Abstract
MicroRNAs (miRs) are endogenously expressed 18-25-nucleotide RNAs that regulate gene expression through translational repression by binding to a target mRNA. Recently, it was indicated that miRs act as key regulators in cell differentiation, cell growth, and cell death. In osteogenesis, several miRs (for example miR-26a, -125b, -133, and -135) regulate osteoblast cell growth or differentiation in human adipose tissue-derived stem cells, mouse mesenchymal ST2 stem cells, and mouse premyogenic C2C12 cells. Additionally, Smad proteins control Drosha-mediated miR maturation. Therefore, miRs are closely related to osteogenesis. Here we investigated miR expression profile by an miR array and identified the candidate miRs, miR-141 and -200a, as pre-osteoblast differentiation-related miRs. The effects of miR-141 and -200a on pre-osteoblast differentiation were examined by using transfection of murine pre-osteoblastic MC3T3-E1 cells with mature miR-141 or -200a and antisense inhibitor for miR-141 or -200a. It was shown that miR-141 and -200a remarkably modulated the BMP-2-induced pre-osteoblast differentiation through the translational repression of Dlx5, which is a bone-generating transcription factor expressed in pre-osteoblast differentiation. Furthermore, it was indicated that Dlx5 is a common target of miR-141 and -200a by using a luciferase reporter assay. Thus, we have observed for the first time that miR-141 and -200a are involved in pre-osteoblast differentiation in part by regulating the expression of Dlx5.