Macrophage phenotype in the epigallocatechin-3-gallate (EGCG)-modified collagen determines foreign body reaction

Collagen has been widely used in guided bone regeneration, and the implantation of collagen membranes will elicit the foreign body reaction (FBR). The imbalance of FBR often leads to failure of dental implants. Therefore, modulation of the FBR after implantation of collagen membranes becomes increasingly important. Macrophages, pivotal in FBR, have been distinguished into pro-inflammatory (M1) and anti-inflammatory (M2) phenotypes. Epigallocatechin-3-gallate (EGCG)-modified collagen membranes have been previously shown to regulate secretion of inflammatory factors. In this study, immunohistochemistry of CD31 showed that areas of blood vessels were significantly enlarged after implantation of EGCG-modified collagen membranes compared with those treated with pure collagen membranes. Besides, haematoxylin-eosin staining and immunofluorescence showed an increased number of M2 macrophages after implantation of EGCG-modified collagen membranes. In addition, quantitative real-time polymerase chain reaction showed that after implantation of EGCG-modified collagen membranes, expression of CXCL1 (predominant chemoattractants to neutrophils and inflammation promotors) was significantly downregulated, whereas expressions of STAB1, CCR2, CCR3, CCL2, and CCL3 (related to M2 macrophages) were significantly upregulated. From these findings, we conclude that EGCG-modified collagen membranes were able to regulate the recruitment and polarization of macrophages, so that ameliorate FBR.