The Mechanism of Simvastatin-Mediated M1 Macrophage Polarization Contributing to Osteogenesis and Angiogenesis

Background: The immune response is essential for bone regeneration, and macrophages in the immune microenvironment contribute to bone metabolism and angiogenesis. Emerging evidence demonstrates that simvastatin is a promising candidate for bone repair and promotes bone formation both in vitro and in vivo. However, the effect of simvastatin on macrophages and the following outcomes are still unclear. Objectives: This study aimed to investigate the potential immunomodulatory effect of simvastatin on M1 macrophages and its subsequent impact on osteogenesis and angiogenesis. Methods: Cell viability was assessed by CCK-8. Osteogenic and angiogenic markers were evaluated by RT-qPCR, Western blotting, and immunofluorescence. M1 macrophage phenotype was analyzed by flow cytometry. Osteogenesis was examined by histological staining, and angiogenic capacity was assessed using functional assays. Results: The present study found that simvastatin decreased M1 macrophage markers (CD86) and stimulated M1 macrophages to express high levels of pro-regenerative cytokines (BMP-2 and VEGF). In addition, simvastatin promoted osteogenic differentiation in MC3T3-E1 cells and angiogenic gene expression in HUVECs. Importantly, simvastatin enhanced the osteogenic capacity of MC3T3-E1 and the angiogenic potential of HUVECs by inhibiting M1 macrophage polarization in vitro. Conclusions: We demonstrated that simvastatin could confer favorable bone immunomodulatory properties and influence the crosstalk behavior between immune cells and osteoblasts and vascular endothelial cells to promote bone healing.