MICROSCOPIC CHANGES IN RAT’S GINGIVA UNDER CONDITIONS OF EXPERIMENTAL PERIODONTITIS AND THE USE OF MESENCHYMAL STEM CELLS
Authors: Duda Kateryna , Klishch Ivan , Nebesna Zoia , Ohinska Nataliia 
Published: October 2023

Abstract. According to the WHO, periodontal disease is an important socio- economic problem, and periodontitis remains the main cause of tooth loss in the adult population. Stem cells have a unique ability to transform into all types of body tissues and cells. In consequence of this, they restore damaged organs and their functions.The aim of the study. To ﬁ nd out the features of histological changes in the gingiva under the conditions of experimental periodontitis and the use of mesenchymal stem cells as a correction.Material and methods. The experimental study was conducted on 30 mature white male rats, which were divided into three groups: I – intact animals (10); II – animals with a model of acute inﬂ ammation of periodontal tissues (10), III – animals with acute inﬂ ammation of periodontal tissues and under conditions of mesenchymal stem cells use (10). To simulate inﬂ ammation of periodontal tissues in experimental animals, we used lipopolysaccharide, the animals of this group were injected with 40 microliters (1 mg/ml) of lipopolysaccharide (LPS) and 1 % starch solution intragastrically into the gingiva tissues every other day for 2 weeks. Rats were euthanized by bloodletting under thiopental- sodium anesthesia. Mesenchymal stem cells (MSCs) were obtained from pregnant females approximately on the 21st – 24th day of pregnancy. Stem cells were injected into the gingiva area of rats by a single injection at the rate of 1 million cells per 1 kg of body weight. For histological examination, pieces of gingiva were processed according to generally accepted methods.The results. The results of the histological studies showed that the tunica mucosa epithelial layer of the marginal part of gingiva in the intact group of animals was represented by a stratiﬁ ed keratinized epithelium, which is a characteristic feature of animals. The lamina propria of the gingival mucosa of intact white rats was represented by papillary and reticular layers. After 7 days of simulated periodontitis, the development of changes in the structural components of the gingiva, which had signs of an inﬂ ammatory nature, was observed. In the marginal part of the gingiva, the stratiﬁ ed squamous keratinized epithelium was characterized by a violation of the integrity of all layers and the appearance of single migrating, intraepithelial lymphocytes into the epithelial layer. The lamina propria of the tunica mucosa of the gingiva was characterized by swelling, destruction of collagen ﬁ bers. Fourteen days after experimental periodontitis, the progression of inﬂ ammatory processes and destructive changes was established. Stratiﬁ ed squamous keratinized epithelium of the gingival mucosa was characterized by hyperkeratinosis. Thickening or signiﬁ cant thinning of the bundles of collagen ﬁ bers were observed, swelling of the amorphous component of the connective tissue was revealed, an increase in foci of histoleukocyte inﬁ ltration was noted. After 21 days of the experiment, microscopic studies showed the development of destructive- degenerative changes in all structural components of the periodontium, in particular the gingiva. The oral and sulcular epithelium of the gingiva was dystrophically altered. The layers were not clear, in some areas there was destruction of the basement membrane and penetration of the connective tissue into the epithelium. The results of the periodontal research of the group of animals which underwent correction with mesenchymal stem cells, after experimental periodontitis, already on the 7th day of the experiment established a lower degree of disruption of its structural components, as well as an improvement in the functional activity of some vessels of the microcirculatory bed, compared to a group of animals without correction. In the epithelial layer of the marginal part of the gingiva, the stratiﬁ ed squamous keratinized epithelium was well structured in some areas, diﬀ erentiation of cell layers was observed. Collagen ﬁ bers were fragmented, the bundles of some of them were thinned or thickened, between which there were degenerative ﬁ broblasts and histoleukocyte inﬁ ltration. Fourteen days after the simulated periodontitis, the course of active regenerative processes in the gingiva was microscopically established when using mesenchymal stem cells. The epithelium of the oral and sulcular part of the gingiva was characterized by the preservation of the layered architecture of epitheliocytes. In the lamina propria of the tunica mucosa of the gingiva, the restoration of the structure of collagen ﬁ bers was observed, they were not thickened, without signs of lysis. In the gingival tissues under the conditions of correction of simulated periodontitis on the 21st day of the experiment, the lowest degree of destructive changes was established compared to all experimental groups. Polymorphonuclear cell inﬁ ltration was not observed in the epithelial plate of the tunica mucosa of all parts of the gingiva. Diﬀ erentiation of layers was well preserved, dystrophically changed cells were not noted. In the lamina propria of the tunica mucosa of the gingiva, an improvement in hemodynamics was noted, swelling of the amorphous component of the connective tissue was insigniﬁ cant. In the spaces between the collagen ﬁ bers, there were numerous ﬁ broblasts, individual macrophages and lymphocytes.Conclusions. The conducted microscopic studies showed that 7 days after the experimental periodontitis, the structural components of the gingiva were characterized by reactive inﬂ ammatory processes, which later became chronic and manifested signiﬁ cant destructive- degenerative changes. The use of mesenchymal stem cells as a corrective factor after simulated periodontitis helped to reduce destructive changes in the gingiva, improved tissue hemodynamics, promoted active regenerative processes, which ultimately ensured the closure of the periodontal pocket and tight fusion of the gingiva and tooth tissues.