Can highly purified collagen coating modulate polypropylene mesh immune-inflammatory and fibroblastic reactions? Immunohistochemical analysis in a rat model

Introduction and hypothesis Collagen has been proposed to be a useful biomaterial, but previous attempts to combine meshes with a collagen membrane have failed. The objective was to verify the effect of high-purified collagen gel coating in the immune-inflammatory response, host collagen metabolism, and angiogenesis around polypropylene mesh. Methods In 20 female Wistar rats were implanted, at one side of the abdominal wall, a monofilament polypropylene mesh (PP), and, on the other side, a mesh coated with a new highly purified collagen gel (PPC). The animals were divided into sub-groups and euthanized at 7, 14, 21, and 90 days after implantation. Immunohistochemical analysis was performed using interleukin 1 (IL-1), matrix metalloproteinases (MMP-2, MMP-3), surface antigen CD-31, and tumor necrosis factor (TNF-α). Objective analysis (percent reactive area, average density, and vessels concentration) was performed using AxioVision Software. Results Comparative analysis showed: higher vessel density in the PPC group after 14 days ( p = 0.002); a decrease in the average density of MMP-2 in the PPC group after 21 and 90 days ( p = 0.046); more stability in the behavior of MMP-3 in the PPC group throughout the periods with the percentage reactive area for MMP-3 showing a significant decrease just in the PP group after 14 and 90 days ( p = 0.017), and also for MMP-3 average density, in which reduction was significant after 21 days in the PP group, but not until after 90 days in PPC group ( p < 0.001). Conclusions Highly purified collagen coating causes significant changes in angiogenesis and in the immune reaction of metalloproteinase around mesh implants in rats. These findings can be useful for improving mesh biocompatibility for pelvic floor surgery if such effects could be properly controlled.