miR-155通过抑制SMAD5调控成骨细胞骨分化

摘要

BACKGROUND:Induction of osteoblasts differentiating into osteocytes is a hot spot in tissue engineering;however, the regulatory mechanism underlying differentiation has not been ful y elucidated. MicroRNA, as an endogenous smal RNA molecule, can regulate post-transcriptional gene expression by binding to the 3’ nontranslated region of the target gene mRNA, which also has been found to play an important regulatory role in osteocyte differentiation. OBJECTIVE:To study the regulation of miR-155 on osteoblast differentiation and the underlying mechanism. METHODS:The mouse osteoblast cel lines MC3T3-E1 were selected and induced by mouse bone morphogenetic protein-2 (BMP2, 200 ng/mL) and then the miR-155 mRNA expression was determined by quantitative real-time PCR at 1, 3, 7 and 14 days. MC3T3-E1 cel s were divided into control, BMP2, miR-155 and miR-155 inhibitor groups, fol owed by cultured withα-MEM medium, BMP2, miR-155 and miR-155 inhibitor, respectively, for 2 weeks. RESULTS AND CONCLUSION:After induction using BMP2, miR-155 expression was downregulated in a time dependent manner. The staining intensity of alizarin red in the BMP2 group was significantly higher than that of the control group, and the activity of alkaline phosphatase and mRNA expression were also significantly higher than those in the control group (P<0.01). The staining intensity of alizarin red, activity of alkaline phosphatase and mRNA expression in the miR-155 group were significantly lower than those in the control group (P<0.01), while al above measurements were reversed significantly by miR-155 inhibitor (P<0.05). miR-155 could bind to the 3’ untranslated region of SMAD5 mRNA and significantly downregulated the expressions of SMAD5 protein and mRNA in MC3T3-E1 cel s (P<0.01). These results show that miR-155 can inhibit MC3T3-E1osteogenic differentiation by downregulating SMAD5 expression.%背景：诱导成骨细胞分化为骨细胞是组织工程中的研究热点，但分化过程中的调节机制尚未完全阐明。MicroRNA是一类内源性小RNA分子，可通过与靶基因mRNA的3’端非编码区结合在转录后水平调控基因表达。研究证实，microRNA在骨细胞分化过程中起到重要的调节作用。　　目的：研究miR-155对成骨细胞骨分化的调节作用以及作用机制。　　方法：取小鼠成骨细胞系MC3T3-E1细胞，加入小鼠骨形态发生蛋白2(200μg/L)进行成骨诱导，并与诱导第1，3，7，14天，通过qRT-PCR检测miR-155 mRNA的表达。并将MC3T3-E1细胞分为对照组、诱导组、miR-155组和miR-155 inhibitor组，对照组用α-MEM培养基培养，诱导组在培养基中加入骨形态发生蛋白2进行成骨诱导，miR-155组和miR-155 inhibitor组在成骨诱导之前分别转染miR-155和miR-155拮抗剂，诱导2周。　　结果与结论：①茜素红染色及碱性磷酸酶活性测定：经骨形态发生蛋白2诱导后，miR-155 mRNA表达呈时间依赖性下调。诱导组MC3T3-E1细胞茜素红着色强度、碱性磷酸酶活性和mRNA表达也显著高于对照组(P<0.01)；miR-155组茜素红着色强度明显低于诱导组，碱性磷酸酶活性和mRNA也明显低于对照组(P<0.01)，而miR-155 inhibitor组则呈反向变化(P<0.05)；②荧光报告基因检测和western blot检测：miR-155可与SMAD5 mRNA 3’非编码区结合，并明显降低MC3T3-E1细胞中SMAD5蛋白和mRNA表达(P<0.01)。结果表明，miR-155可通过负性调控SMAD5表达，抑制MC3T3-E1细胞的成骨分化。