Introduction: Naringenin, a dihydro-flavonoid compound that shows chemotactic activity, may have a good application prospect in repairing bone tissue, but its specific mechanism in bone regeneration, especially the osteogenic differentiation of stem cells, needs for a further study. The aim of this study was to investigate the effect of naringenin on the osteogenic differentiation and its roles in the C-X-C chemokine receptor type 4/stromal cell-derived factor 1 (SDF-1/CXCR4) signal pathway of bone marrow-derived mesenchymal stem cells (BMSCs).
Material and methods: BMSCs were harvested from the femurs and tibias of 4-to-6-week-old male Sprague-Dawley rats. Cell Counting kit-8 assay was used to determine cytotoxicity of naringenin. Alkaline phosphatase (ALP) activity was measured in cell's precipitates and alizarin-red staining was performed to determine the osteogenic differentiation capacity of the BMSCs. Real-time polymerase chain reaction, enzyme-linked immunosorbent assay and western blotting were adopted to determine the expression of genes and proteins.
Results: The cellular morphology was spindle-shaped, and arranged in radial and whorled patterns. The flow cytometric analysis have confirmed the presence of characteristic surface proteins in the harvested BMSCs. Different concentrations (0-200 μg/ml) of naringenin have no influence on the viability and proliferation rate of the BMSCs. The highest ALP activity was found at culture day 7 and 9 when the concentration of naringenin was 75 and 100 μg/ml. Positive red or dark red stained cells with mineralized nodules can be observed on day 14. The expression of ALP, Runt-related transcription factor 2, CXCR4 and SDF-1a at the gene and protein levels in naringenin-treated cells were significantly higher than those in the control cells. Moreover, AMD3100, an inhibitor of CXCR4, suppressed the expression of the studied genes and proteins.
Conclusions: Naringenin does not show toxic effect on BMSCs. Naringenin promotes the expression of the SDF-1a gene and protein via the SDF-1/CXCR4 signaling pathway. A better understanding of the mechanisms of naringenin action would be helpful for developing specific therapeutic strategies to improve bone regeneration after injuries.
Keywords: CXCR4; RT-qPCR; SDF-1; alizarin red; bone marrow-derived mesenchymal stem cells; cell viability; naringenin.