Radial-Flow Bioreactor Enables Uniform Proliferation of Human Mesenchymal Stem Cells Throughout a Three-Dimensional Scaffold

Mesenchymal stem cells (MSCs) obtained from human bone marrow are pluripotent and have been expanded and differentiated into several kinds of mesodermal tissue in vitro. To create bioartificial tissues and organs for implantation, it is necessary to induce proliferation in such cells. In this study, a radial-flow bioreactor (RFB) was used to induce three-dimensional (3D) expansion of human MSCs (hMSCs) on a large scaffold. The effect of this expansion on cellular characteristics was investigated. To produce precultured sheets, the hMSCs were first seeded onto type 1 collagen sheets and incubated for 12 h, after which they were placed in the RFB for fabrication of scaffolds. The culture medium was circulated at 3 mL/min, and the cells were dynamically cultured for 1 week at 37°C. As a control, static cultivation in a culture dish was also carried out. Cellular expansion and characteristics were analyzed. Alkaline phosphatase (ALP) activity in the hMSCs was also investigated after dynamic culture in an osteogenesis induction medium to explore their potential for osteogenic differentiation. At 1 week of dynamic cultivation, a >60% increase was observed in a number of cells together with a uniform distribution throughout the scaffolds compared with under static conditions; no change in hMSC markers was observed. The hMSCs retained the ability for osteogenic differentiation after culture in the RFB. The present results indicate that 3D dynamic culture in an RFB enables uniform expansion of hMSCs with no change in cellular characteristics, suggesting the usefulness of this technique in tissue engineering.