Multiple Biological Effects of Citrate in Magnesium Phosphate - Based Cement During Bone Regeneration

The development of multiple biofunction materials is still a challenge in bone tissue engineering biomaterials. Exogenous citrate is involved in multiple biological processes such as metabolism, osteogenesis and angiogenesis. However, it is difficult to obtain a thorough and comprehensive understanding on osteogenic effects of exogenous citrate from different experimental conditions and treatment methods. In this study, by using a magnesium phosphate - based cement (MPBC) matrix, we not only investigated the dual effect of exogenous citrate to osteogenesis and angiogenesis in vivo and vitro, but also explored the regulation of citrate on bone apatite crystal structure in an osteoblast differentiation model. Our studies show that citrate elevates the osteogenic function of osteoblasts under low doses and angiogenic function of vascular endothelial cells under a broader dose range. Furthermore, citrate, as an ionic chelator and mineralization inhibitor, improves the cell survival in high calcium and phosphorus environment and regulates the phase structure of osteogenic minerals. These findings provide a new strategy to regulate angiogenesis and osteogenic differentiation by adjusting citrate content and release in MPBC, guiding the development of bioactive materials for bone tissue regeneration. Funding Statement: This work was supported by grants from the National Natural Science Foundation of China (No. 51672206), the National Key Research and Development Program of China (2016YFC1101605 and 2018YFB1105500), the Major Special Projects of Technological Innovation of Hubei Province (No. 2019ACA130) and the Application Foundation and Front Research Program of Wuhan (No. 2018010401011273). Declaration of Interests: The authors have no conflicts of interest to declare. Ethics Approval Statement: All animal experiments were conducted using protocol approved by the China National Institutional Animal Care and Use Committee.