Previous studies have proved that dynamic culture could facilitate nutrients transport and apply mechanical stimulation to the cells within three-dimensional scaffolds, thus enhancing the differentiation of stem cells towards the osteogenic phenotype. However, the effects of macropore size on osteogenic differentiation of stem cells under dynamic condition are still unclear. Therefore, the objective of this study was to investigate the effects of macropore size of hydroxyapatite (HAp) scaffolds on osteogenic differentiation of bone mesenchymal stem cells under static and perfusion culture conditions. In vitro cell culture results showed that cell proliferation, alkaline phosphate (ALP) activity, mRNA expression of ALP, collagen-I (Col-I), osteocalcin (OCN) and osteopontin (OPN) were enhanced when cultured under perfusion condition in comparison to static culture. Under perfusion culture condition, the ALP activity and the gene expression of ALP, Col-I, OCN and OPN were enhanced with the macropore size decreasing from 1300 to 800 µm. However, with the further decrease in macropore size from 800 to 500 µm, the osteogenic related gene expression and protein secretion were reduced. Computational fluid dynamics analysis showed that the distribution areas of medium- and high-speed flow increased with the decrease in macropore size, accompanied by the increase of the fluid shear stress within the scaffolds. These results confirm the effects of macropore size on fluid flow stimuli and cell differentiation, and also help optimize the macropore size of HAp scaffolds for bone tissue engineering.

中文翻译：

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羟基磷灰石支架大孔径对灌注培养下骨间充质干细胞成骨分化的影响

先前的研究证明，动态培养可以促进营养物质的运输，并对三维支架内的细胞施加机械刺激，从而增强干细胞向成骨表型的分化。然而，大孔径对动态条件下干细胞成骨分化的影响仍不清楚。因此，本研究的目的是研究静态和灌注培养条件下羟基磷灰石（HAp）支架的大孔径对骨间充质干细胞成骨分化的影响。体外细胞培养结果显示细胞增殖、碱性磷酸盐（ALP）活性、ALP mRNA表达、胶原蛋白-I（Col-I）、与静态培养相比，在灌注条件下培养时骨钙素 (OCN) 和骨桥蛋白 (OPN) 增强。在灌注培养条件下，ALP活性和ALP、Col-I、OCN和OPN的基因表达随着大孔径从1300μm减小到800μm而增强。然而，随着大孔径从 800 µm 进一步减小到 500 µm，成骨相关基因表达和蛋白质分泌减少。计算流体动力学分析表明，中高速流动的分布区域随着大孔径的减小而增加，伴随着支架内流体剪切应力的增加。这些结果证实了大孔径对流体流动刺激和细胞分化的影响，