Evaluation of the osteo-inductive potential of hollow three-dimensional magnesium-strontium substitutes for the bone grafting application

- Novel biodegradable MgSr bone substitutes with the hollow and marginal design was fabricated
- The MgSr substitutes exhibited excellent cyto-compatibility and osteo-inductivity effects
- The osteo-inductivity mechanism was significant up-regulation of the typical osteogenesis-related factors

Regeneration of bone defects is a clinical challenge that usually necessitates bone grafting materials. Limited bone supply and donor site morbidity limited the application of autografting, and improved biomaterials are needed to match the performance of autografts. Osteoinductive materials would be the perfect candidates for achieving this task. Strontium (Sr) is known to encourage bone formation and also prevent osteoporosis. Such twin requirements have motivated researchers to develop Sr-substituted biomaterials for orthopedic applications. The present study demonstrated a new concept of developing biodegradable and hollow three-dimensional magnesium-strontium (MgSr) devices for grafting with their clinical demands. The microstructure and performance of MgSr devices, in vitro degradation and biological properties including in vitro cytocompatibility and osteoinductivity were investigated. The results showed that our MgSr devices exhibited good cytocompatibility and osteogenic effect. To further investigate the underlying mechanisms, RT-PCR and Western Blotting assays were taken to analyze the expression level of osteogenesis-related genes and proteins, respectively. The results showed that our MgSr devices could both up-regulate the genes and proteins expression of the transcription factors of Runt-related transcription factor 2 (RUNX2) and Osterix (OSX), as well as alkaline phosphatase (ALP), Osteopontin (OPN), Collagen I (COL I) and Osteocalcin (OCN) significantly. Taken together, our innovation presented in this work demonstrated that the hollow three-dimensional MgSr substitutes had excellent biocompatibility and osteogenesis and could be potential candidates for bone grafting for future orthopedic applications.