Improvements in the resolution of the foreign body reaction by the modulation of macrophage polarization towards an M2 phenotype at the tissue-implant interface by local release of IL-4 from layer by layer coated polypropylene meshes

摘要

Introduction: Surgical mesh implantation is a common option for hernia repair and pelvic organ prolapse; however, associated with severe complications such as pain, organ perforation and mesh exposure. Mesh complications are mostly due to host chronic foreign body reaction, performed by pro-inflammatory (M1) macrophages at the tissue implant interface. On the other hand, pro-remodeling (M2) macrophages have been found to be important players in tissue remodeling. Also, the M2:M1 ratio has been described to be a predictor of success of a biomaterial in-vivo. It has been hypothesized that transient polarization of macrophages at the tissue-implant interface to an M2 phenotype will mitigate the foreign body reaction. Therefore, a nanometer thickness coating with the ability to provide local delivery of IL-4 (an in-vitro M2 polarizing cytokine) has been developed. Materials and Methods: Gynemesh® Polypropylene (PP) meshes were treated with radio frequency glow discharge (RFGD) to produce a negatively charged surface. To construct the coating, a layer-by-layer (LbL) procedure was performed using chitosan as polycation and dermatan sulfate as polyanion. Cycles were repeated with intermediate washing steps until desired number of layers. Loading of IL-4 was performed by prior incubation with dermatan sulfate. X-ray photoelectron spectroscopy (XPS), ATR-FTIR and alcian blue staining were used to characterize the coating. ELISA assays were used to evaluate the release of IL-4 at different time points. Also, a murine macrophage culture was used to corroborate the bioactivity of the released IL-4 by means of an arginase-1 immunolabeling and quantitative analysis. Finally, 1 cm2 pieces of mesh were implanted subcutaneously on the abdomen of female C57BL/6J mice and then sections of mesh-surrounding tissue were harvested at 7,14 and 90 days for histology. Results and Discussion: Appearance of new peaks on the XPS and ATR-FTIR spectra but also stained meshes by alcian blue consistently confirmed the presence of a uniform, conformal coating made of both chitosan and dermatan sulfate. Similarly, confocal microscopy images of immunolabeled meshes showed a uniform loading of IL-4 through all the mesh surface (Figure 1 A). ELISA assays showed that the amount and release time of IL-4 from coated meshes were dependent on the number of coating bilayers, but the power law dependence profile of release remained constant (Figure 1B). Additionally, higher expression of arginase-1 from macrophages exposed to IL-4 loaded meshes demonstrated M2 polarization and maintenance of IL4 bioactivity (Figure 1C). Interestingly, histological studies of mice implanted with IL-4 loaded meshes revealed less dense cellular inflammatory infiltrates around mesh fibers and a higher percentage of M2 macrophages compared to control meshes at 7 (Figure 2) and 14 days. Finally, mice implanted with IL-4 loaded meshes resulted in a diminished capsule formation at 90 days, as shown by Masson's Trichrome (Figure 2) and Picro Sirius Red staining, compared to control meshes. Conclusions: Local release of IL-4 from coated polypropylene meshes is tunable and capable to polarize macrophages to an M2 phenotype both in-vitro and in-vivo, but also have shown to decrease inflammation and capsule formation in-vivo, suggesting improvements in the resolution the foreign body reaction against implanted mesh.