Macrophage-mediated control of implant-associated biofilms in a three-dimensional human oral mucosa model

Macrophages are pivotal in regulating inflammation and facilitating pathogen clearance, particularly in peri-implant environments prone to biofilm infections. For a better understanding of the role of these immune cells in host-biofilm-implant interactions, we developed a complex three-dimensional (3D) implant-tissue-oral-bacterial-biofilm model (INTER b ACT) with integrated macrophages to mimic the intricate triangular interactions between implant materials, biofilms, and the host, in conditions simulating the in vivo environment. The INTER b ACT model includes a peri-implant mucosa with collagen-embedded fibroblasts and macrophages, overlaid with a multi-layered oral epithelium, as well as a multi-species biofilm. Histological analysis demonstrated a preserved peri-implant architecture with high cell viability. Co-cultivation with multi-species biofilms provided valuable insights into macrophage roles in pathogen defence and inflammation regulation. In tissues lacking macrophages, biofilm exposure led to compromised epithelial integrity, whereas macrophage-containing tissues maintained their epithelial structure. Macrophages significantly reduced the biofilm biomass while promoting bacterial death. Inflammatory cytokine levels elevated under sterile conditions decreased upon biofilm exposure, suggesting a biofilm-mediated immune suppression. Cytokine expression levels differentially reacted to biofilm exposure and macrophage concentration, with IL-1β and IL-17 levels notably elevated in biofilm-exposed tissues, aligning with clinical observations of peri-implant inflammation. Our findings demonstrate that the INTER b ACT model, after incorporation of macrophages, serves as a physiologically relevant platform for studying host-pathogen dynamics and allows to identify key inflammatory markers associated with biofilm-related complications. Furthermore, this model holds significant potential for evaluating novel therapeutic strategies, such as sensor-actuator systems to detect and combat pathogenic biofilms, improving clinical outcomes in peri-implantitis management.