An in vitro investigation of the marked impact of dendritic cell interactions with bone grafts.

The immune response to bone biomaterials plays a critical role during early inflammation and biomaterial-induced osteogenesis. Dendritic cells (DCs) possess a significant impact during immune responses to biomaterials. While conventional strategies to evaluate the osteogenic potential of bone substitute materials focus mainly on osteoblast differentiation. Therefore the present study was to investigate the interactions DCs to porous β-tricalcium phosphate (β-TCP) to investigate whether DCs participate in the material-coordinated osteogenic process. DC maturation and function were investigated by detecting the expression of cell surface markers and inflammatory cytokines by RT-PCR. DCs seeded on β-TCP showed a decrease in co-stimulatory molecules (CD86 and CD40) and pro-inflammatory gene IFN-γ but an increase in anti-inflammatory genes including IL-1ra, IL-4, and IL-10, as well as TGF-β1. Thereafter, conditioned media was harvested from DCs seeded on standard tissue culture plastic and β-TCP to be utilized with osteoblast cell cultures. It was found that conditioned media from DCs seeded on β-TCP markedly promoted osteoblast differentiation by increasing the expression of osteogenic genes RUNX2, ALP, OCN as well as increased ALP activity and alizarin red staining in vitro. In conclusion, the findings from the present study point to the potential crucial role of DCs in biomaterial-induced osteogenesis.