β-TCP支架体外构建组织工程骨及其流体力学研究

Study of Flow Field on In vitro Construction of Tissue Engineering Bone by a β-Tricalcium Phosphate Scaffold

骨髓基质干细胞在β-tricalciumphosphate(β-TCP)支架上分别进行了1、2和4周的三维动态培养,对支架上不同时间和部位的细胞面积/微孔面积及支架动态培养的流体环境进行了研究.研究表明,第1周细胞在支架大部分孔道内粘附生长并出现一定区域的单细胞层和多细胞层,第2周部分区域的部分孔道已填满了细胞并出现多细胞层,第4周大部分孔道几乎填满了细胞,主管道内壁出现了较多的细胞生长.同时发现,支架上各个区域细胞粘附面积不等,部分区域无细胞存在,有的部位2周后细胞逐渐减少.为了研究支架各个位置细胞増殖与流速、剪切应力的关系,建立了支架随机孔道结构的流体分析模型,通过支架上流速和剪切应力分布探讨实验中细胞分布现象的机理.结合计算和实验发现,流体能流到的部位几乎都有细胞生长,细胞生长较快的部位速度大多集中在0.24～0.53mm/s,剪切力大多在0.0050～0.023Pa,主管道底部及靠近进口的部位可能存在由于过大的剪切力影响细胞生长的区域.上述结果在一定程度上反映了细胞-支架-流体三者在成骨转化过程中的作用,对指导体外灌注培养的流量确定、灌注工艺及骨转化动力学研究有重要的意义.

Abstract The massive β-tricalcium phosphate （β-TCP） scaffold with a central tunnel was impregnated with the sheep mesenchymal stem cells and were continuously perfused with the complete α-MEM medium by a peristaltic pump for 7, 14 and 28 days. Histological study showed that the cells proliferated through the whole scaffolds under dynamic culture. The cells formed a continuous monolayer or multilayer in the first 7 days and some pores in the scaffold packed with cells in 14 days. Most of pores were almost fully filled with cells after 28 days＇ culture. And the cell coverage were various in various spaces of the scaffold. Unoccupied spaces were found in many macropores and cell death was found in some spaces after 14 days＇ culture. The CFD was used to simulate the flow conditions within perfused cell-seeded cylindrical scaffolds to give insight into the mechanisms of the cell growth phenomena. Relating the simulation results to perfusion experiments, the average fluid velocity （approximately 0.24-0.53 mm/s） and shear stress （approximately 0.0050-0.023 Pa） were found to correspond to increased cell proliferation within the cell-scaffold constructs.