Plastrum Testudinis Extract Promotes Endogenous Bone Marrow Mesenchymal Stem Cell Migration in Osteoporotic Fracture Repair Partly by Activating the SDF-1/CXCR4 Axis.

Osteoporotic fracture (OPF) is a major global health concern, particularly among aging populations, and the compromised migration and osteoblast differentiation potential of bone marrow mesenchymal stem cells (BMSCs) in osteoporosis significantly hinder fracture repair. The stromal cell-derived factor-1 (SDF-1)/C-X-C chemokine receptor 4 (CXCR4) axis is vital for guiding BMSC migration and bone regeneration. However, Plastrum Testudinis (PT) extract (PTE), a traditional Chinese medicine (TCM) derived from turtle shell, has revealed promise in promoting BMSC proliferation and differentiation, although its mechanism of regulating endogenous stem cell migration in OPF remains unclear. To address this, we combined bioinformatics screening, molecular docking, clinical tissue analysis, and in vivo experiments to identify key pathways via Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses. We established a bilateral ovariectomy-induced osteoporotic mouse model with tibial defects and treated the mice with PTE alone or with the CXCR4 inhibitor AMD3100, followed by histological, micro-CT, immunofluorescence, and in vitro Transwell assays. Bioinformatics analysis revealed enriched chemokine signaling pathways and identified CXCR4 as a key target of PTE. Molecular docking confirmed stable binding between PTE's active components (phenylalanine, methionine, threonine, and aspartic acid) and CXCR4. PTE significantly improved bone volume/total volume (BV/TV) and trabecular microarchitecture in osteoporotic tibial defect (OTD) mice, reversed reduced SDF-1/CXCR4 expression in osteoporotic tissues, and enhanced BMSC migration and SDF-1/CXCR4 mRNA levels in vitro; these effects were blocked by AMD3100. In summary, PTE effectively rescues the migration deficit of endogenous BMSCs under osteoporotic conditions by targeting the SDF-1/CXCR4 axis. This enhanced recruitment accelerates OPF healing, highlighting the potential of PTE as a regenerative therapeutic strategy.