Bio-Testing and Tissue Engineering

AG Blume is investigating new implant materials in 3D cell culture models and the dynamic cultivation of autologous (endothelial) cell systems in special pulse wave bioreactors for a vascular graft. Microstructured scaffolds and new bioinks are designed using 3D printing. In addition, lateral flow tests are developed, e.g., after kidney transplantation, as well as optogenetically active cell systems for drug release in the inner ear (Hearing4All). KI-based indicators from complex databases support, among other things, health care research projects (MinDial, focus: patients with kidney disease).

Research

Vascular Bio-Prosthesis Development

Tissue engineering is a rapidly growing sector in the field of future-oriented medicine and offers enormous potential in the development of bioartificial vascular prostheses, which are becoming increasingly important in a rapidly aging society. One of the main problems within this project is the isolation and cultivation of endothelial cells under the aspect of autologous transplantation. However, recent studies show that human mesenchymal stem cells isolated from adipose tissue of patients (hASCs, cooperation with the Department of Plastic Surgery of the MHH) have approaches for differentiation in an endothelial direction and positively influence the differentiation of immature endothelial cells into capillaries. Therefore, we developed a protocol for the targeted use of stem cells in coculture with endothelial cells. For the induced secretion of proangiogenic markers, the cultivation parameters hypoxia and shear stress play an important role. In parallel, we isolate endothelial progenitor cells from peripheral blood (cooperation with the blood bank of the MHH) and optimize their extracorporeal expansion and development into a confluent cell layer on scaffold materials for endothelialization. Flow cytometric analysis of specific cell subsets and selective subcultivation supports the formation of mature endothelial monolayers. In addition, we investigate the influence of different shear stress conditions (static vs. dynamic cultivation under pulsatile or laminar flow of different flow velocities) on these endothelial progenitor cells isolated from peripheral blood.

Bio-Printing

In the field of bioprinting, we are collaborating with the AG "Blume" (eNIFE) on a BioX bioprinter from Cell-Ink (Sweden) and Regen-Hu (Basel, Switzerland). Novel biodegradable polymers are tested as scaffold material and 3D-printed in fine lattice structures by 3D bioprinting or electrospinning-writing which are coated with native proteins and seeded with endothelial cells. Here, we cooperate with Prof. Dr. M. Wilhelmi and his group working on decellularized animal arteries and performing large animal experiments. Microstructured two-component scaffolds are seeded using viscous bioinks. Isolation of progenitor cells from the bloodstream for endothelialization of the vascular prosthesis was optimized using the principle of dynamic cell cultivation, which places cells under shear stress. Porous scaffolds prepared by porogen leaching are co-cultured with mesenchymal stem cells and endothelial cells (so called HUVECS = human umbilical venous endothelial cells) and capillary structures are grown.

Bio-Reactor Development

In cooperation with eNIFE, our research group developed a functional bioreactor for the clinical supply and cultivation of a "vascular graft" (bioartificial vascular prosthesis). In contrast to existing systems, this bioreactor also regulates the differentiation process of the growing graft and controls the cultivation conditions. For this purpose, sensor systems for pH, temperature, glucose, etc. were adapted and non-contact monitoring via ultrasound was established. The bioreactor has already been awarded with the VDI prize in 2018 and is now being optimized in line with current concepts of Medical Device Regulation. The following topics are being worked on here: Sterility tests, tightness tests, monitoring concepts by means of sensor technology, pressure monitoring in comparison with Comsol-estimation for near-wall shear stress during a cultivation, flow measurements by means of various tubular scaffolds, among others, from pig and horse, but also from the 3D bio-printer.

Bio-Testing

Another field of activity of the working group is biotesting. This involves the screening of different pharmacologically active substances with regard to their effect on proliferation behavior and their toxicity to human primary cells and cell lines. For the screening established assays (CTB, MTT, ECIS, Apo ONE) are used as well as new methods are established, which include experiment-specific questions in more detail. These include toxicity determination of modern immunosuppressants in established 3D spheroid systems. For example, our results explain the endothelium-destroying effect of the calcineurin inhibitor tacrolimus, which is observable in the clinic, even under controlled clinical conditions. Newly developed implant materials - such as special precision-engineered titanium plates for use in dental implants - are also being tested with regard to the effective adhesion of human cell systems and researched for optimal osseointegration, e.g. of dental implants (cooperation with the Institute of Production Engineering and Machine Tools, Prof. B. Denkena, and with the working group of Prof. M. Stiesch in NIFE). Furthermore, a postdoc and two PhD students at the Institute of Technical Chemistry in the Nordstadt are engaged in the development of diagnostic test systems such as living cell microarrays (Dr. R. Jonczyk) and lateral flow assays for renal transplant rejection based on sensitive antibodies and aptamers. These DFG- and EFRE-funded projects are networked with the Institute of Transfusion Medicine as well as with the Department of Nephrology of the MHH.

Optogenetics

As part of the Cluster of Excellence “Hearing for All” we use our experience with mesenchymal stem cells and cell transfections for the development of optogenetically activatable cells for human therapy. In cooperation with the group of Prof. A. Warnecke, light induction by means of an optogenetic switch will be used to induce the transcription of certain pharmacologically or neuroprotectively important proteins, e.g. during the healing of cochlear implants in the context of accompanying cell therapies. Enzymes can also be specifically switched on for the activation of nanoparticles in drug delivery (cooperation with the research group of Prof. P. Behrens, Inorganic Chemistry, NIFE). An optogenetic system of the WG of Prof. W. Weber, University of Freiburg could already be successfully optimized in CHO cells for induction by laser systems of the WG Prof. A. Heisterkamp in NIFE and is currently being transferred to mesenchymal stem cells from adipose tissue or bone marrow.