Host response to sponge implants differs between subcutaneous and intraperitoneal sites in mice

Synthetic matrices have been used widely to repair and/or to replace biological tissues. However, there is relatively little information on the effect of different anatomical compartments on the host response to foreign implants. We have analyzed such responses to sponge implants in subcutaneous and in intraperitoneal sites in mice at days 3, 5, and 8 postimplantation by measuring inflammation, angiogenesis, and production of proangiogenic/inflammatory cytokines. The angiogenic response, assessed by hemoglobin content and by morphometric analysis of the number of vessels, was higher in intraperitoneal implants. Levels of vascular endothelial growth factor in intraperitoneal implants were 14-fold higher than in subcutaneous implants at day 3 and remained high for the next 5 days. Neutrophil accumulation as determined by myeloperoxidase activity was the same in both types of implants. Macrophage accumulation (N-acetylglucosaminidase activity) was also similar on days 3 and 8 in both implants. Levels of the chemokine CXCL2/KC were always higher, but those of CCL2/JE lower, in the intraperitoneal implant. These results demonstrate that the anatomical site of the implant markedly influenced the host response to synthetic matrices. Our results provide a greater understanding of factors affecting the biocompatibility of exogenous materials placed at different anatomical sites.