The genetic background determines material-induced bone formation through the macrophage-osteoclast axis

Area of Science:

• Biomaterials Science
• Immunology
• Bone Biology

Background:

• Osteoinductive materials promote bone formation but their mechanism is unclear, hindering the design of potent materials.
• Understanding material-induced bone formation is crucial for effective bone defect repair.
• Ectopic bone formation, while promising for regeneration, requires deeper mechanistic insight.

Purpose of the Study:

• To elucidate the mechanism of material-induced bone formation.
• To investigate the link between macrophage polarization, osteoclastogenesis, and bone formation.
• To identify genetic factors controlling these processes for precision medicine applications.

Main Methods:

• Intramuscular implantation of osteoinductive material in FVB and C57 mice.
• In vitro studies using mouse-derived monocytes to assess macrophage polarization and osteoclast formation.
• Transcriptomic analysis to identify key genes involved in macrophage-osteoclast coupling.
• Validation using gene inhibitors and testing in multiple mouse strains.

Main Results:

• FVB mice showed increased M2 macrophages, osteoclasts, and bone formation compared to C57 mice.
• In vitro, FVB monocytes exhibited greater M2 polarization and osteoclast formation.
• Transcriptomic analysis identified Csf1, Cxcr4, and Tgfbr2 as key genes in macrophage-osteoclast coupling.
• In vitro findings accurately predicted in vivo bone formation across different mouse strains.

Conclusions:

• A genetic link exists between macrophage polarization, osteoclastogenesis, and material-induced bone formation.
• Macrophage polarization and osteoclast formation serve as reliable predictors of in vivo bone formation.
• These findings offer insights into precision medicine for bone regeneration and treating pathological heterotopic bone formation.