a developed specific surface S_BET ≈ 260 m²·g⁻¹. Biodegradation for 24 h led to a ten percent decrease in the mean crystal size D_hkl of BC, to two-fold increase in the sizes of nanoribbons, and in the specific surface area S_BET up to ≈ 100 m²·g⁻¹. Atomic force and scanning electron microscopy images showed BC microstructure “loosening“after enzymatic treatment, as well as the formation and accumulation of submicron particles in the cells of the 3D polymer network. Experiments in vitro and in vivo did not reveal cytotoxic effect by the enzyme addition to BC dressings and showed a generally positive influence on the treatment of extensive III-degree burns, significantly accelerating wound healing in rats. Thus, in our opinion, the results obtained can serve as a basis for further development of effective biodegradable dressings for wound healing.