Hdac4 Modulates Bone Biology Via Regulation Of Mineralization And Ferroptosis

To investigate the role of HDAC4 in bone homeostasis and regeneration, focusing on its epigenetic regulation of mesenchymal stem cells (MSCs) mineralization and osteoblasts ferroptosis. Single-cell RNA Sequencing Analysis of transcriptomic profiles from human PMOP samples, identifying PDGFRα⁺ mesenchymal cell clusters with epigenetically dysregulated genes. Genetic Mouse Model Generation of Pdgfra-CreERT2; Hdac4fl/fl mice for tamoxifen-inducible conditional knockout of HDAC4 in PDGFRα⁺ mesenchymal lineage cells. Phenotypic Characterization Evaluation of bone homeostasis via microCT and histomorphometry. Mechanistic Studies Paracrine Interaction: Co-culture of HDAC4-knockdown MSCs with osteoblasts revealed enhanced osteogenesis and suppressed ferroptosis. Exosome Function: Treatment of osteoblasts with exosomes derived from HDAC4-knockdown MSCs confirmed ferroptosis inhibition. In Vivo Delivery: Development of alginate-based hydrogel encapsulating HDAC4-silenced MSC exosomes accelerated calvarial defect healing. Anti-Osteoporotic Phenotype HDAC4 conditional knockout in PDGFRα⁺ cells rescued PMOP phenotypes, increasing trabecular bone volume and reducing osteoclast activity. Enhanced Osteogenesis HDAC4-knockdown MSCs upregulated osteogenic markers and promoted mineralization. Ferroptosis Suppression HDAC4-knockdown MSCs co-cultured with osteoblasts exhibited enhanced osteogenic capacity and reduced ferroptotic stress. Exosomes derived from HDAC4-knockdown MSCs suppressed osteoblast ferroptosis. ​In Vivo Regeneration Exosome-loaded hydrogel accelerated calvarial defect healing and attenuated osteoblast ferroptosis in the bone regeneration niche, demonstrating dual therapeutic effects. This study reveals a dual role of HDAC4 in bone biology: (1) suppressing MSCs mineralization through epigenetic repression of osteogenic genes, and (2) promoting osteoblast ferroptosis. Targeting HDAC4 in MSCs may offer novel therapeutic strategies for osteoporosis and bone regeneration.