Salvianolic Acid B Accelerates Osteoporotic Fracture Healing via LncRNA-MALAT1/miR-155-5p/HIF1A Axis

Background: Osteoporotic fracture is a pathological fracture secondary to osteoporosis, causing disabilities and a heavy burden to the patients. In the previous study, we found that salvianolic acid B (SalB) promoted the osteogenesis of Mesenchymal Stem Cells (MSCs). Objective This study aimed to explore the role of SalB in osteoporotic fracture healing, as well as the potential molecular mechanism. Methods; Human bone marrow mesenchymal stem cells (hMSCs) were treated with SalB or PBS in vitro, and an osteoporotic fracture model in Sprague-Dawley (SD) rats was established successfully. SalB or PBS was locally injected at the fracture. Eight weeks later, microCT was used to compare the healing of osteoporotic fractures with or without SalB. The relative expressions of mRNAs were measured by qRT-PCR. Bioinformatics analysis, RT-PCR, and dual luciferase reporter assay were utilized to detect the interrelation of genes. Immunohistochemistry staining was used to test expressions of proteins. Results: In the present study, we found that SalB significantly increased the level of lncRNA- MALAT1 in a dose-dependent manner. Additionally, silencing lncRNA-MALAT1 inhibited the expressions of osteogenesis-related marker genes and abolished the effect of SalB on osteogenesis. Also, we found that lncRNA-MALAT1 sponged miR-155-5p, and miR-155-5p directly targeted HIF-1 alpha. Using the osteoporotic fracture healing model, our result demonstrated that local administration of SalB could promote both bone and type H vessel formation in the calluses. The mechanical test further showed that SalB could improve the mechanical properties of fractured femurs. Conclusion: Taken together, our study reported that SalB could promote osteogenesis and type H vessel formation to accelerate osteoporotic fracture healing through the lncRNA- MALAT1/miR-155-5p/HIF-1 alpha axis.