[Extracellular HMGB1 promotes the migration of cord Blood CD34⁺ cells via SDF-1/CXCR-4 axis].

This study was aimed to investigate the effect of high mobility group box1(HMGB1) and/or stromal cell derived factor-1(SDF-1) on the migration of cord blood CD34⁺ cells, and to explore whether HMGB1 promotes cord blood CD34⁺ cell migration via SDF-1/CXCR4 axis. Cord blood mononuclear cells were isolated by Ficoll-Paque density centrifugation, CD34⁺ cells were collected by a positive immunoselection procedure (CD34 MicroBeads) according to the manufacturer's instructions, the purity of the isolated CD34⁺ cells was detected by flow cytometry. In vitro chemotaxis assays were performed using Transwell cell chambers to detect cells migration. 1 × 10⁵ cells/well cord blood CD34⁺ cells were added into the upper chambers. Different concentrations of HMGB1 and/or SDF-1 (0, 10, 25, 50, 100, 200 ng/ml) were used to detect the optimal concentrations of HMGB1 and/or SDF-1 for inducing migration of cord blood CD34⁺ cells. Freshly isolated cord blood CD34⁺ cells express CXCR4 (SDF-1 receptor), and HMGB1 receptor TLR-2,TLR-4 and RAGE. To explore which receptors were required for the synergy of HGMB1 and/or SDF-1 on cells migration, the anti-SDF-1, anti-CXCR4 and anti-RAGE antibodies were used to detect the effect of HGMB1 alone or with SDF-1 on cord blood CD34⁺ cells migration. The results showed that the purity of CD34⁺ cells isolated from cord blood mononuclear cells by magnetic cell sorting was 97.40 ± 1.26%, the 25 ng/ml SDF-1 did not induce migration of cord blood CD34⁺ cells, whereas the optimal migration was observed at 100 ng/ml. HMGB1 alone did not induce migration up to 100 ng/ml. The dose test found that the the best synergistic concentrations for cells migration were 100 ng/ml HMGB1 combined with 50 ng/ml SDF-1. The blocking test showed that both the anti-SDF-1 (4 µg/ml) and anti-CXCR4 (5 µg/ml) antibodies could block cell migration induced by HMGB1 or combined with SDF-1, but the cord blood CD34⁺ cells in the presence of anti-RAGE, anti-TLR-2 and anti-TLR-4 antibodies did not modify the response to SDF-1 in the presence of HMGB1. It is concluded that both HMGB1 and SDF-1 can induce cord blood CD34⁺ cells migration, HMGB1 enhances SDF-1-induced migration exclusively via CXCR4 and in a RAGE and TLR receptors-independent manner, the exact mechanism needs to be further explored.