In Vitro Effects Of Low-Dose-X-Irradiation For Bone Marrow Mesenchymal Stem Cells

Objectives: Previous studies have confirmed that the application of Low dose Xirradiation (LDI) could affect the Fracture healing process, however, the mechanism ofwhich remains unclear. The aim of this study was designed to investigate the mechanismsof LDI’s promotion to fracture healing.Methods:1. BMSCs were harvested from rat fresh bone marrow and exposed to a0Gy、25mGy、50mGy、75mGy、100mGy、1000mGy X-ray irradiation. Cell proliferation wasevaluated by using cell-counting-kit-8(CCK-8) assay after culturing6h、12h、24h、48h、72h. Cell cycles were assayed by flow cytometry.2. BMSCs were induced to osteoblast cell differentiation. Ossifying potential ofosteoblast were then evaluated. Ossify capability was estimated as below: Vonkossa testkits were used for the quantitative determination of osteocalcin and mineralized nodulenumbers were counted. The expression of three genes, OPG、COL-1、BGP were quantifiedby RT-PCR method. The statistics of the tests mentioned above were analyzed throughSPSS13.0software.Results:1. The CCK-8assay showed significant difference between the non-irradiated group and low dose irradiated group. the proliferation of BMSCs wasaccelerated significantly in vitro in the75mGy irradiation group (P <0.05). While in the1000mGy group, which was set as high dose irradiation, the proliferation of BMSCs wasdecreased.2. For osteoblast, mineralized nodule numbers in the low dose irradiation groupwere more than the control group, especially in the75mGy and100mGy group (P<0.05), and there is significant difference between1000mGy irradiation group and control group.(P<0.05). RT-PCR shows that the expression of three genes, OPG、COL-1、BGP increasedin the LDI group, especially in the75mGy and100mGy group (P<0.05), while irradiationat1000mGy decreased the expression.Conclusion: The results show that the LDI can efficiently stimulate the proliferationand differentiation of mesenchymal stem cells. And the ability of ossification of theosteoblast are potentialized. This can explain the mechanisms of LDI’s promotion tofracture healing on the aspect of cells.