miR-155 Inhibits Mouse Osteoblast Differentiation by Suppressing SMAD5 Expression

Figure 4

Overexpression of SMAD5 attenuated the inhibitory effect of miR-155 on osteoblastic differentiation. MC3T3-E1 cells transfected with SMAD5 lentiviral particles or the vector were cotransfected with either miR-155 or the scramble control and subsequently induced toward osteogenic differentiation. (a) Alizarin Red staining for calcification deposition. (b) Alkaline phosphatase (ALP) activity. (c) Relative mRNA expression of ALP. (d) A proposed model for the inhibitory effects of miR-155 on osteoblast differentiation in MC3T3-E1 cells. After BMP2 binds to the receptors, SMAD5 is directly activated via phosphorylation and forms a homomeric complex with SMAD1 and SMAD8. The heterooligomer translocates to the nucleus and then positively regulates the transcription of osteogenesis-related genes. miR-155 suppresses SMAD5 expression by directly targeting its mRNA and decreases the levels of p-SMAD5, thus leading to inhibition of osteoblastic differentiation of MC3T3-E1 cells. Data are presented as mean ± SD; ; versus miR-155 + vector group.

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