MT1-MMP is required for PDGF-BB-mediated fibroblast migration through tendon ECM. A: representative images of tail tendon fibroblasts transfected with scrambled siRNA or MT1-MMP siRNA, and treated with PDGF-BB, measured after 6 days. B and C: quantification of the number of migrating cells per field (B) and maximum distance migrated of the MT1-MMP-silenced tendon fibroblasts (C). Sections were stained with hematoxylin and eosin. D: quantitative expression of MMP2, MMP9, and MT1-MMP mRNA in tendon fibroblasts transfected with scrambled or MT1-MMP siRNA for 48 h demonstrating specificity and efficiency of MT1-MMP mRNA knockdown. Values are means ± SD; n = 4 replicates per group. Differences between groups were tested using an unpaired Student’s t-test; a, P < 0.05.