Local delivery of lipid-based nanoparticles containing microbial nucleic acid for osteoimmunomodulation

Area of Science:

• Biomaterials Science
• Immunology
• Regenerative Medicine

Background:

• Osteoimmunomodulation enhances bone regeneration by manipulating the immune microenvironment.
• CpG-containing oligonucleotides type C (CpG ODN C) and Polyinosinic:polycytidylic acid (Poly[I:C]) are microbial nucleic acid analogs with immunotherapeutic potential.

Purpose of the Study:

• To investigate CpG ODN C and Poly(I:C) as osteoimmunomodulatory agents for bone regeneration.
• To evaluate the efficacy of lipid-based nanoparticles delivering these nucleic acids for bone implant applications.

Main Methods:

• CpG ODN C and Poly(I:C) were encapsulated in lipid-based nanoparticles (Lip/CpG ODN C, Lip/Poly[I:C]).
• Effects on macrophage cytokine production (TNF, IL-6, IL-10) and osteoblast differentiation were assessed.
• Bone implants containing scaffolds, BMP-2, and nanoparticles in GelMA hydrogel were tested in a rabbit extra-skeletal model for 5 weeks.

Main Results:

• Lip/CpG ODN C and Lip/Poly[I:C] enhanced cytokine production in macrophages compared to free nucleic acids.
• CpG ODN C and Lip/CpG ODN C promoted osteoblast differentiation in vitro.
• In vivo, all implant groups showed bone formation, but new bone volume and scaffold degradation were similar across groups.

Conclusions:

• Lip/CpG ODN C demonstrates potential for osteoimmunomodulation in vitro.
• Inadequate nucleic acid concentrations and potential BMP-2 masking effects may have limited in vivo outcomes.
• Further in vivo studies are needed to confirm the osteoimmunomodulatory potential of Lip/CpG ODN C for bone regeneration.