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Vaspin regulates the osteogenic differentiation of MC3T3-E1 through the PI3K-Akt/miR-34c loop.

ABSTRACT: Vaspin (visceral adipose tissue-derived serine protease inhibitor) is a newly discovered adipokine that widely participates in diabetes mellitus, polycystic ovarian syndrome and other disorders of metabolism. However, the effect of vaspin on the regulation of osteogenesis and the mechanism responsible are still unclear. Here, we found that vaspin can attenuate the osteogenic differentiation of the preosteoblast cell line MC3T3-E1 in a dose-dependent way; also, during this process, the expression of miRNA-34c (miR-34c) was significantly increased. Down-regulation of the expression of miR-34c in MC3T3-E1 diminished the osteogenic inhibitory effect of vaspin, while the up-regulation of miR-34c increased this effect through its target gene Runx2. Meanwhile, we found that vaspin could also activate the PI3K-Akt signalling pathway. Blocking the PI3K-Akt signalling pathway with specific inhibitors could decrease the osteogenic inhibitory effect of vaspin as well as the expression level of miR-34c. Furthermore, knock-down of miR-34c could promote the activation of Akt, which was probably realised by targeting c-met expression. Thus, PI3K-Akt and miR-34c constituted a modulation loop and controlled the expression of each other. Taken together, our study showed that vaspin could inhibit the osteogenic differentiation in vitro, and the PI3K-Akt/miR-34c loop might be the underlying mechanism.

SUBMITTER: Liu Y

PROVIDER: S-EPMC4860647 | biostudies-other | 2016

REPOSITORIES: biostudies-other

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Project description:ObjectiveMicroRNAs (miRNAs) are well-recognized for their abilities to regulate gene expression post-transcriptionally in plants and animals. Recently, miRNA-messenger RNA (mRNA) regulatory relationships have been confirmed during biological processes, including osteogenic differentiation. This study aimed to find out more candidate miRNA-mRNA pairs involved in the osteogenic differentiation of MC3T3-E1 cells.MethodsAn MC3T3-E1-based microarray dataset (accessioned as GSE46400) downloaded from the Gene Expression Omnibus included MC3T3-E1 cells with or without 14-day osteoblast differentiation osteoblast induction. Multiple miRNA-mRNA prediction databases were searched by differentially expressed genes (DEGs) to obtain pairs of a miRNA-DEG regulatory network. The MC3T3-E1 cells were cultured and incubated in the osteogenic differentiation medium for 14 days. The expressions of candidate miRNAs and mRNAs were determined by real-time quantitative PCR(RT-qPCR) in MC3T3-E1 cells. The miRNA-mRNA interactions were verified by dual-luciferase reporter gene assays and experiments using mimics miRNA or their inhibitors.ResultsWe identified 715 upregulated DEGs and 603 downregulated DEGs between MC3T3-E1 cells with and without osteoblast induction by analyzing the raw data of the GSE46400 dataset. There were 7 overlapped miRNA-mRNA pairs identified during osteogenic differentiation of MC3T3-E1 cells, including mmu-miR-204-5p-Arhgap11a, mmu-miR-211-5p-Arhgap11a, mmu-miR-24-3p-H2afx, mmu-miR-3470b-Chek2, mmu-miR-3470b-Dlgap5, mmu-miR-466b-3p-Chek1, and mmu-miR-466c-3p-Chek1. The Arhgap11a, H2afx, Chek2, Dlgap5, and Chek1 were hub genes downregulated in MC3T3-E1 cells after osteogenic differentiation, verified by RT-qPCR results. The RT-qPCR also determined declined expressions of miR-204-5p and miR-24-3p concomitant with elevated expressions of miR-211-5p, miR-3470b, miR-466b-3p, and miR-466c-3p in the MC3T3-E1 cells, with osteoblast induction compared with undifferentiated MC3T3-E1 cells. Dual-luciferase reporter gene assays demonstrated Arhgap11a as the target of miR-211-5p. MiR-211-5p upregulation by its mimic increased Arhgap11a expression in MC3T3-E1 cells.ConclusionOur study characterizes miR-211-5p targeting Arhgap11a promotes the osteogenic differentiation of MC3T3-E1 cells, which provides novel targets to promote the osteogenesis process during bone repair.

Project description:BackgroundWe have previously reported that repeated treatment of human periodontal ligament cells and murine pre-osteoblast MC3T3-E1 cells with transforming growth factor-beta 1 (TGF-β1) inhibited their osteoblastic differentiation because of decreased insulin-like growth factor-1 (IGF-1) secretion. We also found that IGF-1/PI3K signaling plays an important role in osteoblast differentiation induced by TGF-β1 treatment; however, the downstream signaling controlling this remains unknown. The aim of this current study is to investigate whether Akt activation is required for osteoblast differentiation.Methodology/principal findingsMC3T3-E1 cells were cultured in osteoblast differentiation medium (OBM) with or without 0.1 ng/mL TGF-β1. OBM containing TGF-β1 was changed every 12 h to provide repeated TGF-β1 administration. MC3T3-E1 cells were infected with retroviral vectors expressing constitutively active (CA) or dominant-negative (DN)-Akt. Alkaline phosphatase (ALP) activity and osteoblastic marker mRNA levels were substantially decreased by repeated TGF-β1 treatment compared with a single TGF-β1 treatment. However, expression of CA-Akt restored ALP activity following TGF-β1 treatment. Surprisingly, ALP activity increased following multiple TGF-β1 treatments as the number of administrations of TGF-β1 increased. Activation of Akt significantly enhanced expression of osteocalcin, but TGF-β1 treatment inhibited this. Mineralization of MC3T3-E1 cells was markedly enhanced by CA-Akt expression under all medium conditions. Exogenous IGF-1 restored the down-regulation of osteoblast-related gene expression by repeated TGF-β1 administration. However, in cells expressing DN-Akt, these levels remained inhibited regardless of IGF-1 treatment. These findings indicate that Akt activation is required for the early phase of osteoblast differentiation of MC3T3-E1 cells induced by TGF-β1. However, Akt activation is insufficient to reverse the inhibitory effects of TGF-β1 in the late stages of osteoblast differentiation.ConclusionsTGF-β1 could be an inducer or an inhibitor of osteoblastic differentiation of MC3T3-E1 cells depending on the state of Akt phosphorylation. Our results indicate that Akt is the molecular switch for TGF-β1-induced osteoblastic differentiation of MC3T3-E1 cells.

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Vaspin regulates the osteogenic differentiation of MC3T3-E1 through the PI3K-Akt/miR-34c loop.

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