Platelet-Rich Plasma Promotes Osteogenic Differentiation by Increasing the OPG/RANKL Ratio in Bone Marrow Stromal Stem Cells

Abstract

Background: Platelet-rich plasma (PRP) is extensively used in both basic research and clinical applications of tissue repair and regeneration. PRP has a variety of different growth factors and particularly plays a crucial role in promoting osteogenic differentiation (OD) of bone marrow stromal stem cells (BMSCs). However, the underlying mechanisms behind this phenomenon remain unrevealed. Therefore, we aimed to investigate the underlying molecular events behind the role of PRP in promoting the osteogenic differentiation of BMSCs. Methods: BMSCs were isolated from mice and exposed to different concentrations of PRP at different time intervals. Cell proliferation was evaluated using the Cell Counting Kit-8 (CCK-8), and the OD of BMSCs was assessed by measuring calcium deposition, alkaline phosphatase (ALP) activity, and osteocalcin content. The expression of osteogenic genes at the mRNA level was analyzed using real-time quantitative PCR (RT-qPCR), and western blot was used to detect the expression of osteogenic proteins. Results: PRP significantly improved the proliferation of BMSCs, calcium deposition, ALP activity, and osteocalcin content in a concentration-dependent manner. Furthermore, PRP significantly increased the expression of ALP, Runx2, Osterix (OSX), osteocalcin (OCN), Osteopontin (OPN), and Bone morphogenetic protein 2 (BMP2) at the mRNA level, and Runx2, BMP2, and OCN at the protein level. Moreover, the findings revealed that PRP significantly increased the Osteoprotegerin (OPG)/Receptor activator of nuclear factor-κb ligand (RANKL) gene ratio in BMSCs in a concentration-dependent manner. Interestingly, PRP-promoted osteogenic differentiation in BMSCs could be reversed by OPG knockdown or RANKL overexpression, as evidenced by altering calcium deposition, ALP activity, and osteocalcin content. Conclusion: PRP improves the osteogenic differentiation of BMSCs by increasing the OPG/RANKL ratio.