To determine the role of osteoblast in the pathogenesis of osteolysis, we evaluated cell proliferation and differentiation of culturedosteoblasts by adding retrieved polyethylene particles.

We cultured the osteoblasts primarily isolated from rat neonate calvariums and then added polyethylene particles retrieved from osteolysis tissue. We evaluated cell proliferation, alkaline phosphatase activity, the expression of Type I procollagen mRNA, the expression of osteocalcin mRNA, bone nodule formation, and the expression of osteoprotegerin (OPG) mRNA and receptor activatorof NF-kappa B ligand (RANKL) mRNA according to culture periods.

Particle groups showed statistically significant decrease in cell proliferation after the 7th day. The expression of type I procollagen mRNA increased on the 14th day. The bone nodules appeared at the 7th day and increased with time. There was no appearance of bone nodule in the control group. The expression of OPG mRNA in particle groups was not changed. The expression of RANKL mRNA was significantly increased in high concentration particle group (4 mg/mL) on the 14th day.

Polyethylene particles ceased the proliferation of osteoblasts and produced early extracellular matrix maturation and mineralization process in vitro and increased the expression of RANKL promoting osteoclast activities.