RECONSTRUCTION OF THE ABDOMINAL WALL DEFECTS USING GELATIN-COATED DECELLULARIZED AND LYOPHILIZED HUMAN AMNIOTIC MEMBRANE.

Ventral hernias, with the incidence of reherniation nearly as high as 50%, still remain to be a real challenge for surgeons worldwide. The use of mesh in the repair of abdominal wall defects reduces the incidence of reherniation; however, using a prosthetic mesh can lead to complications like wound infection, hematoma, seroma, enterocutaneous fistula, small bowel obstruction, recurrent herniation and erosion into adjacent structures including the intestine. The aim of the study was to develop a method for producing gelatin-coated decellularized and lyophilized human amniotic membrane graft and to determine its effectiveness for the reconstruction of the anterior abdominal wall defects. Experiments were conducted on 40 Lewis white laboratory rats. Animals were divided into four equivalent groups. Abdominal wall defects were created in all rats and repaired using the ULTRAPROTM mesh (group I), ULTRAPROTM mesh which was covered by decellularized and lyophilized human amniotic membrane from both sides (group II), mesh from gelatin-coated decellularized and lyophilized human amniotic membrane (group III) and biological surgical mesh XI-S+® (group IV). Three months after implantation, meshes from gelatin-coated decellularized and lyophilized human amniotic membrane were integrated with host tissues so that it was difficult to distinguish it from the surrounding tissues. However, in the second group, ULTRAPROTM mesh was still detectable through the decellularized amniotic membrane. Encouraging results were also observed when using a XI-S+® graft. Three months after implantation, XI-S+® graft was surrounded by a well-defined connective tissue capsule and was tightly fixed to the host tissues. While using gelatin-coated decellularized and lyophilized human amniotic membrane grafts and XI-S+® grafts, all the defects were repaired successfully and none of the rats in these groups showed any evidence of bulging or herniation, development of wound rupture, wound infection or fistula formation in postoperative period. Gelatin-coated Decellularized human amniotic membrane can be used as anti-adhesive barrier in abdominal and pelvic surgery, as well as for the repair of the abdominal wall hernia.

RELATIONSHIP BETWEEN ORAL SQUAMOUS CELL CARCINOMA AND IMPLANTS (REVIEW).

In this review, we have discussed the relationships between oral squamous cell carcinoma (OSCC) and dental implants. In the last decade, dental implants have been widely used for the treatment of complete or partial edentulism. Despite the fact that they have seen incredible success and the use of dental implants increases, concerns over safety and efficiency is rising as well. The literature analysis has shown that the number of reported cases when the OSCC development is associated with peri implantitis is gradually increasing. The possibility of squamous cell carcinoma development must be considered when evaluating the peri-implantitis. We highly recommend periodic oral and radiographic examination after the implant placement. The patients with peri-implantitis that do not respond to conventional treatment methods, and the patients who have a severe or rapid progression of peri-implantitis require biopsy. The histopathological examination will aid with the differential diagnosis between peri-implantitis and OSCC, and hence, provide the correct diagnosis.

BONE GRAFTS FOR RECONSTRUCTION OF BONE DEFECTS (REVIEW).

Reconstruction of large size defects of bone is a challenging task. To this date, discussions and controversies on selection of auto-, allo-, xeno- or synthetic grafts continue to take place. Vascularized autologous bone graft is considered as gold standard in reconstruction of large size defects of bone; however an additional surgery is required for obtaining it. Allografts and xenografts possess osteoconductive features, but osteogenesis is less expressed and risk of various infection transmissions is high and may have probability of developing immunological conflict. Main advantages of grafts created from synthetic materials through bioengineering methods are biocompatibility and good bioreabsorption. Despite these features, studies related to the creation of an ideal bone graft continue to take place that should have biomechanical stability, be able to degrade within an appropriate period, exhibit osteoconductive, osteogenic and osteoinductive properties. Nowadays, there is an attempt of creating grafts that contain platelet-rich plasma, growth factors or stem cells for strengthening osteoconduction and osteoinduction of bone grafts. In 2016, we created bioactive bone from decellularized bovine femoral bone and freeze-dried bone marrow stem cell paracrine factors. We hypothesized that freeze-dried BMSC paracrine factors would have ability to strengthen osteoinduction, osteoconduction and osteointegration. Experimental and preliminary clinical investigations indicated that bioactive bone grafts containing freeze-dried BMSC paracrine factors may be used for reconstruction of large size bone defects. Despite acquired positive results, it requires multiple experimental and clinical studies for further improvement of graft.

CURRENT CONDITION AND CHALLENGES IN TREATMENT OF NON-HEALING WOUND AFTER RADIATION THERAPY (REVIEW).

