Fig. 4

ERK signaling-mediated autophagy in stromal progenitor cells. The mRNA (A) and protein (B) levels of the key factors for autophagy in ST2 were examined 48 h after U0126 treatment (20 μM). ST2 cells were treated with 20 μM U0126 or chloroquine (CQ) for 24 h, followed by osteogenic treatment. ALP staining (C, G) and alizarin red staining (D, H) of differentiated osteoblasts from ST2 were done. The mRNA (E, I) and protein (F, J) levels of osteogenic factors were detected 72 h after osteogenic treatment. Values are mean ± SD (n = 3). *p < 0.05 vs. vehicle treatment