Magnesium-doped bioactive glass enhances bone regeneration by reversing replicative senescence of human dental pulp stem cells in bone defect therapy

Human dental pulp stem cells (hDPSCs) exhibit replicative senescence during <i>in vitro</i> expansion, leading to a reduction in osteogenic differentiation capacity and thereby limiting their potential for bone defect regeneration. Magnesium ion (Mg²⁺), one of the most abundant divalent cations in the human body, is involved in numerous physiological processes. Mg²⁺ deficiency has been closely associated with bone fragility and various systemic aging-related diseases, underscoring its critical role in aging and bone metabolism. However, the effects of Mg²⁺ on mesenchymal stem cells (MSCs) replicative senescence remain poorly understood. In this study, we developed magnesium-doped bioactive glass (Mg-BG) powder with a graded magnesium doping ratio through the sol-gel method, and characterized the pore structure and ion release profiles of each Mg-BG group. We demonstrated that 20 Mg-BG (Mg-BG containing 20 mol% MgO) can effectively reverse the replicative senescence of hDPSCs, improve mitochondrial function, reduce ROS levels and enhance the expression of surface markers associated with differentiation, migration and adhesion in replicatively senescent hDPSCs, thereby enhancing their osteogenic differentiation potential. Furthermore, <i>in vivo</i> experiments using a rat calvarial defect model also confirmed that 20 Mg-BG significantly enhances bone defect repair mediated by replicatively senescent hDPSCs. Mechanistically, we found that the IKBKGP1-mediated NF-κB pathway may play a key role in this process, as revealed by transcriptome sequencing. These findings indicate that Mg-BG could serve as an effective, innovative approach to reverse replicative senescence in hDPSCs and enhance their bone defect repair capabilities.