Transforming growth factor beta-1 contributes to a mast cell-induced increase in COX-2 mRNA and protein expression by human tenocytes. Tenocytes were cultured in the presence or absence of HMC-1 conditioned media (cond med), recombinant active transforming growth factor beta-1 (TGF-β1), and A83-01 for the indicated times. Quantitative polymerase chain reaction and western blots show increased cyclooxygenase COX-2 mRNA (A) and protein (B) in response to HMC-1 conditioned media. A83-01 reduced COX-2 mRNA (C) and Cox-2 protein (D) by tenocytes in response to treatment with mast cell conditioned media or TGF-β1 for 6 hours. Data represent mean ± standard error of the mean of at least three independent experiments, each run in triplicate. Mann–Whitney U test. *P = 0.022, **P = 0.0037.