(A-14) PEEK Promotes Pro-Inflammatory T Cell Subset Polarization In Vitro and In Vivo

Introduction:: T cells are adaptive, lymphoid-derived immune cells that produce inflammatory cytokines that impact the inflammatory microenvironment during wound healing. αβ-T cells differentiate into two distinct lineages, CD4⁺ T cells and CD8⁺ T cells. Our group has previously shown that implanted biomaterials lead to the activation of T cells and that macrophages mediate this process at the implant-cell interface. However, the profile of T cell subsets present in the peri-implant microenvironment and the T cell subsets dynamics in the inflammatory following biomaterial implantation remains unclear. Therefore, this study aimed to characterize T cell subset polarization in response to injury induced by biomaterial implantation.

Materials and Methods:: To characterize T cell subsets in vivo, smooth titanium (Ti) or polyether ether ketone (PEEK) rods were surgically placed in the femoral canal of 12-week-old male C57BL/6J mice (n=6/variable). Sham surgeries in which surgical procedures were performed without implants were used as a control. Immunophenotypic characterization of neutrophils, macrophages, pro-inflammatory macrophages, anti-inflammatory macrophages, dendritic cells, mesenchymal stem cells, CD4⁺ (Th1, Th2, Th9, Th17, Th22, Treg) and CD8+ (Tc1, Tc2, Tc9, Tc17, Treg) T cell subsets were analyzed from peri-implant bone marrow at 3-, 7-, and 14-days post implantation and in the inguinal lymph node nearest the site of implantation at 3-, 7-, 14-, and 21-days post-implantation by flow cytometry. To understand the role of immune cell-cell communication between macrophages and T cells in response to biomaterials, primary bone-marrow-derived macrophages and spleen-derived T cells were isolated from 12-week-old C57BL/6J mice. Macrophages were seeded on polystyrene (TCPS), Ti, or PEEK (n=6/variable). After 24 hours, T cells were added to the macrophages and co-cultured for an additional 48 hours. T cells were collected from media and characterized by flow cytometry. Data were analyzed by ANOVA with Tukey HSD assessment of differences.

Results, Conclusions, and Discussions:: In vivo, more neutrophils, total macrophages, and pro-inflammatory macrophages were recruited to PEEK implants than Ti or Sham (Fig 1). Fewer MSCs were recruited to the peri-implant area in response to PEEK implants when compared to Ti or Sham. CD4⁺ and CD8⁺ T cells were the highest in response to PEEK implants. Th1, Th2, and CD4⁺ Tregs were the lowest in response to PEEK across all time points, while Th17 cells were the highest in response to PEEK when compared to Ti or Sham. Tc1 and Tc17 subsets were higher in response to PEEK implants, while Tc2 and Tc9 were lower in response to PEEK. CD8⁺ Tregs were the lowest in response to PEEK at day 3 post-implantation, with increased levels observed at post-operative days 7, and 14. In vitro, co-cultures between macrophages and T cells showed higher polarization towards Th1 and Th17 in response to PEEK when compared to Ti. Similarly, co-cultured cells on PEEK polarized more Tc1 and Tc17 when compared to Ti. Our results show that T cell subsets are present following biomaterial implantation and that these cells' profiles vary based on the material used. We also demonstrated that T cell subset polarization is influenced by macrophage response to biomaterials. Furthermore, our results also showed that T cell subsets are polarized more towards pro-inflammatory phenotypes in response to PEEK implants and may be associated with the inflammatory outcomes of biomaterial implantation.


Acknowledgements (Optional): :

References (Optional): :