Bmi‐1 alleviates alveolar bone resorption through the regulation of autophagy

Abstract Background B‐cell‑specific Moloney MLV insertion site‐1(Bmi‐1)is a crucial osteopenic target molecule. The aim of this study is to explore the effects of Bmi‐1 on alveolar bone resorption and the underlying mechanisms in vitro and vivo. Methods A Bmi‐1 ‐knockout ( Bmi‐1 −/− ) mouse model was used to investigate the effect of Bmi‐1 on alveolar bone metabolism, with micro‐computed tomography imaging, histology, and immunohistochemistry staining. Furthermore, we utilized a ligature‐induced experimental periodontitis model to examine the impact of Bmi‐1 ‐knockdown ( Bmi‐1 ± ) on inflammatory alveolar bone resorption. Finally, we stimulated human periodontal ligament stem cells (hPDLSCs) with lipopolysaccharide (LPS) to explore the potential mechanism of Bmi‐1 overexpression in the process of osteogenesis. Results Compared with wild‐type mice, Bmi‐1 −/− mice demonstrated more alveolar bone resorption by inhibiting osteogenesis, which was characterized by decreases in Runt‐related transcription factor 2 and type 1 collagen formation. In addition, Bmi‐1 −/− mice had lower levels of autophagy markers such as Parkin and LC3, but higher levels of inflammation‐related factors such as interleukin (IL)‐6 and IL‐1β in periodontal tissues. In addition, Bmi‐1 ‐knockdown aggravated ligature‐induced alveolar bone loss. Under in vitro inflammatory conditions, Bmi‐1 overexpression stimulated osteoblast differentiation and inhibited the production of inflammatory factors, as well as the autophagy and apoptosis in hPDLSCs stimulated with LPS. When 3‐methyladenine (3‐MA), an autophagy inhibitor, was added, the osteogenic effect of Bmi‐1 was further enhanced. Conclusions Bmi‐1 alleviates alveolar bone resorption by regulating autophagy, indicating that it could be a potential target for periodontitis prevention and treatment. Plain Language Summary Periodontitis is a chronic inflammatory disease, which leads to progressive destruction of periodontal tissues, manifested as periodontal pocket formation, loss of periodontal attachment and alveolar bone resorption. Currently, there is a lack of effective treatments to regenerate damaged periodontal tissues. Therefore, it is of great clinical significance to explore new mechanisms of periodontitis and effective intervention targets. B‐cell‑specific Moloney MLV insertion site‐1 (Bmi‐1) is involved in the regulation of the cell cycle, DNA damage repair, autophagy, bone metabolism, tumor, and other physiopathological processes. Autophagy, as an important mechanism of intracellular self‐regulation, plays an indispensable role in the destruction and repair of periodontal tissues. The aim of this study was to investigate the role of Bmi‐1 on periodontal tissues and its intrinsic mechanism. The results revealed that Bmi‐1 regulates autophagy to protect periodontal tissues, suggesting that it may be a potential target for the prevention and treatment of periodontitis.