Ipriflavone promotes proliferation and osteogenic differentiation of periodontal ligament cells by activating GPR30/PI3K/AKT signaling pathway

Objectives: This study was performed to investigate the effects and mechanism of ipriflavone (IP) on the proliferation and osteoblastic differentiation of periodontal ligament cells in vitro and periodontal tissue remodeling following orthodontic tooth movement (OTM) in vivo.

Materials and methods: Human periodontal ligament cells (hPDLCs) were cultured in vitro and cell counting kit-8, Alkaline Phosphatase (ALP) activity assay, plate clone formation assay, and alizarin red staining were used to test proliferation and osteogenic differentiation of hPDLCs. What is more, the expression of ALP, Runx2, and GPR30 was examined by real-time polymerase chain reaction and Western blot. To find out if PI3K/Akt signaling pathway was involved in the process, Akt and p-AKT were examined by Western blot. LY294002 (PI3K signaling pathway inhibitor) and small interfering RNA targeting GPR30 mRNA (siGPR30) were used to verify the function of GPR30-mediated PI3K/Akt pathway in this process. Twenty-four male Wistar rats were randomized into 2 groups, the control group with force application and the IP group with force application plus IP. Morphological changes in the periodontal tissue between roots of teeth were investigated using hematoxylin and eosin (HE) staining and bone morphogenetic protein-2 was detected to assess bone remodeling by immunohistochemical staining.

Results: In vitro, 10^-7 M IP was selected significantly promoting proliferation, ALP activity, colony forming efficiency, and mineral deposition (P<0.05) on hPDLCs. Gene expressions of ALP, Runx2, GPR30, and p-AKT were all upregulated than the control group (P<0.05). According to the mechanism, promotion of ALP and Runx2 interdicted by LY294002 and siGPR30 reduced the activation of PI3K/Akt signaling pathway. In addition, HE staining and immunohistochemical staining results showed that the IP group had more new bone formation in the periodontal tissue compared to the control group in vivo.

Conclusion: IP can promote the expression of ALP and Runx2 which was probably related to the GPR30-mediated PI3K/Akt signaling pathway. Moreover, IP coordination seemed to have the potential to prevent relapsing following OTM.