IADR Abstract Archives
Hierarchically Staggered Nanotopography Orchestrates Macrophage Response to Promote Bone Regeneration
Objectives: Mineralized collagen with bone-like, hierarchically staggered nanotopography could regenerate neo-bone with similar micro- and nano-structure to natural bone; however, how the mineralized collagen utilizes its biomimetic, staggered nanotopography to create a favorable osteoimmune environment for bone regeneration is still unclear.In this study, the immunomodulatory properties of hierarchically staggered nanotopography via macrophage polarization during endogenous bone regeneration were investigated.
Methods: Hierarchical intrafibrillarly-mineralized collagen (HIMC) with bone-like, staggered nanotopography was fabricated using a modified, biomimetic bottom-up approach. Scanning and transmission electron microscopy was applied to observe the micro-and nano-topography of HIMC. To assess the bone regeneration potential of HIMC, critical-sized defects with 5 mm in diameter were created in Sprague-Dawley rat mandibles. Micro-CT, HE and immunohistochemical stainings were applied to evaluate neo-bone volume, macrophage polarization and bone marrow mesenchymal stem cell (BMMSC) recruitment. The in vitro interactions between BMMSCs and macrophages were investigated by Flow cytometry, RT-PCR and Western-blot.
Results: Without xenogenous stem cell and cytokine loading, the HIMC induced massive neo-bone formation, accompanied with CD146+ host BMMSC recruitment and CD68+CD163+ M2 macrophage accumulation in critical-sized defects. We further demonstrated in vitro that BMMSC osteogenesis was significantly enhanced after incubation with the supernatants from HIMC-treated macrophages. Meanwhile, macrophages cultured on the HIMC polarized towards M2 phenotype, with significantly enhanced secretion of interleukin (IL)-4, which further promoted BMMSC osteogenesis and mineralization. IL-4 loaded HIMC could significantly improve neo-bone regeneration, compared with HIMC.
Conclusions: Taken together, these findings suggest that emulating natural design, HIMC possesses the capacity to recruit host stem cells and promote osteogenesis by immunomodulation of macrophages; and IL-4, as a key cytokine of M2 macrophage polarization, plays an important role during this process.
Methods: Hierarchical intrafibrillarly-mineralized collagen (HIMC) with bone-like, staggered nanotopography was fabricated using a modified, biomimetic bottom-up approach. Scanning and transmission electron microscopy was applied to observe the micro-and nano-topography of HIMC. To assess the bone regeneration potential of HIMC, critical-sized defects with 5 mm in diameter were created in Sprague-Dawley rat mandibles. Micro-CT, HE and immunohistochemical stainings were applied to evaluate neo-bone volume, macrophage polarization and bone marrow mesenchymal stem cell (BMMSC) recruitment. The in vitro interactions between BMMSCs and macrophages were investigated by Flow cytometry, RT-PCR and Western-blot.
Results: Without xenogenous stem cell and cytokine loading, the HIMC induced massive neo-bone formation, accompanied with CD146+ host BMMSC recruitment and CD68+CD163+ M2 macrophage accumulation in critical-sized defects. We further demonstrated in vitro that BMMSC osteogenesis was significantly enhanced after incubation with the supernatants from HIMC-treated macrophages. Meanwhile, macrophages cultured on the HIMC polarized towards M2 phenotype, with significantly enhanced secretion of interleukin (IL)-4, which further promoted BMMSC osteogenesis and mineralization. IL-4 loaded HIMC could significantly improve neo-bone regeneration, compared with HIMC.
Conclusions: Taken together, these findings suggest that emulating natural design, HIMC possesses the capacity to recruit host stem cells and promote osteogenesis by immunomodulation of macrophages; and IL-4, as a key cytokine of M2 macrophage polarization, plays an important role during this process.