Effects Of Low Dose X-ray Radiation On The Expressi-on Of SDF-1 Receptors CXCR₄ And Characteristic Of Mesenchymal Stem Cells Derived From Human Umbi-lical Cord

Object:To explore the characteristics of SDF-1 receptor, CXCR4, in different number of passages in mesenchymal stem cells (MSCs) derived from Wharton's jelly of human umbilical cord. Then to observe the effects of low dose irradiation on the expression of CXCR4 and proliferation,adipogenesis,osteogenic potential of human umbilical cord mesenchymal stem cells.Methords:Mononuclear cells were isolated from Wharton's jelly of human umbilical cord by tissue culture. Expressions of marker in hucMSCs were detected by flow cytometry. Expressions of CXCR4 in hucMSCs of P2-P5 were detected by flow cytometry, and CXCR4 mRNA levels in hucMSCs of P2-P5 were evaluated by real-time quantitative PCR. MTT methord was applied to evaluate the prolifreation of hucMSCs at different time points with various doses radiation.To observe the effects of low dose irradiation on adipogenesis and osteogenic potential. The expression of CXCR4 under the LDR were detect by the real-time quantitative PCR and flow cytometry.Results:Analysed by flow eytometry, hucMSCs were demonstrated that they were positive for CD29,CD44, but negative for CD34,CD45,HLA-DR. The CXCR4 was found in hucMSCs of P2-P5, and their expression were (89.82±0.62)%, (86.87±1.32)%, (80.50±4.46)%, (70.10±0.68)% respectively. The CXCR4 mRNA was found in hucMSCs of P2-P5, and expression of CXCR4 of P3-P5 is respectively 0.5585±00875,0.6205±0.1377,0.4634±0.0447 times that of expression of P2. Compared with control group, the hucMSCs of each irradiated group showed remarkably proliferated within seven days, 100mGy group proliferation was significantly higher than that of control group. After being induced with induction medium, liquid vacuoles in irradiated group were observed at 48 hours. At 21 days, the adipogenic rates of irradiated group was significantly higher than that of the control group; The ALP activity increased in the irradiated group compared with control group, while the expression level of Cbf-al mRNA was up-regulated obviously. Expression of CXCR4 was increased significantly in a time and dose dependent manner by LDR.Conclusion:CXCR4 was expressed in hucMSCs of P2-P5, and declined when the number of passages increased. Compared to P2, CXCR4 mRNA levels in hucMSCs of P3-P5 declined, but the expression level of CXCR4 mRNA was stable. LDR could promote the proliferation of hucMSCs, accelerate the hucMSCs' differentiation obviously to adipocytes and osteoblasts. LDR could promote the expression of CXCR4.