Ligand-Selective Targeting of Macrophage Hydrogel Elicits Bone Immune-Stem Cell Endogenous Self-Healing Program to Promote Bone Regeneration.

Abstract

Targeting macrophages can facilitate the site-specific repair of critical bone defects. Herein, a composite hydrogel, gelatin-Bletilla striata polysaccharide-mesoporous bioactive glass hydrogel (GBM^gel), is constructed via the self-assembly of mesoporous bioactive glass on polysaccharide structures, through the Schiff base reaction. GBM^gel can efficiently capture macrophages and drive the recruitment of seed stem cells and vascular budding required for regeneration in the early stages of bone injury, and the observed sustained release of inorganic silicon ions further enhances bone matrix deposition, mineralization, and vascular maturation. Moreover, the use of macrophage-depleted rat calvarial defect models further confirms that GBM^gel, with ligand-selective macrophage targeting, increases the bone regeneration area and the proportion of mature bone. Mechanistic studies reveal that GBM^gel upregulates the TLR4/NF-κB and MAPK macrophage pathways in the early stages and the JAK/STAT3 pathway in the later stages; thus initiating macrophage polarization at different time points. In conclusion, this study is based on the endogenous self-healing properties of bone macrophages, which enhances stem cell homing, and provides a research and theoretical basis upon which bone tissue can be reshaped and regenerated using the body's immune power, providing a new strategy for the treatment of critical bone defects.