IADR Abstract Archives
Activated Macrophages Control T-cell Populations and MSC Recruitment
Objectives: Immune cells, specifically macrophages, determine the fate of implanted biomaterials. Titanium (Ti) surface modifications modulate macrophage activation, with hydrophilic-surfaces promoting anti-inflammatory and hydrophobic supporting pro-inflammatory activation. These cells may influence activation and recruitment of additional immune cells or mesenchymal-stem-cells (MSCs). The aim of this study was to determine if macrophage response to Ti-surface properties will control T-helper-cell populations in-vitro and in-vivo as well as MSC recruitment.
Methods: For in-vivo studies SLA and hydrophilic-SLA (mSLA) Ti 1mm-diameter cylindrical implants were placed intrafemorally in 10-wk C57Bl/6 or macrophage-ablated (clod) mice. After 3 or 7days, mice were euthanized and bone-marrow, contralateral-bone-marrow, and spleens harvested and analyzed by qPCR and flow cytometry. Additionally, primary murine T-cells and macrophages were co-cultured (1:1) directly and indirectly on Ti-surfaces for 24 hours. T-cell populations (TH1, TH2, TH17, Treg) were assessed through flow cytometry. Differences (n=6) determined by ANOVA with Tukey HSD comparisons between groups (α=0.05).
Results: Implants increased inflammatory markers and immune-cell recruitment at day3, which were resolved at day7 and MSC-recruitment increased, with the greatest on mSLA. T-cell populations changed between sham, SLA, and mSLA animals in the spleen, bone-marrow and contralateral leg bone-marrow at both day3 and day7. Higher levels of anti-inflammatory-TH2 and Tregs were measured at day3 on implants, by day7 TH2 was higher on SLA and Treg greatest on mSLA. Direct co-culture with macrophages induced greater changes in T-cell populations than in-direct, with the highest TH2 and Treg on mSLA. Hydrophilic-SLA increased MSC-recruitment and Treg-activation with macrophages in-vivo. Following macrophage ablation, fewer MSCs and Tregs were attached to implants and no differences were found between surfaces.
Conclusions: This study highlighted the importance of the immune response in implant healing. Macrophage activation controlled changes in T-cell populations and MSC-recruitment based on implant, while hydrophilic implants generated an anti-inflammatory microenvironment, through macrophages and T-helper-cells, and increased MSC levels.
Methods: For in-vivo studies SLA and hydrophilic-SLA (mSLA) Ti 1mm-diameter cylindrical implants were placed intrafemorally in 10-wk C57Bl/6 or macrophage-ablated (clod) mice. After 3 or 7days, mice were euthanized and bone-marrow, contralateral-bone-marrow, and spleens harvested and analyzed by qPCR and flow cytometry. Additionally, primary murine T-cells and macrophages were co-cultured (1:1) directly and indirectly on Ti-surfaces for 24 hours. T-cell populations (TH1, TH2, TH17, Treg) were assessed through flow cytometry. Differences (n=6) determined by ANOVA with Tukey HSD comparisons between groups (α=0.05).
Results: Implants increased inflammatory markers and immune-cell recruitment at day3, which were resolved at day7 and MSC-recruitment increased, with the greatest on mSLA. T-cell populations changed between sham, SLA, and mSLA animals in the spleen, bone-marrow and contralateral leg bone-marrow at both day3 and day7. Higher levels of anti-inflammatory-TH2 and Tregs were measured at day3 on implants, by day7 TH2 was higher on SLA and Treg greatest on mSLA. Direct co-culture with macrophages induced greater changes in T-cell populations than in-direct, with the highest TH2 and Treg on mSLA. Hydrophilic-SLA increased MSC-recruitment and Treg-activation with macrophages in-vivo. Following macrophage ablation, fewer MSCs and Tregs were attached to implants and no differences were found between surfaces.
Conclusions: This study highlighted the importance of the immune response in implant healing. Macrophage activation controlled changes in T-cell populations and MSC-recruitment based on implant, while hydrophilic implants generated an anti-inflammatory microenvironment, through macrophages and T-helper-cells, and increased MSC levels.
