AIMS The present study aimed to evaluate whether the non-Smad dependent TAK1 signaling pathway (BMP-2-TAK1-p38-Osx signaling pathway) played an important role in bone repair mediated by hollow hydroxyapatite (HA) microspheres/chitosan (CS) composite. METHODS Firstly, the biological activity of rhBMP-2 released from the complex was investigated. Then, differentiation test of osteoblasts including ALP activity and calcium deposition, X-ray scoring and three-point bending test were performed. Finally, the mRNAs expression of TAK1, p38, Osx and osteogenic markers was tested by reverse transcription-polymerase chain reaction (RT-PCR). RESULTS RhBMP-2 could be loaded and released from the complex in bioactive form. Additionally, the complex provided a prolonged period of time compared with HA/CS scaffolds. Serum ALP activity was significantly decreased in the TAK1 inhibitor group and p38 inhibitor group. In the X-ray radiography, bone callus was observed in rhBMP-2-loaded hollow HA microspheres/CS composite group. In the three-point bending test, load values in p38 inhibitor group decreased. In the animal model, the mRNA expression of BSP on day 90 was significantly decreased in the p38 inhibitor group and TAK1 inhibitor group. In MC3T3-E1 cells, the mRNA expression of OSX was remarkably up-regulated in both rhBMP-2 group or rhBMP-2-loaded hollow HA microspheres/CS composite group; while the mRNA expression of OSX was significantly down-regulated in TAK1 inhibitor group and p38 inhibitor group. CONCLUSION The BMP-2-TAK1-p38-OSX signaling pathway may play an important role in bone formation and repair mediated by rhBMP-2-loaded hollow HA microspheres/CS composite.

中文翻译：

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非Smad依赖性TAK1信号通路通过重组载有BMP-2的空心羟基磷灰石微球/壳聚糖复合物治疗骨缺损的机制研究。

目的本研究旨在评估非Smad依赖性TAK1信号通路（BMP-2-TAK1-p38-Osx信号通路）是否在中空羟基磷灰石（HA）微球/壳聚糖（CS）复合物介导的骨修复中起重要作用。 。方法首先，研究了从复合物中释放的rhBMP-2的生物学活性。然后，进行了成骨细胞的分化试验，包括ALP活性和钙沉积，X射线评分和三点弯曲试验。最后，通过逆转录-聚合酶链反应（RT-PCR）检测TAK1，p38，Osx和成骨标记物的mRNA表达。结果RhBMP-2可以生物活性形式从复合物中上载和释放。另外，与HA / CS支架相比，该复合物提供了延长的时间。TAK1抑制剂组和p38抑制剂组的血清ALP活性显着降低。在X射线摄影中，在装满rhBMP-2的空心HA微球/ CS复合材料组中观察到骨call。在三点弯曲试验中，p38抑制剂组的负荷值降低。在动物模型中，p38抑制剂组和TAK1抑制剂组第90天BSP的mRNA表达显着降低。在MC3T3-E1细胞中，在rhBMP-2组或负载rhBMP-2的空心HA微球/ CS复合物组中，OSX的mRNA表达均显着上调。TAK1抑制剂组和p38抑制剂组OSX的mRNA表达明显下调。