Exogenous VEGF promotes hematopoietic stem cell mobilization / 中国实验血液学杂志

ABSTRACT

This study was aimed to investigate the effect of exogenous VEGF on hematopoietic stem cell mobilization and immune system. The C57BL/6J mice were randomly divided into the normal control group, VEGF short-term group (5 d) and VEGF long-term group (27 d). Mice in the experimental group were injected ip with VEGF (100 ng/d); mice in control group were injected ip with PBS. The white blood cell (WBC) count and the ratio of lymphocyte in the peripheral blood at different time point were assayed by hemacytometer. The percentage of hematopoietic stem cell (HSC), lymphocyte subgroup, regulatory T cell (Treg), myeloid-derived suppressor cells (MDSC) in the peripheral blood and spleen of different groups were detected by flow cytometry. The morphological changes of spleen and spleen index of mice in the control and long-term group were observed by microscopy. The results showed that the absolute number of WBC in the peripheral blood of mice significantly increased after injection of VEGF, and the peak value was at day 3. The percentage of Lin(-)Sca-1(+)CD117(+) cells in the peripheral blood and spleen of the long-term group were significantly higher than that in the normal control group (P < 0.05). The spleen of the mice in VEGF long-term group was larger than that of the control group, the spleen index also increased (P < 0.05), and remarkable extramedullary hematopoietic signs were found in the HE stained sections. There was no significant change in the total ratio of lymphocytes in the peripheral blood after injection, but the percentage of CD3(+) cells and the CD3(+)/B220(+) ratio in the long-term group deceased; the percentages of Treg and Gr-1(+)CD11b(+) MDSC in the experimental groups increased (P < 0.05), which more significantly increased in the long-term group than that in the short-term group (P < 0.05). It is concluded that the exogenous VEGF promotes hematopoietic stem cell mobilization, and at same time up-regulates the many kinds of suppressive immune cell levels which leads to changes of immuno-function.