Fig. 4

The association of SDF-1/CXCR4 axis with high motility of MSC-H cells. a The SDF-1 expression in the aortic specimens were measured by quantitative PCR. The assay was repeated three times for each group, and the RNA level was expressed in the fold change to the level at day 0. The SDF-1 expression was increased by three-fold in the irradiated aortas (RT group) on day 7 after irradiation and then dropped down gradually to the 1.6-fold increase level at day 90. In comparison, the expression of SDF-1 in nonirradiated aortas (Sham RT group) kept stable throughout the experiment. An asterisk indicated that the SDF-1 levels were statistically different (P < 0.05) between RT and Sham RT group at a specific time checkpoint. b The SDF-1 expression was compared between groups with and without MSC treatment at day 90 after irradiation. The SDF-1 level was significantly lower in MSC-treated groups (RT + MSC-C and RT + MSC-H). Although RT + MSC-H group yielded a lower average SDF-1 level than RT + MSC-C group, the difference did not reach statistical significance. The assay was repeated three times for each group, and the RNA level was expressed in the fold change to that of Sham RT group. Group comparisons were made by using Student’s t test. *P < 0.05. c The expression of CXCR4 and CXCR7 in MSCs were measured by Western blot. The assay was repeated three times for each cell type, and the representative images of protein bands were shown. The CXCR4 expression was significantly higher in MSC-H cells than MSC-C cells. However, both of them expressed a low level of CXCR7. The similar results were obtained after MSC-H and MSC-C cells were cocultured with ECs for 7 days. d The mobility of MSCs was assessed by SDF-1-induced transwell migration assay and expressed as a number of migrated cells per high powered field. The cell migration was analyzed after stimulation with SDF-1 at the concentration gradient of 25, 50, 100, and 200 ng/ml. The number of migrated cells was significantly higher in MSC-H cells than MSC-C cells when the SDF-1 concentration increased to 50 ng/ml or more. The assays were repeated five times for each group. Group comparisons were made by using Student’s t test. *P < 0.05. e The MSC-H cell migration stimulated by 200 ng/ml SDF-1 was inhibited by the CXCR4 antagonist, AMD3100. The assays were repeated five times for each group. Group comparisons were made by using Student’s t test. *P < 0.05 MSC-H vs MSC-C. # P < 0.05 MSC-H + AMD3100 vs MSC-H