Effects of low-dose-X-irradiation on vascular endothelial growth factor and bone marrow mesenchymal stem cells

Objective To explore the inechanism of low-dose X-irradiation (LDI) promoting callus mineralization through vascular endothelial growth factor (VEGF) and hone marrow mesenchymal stem cells (BMSCs).Methods The expression of VEGF in serum and callus samples was quantified and the osteogenic differentiation of BMSCs was detected after exposure.Results MicroCT based angiography visually revealed that the number of neovascularization was conspicuously increased since 2 weeks in the LD1 group [(315.00 ±21.33) ng/L] as compared with that in sham group [(175.05 ± 18.17) ng/L] (P ＜0.05).The serum VEGF in the LDI group was higher than in control group (P ＜ 0.05) at 3rd week.Elevated mRNA expression of VEGF was observed,and reached the peak at 2nd and 3rd week respectively in the LDI group as compared with control group (P ＜ 0.05).The cell counting kit-8 (CCK-8) assay showed that the proliferation of BMSCs was accelerated significantly in vitro in the 10 cGy irradiation group (1.697 ±0.048,24 h after exposure) (P ＜ 0.05).Mineralized nodule number in the LDI group [(24.0 ± 1.6)] was greater thau in control group,especially in the 10 cGy group (P ＜0.05).RT-PCR showed that the expression of Osteoprotegerin (OPG),collagenase-1 (COL-1),and osteocalcin (BGP) genes was increased in the LDI groups,especially in the 10 cGy group (P ＜ 0.05).Conclusion The results indicate that LDI promotes callus mineralization through up-regulating VEGF and promoting the mobilization of BMSCs. Key words: Low-dose X-irradiation; Vascular endothelial growth factor; Bone marrow mesenchymal stem cells