Radiotherapy is a common cancer treatment, but often together with tumor cells, the surrounding normal tissues are damaged as well, which leads to the complications such as skin atrophy, soft tissue fibrosis, desquamation, epithelial ulceration which leads to poor healing of wounds. In this review, our main attention will be paid to the treatment of non-healing wound after radiation therapy. Irradiated wounds are often resistant to conventional treatment modalities and may often require surgical reconstructive intervention. The reconstructive options usually include skin grafts, local and regional flaps. Local flaps may be unreliable, since in some of the cases they are affected by irradiation. However, the complication rate with regional flaps is just as high as that with local flaps, and is not significantly different when analyzed according to the type of reconstructive procedure performed. In addition, such wounds affect not only the physical, but also the mental health of patients and their productivity. Therefore, non-healing wounds represent a significant problem for patients and remain a major challenge in modern medicine. Recently, for the healing of non-healing wound, several novel approaches have been proposed such as using the bone marrow stem cells (BMSC), biologically active dressings, bioengineered skin equivalents and others. Of special interest are bioactive membrane consisting of decellularized human amniotic membrane and BMSC paracrine factors, which may be effectively used for the treatment of non-healing wounds that have developed following the radiotherapy. Despite the positive results achieved in a number of cases, it is early to state that the all of the above methods is an ideal for the treatment of non-healing wounds, since it requires additional experimental and clinical studies for ascertaining positive and negative features.

CHALLENGES AND MANAGEMENT OF CONGENITAL ABDOMINAL WALL DEFECTS (REVIEW).

Management of congenital abdominal wall malformations is still a challenge in paediatric surgery due to visceroabdominal disproportion, large defects of abdominal wall and immature abdominal cavity. Most of the patients treated with primary closure need artificial substitutes like patches or biomaterials for non-permanent abdominal wall closure. Patches represent the source of constant infections and complications like separation of prosthesis from fascia. Removal of these patches and ventral hernia repair is essential afterwards. As for component separation technique, this method helps to restore normal anatomy of anterior abdominal wall, results in good cosmetic appearance, requires only one-stage operation procedure, minimal skin flap advancement and is associated with lower infection risk. Although, while performing component separation technique, perforator branches of epigastric artery (periumbilical perforators) are damaged and puts the vascularization of the skin at the risk. Only pudendal artery branches and intercostal arteries are left to supply the skin with the blood, which from our point of view is insufficient. Accordingly, for successful treatment of congenital abdominal wall defects, further research in order to develop new operation techniques, as well as search for the ideal biomaterials for the closure of the large defects of anterior abdominal wall is essential. These biomaterials should possess unique biological properties that are important for tissue repair, including anti-inflammatory, antimicrobial, antifibrosis, antiscarring, as well as a reasonable cost and low immunogenicity.

ACELLULAR HUMAN AMNIOTIC MEMBRANE AS A THREE-DIMENSIONAL SCAFFOLD FOR THE TREATMENT OF MUCOGINGIVAL DEFECTS.

This study was conducted to evaluate the usefulness of decellularized and lyophilized extracellular matrix, which was acquired from human amniotic membrane, for surgical closure of the mucogingival defects. Preliminarily, to create a gingival recession defect, silk ligature was applied on the gingival part of the upper incisor in the first (experimental) (n=20) and second (control) (n=20) groups. On the 14th day, the ligature was removed and the damaged gingival tissues were resected. The formed mucogingival defect, in the animals of the first group, was covered with acellular human amniotic three-dimensional scaffold with bone marrow stem cells. Animals with mucogingival defect of the second group were left untreated and served as controls. Unlike the animals from the control group, in animals from the experimental group the mucogingival defect already on the seventh day was completely closed and there was the newly formed epithelial lining, which in shape and color did not differ from the normal. Acellular human amniotic membrane as a three-dimensional scaffold boosts angiogenesis and increases the reparative regeneration of the damaged tissues; and it is well-tolerated by the gingival tissues. Hence, human amniotic membrane might be a suitable alternative to other conventional methods of treating gingival recession.

[Clinical and biochemical analysis of ligature-induced periodontitis in rats].

The most common experimental model of periodontitis is a "ligature" model. However due to the complexity connected with performing on rats, modification of existing model is proposed, which differs by fixture of cotton ligature around the central incisor and not around the second molar. The purpose of research - a comparative evaluation of "peroxide" and modified by us, "ligature" models of periodontitis in rats. 2 series of experiments on 36 white Wistar rats were conducted. The animals were divided into two groups: intact rats (control) and rats with a "peroxide" model of periodontitis, which was reproduced by the addition to the diet of rats overoxidized sunflower oil (5% by weight of the feed), daily, for 45 days. "Ligature" model in rats was reproduced by applying a cotton ligature on the central incisor of the upper jaw for 14 days. Elastase activity, malondialdehyde content and catalase activity in the gums and in the blood serum was measured by biochemical methods. The degree of atrophy of the alveolar bone of the mandible was determined by morphometric method. It is found that in both models of periodontitis in rats, changes in the periodontal tissues and in the organism as a whole, is common for periodontal disease in humans. Clinically apparent inflammation of the periodontal tissues is observed, metabolic disorders in the gums, change of biochemical parameters in serum and progressive decline in the alveolar bone are determined. A comparative analysis of the two models showed that the modified "ligature" model of periodontitis in rats has several advantages over the "peroxide" model: shorter term of modeling, more pronounced clinical inflammation of periodontal tissues and faster resorption of alveolar bone.