HELLS Reduction Contributes to Compressive Force-Induced Functional Changes in PDLSCs

Orthodontic tooth movement (OTM) is driven by force-induced alveolar bone remodeling, yet the molecular mechanisms by which periodontal ligament stem cells (PDLSCs) sense and transduce mechanical signals remain incompletely understood. Here, we identify the epigenetic regulator HELLS as a compressive force-responsive gene and investigate its role as a mechanosensitive mediator in human PDLSCs (hPDLSCs). Compressive force downregulated HELLS expression both in vitro and in a mouse OTM model. Functionally, siRNA-mediated HELLS knockdown impaired osteogenic differentiation, as evidenced by reduced Alizarin Red S staining and alkaline phosphatase activity, and induced global transcriptomic changes indicative of altered mechanotransduction pathways. Moreover, HELLS knockdown increased YAP and RANKL expression and potentiated osteoclast differentiation of co-cultured RAW264.7 cells. Finally, we identified E2F1 as a candidate transcription factor mediating the force-induced downregulation of HELLS. Collectively, these findings establish HELLS as a potential mechano-epigenetic regulator in hPDLSCs, and suggest that its force-induced downregulation may contribute to alveolar bone remodeling during OTM by simultaneously attenuating osteogenesis and enhancing pro-osteoclastogenic signaling via transcriptional reprogramming.