ABSTRACT
Embryonic stem (ES) cells are pluripotent cells capable of extensive proliferation while maintaining their potential to differentiate into any cell type in the body. ES cells can therefore be considered a renewable source of therapeutically useful cells. While ES-derived cells have tremendous potential in many experimental and therapeutic applications, the scope of their utility is dependent on the availability of relevant cell quantities. Therefore, most of the researches are being focused on the differentiation of ES cells. ES cell aggregation is important for embryoid body (EB) formation and the subsequent generation of ES cell derivatives. EB has been shown to recapitulate aspect of early embryogenesis, including the formation of a complex three-dimensional architecture wherein cell-cell and cell-matrix interactions are thought to support the development of the three embryonic germ layers and their derivatives. Standard methods of EB formation include hanging drop and liquid suspension culture. Both culture systems maintain a balance between allowing ES cell aggregation necessary for EB formation and preventing EB agglomeration for efficient cell growth and differentiation. However, they are limited in their production capacity. In this paper, we established a new approach for the mass production of EBs in a scalable culture system. The rotary cell culture system (RCCS, STLV type) was adopted to produce EBs. The vessel was placed on its rotary base and the experiment started with a beginning rotation rate of approximately 8 r/min which has been previously determined empirically as the optimal initial speed to yield randomized gravitational vectors while minimizing fluid shear stress. To keep the aggregations pfloating in simulated microgravityq, the rotation rate was increased as the EBs visibly grew. The EB production efficiency was calculated when different cell densities were inoculated. The kinetic change of EBs was measured during the time course of EB formation. Compared with the traditional method of producing EBs with hanging drop, the multi-potential of the resulting EBs in RCCS was analyzed by the capability of cardiomyocyte genesis. The results showed that EBs could be produced by RCCS with high efficiency. The optimal cell density inoculated in RCCS was 10000 cells/ml, in which EB production was about twice higher than that in the suspending culture. Day 4-5 was the optimal time point for harvesting EBs. To clarify whether the differentiated potential of EBs might be affected by the microgravity produced by the rotary cell culture system, cardiogenic induction during ES cell differentiation was evaluated in our study. It was manifested by appearance of spontaneously and rhythmically contracting myocytes. In addition, immuno-histological and RT-PCR detection showed that the harvested EBs in RCCS exhibited the expected cardiac genesis and morphology. So, scalable production of EBs is obtained by RCCS. It will provide a useful approach to generate a large quantity of ES-derived cells for further research or application.