Single-cell RNA sequencing and spatial transcriptomics reveal the osteoimmune microenvironment of biomaterial-mediated bone regeneration [ST-seq]
The bone-defect-repair process involves complex interaction between mesenchymal stem cells (MSCs) and immune cells, while the heterogeneity of osteoimmune microenvironment around implanted biomaterials remains elusive. By combining analysis of scRNA-seq and spatial transcriptomics technologies, we revealed that MgphiMSCs subpopulation served as the pioneers during the early stage of biomaterials-mediated bone defect healing process. They performed efficient osteogenic differentiation potential and had close interactions with immune cells. Remarkably, the MgphiMSCs could response to biomaterials-mediated osteoimmune microenvironment, rewired the polarization and osteoclastic differentiation of macrophages via midkine (MDK) signaling pathway. The inhibition of MDK activated the pro-inflammatory programs of macrophages and osteoclastogenesis. Meanwhile, multiple innate and adaptive immune-cell subsets exhibited close crosstalk between MgphiMSCs via SPP1 signaling pathway. These cellular profiles and interactions characterized in this study could broaden our understanding of the functional MSCs subpopulations at the early stage of biomaterial-mediated bone regeneration and provide the basis for the materials-designed strategies that target osteoimmune modulation. Overall design: The calvarial bone defects were repaired with or without collagen/nHA materials, the tissues within bone defect regions were analyzed via spatial transcriptomics