Correlation between VLA-4 integrin and hematopoietic cell migration

To clarify the relationship between VLA-4 (CD49d) expression and hematopoietic cell migrating direction, mice were injected subcutaneously with diluted rhG-CSF for different times. The expressions of CD49d on Sca-1(+) cells were examined by flow cytometry. The relations between CD49d expression and Sca-1(+) cell enumerations were performed by statistical analysis. The results showed that with the administration of G-CSF, the expressions of CD49d in bone marrow (BM) and peripheral blood (PB) declined, meanwhile the number of Sca-1(+) cells in peripheral blood reached the peak in sharp contrast to BM nucleated cell number dropping on the seventh to ninth day. When CD49d expression rose again, the PB Sca-1(+) cells descended with the rising of BM nucleated cell number. In conclusion, VLA-4 mediates the hematopoietic cell adhesion to BM microenvironment. The regulation of CD49d expression may result in different migrating direction of hematopoietic cell between bone marrow and peripheral blood.