AFF4 Loss Compromises Osteogenesis of Orofacial Mesenchymal Stem Cells During Alveolar Bone Repair via AMPK-Mediated Mitophagy.

Abstract

Repair of maxillofacial bone defects presents significant clinical challenges. Orofacial mesenchymal stem cells (OMSCs) mediate maxillofacial bone repair, while the molecular mechanisms governing osteogenic commitment of OMSCs remain incompletely understood. Here, we investigate the function of AF4/FMR2 family member 4 (AFF4) in OMSCs osteogenesis and maxillofacial bone healing. By using a tamoxifen-inducible Aff4 knockout mouse model, we demonstrate that AFF4 depletion significantly delays the alveolar bone repair post-tooth extraction. OMSCs of Aff4 knockout mice exhibit decreased expression of osteogenic markers (RUNX2, ALPL, OSX, COL1A1) and reduced mineralization in vitro. Mechanistically, AFF4 loss suppresses AMPK signalling and downstream mitophagy, manifested by reduced Parkin translocation and LC3B recruitment to mitochondria, and impaired mitophagosome-lysosome fusion. Notably, the rescue of mitophagy and the osteogenic capacity of Aff4-deficient OMSCs by AICAR (an AMPK activator) was abolished by Compound C (an AMPK inhibitor). Collectively, our findings establish the critical role of AFF4 in maxillofacial bone regeneration and demonstrate that it functions through the AMPK-mitophagy axis in OMSCs. This study provides a novel insight into the function of AFF4 in maxillofacial bone biology.