Integrative multi-omics and causal inference reveal periodontal ligament cell-macrophage crosstalk under orthodontic force

Orthodontic tooth movement requires synchronized mechanoadaptive and osteoimmune interactions, yet molecular pathways linking mechanical forces to immune-mediated bone remodeling remain incompletely characterized. This study aimed to elucidate molecular drivers and dissect cell crosstalk under orthodontic force, with a focus on their immunoregulatory consequences. This study combined in vitro compressive loading of human periodontal ligament (PDL) cells with transcriptomic/proteomic profiling, and in vivo single-cell RNA sequencing of alveolar bone macrophages from murine orthodontic models. Mendelian randomization (MR) analysis leveraged genetic instruments from transcriptome-wide (n = 31,684), proteome-wide (n = 35,559), and immune trait genome-wide association studies (n = 3,757). The two-phase framework first identified mechanoresponsive molecular signatures across omics layers, then established causal links to immune cell dynamics through MR. Transcriptomic and proteomic analyses of PDL cells under compressive force revealed LBH upregulation and TGF-β pathway activation and collagen disassembly, evidenced by COL1A1/COL2A1 downregulation. Single-cell RNA sequencing identified Cd40 + macrophages enriched in IL-17 signaling. MR causally linked PDL-derived molecular changes to CD40 + monocyte dynamics: LBH (OR = 0.860, P = 0.019) reduced CD40 + monocyte prevalence, while COL2A1 (OR = 1.115–1.133, P = 0.010) elevated CD40 expression in monocytes. Orthodontic forces induce transcriptional reprogramming and proteomic remodeling in PDL cells, which drive CD40 signaling in monocytes through mechano-immunological coupling. These adaptations activate Cd40 + macrophages, ultimately redefining orthodontic bone remodeling as a mechano-driven stromal-immune partnership essential for tooth movement.