Albiflorin Alleviates Osteoporosis through Suppression of Osteoclast Mitophagy via the Rap1a/ERK Signaling Pathway

Objectives：Dysregulated mitophagy coupled with osteoclast activation orchestrates the development and progression of osteoporosis.Although albiflorin (ALB) exhibits bone-protective effects through anti-inflammatory and antioxidant activities, its precise mechanism—particularly regarding mitochondrial regulation—remains unknown. This study therefore investigates ALB as a novel osteoclast inhibitor by examining its molecular mechanism in regulating mitophagy via the Rap1a/ERK signaling pathway. Materials and Methods: ALB was evaluated using murine models of postmenopausal osteoporosis. Key methodologies included RNA sequencing (RNA-seq) for gene expression pathway analysis, transmission electron microscopy (TEM) for visualization of mitochondrial and autophagic structures, MitoTracker/LysoTracker co-staining for assessment of mitophagy, and Western blotting for protein signaling validation. The effects of ALB on osteoclast differentiation and bone loss mitigation were assessed both in vitro and in vivo. Results:ALB significantly inhibited osteoclastogenesis and osteoclast differentiation, thereby effectively reducing osteoporosis in murine models. RNA-seq analysis revealed that ALB modulated mitophagy by regulating the expression of Rap1a and components of the ERK signaling pathway. Validation through TEM demonstrated suppressed mitochondrial autophagy, while MitoTracker/LysoTracker co-staining confirmed a reduction in mitophagy. Furthermore, Western blot analysis showed that ALB inhibited osteoclast activation via the Rap1a/ERK signaling axis. Conclusion:ALB mitigates postmenopausal osteoporosis by suppressing osteoclast activation through Rap1a/ERK-dependent inhibition of mitophagy. These findings identify ALB as a promising therapeutic strategy for osteoporosis, addressing the need for safer long-term treatment options.