Model depicting DDR2 regulation of neutrophil chemotaxis in a 3D collagen matrix. In response to a gradient of IL-8, neutrophils embedded in collagen (gray lines) release low levels of MMPs (orange circles) and migrate with a low persistence. After DDR2 activation (depicted by the change from black to green), MMP release, mainly MMP-8, is increased resulting in substantial cleavage of collagen and generation of PGP-containing peptides, which are further processed into PGP by PE (blue halo). As a consequence, a local gradient of PGP is produced stabilizing neutrophil persistence and directionality.