CCN1 induced adhesion of CD34⁺cells is integrin-dependent. (A) CD34⁺ cells were preincubated with 1 mM RGD peptides (RGD and GRGDSP) or left untreated. Cells (5 × 10⁴) were added to uncoated wells (control) and wells coated with 1 μg/mL CCN1 or 1 μg/mL fibronectin and subjected to adhesion for 4 hours. Nonadherent cells were washed, and adherent cells were counted microscopically. (B) CD34⁺ cells were labeled with TAMRA, left untreated (control) or preincubated with 1 μg/mL CCN1 or 1 μg/mL fibronectin and/or with 1 mM RGD peptides (RGD and GRGDSP). Cells (1 × 10⁵) were added to confluent HUVEC monolayers and subjected to adhesion for 4 hours. Nonadherent cells were washed, and adherent cells were identified by TAMRA fluorescence and counted microscopically. Increase in cell adhesion was significantly different from control (*P < .05) and significantly reduced compared with CCN1 alone (#P < .05) and fibronectin alone (§P < .05). Data represent the mean (± SEM) of at least 3 independent experiments.