TSG-6 effects on ASMC are mediated through the RhoA pathway. Primary mouse ASMC were cultured to 80% confluence and then washed repeatedly and serum-starved for 4 h and finally exposed to sHA or vehicle, as indicated. A, sHA induces activation of RhoA in murine ASMC, but only in TSG-6–sufficient cells. The experiment was repeated at least twice. n = 4–5/group. B, exogenous TSG-6 rescues sHA-induced hyperresponsiveness to methacholine, but this effect is inhibited by ROCK inhibitor Y27632. Isolated tracheal rings were bathed for 30 min in Krebs solution with sHA and added TSG-6 with Y27632 or respective vehicles, as indicated, and then assayed for their contractile response to methacholine. Results are represented as means ± S.E. (error bars). The experiment was repeated at least twice. n = 8/group. *, p < 0.05; **, p < 0.01; ***, p < 0.001, TSG-6 sHA + vehicle compared with TSG-6 sHA + TSG-6 + Y27632; ##, p < 0.001; ###, p < 0.001, TSG-6 sHA + TSG-6 + vehicle compared with TSG-6 sHA + vehicle and with TSG-6 sHA + TSG-6 + Y27632; ANOVA with Tukey's multiple-comparison correction.