PDGF-BB stimulation of tendon fibroblasts activates PI3K/Akt and ERK1/2 pathways, which both in turn mediate tendon fibroblast migration through tendon ECM. A: representative immunoblots of total and phospho PDGFRα, PDGFRβ, ERK1/2, Akt, and p70S6K from serum-starved tail tendon fibroblasts treated with PDGF-BB for 5, 15, 30, and 60 min. β-Tubulin is shown as a loading control. B: representative images of tail tendon fibroblasts obtained 6 days after being placed on the surface of a tendon ECM Transwell system, treated with PDGF-BB, PDGF-BB + PD98059, or PDGF-BB + wortmannin. C and D: quantification of the number of migrating cells per field (C) and maximum distance migrated (D). Sections were stained with hematoxylin and eosin. Values are means ± SD; n = 4 replicates per group. Differences between groups were tested using a one-way ANOVA (α = 0.05) followed by Tukey’s post hoc sorting: different (P < 0.05) from a, PDGF-BB; b, PDGF-BB + PD98059.