UTP enhances CD34⁺ HSC adhesion onto FN-coated culture wells. Adhesion assays were performed using culture wells coated overnight with FN (20 μg/cm²). CD34⁺ HSCs were treated with control medium, UTP (10 μM), ATP (1 nM), and CXCL12 (150 ng/mL) during adhesion assays (60 minutes at 37°C, 5% CO₂). Similarly to CXCL12, extracellular UTP, but not ATP, significantly enhanced the percentage of CD34⁺ HSCs adhering to FN (P < .05). The combination of UTP and CXCL12 did not improve the adhesion of HSCs over each single factor. Cell adhesion was calculated as described in “Materials and methods.” Results are expressed as mean ± SEM and were obtained from 4 independent experiments. *P values less than .05.