[Mechanism of VPS26 gene promoting implant osseointegration through Wnt/β-catenin pathway in hyperlipidemia rats]

Objective: To investigate the mechanism of VPS26 effect on osteogenesis and adipogenesis differentiation of rat bone marrow mesenchymal stem cells (BMSC) in high fat environment, and to explore the effect of VPS26 on implants osseointegration of high fat rats and ectopic osteogenesis in nude mice. Methods: BMSC were cultured under normal osteogenic induction (osteogenic group) and high-fat osteogenic induction (high-fat group).High-fat group was transfected with VPS26 enhancer and inhibitor, and the expression levels of osteogenesis related genes and adipogenesis related genes were examined. Osteogenesis and adipogenesis of BMSC were detected by alkaline phosphatase (ALP) staining and oil red O staining after 7 and 14 days of induction.In osteogenic group,the binding of VPS26 to β-catenin was detected by immunofluorescence staining and immunoprecipitation, and dual luciferase reporter assay (TOP Flash) was used to analyze the TOP/FOP ratio. Eighteen male 12-week hyperlipidemic Wista rats (160-200 g) were implanted with implants, and six in each group were injected with VPS26 overexpression lentivirus (LV-VPS26 group), negative control lentivirus (LV-nc group) and saline (blank control group).Micro-CT analysis , HE and oil red O staining were used to evaluate the osseointegration of the implants and lipid droplets formation of the femur samples. Twenty female 6-week nude mice (30-40 g) were divided into five groups and subcutaneously implanted with osteogenic BMSC non-transfected and transfected LV-VPS26, LV-nc, shVPS26, and shscr lentivirus on the back. Samples were used to observe ectopic osteogenesis. Results: The mRNA expression levels of ALP in the high-fat group BMSC after overexpression of VPS26 (1.56±0.09) were significantly higher than those of the negative control (1.01±0.03) (t=10.09, P<0.001), while those of peroxisome proliferator-activated receptor-γ (PPAR-γ) (t=6.44, P<0.001) and fatty acid-binding protein4 (FABP4) (t=10.01, P<0.001) were lower than those of the negative control. Western blotting results showed that compared with the negative control, protein expression of ALP and Runt-related transcription gene 2 was enhanced in the high-fat group BMSC after overexpression of VPS26 while PPAR-γ and FABP4 were inhibited. ALP activity of BMSC in the high-fat group was stronger after overexpression of VPS26, and the formation of lipid droplets was weaker than that in negative control. The results of immunofluorescence, immunoprecipitation and dual luciferase reporter assays showed co-localization and interaction of VPS26 with β-catenin and a significant 43.10% increase in the TOP/FOP ratio (t=-3.17, P=0.034). VPS26 overexpression enhanced osseointegration and decreased the number of lipid droplets in high-fat rat and enhanced ectopic osteogenesis of nude mice. Conclusions: VPS26 activated osteogenesis differentiation and inhibited adipogenic differentiation of BMSCs through Wnt/β-catenin pathway, promoting osseointegration of high-fat rat implants and ectopic osteogenesis of nude mice.