Bone homeostasis regulation by in vivo generation of osteoclast-derived apoptotic bodies using targeted self-assembly

Area of Science:

• Biomaterials Science
• Nanotechnology
• Regenerative Medicine

Background:

• Current osteoporosis treatments non-specifically inhibit osteoclasts, impairing bone remodeling and increasing fracture risk.
• There is a need for targeted therapies that eliminate pathological bone resorption while preserving physiological bone maintenance.

Purpose of the Study:

• To develop enzyme-responsive nanoparticles for selective targeting of mature osteoclasts.
• To investigate a dual-action therapeutic strategy that eliminates pathological osteoclasts and promotes bone regeneration.

Main Methods:

• Design of OsteoSAVE nanoparticles with a cathepsin K (CTSK)-cleavable linker, bone-targeting motif, and self-assembling core.
• In vitro and in vivo studies using ovariectomized mice to assess therapeutic efficacy.
• Mechanistic studies to confirm CTSK-selective cleavage and cellular specificity.

Main Results:

• OsteoSAVE nanoparticles undergo CTSK-mediated self-assembly into nanofibers within osteoclasts, inducing apoptosis.
• Released apoptotic bodies are enriched with PDGF-BB, promoting osteogenesis via PI3K/AKT activation in mesenchymal stem cells.
• OsteoSAVE treatment restored bone density in ovariectomized mice by coupling osteoclast elimination with enhanced osteogenesis.

Conclusions:

• Enzyme-triggered supramolecular self-assembly offers a paradigm for dual-action osteoporosis therapies.
• OsteoSAVE selectively targets pathological osteoclasts, recalibrating bone homeostasis without disrupting physiological bone remodeling.
• This approach presents a promising strategy for treating osteoporosis by simultaneously inhibiting bone resorption and stimulating bone formation.