A bioreactor system for clinically relevant bone tissue engineering

Tissue engineering of bone by combining mesenchymal stem cells (MSCs) with a suitable ceramic carrier provides a potential alternative for autologous bone grafts. However, for large scale-production, the current two dimensional (2D) multiplication process in tissue culture flasks has some serious drawbacks. These flasks are limited in their productivity by the number of cells that can be supported by a given area, while repeated handling for culture maintenance makes the process labor-intensive and susceptible to human error (e.g. infections). As a result, manufacturing costs of these conventional processes are limiting the clinical use of tissue- engineered products. Additionally, the microenvironment of the cells is not monitored and controlled in these tissue culture flasks which results in sub-optimal culture conditions. In this thesis we developed a bioreactor system for clinically relevant human bone tissue engineering which can drastically reduce the amount of space and handling steps involved and has the potential to achieve considerable cost reductions. In addition, this system is closed, largely disposable, semi automated and culture conditions like oxygen concentration, pH and temperature can be monitored and controlled online. In this thesis we showed that • Viable human tissue engineered bone could be produced in clinically relevant amounts (10 cm3) from BMSCs in different seeding densities for different donors and at different perfusion rates showing the robustness of the system • As a first step towards clinically applicable bone tissue engineering, we could generate tissue engineered bone directly from the bone marrow aspirate and exclude all 2D cultivation steps. • The produced hybrid constructs showed their osteogenic potential in vitro and in vivo. • Bioreactors can be used as a model system and as an example the combination of dynamic cultivation and cAMP did significantly enhance bone formation in vivo. Overall, we conclude that bioreactor based bone tissue engineering is feasible generating in vitro and in vivo clinically relevant amounts of hybrid osteogenic constructs in a more efficient and controlled way. Therefore, the semi automated disposable perfusion system presented in this thesis could potentially facilitate the introduction of bone tissue engineered products in clinical practice.