Abstract
BACKGROUND: Craniomaxillofacial sutures play a critical role in craniomaxillofacial development through continuous bone reconstruction and regeneration, processes modulated by mechanical tension. Bone suture stem cells (SuSCs) are central to these functions. Distraction osteogenesis, which promotes craniomaxillofacial suture growth, is a common therapeutic approach for craniofacial deformities. However, the underlying mechanisms by which mechanical forces drive suture and bone remodeling remain poorly understood, posing significant clinical challenges. METHODS: To investigate these mechanisms, we established a rapid maxillary expansion (RME) model in mice to widen the midpalatal suture. Single-cell RNA sequencing (scRNA-seq) was employed to identify subsets of SuSCs responsive to mechanical tension and analyze their differentiation potential under varying conditions. Further functional studies were conducted to explore the role of DALR anticodon binding domain containing 3 (Dalrd3) and its associated tRNA 3-methylcytosine (m3C) modification in SuSCs under mechanical tension. RESULTS: Our study identified a subset of SuSCs with multidirectional differentiation potential that shifted from a chondrogenic to an osteogenic trajectory in response to mechanical tension. Mechanical tension also upregulated Dalrd3 expression and its associated tRNA m3C modification in activated SuSCs. Knockdown of Dalrd3 in SuSCs significantly impaired osteogenic differentiation, proliferation, migratory capacity, and translational activity within the bone morphogenetic protein (BMP) signaling pathway. Furthermore, Dalrd3 knockdown suppressed the translational activity of inhibitor of DNA binding 3 (Id3), a key BMP-induced mediator of osteoblastogenesis. Restoring Id3 expression in Dalrd3-deficient SuSCs rescued their osteogenic, proliferative, and migratory functions. CONCLUSIONS: These findings reveal a translational regulatory mechanism in SuSCs activated by mechanical tension and underscore the pivotal role of Dalrd3 in suture remodeling and bone formation. The insights provided by this study have the potential to guide targeted therapeutic strategies for optimizing distraction osteogenesis and other treatments for craniofacial deformities.