Chen Xi, Guo Jianmin, Yuan Yu, Sun Zhongguang, Chen Binglin, Tong Xiaoyang, Zhang Lingli, Shen Chao, Zou Jun
School of Sports Science, Wenzhou Medical University, Wenzhou, Zhejiang 325035, P.R. China.
School of Kinesiology, Shanghai University of Sport, Shanghai 200438, P.R. China.
Mol Med Rep. 2017 May;15(5):2890-2896. doi: 10.3892/mmr.2017.6327. Epub 2017 Mar 15.
It is widely accepted that mechanical stress is an important factor in bone associated cell differentiation, including that of mesenchymal stem cells, osteoblasts and osteocytes. The present study aimed to determine the effect of mechanical cyclic compressive load on osteoblast differentiation, and whether this was associated with activation of the wingless‑type (Wnt)/β-catenin signaling pathway. Using a 3D scaffold model, MC3T3‑E1 cells were exposed to cyclic compressive loading via the Flexcell‑5000C™ Compression system. Sinusoidal wave magnitudes of 0.33, 0.5 and 1 MPa were applied for 4, 6 and 8 h, at 1 Hz frequency. Expression levels of genes associated with osteoblast differentiation were enhanced following compression, including alkaline phosphatase, osteocalcin, runt‑related transcription factor 2 and osterix. Optimal compression was observed using a magnitude of 0.5 MPa for 6 h, whereas a magnitude of 1 MPa had no effect on osteoblast differentiation, and had a negative effect when applied for prolonged time periods. Compressive loading additionally enhanced the mRNA expression levels of the Wnt/β‑catenin signaling pathway component, low density lipoprotein receptor‑related protein 5, and the protein expression levels of Wnt1, disheveled segment polarity protein‑2 (DVL2) and β-catenin. By contrast, mRNA expression levels of sclerostin and the inactive form of β-catenin (phosphorylated at Ser33/37/Thr41) were reduced following compressive loading. Following compressive loading of cells, dickkopf-related protein 1 (DKK‑1), an inhibitor of the Wnt signaling pathway, increased protein expression levels of the inactive form of the Wnt‑associated protein, phosphorylated‑β‑catenin, compared with compression alone. However, DVL2 and Wnt1 protein expression levels were unaffected, suggesting that the loading‑induced activation of Wnt/β‑catenin signaling decreased however, it was not prevented by DKK‑1 treatment. In conclusion, the present study demonstrated that cyclic compressive load promoted osteoblast differentiation and may be dependent on the Wnt/β-catenin signaling pathway in regard to magnitude and duration.
机械应力是影响包括间充质干细胞、成骨细胞和骨细胞在内的骨相关细胞分化的重要因素，这一观点已被广泛接受。本研究旨在确定周期性机械压缩负荷对成骨细胞分化的影响，以及这是否与无翅型（Wnt）/β-连环蛋白信号通路的激活有关。使用三维支架模型，通过Flexcell-5000C™压缩系统对MC3T3-E1细胞施加周期性压缩负荷。以1Hz频率分别施加幅值为0.33、0.5和1MPa的正弦波，持续4、6和8小时。压缩后，与成骨细胞分化相关的基因表达水平增强，包括碱性磷酸酶、骨钙素、 runt相关转录因子2和osterix。观察到幅值为0.5MPa、持续6小时的压缩效果最佳，而幅值为1MPa对成骨细胞分化没有影响，长时间施加则有负面影响。压缩负荷还增强了Wnt/β-连环蛋白信号通路成分低密度脂蛋白受体相关蛋白5的mRNA表达水平，以及Wnt1、散乱节段极性蛋白-2（DVL2）和β-连环蛋白的蛋白表达水平。相比之下，压缩负荷后硬化蛋白和β-连环蛋白的无活性形式（Ser33/37/Thr41磷酸化）的mRNA表达水平降低。细胞压缩负荷后，Wnt信号通路抑制剂Dickkopf相关蛋白1（DKK-1）与单独压缩相比，增加了Wnt相关蛋白无活性形式磷酸化-β-连环蛋白的蛋白表达水平。然而，DVL2和Wnt1蛋白表达水平未受影响，表明负荷诱导的Wnt/β-连环蛋白信号激活降低，但是DKK-1处理并不能阻止这种降低。总之，本研究表明，周期性压缩负荷促进成骨细胞分化，并且在幅度和持续时间方面可能依赖于Wnt/β-连环蛋白信号通路。
