Single-Cell Atlas of Human Orthodontic Tooth Movement

Orthodontic tooth movement (OTM) requires coordinated remodeling of the periodontal ligament and alveolar bone, but the cellular architecture underlying this process in human tissues remains incompletely understood. We generated the first single-cell transcriptomic atlas of the human periodontal ligament during OTM by profiling control tissues and pressure- and tension-side tissues collected at days 3 and 7 following force application. Analysis of 65,032 cells identified 15 cell populations and revealed pronounced remodeling of stromal, immune, vascular, and neural compartments that varied by force direction and stage. Within the fibroblast compartment, we identified a CTHRC1 ⁺ fibroblast subset that was enriched on the pressure side at day 3 and exhibited heightened mechanotransduction, inflammatory signaling, and chemokine programs. TRPA1 was preferentially expressed in this subset, and computational perturbation, tissue validation, and pharmacologic inhibition supported its involvement in early remodeling on the pressure side. Ligand–receptor and functional analyses further implicated C3 as a downstream remodeling mediator linking regions rich in CTHRC1 ⁺ fibroblasts to monocyte recruitment and osteoclastogenic activity. In a mouse OTM model, systemic treatment with HC-030031 and local Trpa1 knockdown mediated by AAV9 under the Postn promoter reduced tooth movement, while HC-030031 also decreased osteoclast surface. Local C3a supplementation partially restored tooth movement during TRPA1 inhibition. These intervention data, with in vitro assays and tissue validation, support the involvement of TRPA1-associated signaling in a pressure-responsive stromal remodeling program and C3 as a potential downstream mediator of osteoclastogenic remodeling. These findings provide a human single-cell framework for periodontal remodeling during OTM and identify a pressure-responsive CTHRC1 ⁺ fibroblast population in which mechanosensitive TRPA1 contributes to osteoclastogenic remodeling on the pressure side.