Hamidouche Zahia, Fromigué Olivia, Ringe Jochen, Häupl Thomas, Marie Pierre J
Laboratory of Osteoblast Biology and Pathology, INSERM U606, Paris F-75475, France.
BMC Cell Biol. 2010 Jun 23;11:44. doi: 10.1186/1471-2121-11-44.
The potential of mesenchymal stromal cells (MSCs) to differentiate into functional bone forming cells provides an important tool for bone regeneration. The identification of factors that trigger osteoblast differentiation in MSCs is therefore critical to promote the osteogenic potential of human MSCs. In this study, we used microarray analysis to identify signalling molecules that promote osteogenic differentiation in human bone marrow stroma derived MSCs.
Microarray analysis and validation experiments showed that the expression of IGF2 and IGFBP2 was increased together with integrin alpha5 (ITGA5) during dexamethasone-induced osteoblast differentiation in human MSCs. This effect was functional since we found that IGF2 and IGFBP2 enhanced the expression of osteoblast phenotypic markers and in vitro osteogenic capacity of hMSCs. Interestingly, we showed that downregulation of endogenous ITGA5 using specific shRNA decreased IGF2 and IGFBP2 expression in hMSCs. Conversely, ITGA5 overexpression upregulated IGF2 and IGFBP2 expression in hMSCs, which indicates tight crosstalks between these molecules. Consistent with this concept, activation of endogenous ITGA5 using a specific antibody that primes the integrin, or a peptide that specifically activates ITGA5 increased IGF2 and IGFBP2 expression in hMSCs. Finally, we showed that pharmacological inhibition of FAK/ERK1/2-MAPKs or PI3K signalling pathways that are enhanced by ITGA5 activation, blunted IGF2 and IGFBP2 expression in hMSCs.
The results show that ITGA5 is a key mediator of IGF2 and IGFBP2 expression that promotes osteoblast differentiation in human MSCs, and reveal that crosstalks between ITGA5 and IGF2/IGFBP2 signalling are important mechanisms that trigger osteogenic differentiation in human bone marrow derived mesenchymal stromal cells.
间充质基质细胞（MSCs）分化为功能性骨形成细胞的潜力为骨再生提供了重要工具。因此，鉴定触发MSCs成骨细胞分化的因子对于提高人MSCs的成骨潜力至关重要。在本研究中，我们使用微阵列分析来鉴定促进人骨髓基质来源的MSCs成骨分化的信号分子。
微阵列分析和验证实验表明，在人MSCs地塞米松诱导的成骨细胞分化过程中，IGF2和IGFBP2的表达与整合素α5（ITGA5）一起增加。由于我们发现IGF2和IGFBP2增强了hMSCs成骨细胞表型标志物的表达和体外成骨能力，所以这种作用是功能性的。有趣的是，我们发现使用特异性shRNA下调内源性ITGA5会降低hMSCs中IGF2和IGFBP2的表达。相反，ITGA5过表达上调了hMSCs中IGF2和IGFBP2的表达，这表明这些分子之间存在紧密的相互作用。与此概念一致，使用激活整合素的特异性抗体或特异性激活ITGA5的肽激活内源性ITGA5会增加hMSCs中IGF2和IGFBP2的表达。最后，我们表明，对由ITGA5激活增强的FAK/ERK1/2-MAPKs或PI3K信号通路进行药理学抑制，会减弱hMSCs中IGF2和IGFBP2的表达。
结果表明，ITGA5是促进人MSCs成骨细胞分化的IGF2和IGFBP2表达的关键介质，并揭示ITGA5与IGF2/IGFBP2信号之间的相互作用是触发人骨髓来源的间充质基质细胞成骨分化的重要机制。
