Implant wear induced inflammation is mitigated in CX3CR1(-/-) mice

Wear debris-induced monocyte recruitment plays a key role in the formation of chronic periprosthetic tissue inflammation associated with aseptic loosening. The purpose of this study was to investigate the role(s) of chemokine receptor CX3CR1 in ultra high molecular weight polyethylene (UHMWPE) particle-induced tissue inflammation using a murine air pouch model developed in CX3CR1 knockout (CX3CR1(-/-) ) mice. UHMWPE debris or saline were introduced into established air pouches on CX3CR1(-/-) and CX3CR1(+/+) mice. Pouch tissues were collected 7 days after UHMWPE inoculation. Results showed that UHMWPE stimulation induced strong pouch tissue inflammation in CX3CR1(+/+) mice, as manifested by inflammatory cellular infiltration (mainly macrophages), pouch tissue proliferation, and increased gene expression of IL-1ß and TNFα. UHMWPE-induced inflammation was significantly mitigated in CX3CR1(-/-) mice, as manifested by reduction of tissue inflammation (pouch thickness and cell density), inflammatory cytokine production (IL-1ß and TNFα) and macrophage accumulation. The observations support the hypothesis that the activation of the CX3CR1 chemokine pathway contributes to the severity of UHMWPE particle-induced tissue inflammation, and suggests that CX3CR1 signaling is involved in the recruitment of monocytes to the wear debris-containing inflammatory tissues. Blocking of CX3CR1 pathway may represent a viable therapeutic approach to the prevention and treatment of patients with aseptic loosening.