Huang C-Y Charles, Reuben Paul M, Cheung Herman S
Research Service, Miami VA Medical Center, 1201 NW 16th Street, Miami, Florida 33125, USA.
Stem Cells. 2005 Sep;23(8):1113-21. doi: 10.1634/stemcells.2004-0202. Epub 2005 Jun 13.
Our recent study suggested that cyclic compressive loading may promote chondrogenesis of rabbit bone-marrow mesenchymal stem cells (BM-MSCs) in agarose cultures through the transforming growth factor (TGF)-beta signaling pathway. It has been shown that the activating protein 1 (AP-1) (Jun-Fos) complex mediated autoinduction of TGF-beta1 and its binding activity was essential for promoting chondrogenesis of mesenchymal cells, whereas Sox9 was identified as an essential transcription factor for chondrogenesis of embryonic mesenchymal cells. The objective of this study was to examine temporal expression patterns of early responsive genes (Sox9, c-Fos, c-Jun, and TGF-beta type I and II receptors) and induction of their corresponding proteins in agarose culture of rabbit BM-MSCs subjected to cyclic compressive loading. The rabbit BM-MSCs were obtained from the tibias and femurs of New Zealand White rabbits. Cell-agarose constructs were made by suspending BM-MSCs in 2% agarose gel (10(7) cells/ml) for cyclic, unconfined compression tests performed in a custom-made bioreactor. In the loading experiment, specimens were subjected to sinusoidal loading with a magnitude of 15% strain at a frequency of 1 hertz for 4 hours per day. Experiments were conducted for 2 consecutive days. This study showed that cyclic compressive loading promoted gene expressions of Sox9, c-Jun, and both TGF-beta receptors and productions of their corresponding proteins, whereas those gene expressions exhibited different temporal expression patterns among genes and between 2 days of testing. The gene expression of c-Fos was detected only in the samples subjected to1-hour dynamic compressive loading. These findings suggest that the TGF-beta signal transduction and activities of AP-1 and Sox9 are involved in the early stage of BM-MSC chondrogenesis promoted by dynamic compressive loading.
我们最近的研究表明，周期性压缩载荷可能通过转化生长因子（TGF）-β信号通路促进兔骨髓间充质干细胞（BM-MSCs）在琼脂糖培养体系中的软骨形成。研究表明，激活蛋白1（AP-1）（Jun-Fos）复合物介导的TGF-β1自诱导及其结合活性对于促进间充质细胞软骨形成至关重要，而Sox9被认为是胚胎间充质细胞软骨形成的关键转录因子。本研究的目的是检测兔BM-MSCs在琼脂糖培养体系中受到周期性压缩载荷时早期反应基因（Sox9、c-Fos、c-Jun以及TGF-β I型和II型受体）的时序表达模式及其相应蛋白的诱导情况。兔BM-MSCs取自新西兰白兔的胫骨和股骨。通过将BM-MSCs悬浮于2%琼脂糖凝胶（10⁷个细胞/ml）中制备细胞-琼脂糖构建物，用于在定制生物反应器中进行的周期性无侧限压缩试验。在加载实验中，样本每天以1赫兹的频率承受幅度为15%应变的正弦载荷4小时。实验连续进行2天。本研究表明，周期性压缩载荷促进了Sox9、c-Jun以及两种TGF-β受体的基因表达及其相应蛋白的产生，而这些基因表达在不同基因之间以及测试的2天之间呈现出不同的时序表达模式。c-Fos的基因表达仅在承受1小时动态压缩载荷的样本中检测到。这些发现表明，TGF-β信号转导以及AP-1和Sox9的活性参与了动态压缩载荷促进BM-MSC软骨形成的早期阶段。
