Involvement of miR-140-3p in Wnt3a and TGFβ3 signaling pathways during osteoblast differentiation in MC3T3-E1 cells.

The Wnt/β-catenin signaling and TGFβ signaling pathways play a key role in osteoblast differentiation. The miRNAs play important roles in regulating gene expression at the post-transcriptional level through fine-tuning of protein-encoding gene expression. However, involvement of miRNAs is not established for Wnt3a and TGFβ signaling pathways in osteoblast differentiation. Here, we examined the role of miRNAs expressed differentially after Wnt3a expression during osteoblast differentiation. Over-expression of the Wnt3a gene increased ALP transcription, but decreased Col1, Runx2, and OCN transcription in osteoblastic MC3T3-E1 cells. Expression profiling and quantitative PCR for miRNAs showed that miR-140-3p decreased in Wnt3a-over-expressing osteoblastic cells. Wnt3a over-expression increased TGFβ3 expression, whereas transfection of the miR-140-3p mimic into MC3T3-E1 cells significantly inhibited TGFβ3 expression. Luciferase assay for the TGFβ3 transcript showed that TGFβ3 was a direct target of miR-140-3p. miR-140-3p mimic transfection resulted in significantly increased OCN transcription, but did not affect ALP, Col1, and Runx2 transcription in MC3T3-E1 cells. rTGFβ3 treatment decreased OCN transcription in MC3T3-E1 cells. These results suggest that the miR-140-3p is involved in osteoblast differentiation as a critical regulatory factor between Wnt3a and TGFβ3 signaling pathways.