(A) Diagram of the experimental design. Adult mice were given 5 days of CTR and BMS diet followed by 28 days of vitamin A–sufficient diet (CTR-28R and BMS-28R, respectively). (B) mASM sorted from Acta2-hrGFP;Cspg4-DsRED;RARE-lacZ lungs shows a persistent increase in Myh11 and Col1a2 expression in BMS-28R mASM compared with CTR-28R, though RA activity, as demonstrated by the level of RARE-lacZ (lacZ) expression, is not different between CTR-28R and BMS-28R lungs (n = 6 per group). (C) Airway responsiveness in BMS-28R mice (right panel) is better compared with BMS mice (left panel), but airway resistance (Res) remains significantly higher with methacholine (MeCh) challenge compared with that of the CTR-28R mice, indicating residual AHR despite restoration of RA activity (n = 9 per group). Scale bar: 10 μm. (D and E) Immunostaining of p-SMAD2 and α-SMA showing persistent p-SMAD2 signals in BMS-28R ASM despite 28-day washout period (yellow arrows) (n = 3 per group). Data represent the mean ± SEM (B) or mean ± range (C). Student’s t test was used to calculate P values in B. Two-way ANOVA was used to compare the curves in C. *P < 0.05, n.s., P ≥ 0.05.