Mast cell-induced contraction of a three-dimensional collagen matrix is mediated through transforming growth factor beta-1. Tenocytes embedded in a three-dimensional collagen gel were stimulated with mast cell sonicate (MCS) or active transforming growth factor beta-1 (TGF-β1), in the presence or absence of A83-01. Data represent mean ± standard error of the mean of at least three separate experiments, each run in triplicate. Two-way analysis of variance followed by Bonferroni’s post-hoc test was used for comparisons. P <0.001 for days 2 to 4 for the following group comparisons: control versus MCS, MCS versus MCS + A83-01, control versus TGF-β1, and TGF-β1 versus TGF-β1 + A83-01.