(A) Densitometric analysis of p-Smad1/5 in SH-SY5Y cells treated with 200 ng/ml of GDF5 for 0 (control), 5, 30 and 60 min. (B) Neurite length of GDF5-treated (200 ng/ml daily for 72 h) SH-SY5Y cells at 72 h. (C–F) p-Smad1/5 levels as determined by (C, D) Western blots or (E, F) immunocytochemistry in SH-SY5Y cells 24 h after transfection with control miRNA or miR-181a inhibitor. Total Smad1/5 was used as a loading control. (G) Neurite length, (H) neurite branching and (I) representative photomicrographs of miR-181a inhibitor or control miRNA transfected SH-SY5Y cells at 72 h (*P<0.05, **P<0.01, ***P<0.001 compared with control; t test; 40 cells for each group per experiment; n=3 experiments). All data are presented as mean ± S.E.M. Scale bar as indicated.