Ex vivo expansion of umbilical cord blood (UCB) CD34+ cells alters the expression and function of α4β1 and α5β1 integrins

We have investigated the influence of ex vivo expansion of human CD34+ cord blood cells on the expression and function of adhesion molecules involved in the homing and engraftment of haematopoietic progenitors. Ex vivo expansion of umbilical cord blood CD34+ cells for 6 d in the presence of interleukin 3 (IL-3), IL-6 and stem cell factor (SCF) or IL-11, SCF and Flt-3L resulted in increased expression of α4, α5, β1, αΜM and β2 integrins. However, a significant decrease in the adhesion of progenitor cells to fibronectin was observed after the ex vivo culture (adhesion of granulocyte-macrophage colony-forming units (CFU-GM) was 22 ± 4% in fresh cells versus 5 ± 2% and 2 ± 2% in each combinatio…