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The overall aim of vascular bioreactor design and operation is the use of a perfusion system to allow adhesion, growth and proliferation of vascular cells under in vitro conditions that emulate the in vivo physiological environment. There are three key factors to be considered: design of a bioreactor that allows the uniform in situ seeding of specific cells to the required scaffold surfaces; use of an appropriate system to generate mechanical forces and transmit them to the cells in the bioreactor; creation of an bioreactor infrastructure to allow long-term, aseptic culture and monitoring of human primary or stem cells and the developing tissue. Due to its relative infancy, literature describing the development of vascular bioreactors is limited with little in the way of standardized design. Such reports describe in some detail the perfusion circuits that incorporate the bioreactors, though few describe the vascular bioreactors in detail. Researchers are using unique, non-standardized systems, drawing on what little information is available. A drawback of this lack of standardisation is the inability to draw common conclusions from the different studies because of the design variation. Given that the mechanical environment is a strong determinant of gene expression, differences in design will effect gene expression and thus the performance of the graft as a whole. Clearly there is a need to define the underpinning design parameters and flow characteristics in order to facilitate comparative studies to improve design and integration methodologies.

Haematopoietic stem cells have been applied successfully in the clinic for over 30 years. This experience, the relative ease with which HSCs can be identified and obtained from a variety of sources and the potential plasticity of these cells makes them ideal for use in haematologic and non-haematologic conditions. Despite these advantages and the significant progress that has been made in the characterisation of factors that govern haematopoiesis, enrichment and ex vivo expansion of repopulating (and possibly plastic) HSCs remains elusive. Conventional 2-D cultures are insufficient to meet the complex demands required and small deviations in the culture parameters can profoundly affect the final cell output. The application of factorial and composite designs to HSC cultures is required in order to fully appreciate the effects and interdependence of stimulatory and inhibitory factors as well as the culture parameters on haematopoietic culture systems. Furthermore, ex vivo expanded HSCs must be safe to use in humans and meet regulations guided by good manufacturing practice (GMP) requirements for clinical therapeutics which includes the development of suitable, closed culture systems that can be easily controlled and monitored. The engineering of optimal haematopoietic cell culture systems requires the design of new expansion systems that mimic the in vivo bone marrow environment that is able to self-regulate and operate under reliable and reproducible conditions. Such a system would offer a broad spectrum of possibilities for different culture strategies in the cultivation of various cell types — from stem cells to differentiated cells for gene, cellular, and tissue therapies.

The NMR-based methods described here are able to evaluate local changes in cell density and metabolic activity, perfusion and flow velocities within a functional engineered tissue. The application of NMR techniques is particularly attractive in the context of bioartificial organs. The application of such techniques over the past 25 years to the study of intact biological systems, including man, has generated a wealth of data, including spectroscopic and imaging profiles of healthy and diseased tissues. This database is a valuable tool that can be used to assess the performance of cells from a given tissue, when incorporated into a bioartificial organ, and/or the physical and morphological properties of an engineered tissue as compared to its native counterpart. This approach could be useful, for example, for monitoring the progress of skin grafts, or to assess GAG and collagen contents locally in a repair site within articular or meniscal cartilage. The possibility of using the same suite of techniques both in vitro , during the production stage of the tissue, and in vivo , post implantation, is probably unique to NMR and represents a tremendous advantage of this technique.