SDF-1 rapidly induces the adhesion of HPCs to HA under both prolonged static conditions and under short contacts in the presence of shear flow conditions. Enriched CB CD34⁺ cells, labeled with ⁵¹Cr for 1 hour at 37°C, were plated onto HA-coated flat-bottomed microplates and exposed to SDF-1, TNF-α, MIP-1α, or SCF. After the indicated times, the unbound cells were removed by gentle washing and the remaining cells were lysed. The released radioactivity values are represented as means ± SDs of triplicate wells calculated after 2 hours of adhesion (A). The kinetics of adhesion is shown (B). CB-derived CD34⁺ cells were allowed to bind for 3 minutes to HA (ctrl) or to HA coimmobilized with SDF-1 (SDF-1), assembled in a parallel-plate flow chamber. Flow was then initiated and increased in 2- to 2.5-fold increments every 5 seconds. The number of adherent cells resisting detachment was determined after each interval by analyses of multiple fields in videotaped cell images. A representative analysis of 3 independent experiments is shown (C). Enriched CB CD34⁺ cells either untreated (ctrl) or preincubated with anti-CD44 mAb (clone BU52) were allowed to adhere to HA for 1 hour in the presence of SDF-1, and the efficiency of adhesion was assayed (D).