Dynamic Adhesion of Umbilical Cord Blood Endothelial Progenitor Cells under Laminar Shear Stress

Late outgrowth endothelial progenitor cells (EPCs) represent a promising cell source for rapid reendothelialization of damaged vasculature after expansion ex vivo and injection into the bloodstream We characterized the dynamic adhesion of umbilical cord blood derived EPCs (CB EPCs) to surfaces coated with fibronectin CB EPC solution density affected the number of adherent cells and larger cells preferentially adhered at lower cell densities The number of adherent cells varies with shear stress with the maximum number of adherent cells and the shear stress at maximum adhesion depending upon fluid viscosity CB EPCs underwent limited rolling transiently tethering for short distances before firm arrest Immediately before arrest the instantaneous velocity decreased independent of shear stress A dimensional analysis indicated that adhesion was a function of the net force on the cells the ratio of cell diffusion to sliding speed and molecular diffusivity Adhesion was not limited by the settling rate and was highly specific to alpha(5)beta(1) integrin Total internal reflection fluorescence microscopy showed that CB EPCs produced multiple contacts of alpha(5)beta(1) with the surface and the contact area grew during the first 20 min of attachment These results demonstrate that CB EPC adhesion from blood can occur under physiological levels of shear stress