Fig. 6.

ALK4/5-mediated SMAD2/3 signaling pathways are required for the GDF-11-suppressed hCG production. A-C BeWo (A), JEG-3 (B), and primary CTB (C) cells were pretreated with vehicle control (DMSO) or 10 µM SB431542 for 1 h, and then treated with 10 ng/mL GDF-11 (G11) every 24 h for 72 h. D-F, BeWo (D), JEG-3 (E), and primary CTB (F) cells were transfected with 50 nM (for BeWo and JEG-3) or 100 nM (for primary CTB) control siRNA (si-Ctrl) or SMAD4 siRNA (si-SMAD4) for 48 h, and then treated with 10 ng/mL GDF-11 (G11) every 24 h for 72 h. The levels of hCG in the culture media were examined by ELISA. The results are expressed as the mean ± SEM of at least three independent experiments. The values without a common letter are significantly different (p < 0.05)