Cornelia Kasper completed her Ph.D. 1998 from Leibniz University of Hannover (Germany) and her habilitation in 2007 at the Institute for Technical Chemistry at the Leibniz University of Hannover. She was appointed as full University Professor for "Biopharmaceutical Production and Technology" at University of Natural Resources and Life Science (BOKU) in Vienna (Austria) at the Department of Biotechnology. She has published more than 80 papers in reputed journals and several book chapters and is editor within the series "Advances in Biochemical Engineering and Biotechnology" (Springer) of several volumes covering actual areas in Tissue Engineering and Stem Cell Research. She is also reviewer for many distinguished journal within the field of biotechnology/bioprocess and bioreactor design and enableling technolgies for stem cell cultivation.
Introduction: Multipotent mesenchymal stromal cells (MSC) are being used with favorable success for tendon regeneration in large animal models as well as in equine patients. Tenogenic differentiation and subsequent matrix synthesis by the MSC was hypothesized to be one of the mechanisms of MSC-supported tendon healing. However, the tenogenic differentiation pathway is not yet completely understood. It is acknowledged that not only growth and transcription factors, but also the extracellular matrix or scaffold composition and mechanical stimulation play a crucial role. Therefore, our aim was to combine natural tendon scaffolds and mechanical stimulation in an in vitro bioreactor model as a basis for the investigation of MSC tenogenic differentiation.
Materials and Methods: To obtain scaffolds with natural matrix proteins in parallel alignment, large equine tendons were decellularized as described previously (Burk et al., 2013). 2 mm thick scaffolds were cut from the decellularized tendons and subjected to mechanical testing. Based on the results of the mechanical scaffold assessment, a cyclic strain bioreactor prototype was designed. The prototype was tested using equine adipose derived MSC which were cultured on the tendon scaffolds and subjected to cyclic strain stimulation (2% strain; 1 Hz; 15 min stimulation- 15 min relaxation- 30 min stimulation). Samples were assessed 24h later by LIVE/DEAD® staining, histology and real-time RT-PCR.
Mette Hemmingsen has completed her Ph.D. about culture and differentiation of cells in micro fluidic array systems and is currently doing postdoctoral studies in liver tissue engineering from The Technical University of Denmark, Department of Micro- and Nanotechnologies.
A huge shortage of organs for transplantation has motivated the research field of tissue engineering to develop bio-artificial liver tissue and even a whole liver. Due to limitations of primary hepatocytes regarding availability and maintenance of functionality, stem cells and especially human induced pluripotent stem cells (hIPS cells) are an attractive cell source for liver tissue engineering. Our approach for engineering liver tissue is to culture and differentiate hIPS cells in a 3D porous polymer scaffold built-in a perfusable bioreactor to ensure supply of oxygen and nutrients and removal of waste. To investigate the hepatic differentiation at flow conditions, IPS-derived definitive endoderm cells were seeded into the scaffold and differentiated according to a protocol developed by our collaborator Cellectis AB. Compared to conventional batch cultures, a similar hepatocyte-like cell morphology and gene expression of the hepatocyte nuclear transcription factor 4α was observed, whereas a decreased expression was for seen for the transcription factor CAR and the CYP enzymes CYP3A5 and CYP3A7. Furthermore, expression of albumin and α-fetoprotein was almost knocked down. However, expression of all markers was increased by the use of conditioned medium or medium with a two times lower concentration of the signalling factors than those optimized for conventional batch cultures. Thus, our results suggest that the flow conditions affect paracrine cell signalling necessary for liver differentiation and/or functionality, as well as the concentration of signalling factors in the differentiation medium has to be adapted to the different environment at flow with constant renewal of the culture medium.