A: hMSC were treated for 5 days with either DMEM, 0.5 µM RA in DMEM (RA), 20 ng/ml EGF+ 5 ng/ml bFGF (EGF+FGF), 20 ng/ml EGF +5 ng/ml bFGF +0.5 µM RA (EGF+FGF+RA), 10%FBS (FBS), or 0.5 µM RA in 10%FBS (FBS+RA). The RNAs were purified and the cDNAs were synthesized using reverse transcriptase. Periostin transcript was quantified in each sample. The error bars represent relative expression normalized to RNF10 expression and referred to the relative expression on DMEM as mean ± s.e.m. All the treatments were performed in triplicates in two independent experiments with cDNA from different donors and the significance of the results was assessed using one way ANOVA and Tukey's multiple comparison test. B–G: hMSC were cultured in osteoblasts differentiation medium supplemented with 0.5 µM RA (B–D), or in 10%FBS +0.5 µM RA (negative control) (E–G), for 21 days over uncoated plastic (B and E), 2.5 µg laminin/well coated plastic (C and F), or 2.5 µg periostin/well coated plastic (D and G). Osteoblasts were stained with alizarin red. Size bars = 100 µm.