ATO inhibits TGF-β-induced fibroblast contractile activity in rat tail type-I collagen gel. (A) NHLFs were cultured in rat tail type I collagen gels (2 mg/ml) and pre-treated with ATO for 24 hrs. Cells were exposed to TGF-β1 (1 ng/ml) for another 48 hrs. TGF-β1treatment decreased the size of the gel while ATO pre-treatment blocked the reduction in gel size. (B) A summation of the percentage of gel surface area in each well of Figure 2A to the control gel surface area. (C) NHLFs were cultured in rat tail type I collagen gels and treated as described above. Gels were digested using type-I collagenase (5 mg/ml) and cells were harvested in SDS loading buffer for western blot. α-SMA protein expression was induced by TGF-β1 and ATO abrogated the induction. Data represent results from three independent experiments with triplicate repeats. *P value < 0.05, **P value <0.01, ***P value < 0.001.