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The in vitro creation of three-dimensional tissues will require well-controlled culture tools to maximise nutrient mass transfer, allow the culture of multiple cell types, and assert mechanical forces on the cells. The development of bioreactor technologies will help greatly in this respect. Although still in its infancy, there are some basic design rules and general biological and physical considerations that we can integrate to create bioreactor systems that will manage the complex interactions that exist in tissue between individual cells, between cells and the matrix and cells and their environment. Furthermore, it is also becoming clear that a single bioreactor type will not be suitable to grow all tissue types. Bespoke bioreactor systems will be required for specific tissues or classes of tissue. This chapter has not detailed all of the issues related to tissue engineering bioreactors; its aim was to outline the key features that will contribute to the development of dynamic culture systems for the growth of human tissues. The following chapters in this book provide a source of knowledge on different aspects of bioreactor design and operation that we hope will provide a foundation for the future successful development of tissue engineering.

Packed bed bioreactors are a promising tool for tissue engineering applications that have not been fully utilised to date. They are capable of supporting various cell lines for long culture periods under low shear conditions, due to the immobilisation of cells within macroporous matrices. Various configurations have been designed that deal with the problems traditionally associated with immobilised cell cultures, such as non-ideal fluid flow and mass transport limitations. These have enabled good scale-up and superior productivity to alternative systems such as hollow-fibre reactors. Packed bed reactors are currently being employed in studies to develop bioartificial liver support systems (Morsiani et al. 2000; Shiba et al. 2003) but have also been used for the ex vivo expansion of bone marrow cells (Highfill et al. 1996).

Cell culture is the most important operation to produce tissues endowed with desired functions and constructions. The approaches to induce the functions of tissues have been done by many researchers using various types of stimuli such as physical and chemical factors existing in solid, aqueous and gaseous phases. The bioreactors can prepare accommodative culture conditions, realizing that the well-ordered assemble of the cells allows the success of tissue reconstruction in vitro . We exemplified the circulating medium flow bioreactor as the typical regulating system of culture under enforced oxygen supply and mechanical stress. In addition, the radial flow bioreactor was superior to oxygen supply in high cell density culture under low shear stress, resulting from high level of cross-sectional area of medium flow. The precise design of bioreactor based on assessments of shear stress and oxygen supply facilitate the production of well designed tissues in vitro .