DDR2 amplifies neutrophil migration at the single-cell level. (A) MMP regulates neutrophil persistence during chemokenesis in a 3D collagen matrix. Human primary neutrophils were pretreated for 30 minutes with 25μM GM6001 and embedded in collagen I. Migration of neutrophils after a uniform10nM IL-8 stimulation was recorded. The percentage, average speed, and persistence (see “Methods” for details) of migrating neutrophils were determined. Percentage and average speed are from 4 independent experiments. The persistence graph is representative of the 4 experiments. (B) rDDR inhibition is independent of cell density. Human primary neutrophils were embedded at different cell density in collagen I (pretreated with or without rDDR). Migration of neutrophils to 50nM IL-8 was recorded. Results are representative of 5 independent experiments. *P = .03, Wilcoxon test.