CpG ODN/Mangiferin Dual Delivery through Calcium Alginate Hydrogels Inhibits Immune-Mediated Osteoclastogenesis and Promotes Alveolar Bone Regeneration in Mice

SIMPLE SUMMARY: The immune system plays an important role in the skeletal system during bone repair and regeneration, especially in the oral environment with its constant host–microbe interactions. This study aims to determine the effect of the controlled delivery of immunomodulatory biologicals on alveolar bone regeneration. This study aims to explore the regulatory effect of a hydrogel microbead, coated with multiple immunomodulatory substances (cytosine-phosphate-guanosine oligodeoxynucleotides and glucosylxanthone Mangiferin), on alveolar bone regeneration. The results showed that the complex microbeads could promote the anti-inflammatory response in splenocytes, inhibit RANKL-mediated osteoclastogenesis in a co-culture model of activated splenocytes and osteoclast precursors cells, and promote new bone deposition in mice. This study demonstrated that alveolar bone regeneration could be regulated by cytosine-phosphate-guanosine oligodeoxynucleotides and glucosylxanthone Mangiferin, which provides a potential therapeutic strategy for the treatment of alveolar bone regeneration. ABSTRACT: The immune system plays an important role in the skeletal system during bone repair and regeneration. The controlled release of biological factors from the immune system could facilitate and optimize the bone remodeling process through the regulation of the activities of bone cells. This study aimed to determine the effect of the controlled delivery of immunomodulatory biologicals on bone regeneration. Immunostimulatory cytosine-phosphate-guanosine oligodeoxynucleotides (CpG ODN) and glucosylxanthone Mangiferin (MAG)-embedded microbeads were incubated with P. gingivalis-challenged splenocytes, or co-cultured with RAW264.7 cells. The effect of CpG ODN/MAG-containing microbeads on bone regeneration was then tested in vivo in a mouse alveolar bone defect model. The results demonstrated that MAG significantly antagonized P. gingivalis proliferation and reduced the live/dead cell ratio. After the addition of CpG ODN + MAG microbeads, anti-inflammatory cytokines IL-10 and IL-4 were upregulated on day 2 but not day 4, whereas pro-inflammatory cytokine IL-1β responses showed no difference at both timepoints. RANKL production by splenocytes and TRAP+ cell formation of RAW264.7 cells were inhibited by the addition of CpG ODN + MAG microbeads. Alveolar bony defects, filled with CpG ODN + MAG microbeads, showed significantly increased new bone after 4 weeks. In summary, this study evaluated a new hydrogel-based regimen for the local delivery and controlled release of biologicals to repair and regenerate alveolar bony defects. The combined CpG ODN + MAG treatment may promote alveolar bone regeneration through the anti-microbial/anti-inflammatory effects and the inhibition of RANKL-mediated osteoclastogenesis.