Fig. 4

The role of ERK in the Ca²⁺/hypoxia-mediated enhancement of hUCB-MSC proliferation. a hMSCs were treated with Ca²⁺/hypoxia and then harvested after 30 min. The phosphorylation of ERK was determined by western blot analysis. b hMSCs were treated with Ca²⁺/hypoxia for 30 min in the absence or presence of U0126. The phosphorylation of ERK was analyzed by western blot analysis. c hUCB-MSCs were pretreated with vehicle or U0126 for 30 min and then exposed to Ca²⁺/hypoxia for 5 days. Proliferation capacity was determined by cell counting assays. d hMSCs were treated with Ca²⁺/hypoxia for 6 h in the absence or presence of U0126. HIF-1α expression was determined by western blot analysis. e At 48 h post-transfection with HIF-1α-specific siRNA (si-HIF-1α), hMSCs were cultured under Ca²⁺/hypoxia for 30 min. The phosphorylation of ERK was determined by western blot analysis. f Schematic illustration of the molecular mechanisms involved in Ca²⁺/hypoxia-induced cell proliferation. Data represent the mean ± SD, n = 3; *P < 0.01