Effect of Alumina Particles on the Osteogenic Ability of Osteoblasts

Biomaterials are used as implants for bone and dental disabilities. However, wear particles from the implants cause osteolysis following total joint arthroplasty (TJA). Ceramic implants are considered safe and elicit a minimal response to cause periprosthetic osteolysis. However, few reports have highlighted the adverse effect of ceramic particles such as alumina (Al₂O₃) on various cell types. Hence, we aimed to investigate the effect of Al₂O₃ particles on osteoprogenitors. A comparative treatment of Al₂O₃, Ti, and UHMWPE particles to osteoprogenitors at a similar concentration of 200 μg/mL showed that only Al₂O₃ particles were able to suppress the early and late differentiation markers of osteoprogenitors, including collagen synthesis, alkaline phosphatase (ALP) activity and mRNA expression of Runx2, OSX, Col1α, and OCN. Al₂O₃ particles even induced inflammation and activated the NFkB signaling pathway in osteoprogenitors. Moreover, bone-forming signals such as the WNT/β-catenin signaling pathway were inhibited by the Al₂O₃ particles. Al₂O₃ particles were found to induce the mRNA expression of WNT/β-catenin signaling antagonists such as DKK2, WIF, and sFRP1 several times in osteoprogenitors. Taken together, this study highlights a mechanistic view of the effect of Al₂O₃ particles on osteoprogenitors and suggests therapeutic targets such as NFĸB and WNT signaling pathways for ceramic particle-induced osteolysis.