Deletion of the chemokine receptor CCR2 attenuates foreign body reaction to implants in mice

• Inflammatory angiogenesis is attenuated in CCR2 knockout mice.
• CCR2 deletion induces aberrant blood vessel formation in subcutaneous implants.
• CCR2 plays an important role in mediating the foreign body reaction.

Subcutaneous implantation of synthetic materials and biomedical devices often induces abnormal tissue healing – the foreign body reaction – which impairs their function. Here we investigated the role of the chemokine receptor CCR2 in this reaction to subcutaneous implants in mice. We measured angiogenesis, inflammation and fibrogenesis induced by implantation, for 1, 4, 7 and 14 days, of polyether–polyurethane sponges in mice with genetic deletion of CCR2 (KO) and WT mice. Blood flow was determined by dye diffusion and laser Doppler perfusion techniques. Cytokines (VEGF, TNF-α, CCL2, TGF-β1) were measured by ELISA. Histochemical methods were used to assess collagen deposition and macrophage-derived giant cells in the implants. Skin and implant blood flow was lower in CCR2 KO than in WT mice, as were other aspects of neo-vascularization of the implants. Neutrophil accumulation was increased in KO implants but macrophage accumulation was decreased. Implant content of CCL2 was higher in KO implants, but TGF-β1, collagen deposition and the number of foreign body giant cells were lower than in WT implants. Deletion of CCR2 decreased blood flow in normal skin and inhibited neo-vascularization, chronic inflammation and fibrogenesis in subcutaneous implants. The chemokine receptor CCR2 plays an important role in both normal skin and in the reaction elicited by subcutaneous implantation of a foreign body.