Spatiotemporal Immunomodulation Using Biomimetic Scaffold Promotes Endochondral Ossification-Mediated Bone Healing

Area of Science:

• Biomaterials Science
• Regenerative Medicine
• Immunology

Background:

• Biomaterials are crucial for bone defect treatment, primarily promoting intramembranous ossification (IO).
• Most bone formation occurs via endochondral ossification (EO), a process poorly replicated by current engineered scaffolds, limiting their use for large bone defects.
• Mimicking EO is essential for developing effective bone regeneration strategies.

Purpose of the Study:

• To engineer biomimetic scaffolds capable of inducing endochondral ossification (EO) for bone defect repair.
• To investigate the role of immune modulation and specific signaling pathways in scaffold-mediated bone regeneration.
• To enhance the clinical utility of biomaterials for treating large segmental bone defects.

Main Methods:

• Developed porous mesoporous bioglass scaffolds loaded with recombinant human bone morphogenetic protein (rhBMP) and dexamethasone.
• Controlled the release kinetics of loaded therapeutics to regulate biological responses.
• Investigated the effects of scaffolds on macrophage polarization and mesenchymal stem cell (MSC) signaling pathways, specifically Hif-3α.

Main Results:

• Achieved significant ectopic bone formation through endochondral ossification (EO) by entrapping dexamethasone within rhBMP-loaded scaffolds.
• Demonstrated that scaffolds regulate immune suppressive macrophage phenotypes, promoting chondrogenesis via Hif-3α activation in MSCs.
• Showed that Hif-3α pathway activation upregulates chondrogenic gene expression, and its inhibition reverses the EO phenotype.

Conclusions:

• Developed a novel biomimetic scaffold strategy that successfully induces endochondral ossification (EO) by modulating immune responses.
• The scaffold activates Hif-3α signaling in MSCs, facilitating chondrogenesis and subsequent bone formation.
• This approach offers new opportunities for biomaterial development to induce natural bone regeneration, particularly for large bone defects.