The application of implant denture is a breakthrough in the field of stomatology in recent years. However, peri-implantitis can affect the long-term success rate of dental implants, which is one of the main reasons for the failure of dental implants. Peri-implantitis is a chronic progressive marginal inflammation, which belongs to peri-implant tissue disease. Peri-implant disease includes peri-implant mucositis and peri-implantitis. The former is a reversible disease involving only soft tissue. The latter is the result of further development of mucositis, not only involving soft tissue, but also violated the deep alveolar bone, resulting in bone resorption. If peri-implantitis is not treated in time, it will lead to continuous bone resorption and implant-bone interface separation, which will eventually lead to implant loosening and falling off . The risk factors include periodontitis, smoking, diabetes, poor oral hygiene, systemic disease, keratinized gingival width, IL-1 gene polymorphism, force and implant site. Most scholars believe that bacterial infection is closely related to peri-implantitis . Currently, the treatment of peri-implantitis can be divided into surgical and non-surgical treatment, in which surgical treatment can remove subgingival plaque and sediment, and Guided Bone Regeneration (GBR) surgery can effectively solve the bone resorption problem. However, due to the large surgical trauma, it is easy to cause gingival retraction, and some scholars proposed that only in cases with severe bone resorption and periodontal exploration depth of more than 5 mm after conventional treatment . The treatment of the peri-implantitis is a problem in the current Implantology, and traditional debridement, scaling, anti-bacterial treatment effect is not very satisfactory.
Similar to periodontitis, immune microenvironment plays an important role in the pathogenesis of peri-implantitis, so it is of great significance to understand the immune response and immune microenvironment to clarify the pathogenesis of peri-implantitis and its clinical treatment. Berglundh et al. found that when the detection rate of neutrophils and macrophages in the peri-implant tissues was relatively high in peri-implantitis. In the state of inflammation, pathogenic bacteria invading the tissue would promote the expression of the adhesion molecule ICAM-1 in the peri-implant mucosa and the binding epithelium, forming a certain chemotaxis gradient in the surrounding tissue, which would induce a large number of neutrophils to enter the gingival groove and engulf the invading pathogenic bacteria . Liskmann et al. believed that the secretion of IL-6 by activated Th1 cells played a promoting role, while the secretion of IL-10 by Th2 cells had an anti-inflammatory effect, and the imbalance of the two roles would lead to intensified inflammatory response in the surrounding tissues of implants and the destruction and absorption of alveolar bone . Lin et al. found that activated CD4+ T cells could express the receptor activator of nuclear factor-κB ligand (RANKL), bind to the receptor activator of nuclear factor κB (RANK) on the surface of the osteoclast precursor cells, and promote the maturation, differentiation and bone absorption of osteoclasts . Periodontal pathogens are the initiating factors of peri-implantitis, and the tissue damage caused by the immune response is often more serious than that caused by pathogens themselves. This suggests that in the treatment of peri-implantitis, one should focus on antibacterial, the other should focus on the regulation of immune microenvironment of peri-implantitis, so as to improve the treatment effect to some extent. Therefore, it is expected to provide a new approach for the treatment of peri-implantitis by exploring the role of immune microenvironment in the development of peri-implantitis and proposing more targeted diagnosis and immunotherapy.
CeRNA regulatory network is a newly discovered mechanism for RNA interaction and regulation of coding genes, which extends the previous understanding of the large number of non-coding RNAs in vivo . MiRNAs are newly discovered small molecules that play an important role in gene expression regulation networks. Although miRNAs account for only a small part of the human genome, they are the key regulators of body development and cell homeostasis. MiRNAs are widely expressed in higher eukaryotes and belong to a class of non-coding small RNA molecules. In mammals, miRNAs generally regulate gene expression at the translation level, and the number of miRNAs correlates with the level of translational silencing at each site .
This study screened the differentially expressed lncRNAs and IRGs between peri-implantitis and normal tissues and we constructed the corresponding ceRNA network to identify the key hub genes in peri-implantitis. In addition, we conducted GO and KEGG enrichment analysis of IRGs in ceRNA network, and we found that these differentially expressed IRGs were mainly associated with inflammatory processes. Then we verified the DElncRNAs, DEmiRNAs and DEmRNAs obtained in another dataset and found that only GSK3B and miR-1297 existed in both ceRNA networks. Next, we further verified the accuracy of the results. We combined GSE33774 and GSE57631 and conducted WGCNA analysis, which showed that GSK3B appeared in key modules and had an important relationship with peri-implantitis. In order to better detect the immune microenvironment of peri-implantitis, the CIBERSORT was used to evaluate the content of immune cells in normal tissues and peri-implantitis, and Pearson correlation was calculated between the gene expression level of GSK3B and 22 immune cells in peri-implantitis. The results showed that GSK3B was closely related to four types of immune cells.
GSK3B is a serine/threonine kinase originally identified as a regulator of glycogen deposition, the role of which in osteoblasts has been well demonstrated as a negative regulator of β-catenin. It has been reported to play a role in regulating a variety of cellular responses, including cell growth, migration, tumorigenesis and cytokine production . Amirhosseini et al. reported that inhibition of GSK3B could regulate osteoblast and osteoclast differentiation to suppress instable-induced osteolysis and bone loss by activating Wnt/β-catenin signaling . In addition, Jang et al. demonstrated a novel role for GSK3B in regulating RANKL signaling, which was vital for osteoclast differentiation . In this study, it was found that GSK3B was associated with four types of immune cells, especially with the highest correlation with resting mast cells (P = 0.0003). Madeleine Radinger et al. determined that GSK3B was constitutively activated in resting human mast cells, which regulated by the phosphorylation status of activating tyrosine residue Y216. In resting human mast cells, they observed constitutive phosphorylation of Y216. However, when the cells were activated, the phosphorylation of this residue have no consistent increase. They found that GSK3B may have functions that precisely control the signal transduction processes required for mast cell chemotaxis and cytokine production . In addition, they also found a small molecule drug that inhibits GSK3B activity could reduce the intensity of allergic inflammatory responses by reducing mast cell survival. They suggested that GSK3B can be a key regulator of mast cell homeostasis through prevention of apoptosis . With regard to miR-1297, a growing number of studies have demonstrated that it may be associated with the pathogenesis and prognosis of a variety of cancers. Bu et al. found that miR-1297 may act as an oncogene by regulating the PTEN/Akt/Skp2 signaling pathway in non-small cell lung cancer (NSCLC) cells . Besides, Chen et al. confirmed that in human cervical cancer tissues, after the overexpression of miR-1297, HeLa cells had an increase in cell proliferation and decrease in apoptosis. PTEN expression was negatively correlated with miR-1297 expression. PTEN silencing showed a similar pattern to the overexpression of miR-1297, which inhibited the growth and apoptosis of HeLa cells in vitro . Through these two ceRNA networks, we found that GSK3B and miR-1297 are interconnected signal axis, and Gao et al. found that GSK3B was the downstream target gene of miR-1297 and growth arrest-specific 5 (GAS5) could be used as a competing endogenous RNA for miR-1297 to weaken its inhibitory effect on GSK3B .
This study has some limitations. First of all, this research mainly focuses on data mining and data analysis. These results have not been verified by experiments, and we will further verify the results of this study in the future. In addition, we only obtained a limited datasets and did not include more clinical status of each individual. More datasets will get a reliable result.