Short-Term Exposure to Tumor Necrosis Factor-Alpha Enables Human Osteoblasts to Direct Adipose Tissue-Derived Mesenchymal Stem Cells into Osteogenic Differentiation
Short-Term Exposure to Tumor Necrosis Factor-Alpha Enables Human Osteoblasts to Direct Adipose Tissue-Derived Mesenchymal Stem Cells into Osteogenic Differentiation
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DOI：
10.1089/scd.2011.0589
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发表时间：
2012-09-01
影响因子：
4
通讯作者：
Zreiqat, Hala
中科院分区：
文献类型：
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作者：
Lu, ZuFu;Wang, Guocheng;Zreiqat, Hala
肿瘤坏死因子- α (tnf - α)是骨折后24小时达到峰值的主要炎症因子之一；它在骨愈合中的作用是有争议的。本研究的目的是调查暴露于tnf - α的持续时间是否对骨再生的启动至关重要，并确定其潜在机制。结果表明，tnf - α处理24小时显著降低了人原代成骨细胞（HOBs）骨钙素基因的表达。然而，当24 h后停用tnf - α时，与未使用tnf - α处理的HOBs相比，第7天HOBs中骨涎蛋白和骨钙素基因表达水平显著上调。相反，持续tnf - α治疗可下调骨涎蛋白和骨钙素基因表达。此外，在间接共培养系统中，经tnf - α预处理24小时的HOBs诱导的脂肪组织源性间充质干细胞（ASCs）的成骨分化明显高于未经tnf - α处理的HOBs。tnf - α处理还促进HOBs中内源性骨形态发生蛋白2 （BMP-2）的产生，而用Noggin阻断BMP-2信号通路可抑制共培养系统中ASCs的成骨分化。此外，tnf - α处理后，p38丝裂原活化蛋白激酶（MAPK）信号通路的激活早于BMP-2蛋白的表达。当用tnf - α联合p38 mapk特异性抑制剂（SB203580）预处理HOBs时，HOBs产生的BMP-2和HOBs共培养系统中ASCs的成骨分化显著降低。综上所述，我们提供的证据表明，暴露时间是决定tnf - α对骨再生影响的关键因素。我们还证明了p38 MAPK信号通路调节成骨细胞中BMP-2的表达，BMP-2随后通过旁分泌环起作用，指导间充质干细胞的成骨谱系承诺。
Tumor necrosis factor-alpha (TNF-alpha) is one major inflammatory factor peaking at 24 h after bone fracture in response to injury; its role in bone healing is controversial. The aims of this study were to investigate whether the duration of exposure to TNF-alpha is crucial for the initiation of bone regeneration and to determine its underlying mechanism(s). We demonstrated that 24 h of TNF-alpha treatment significantly abrogated osteocalcin gene expression by human primary osteoblasts (HOBs). However, when TNF-alpha was withdrawn after 24 h, bone sialoprotein and osteocalcin gene expression levels in HOBs at day 7 were significantly up-regulated compared with the HOBs without TNF-alpha treatment. In contrast, continuous TNF-alpha treatment down-regulated bone sialoprotein and osteocalcin gene expression. In addition, in an indirect co-culture system, HOBs pretreated with TNF-alpha for 24 h induced significantly greater osteogenic differentiation of adipose tissue-derived mesenchymal stem cells (ASCs) than the HOBs without TNF-alpha treatment. TNF-alpha treatment also promoted endogenous bone morphogenetic protein 2 (BMP-2) production in HOBs, while blocking the BMP-2 signaling pathway with Noggin inhibited osteogenic differentiation of ASCs in the co-culture system. Furthermore, activation of the p38 mitogen-activated protein kinase (MAPK) signaling pathway after TNF-alpha treatment occurred earlier than BMP-2 protein expression. BMP-2 production by HOBs and osteogenic differentiation of ASCs in the co-culture system with HOBs was significantly decreased when HOBs were pretreated with TNF-alpha in combination with the p38 MAPK-specific inhibitor (SB203580). Taken together, we provide evidence that exposure duration is a critical element in determining TNF-alpha's effects on bone regeneration. We also demonstrate that the p38 MAPK signaling pathway regulates the expression of BMP-2 in osteoblasts, which then acts through a paracrine loop, to direct the osteoblast lineage commitment of mesenchymal stem cells.