Figure 2.

Exogenous Dkk-1 inhibits the migration of intestinal epithelial cells without affecting proliferation. (A) Scratch-wounded Caco-2 monolayers were treated with buffer, rDkk-1, or rDkk-1 (100 ng/ml) + anti-Dkk-1 antibody (20 μg/ml). Vertical bars represent the position of the leading edge. Bar, 200 μm. *p < 0.01 versus control. (B) Knockdown of Dkk-1 in Caco-2 cells after 48 h was confirmed by Western blot. Addition of rDkk-1 to cells treated with the indicated siRNA significantly inhibited cell migration (*p < 0.01; **p < 0.05 vs. control). (C) Migrating primary IEC-6 cells were treated with buffer or rDkk-1 (100 ng/ml), and wound closure was assessed after 24 h (*p < 0.01 vs. control). (D) EdU incorporation (green) in migrating Caco-2 cells treated with rDkk-1 or buffer. Nuclei are shown in blue. No difference in the number of EdU-positive cells was seen at the leading edge and in the confluent monolayer. Bar, 50 μm. (E) Noninterphase nuclei were counted in migrating cells treated with increasing concentrations of rDkk-1. No difference to untreated control was observed.