Novel injectable composite incorporating denosumab promotes bone regeneration via bone homeostasis regulation

Repair of large bone defects remains to be clinically challenging, yet current bone repair strategies focus on optimizing the osteogenic capacity of bone grafts, while the role of osteoclasts in bone regeneration has been largely ignored. Herein, we designed a injectable self-curing bone grafting paste capable of regulating both anabolic/catabolic activities during bone healing by immobilizing the RANKL inhibitor denosumab on dermal-derived extracellular matrix (ECM) microfibres, which were then incorporated into an injectable paste via a hydration reaction between β-tricalcium phosphate (β-TCP), monocalcium phosphate monohydrate (MCPM) and calcium sulfate hemihydrate (CSH). The incorporation of ECM microfibres not only serves as a sustained-release denosumab carrier to inhibit osteoclastogenesis but also improves the mechanical properties of the resulting composite by increasing the interaction between the organic and inorganic phases. In vitro, calcium supply from the composite along with ECM enhanced osteogenic differentiation of BMSC while release of denosumab effectively inhibits osteoclast fusion and alleviate osteoclastic activity. In vivo, it was observed that CSH/CP@ECM-Deno significantly reduced the number of osteoclasts, slowed down the process of bone resorption, and accelerated collagen deposition to promote new bone generation. These results suggest that modulation of osteoclastogenesis by interfering with bone homeostasis may be an effective bone repair strategy.