MicroRNA-218, microRNA-191*, microRNA-3070a and microRNA-33 are responsive to mechanical strain exerted on osteoblastic cells

Abstract

MicroRNA (miRNA) is an important regulator of cell differentiation and function. Mechanical strain is important in the growth and differentiation of osteoblasts. Therefore, mechanresponsive miRNA may be important in the response of osteoblasts to mechanical strain. The purpose of the present study was to select and identify the mechanoresponsive miRNAs of osteoblasts. Mouse osteoblastic MC3T3-E1 cells were cultured in cell culture dishes and stimulated with a mechanical tensile strain of 2,50 με at 0.5 Hz, and the activity of alkaline phosphatase (ALP), mRNA levels of ALP, osteocalcin (OCN), and collagen type I (Col I), and protein levels of bone morphogenetic proteins (BMPs) in the cell culture medium were assayed. Following miRNA microarray and reverse transcription-quantitative polymerase chain reaction analyses, differentially expressed miRNAs in the mechanically strained cells and unstrained cells were selected and identified. Using bioinformatics analysis, the target genes of the miRNAs were then predicted. The results revealed that the mechanical strain of 2,500 με increased the activity of ALP, the mRNA levels of ALP, OCN and Col I, and the protein levels of bone morphogenetic protein(BMP)-2 and BMP-4 Continuous mechanical stimulation for 8 h had the most marked stimulant effects. miR-218, miR-191*, miR-3070a and miR-33 were identified as differentially expressed miRNAs in the mechanically strained MC3T3-E1 cells. Certain target genes of these four miRNAs were involved in osteoblastic differentiation. These findings indicated that a mechanical strain of 2,500 με, particularly for a period of 8 h, promoted osteoblastic differentiation, and the four mechanoresponsive miRNAs identified may be a potential regulator of osteoblastic differentiation and their response to mechanical strain.

Mechanical Stress Regulates Bone Metabolism Through MicroRNAs

“…Mechanical loading was reported to induce significant changes in miRNAs in pre‐osteoblastic MC3T3 cells (Guo et al, ), which suggests that miRNA might play an important role in mechanical loading mediated bone formation. Mechanical strain was shown to up‐regulate the gene expression of ALP, osteocalcin and collagen I, and enhance the activity of ALP, accompanied by the induction of miR‐218, miR‐191*, miR‐3070a, and miR‐33 expression (Guo et al, ).…”

“…Mechanical loading was reported to induce significant changes in miRNAs in pre‐osteoblastic MC3T3 cells (Guo et al, ), which suggests that miRNA might play an important role in mechanical loading mediated bone formation. Mechanical strain was shown to up‐regulate the gene expression of ALP, osteocalcin and collagen I, and enhance the activity of ALP, accompanied by the induction of miR‐218, miR‐191*, miR‐3070a, and miR‐33 expression (Guo et al, ). Besides these miRNAs, the miRNA microarray also showed that the expression levels of miR‐M1‐2‐3p, miR‐let‐7e*, and miR‐3470a were much higher in the strained group than the unstrained control group while the expression levels of miR‐32, miR‐5110, and miR‐5121 were significantly lower under mechanical strain than unstrained group (Guo et al, ).…”

“…MiRNAs regulate the proliferation, differentiation, and apoptosis of bone cells by inhibiting protein translation and regulating gene expression via selectively binding to complementary sequences in the 3′ untranslated region (UTR) of mRNAs. Recently, it has been reported that mechanical loading induced significant changes in miRNAs in bone marrow mesenchymal stem cells (BMSCs) and osteoblasts (Guo et al, ), suggesting that miRNAs might be one of the main mechanisms by which exercise or mechanical loading regulates bone metabolism and promotes bone formation. To further study the role of miRNAs in mechanical stress mediated bone metabolism, the present paper reviews the expression of miRNAs and their mechanism of action in mechanical loading regulated bone metabolism.…”

Mechanical strain affects some microRNA profiles in pre-oeteoblasts.

“…Mechanical strain could promote osteoblast differentiation [16,17]. In our previous study, a mechanical strain of 2500 με at 0.5 Hz for 8 hours also promoted osteoblast differentiation and four miRNAs (miR-218, 191*, 3070a and 33) were responsive to the mechanical strain [42]. However, the mechanoresponsive miRNAs of our previous study were different from the mechanoresponsive miRNAs found in this study.…”

microRNA Regulation of Skeletal Development

“…Identified in several miRNA screens, miR-199a associates with osteoblast differentiation [63,64], suggesting that its identification as an ‘ostemiR’ may be linked to its control of Cox2. Additionally, while not directly linked to Cox2 , miR-218, miR-191*, miR-3010a and miR-33 were recently identified in MC3T3-E1 osteoblastic cells to be responsive to mechanical strain [65]. …”