Human umbilical cord blood-derived CD34(+) cells were used to elucidate the mechanisms underlying the beneficial effects exerted by cord blood cells in spinal cord injury (SCI). Rats were divided into four groups: (1) sham operation (laminectomy only); (2) laminectomy + SCI + CD34(-) cells (5 x 10(5) human cord blood lymphocytes and monocytes that contained <0.2% CD34(+) cells); (3) laminectomy + SCI + CD34(+) cells (5 x 10(5) human cord blood lymphocytes and monocytes that contained approximately 95% CD34(+) cells); and (4) laminectomy + SCI + saline (0.3 mL). Spinal cord injury was induced by compressing the spinal cord for 1 min with an aneurysm clip calibrated to a closing pressure of 55 g. CD34 cells or saline was administered immediately after SCI via the tail vein. Behavioral tests of motor function measured by maximal angle an animal could hold to the inclined plane were conducted at days 1 to 7 after SCI. The triphenyltetrazolium chloride staining and terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-biotin nick end labeling assay were also conducted after SCI to evaluate spinal cord infarction and apoptosis, respectively. To elucidate whether glial cell line-derived neurotrophic factor (GDNF) or vascular endothelial growth factor (VEGF) can be secreted in spinal cord-injured area by the i.v. transplanted CD34(+) cells, analysis of spinal cord homogenate supernatants by specific enzyme-linked immunosorbent assay for GDNF or immunofluorescence for VEGF was conducted. It was found that systemic administration of CD34(+), but not CD34(-), cells significantly attenuated the SCI-induced hind limb dysfunction and spinal cord infarction and apoptosis. Both GDNF and VEGF could be detected in the injured spinal cord after transplantation of CD34(+), but not CD34(-), cells. The results indicate that CD34(+) cell therapy may be beneficial in reversing the SCI-induced spinal cord infarction and apoptosis and hindlimb dysfunction by stimulating the production of both VEGF and GDNF in a spinal cord compression model.
The production of chemokine stromal cell-derived factor (SDF)-1 is significantly higher in synovial fluid of patients with osteoarthritis (OA). IL-6 is a multifunctional cytokine that plays a central role in both OA and rheumatoid arthritis. However, the effects of SDF-1α on human synovial fibroblasts are largely unknown. In this study, we investigated the intracellular signaling pathway involved in SDF-1α-induced IL-6 production in human synovial fibroblast cells. SDF-1α caused concentration- and time-dependent increases in IL-6 production. SDF-1α also increased the mRNA and surface expression of CXCR4 receptor in human synovial fibroblasts. CXCR4-neutralizing antibody, CXCR4-specific inhibitor (AMD3100), or small interfering RNA against CXCR4 inhibited the SDF-1α-induced increase of IL-6 expression. The transcriptional regulation of IL-6 by SDF-1α was mediated by phosphorylation of phosphatidylinositol 3-kinase (PI3K)/Akt and activation of the activator protein (AP)-1 component of c-Jun. The binding of c-Jun to the AP-1 element on the IL-6 promoter and the increase in AP-1 luciferase activity was enhanced by SDF-1α. Co-transfection with CXCR4, PI3K, Akt, and c-Jun mutants or siRNA inhibited the potentiating action of SDF-1α on AP-1 promoter activity. Taken together, our results suggest that SDF-1α-increased IL-6 production in human synovial fibroblasts via the CXCR4 receptor, PI3K, Akt, c-Jun, and AP-1 signaling pathways.
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