Mechanical Stretch Prevents Senescence-Associated Osteogenic Impairment in Mesenchymal Stem Cells via CXCR4/PI3K/AKT...

The reduced osteogenic differentiation of senescent mesenchymal stem cells (MSCs) contributes to impaired bone formation and limits their therapeutic potential in bone regeneration. CXCR4 has been implicated in both MSC aging and osteogenesis. Mechanical loading is known to benefit the aged skeleton and increase CXCR4 expression. However, it remains unclear whether mechanical stimuli can alleviate MSC senescence and improve senescence-associated osteogenic dysfunction via CXCR4. In this study, D-galactose (D-gal)-induced premature MSCs were preconditioned with cyclic stretch. The expression levels of CXCR4, senescence markers, and osteogenic markers were assessed and compared with those in young and naturally aged MSCs. The results showed that both aged and premature MSCs presented reduced osteogenic capacity and increased senescent phenotypes. Mechanical stretch significantly upregulated CXCR4, downregulated p16, p21 and p53, reduced the senescence-associated β-galactosidase (SA-β-gal)-positive cells, suppressed the senescence-associated secretory phenotype (SASP), and restored osteogenic potential-all of which were abolished by the CXCR4 inhibitor AMD3100. Conversely, CXCR4 knockdown in young MSCs exacerbated the senescent phenotype and suppressed osteogenic differentiation. Transcriptome sequencing and Western blot revealed that the CXCR4/PI3K/AKT signaling pathway was involved in the anti-senescent and pro-osteogenic effects of mechanical stimulation. These findings underscore the protective role of mechanical stretch in preserving MSC function against senescence-induced osteogenic dysfunction via CXCR4 signaling. This study may provide insights into potential therapeutic approaches for senescence-associated bone disorders and the enhancement of bone regeneration in the elderly.