Objective       To observe the effects of NF-κB essential modifier binding domain (NBD) peptide

alone or in combination with osteoprotegerin (OPG)

on bone destruction reduction as well as prevention and treatment of artificial joint loosening with a mouse air pouch model.      Methods       The mouse air pouch model was constructed through injecting air into mouse back to form a pouch and implanting skull bone from homologous mouse into the air pouch. The model mice were divided into three groups: an NBD peptide group (polyethylene particles and NBD peptides were injected into the air pouch)

a combination group (polyethylene particles

NBD peptides

and OPG were injected into the air pouch)

and a control group (polyethylene particles and saline were injected into the air pouch). Pouch tissues and implants were collected after three weeks for detection. HE staining was used to detect inflammatory response and inflammatory cell infiltration. ELISA was used to detect cytokine (IL-1 and TNF) concentrations in tissue homogenate. Tartrate-resistant acid phosphatase staining was used to observe osteoclast differentiation and maturation. Scanning electron microscopy was used to detect bone slice resorption. RT-PCR was used to detect type-Ⅱ carbonic anhydrase (CA-Ⅱ) mRNA expression.      Results       HE staining results showed that inflammatory cell amounts in the NBD peptide group (870±236) and combination group (820±198) were significantly smaller than that in the control group (3 325±467) (P0.05). ELISA results showed that inflammatory cytokine (IL-1 and TNF) concentrations in the NBD peptide group (138.34±2.32 and 156.14±4.17) and combination group (129.32±4.62 and 148.78±5.36) were significantly lower than those in the control group (187.56±4.78 and 179.45±8.34) (P0.05). Tartrate-resistant acid phosphatase staining results showed that the percentages of positive area to visual field area in the NBD peptide group [(1.06±0.67)%] and combination group [(0.64±0.33)%] were significantly lower than that in the control group [(4.12±1.09)%]

with a significant difference between the NBD peptide group and the combination group (P0.05). Scanning electron microscopy  showed that the percentages of bone slice resorption area to visual field area in the NBD peptide group [(4.03±0.76)%] and combination group [(2.65±0.58)%] were significantly lower than that in the control group [(12.38±1.98)%]

with a significant difference between the NBD peptide group and the combination group (P0.05). RT-PCR results showed that the expression of CA-Ⅱ mRNA in the NBD peptide group (0.254±0.048) and the combination group (0.180±0.033) was significantly lower than that of the control group (0.382±0.072)

with a significant difference between the NBD peptide group and the combination group (P0.05).      Conclusion       In a mouse air pouch model

NBD peptide can significantly reduce inflammation and thereby inhibit osteoclast activation indirectly

while OPG can inhibit osteoclast activation and maturation directly. NBD peptide in combination with OPG has more obvious inhibitory effects on bone resorption induced by polyethylene wear particles.