School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney NSW, Australia.
Biotechnol Bioeng. 2012 Apr;109(4):1060-73. doi: 10.1002/bit.24372. Epub 2011 Dec 22.
The effect of dynamic mechanical shear and compression on the synthesis of human tissue-engineered cartilage was investigated using a mechanobioreactor capable of simulating the rolling action of articular joints in a mixed fluid environment. Human chondrocytes seeded into polyglycolic acid (PGA) mesh or PGA-alginate scaffolds were precultured in shaking T-flasks or recirculation perfusion bioreactors for 2.5 or 4 weeks prior to mechanical stimulation in the mechanobioreactor. Constructs were subjected to intermittent unconfined shear and compressive loading at a frequency of 0.05 Hz using a peak-to-peak compressive strain amplitude of 2.2% superimposed on a static axial compressive strain of 6.5%. The mechanical treatment was carried out for up to 2.5 weeks using a loading regime of 10 min duration each day with the direction of the shear forces reversed after 5 min and release of all loading at the end of the daily treatment period. Compared with shaking T-flasks and mechanobioreactor control cultures without loading, mechanical treatment improved the amount and quality of cartilage produced. On a per cell basis, synthesis of both major structural components of cartilage, glycosaminoglycan (GAG) and collagen type II, was enhanced substantially by up to 5.3- and 10-fold, respectively, depending on the scaffold type and seeding cell density. Levels of collagen type II as a percentage of total collagen were also increased after mechanical treatment by up to 3.4-fold in PGA constructs. Mechanical treatment had a less pronounced effect on the composition of constructs precultured in perfusion bioreactors compared with perfusion culture controls. This work demonstrates that the quality of tissue-engineered cartilage can be enhanced significantly by application of simultaneous dynamic mechanical shear and compression, with the greatest benefits evident for synthesis of collagen type II.
采用能够模拟关节在混合液环境中滚动作用的力学生物反应器，研究了动态力学剪切和压缩对人组织工程软骨合成的影响。将人软骨细胞接种到聚乙醇酸（PGA）网或 PGA-藻酸盐支架中，在力学生物反应器中进行机械刺激之前，在摇瓶或再循环灌注生物反应器中预培养 2.5 或 4 周。构建体在 0.05 Hz 的频率下受到间歇性无约束的剪切和压缩加载，施加的峰峰值压缩应变幅度为 2.2%，外加静态轴向压缩应变 6.5%。在每天 10 分钟的加载周期内进行长达 2.5 周的机械处理，在 5 分钟后改变剪切力的方向，并在每天处理期结束时释放所有加载。与没有加载的摇瓶和力学生物反应器对照培养物相比，机械处理提高了软骨的产生量和质量。以每细胞为基础，两种主要软骨结构成分，糖胺聚糖（GAG）和 II 型胶原的合成分别提高了 5.3 倍和 10 倍，具体取决于支架类型和接种细胞密度。机械处理后，PGA 构建体中 II 型胶原占总胶原的百分比也增加了 3.4 倍。与灌注培养对照相比，机械处理对在灌注生物反应器中预培养的构建体的组成的影响较小。这项工作表明，通过应用同时的动态力学剪切和压缩，可以显著提高组织工程软骨的质量，对 II 型胶原的合成有最大的益处。
