Manufacturing of bone forming tissue engineering constructs using anintegrated 3D bioreactor-driven process.

Tissue engineering has been defined as an interdisciplinary field which aims at developing implants to induce or support the regeneration of tissues and organs in compromised defect environments. Despite significant scientific advances no large scale clinical translation of current concepts has taken place yet. As numerous scientific questions remain unanswered on for example mechanism of action, the current focus of the field is predominantly aimed at the development and validation of novel concepts with potential future clinical applications. Although essential for product development, clinical translation and implementation of these concepts will only be possible if the production of the resulting products can be accomplished using standardized, automated, controlled, reproducible and safe processes. The translation of lab scale processes to a clinical and industrial relevant environment can however have significant implications on the process and resulting product. An integrated approach combining product and process development, thereby taking into account future translational aspects from the conceptual development onwards, can facilitate significant advances in the field towards clinical applications Within this context the use of various bioreactor systems for cell based product development has already been explored as these systems can provide the required controlled, automated and closed process environment. The integration of essential up- and down-stream process steps such as cell expansion as well as the development of tools for process monitoring and quality control towards integrated bioprocess development is however lacking. Although in this respect, numerous technological issues remain which will be essential for successful clinical implementation, the influence of the artificial environment within which the cells reside during these up- and down-stream processes on their behavior, functional characteristics and identity will determine the final applicability of the bioreactor systems.

In order to assess the potential use of a three dimensional perfusion bioreactor system for the expansion of a progenitor cell population the primary objective of this dissertation was to elucidate the influence of this culture system on the proliferation, differentiation, matrix deposition and post-harvest functionality of the expanded cell population. To facilitate these observations two additional objectives were defined to enable (i) the quantitative monitoring of the cell proliferation within the bioreactor system and (ii) to visualize and quantify the neo-tissue formation within the three dimensional culture environment.