Labeling and Conditioning of mesenchymal stem cells for Tissue Engineering
In recent years, stem cell therapy has gained relevance in the treatment of injuries and diseases. In this context, human adult mesenchymal stem cells appear to be promising, as they resemble an autologous cell source for transplantation and therefore provoke fewer immunological reactions in recipients when compared to non-autologous cells. In some clinical studies, stem cell therapy was associated with the occurrence of cancer. It is still unclear whether this was caused by the stem cells or whether the tumorigenic process was coincidental. To find out, stem cells will be marked before transplantation to make their identification easier afterwards. For this purpose, work is currently underway on two different labeling methods: Firstly, a specific non-coding DNA sequence is transfected transiently into the target cells, secondly, a conserved sequence suitable for an epigenetic barcode is identified in the genome of the stem cells. For transfection of the marker into the cells, different methods are being tested such as lipofection, electroporation and lentiviral transfection. The epigenetic code is explored before and after bisulfit-conversion and comparisons made. The gene expression of the epigenetically regulated target genes will be investigated using real time PCR.
Tissue Engineering is a growing sector within the future of medicine and offers enormous potential for developing bioartificial vascular grafts with increased relevance in a senescence society. One of the major problems to be solved is the isolation and cultivation of sufficient endothelial cells from an autologous cell source in order to prevent rejection by the recipient. Recent studies show, however, that human mesenchymal stem cells isolated out of adipose tissue from patients (hASCs) can be differentiated in endothelial-like cells. We are currently exploring the impact of different cultivation conditions, such as hypoxia and shear stress, on the secretion of angiogenetic factors and therefore on the differentiation into endothelial cells.
A further approach includes the co-cultivation of human umbilical venous endothelial cells (HUVECs) and undifferentiated hASCs. Here we explore the effect of hASC-produced angiogenetic factors on the proliferation of HUVECs and therefore on their capability to grow on biocompatible scaffolds.
For preparation and cultivation of a vascular graft in location next to the clinic, our working group develops a suitable bioreactor. In contrast to existing systems, it should regulate and control the differentiation process of the growing graft. For that purpose, sensor systems for pH, temperature, glucose etc. will be adapted and a touchless monitoring via ultrasound will be established.
Another field of work includes biotesting. Here we screen different pharmacological substances with respect to their antiproliferative efficiacy and toxicity on human primary cells and human cell lines. We screen using ready-to-use-assays (CTB, MTT, ECIS, Apo ONE) and establish new methods of integration, recording approach-specific problems in detail. One example is the determination of the toxicity of modern immunosuppressive drugs in a dynamic 3D- cell culture.
The EFRE-funded cooperative project ScreenReject deals with immunulogical biomarkers cencerning kidney transplant rejection. The insitute leads the cooperation between the Medical School Hannover, the Hochschule Hannover an the Leibniz University Hannover.