Periodontal ligament cell osteogenesis under compression/unloading via SOST: coronectomy validation.

INTRODUCTION AND AIMS: Periodontal ligament cells (PDLCs) reside in a mechanically complex niche and respond to static compression, which contributes to alveolar bone remodelling. Sclerostin (SOST) is a mechanosensitive regulator with established antiosteogenic roles in bone biology. This study investigated how SOST modulates the osteogenic response of PDLCs to static compression and unloading, and how this may relate to postcoronectomy periapical bone remodelling and root migration. METHODS: PDLCs were subjected to static compression followed by unloading, and osteogenic markers were quantified during both phases. A public transcriptomic dataset of compressed PDLCs was reanalysed using DESeq2 to identify compression-responsive genes, and SOST was selected for further validation at the mRNA and protein levels. The function of SOST was examined using small interfering RNA (siRNA)-mediated knockdown and recombinant SOST protein. A rat model involving high-occlusal-load adaptation followed by coronectomy was used to assess periapical osteogenic signalling and SOST expression in relation to postcoronectomy root migration. RESULTS: Static compression reduced osteogenic differentiation in PDLCs, whereas osteogenic activity recovered after force release. SOST knockdown attenuated compression-induced inhibition of osteogenesis, while exogenous SOST protein diminished osteogenic recovery during unloading. In vivo, coronectomy after high occlusal-force adaptation led to transient coronal migration of retained roots. This displacement was accompanied by a temporary rise in periapical osteogenic markers and a transient decrease in SOST expression. CONCLUSION: SOST acts as a mechanosensitive negative regulator of PDLC osteogenesis during static compression and subsequent unloading and may contribute to periapical bone remodelling associated with transient root migration after coronectomy. CLINICAL RELEVANCE: SOST-mediated responses to compression and unloading may provide a biological basis for understanding periapical remodelling and transient retained-root migration after coronectomy. These findings support further investigation of the role of the mechanical environment in clinically relevant models and human third-molar studies.