The immunomodulatory effects and mechanisms of magnesium-containing implants in bone regeneration: A review

Traditional designs and developments of bone biomaterials mostly concentrate on the positive regulation of osteoblast lineage cells, but often ignore the importance of immune responses and the equilibrium between bone resorption mediated by osteoclasts and bone formation mediated by osteoblasts. Immune dysregulation is associated with an imbalance between pro-inflammatory and anti-inflammatory processes, which may influence the efficacy of bone therapy. Therefore, implanted biomaterials should appropriately and precisely modulate subsequent immune responses. Magnesium (Mg) has been used to fabricate various Mg alloys for bone repair because of its favorable attributes such as osteogenic potential, immune regulation characteristics, biodegradability, and biocompatibility. Various basic research and clinical trials have been already conducted in many countries to explore the physical properties of Mg-containing implants and their clinical outcomes in bone fracture and defect repair. Therefore, this review summarizes the immune response to Mg-containing implants, and further organizes the current research and development progress of Mg-containing implants. The review aims to offer an overview of the current knowledge on immunomodulation of Mg-containing implants and future challenges in their clinical application, which could provide further insight in the development of better strategies for the treatment of bone defect and fracture.