Single cell transcriptomic atlas reveals macrophage polarization dynamics and intercellular communication networks in gingival tissue of periodontitis patients undergoing orthodontic treatment

Background: Periodontitis combined with orthodontic treatment creates a complex inflammatory and biomechanical microenvironment in gingival tissue, where macrophages play pivotal roles in tissue remodeling and immune regulation. However, the heterogeneity of macrophage subtypes and their polarization dynamics in this clinical context remain poorly understood. Methods: We performed single-cell RNA sequencing (scRNA-seq) on gingival tissue samples from periodontitis patients undergoing orthodontic treatment. Using integrated bioinformatics approaches including dimensionality reduction, pseudotime trajectory analysis, RNA velocity, cell-cell communication inference, and functional enrichment analysis, we comprehensively characterized macrophage subtypes, their polarization states, and intercellular signaling networks. Results: We identified 11 distinct cell populations with significant macrophage heterogeneity, including M1-like pro-inflammatory and M2-like tissue-remodeling subtypes along with intermediate transitional states. Trajectory analysis revealed dynamic polarization pathways with multiple branching points, demonstrating remarkable phenotypic plasticity. Macrophages served as central communication hubs, engaging in extensive crosstalk with fibroblasts, epithelial cells, endothelial cells, and lymphocytes through cytokine, growth factor, chemokine, and extracellular matrix signaling pathways. Transcription factor analysis identified NF-κB, STAT1, and IRF family members driving M1 polarization, while PPARγ, C/EBPβ, and KLF4 promoted M2 phenotypes. Telomere maintenance gene profiling revealed differential cellular aging patterns across subtypes, with pro-inflammatory macrophages showing stress-induced senescence signatures. Functional enrichment demonstrated that macrophages integrate inflammatory responses with mechanotransduction pathways, responding to both periodontal pathogens and orthodontic mechanical forces. Conclusions: This single-cell transcriptomic atlas provides unprecedented insights into macrophage heterogeneity and functional specialization in periodontitis patients undergoing orthodontic treatment.