Stem cells in biotechnology Lectures

In cell therapy the pathway from bench to bedside has shown a quick adoption into clinical trials. Thus preclinical and clinical studies progress along parallel trajectories. A great effort is being undertaken to find out universal tools and strategies, which can be applied to pluripotent stem cells differentiated to distinct cell types. The major unresolved problem is obtaining the sufficient number of autologous pluripotent cells and the inherited association of pluripotency with the risk of teratoma formation. The second obstacle, easier to be solved, is a massive death of progenitor cells after transplantation. It has been convincingly shown that the cell survival can be improved by overexpression of cytoprotective genes. One of the candidates is heme oxygenase-1 (HO-1), the antioxidative, anti-apoptotic and anti-inflammatory enzyme. We have demonstrated that overexpression of HO-1 significantly improved the survival of murine proangiogenic progenitors (PPC, a population enriched in CD45-/Sca1+/VEGFR2+ cells) after transplantation to the wounded skin of the syngeneic mice. Moreover, expression of HO-1 significantly improved the angiogenic response of PPC and mature endothelial cells to VEGF and SDF-1α, acting mostly through cGMP-dependent pathway and through facilitating the phosphorylation of VASP-1 protein. Accordingly, overexpression of HO-1 after adenoviral or AAVmediated gene transfer, improved the skin wound healing in diabetic mice and enhanced revascularization of murine ischemic limbs. Thus, HO-1 overexpression can be beneficial in endothelial progenitors. However, the same strategy can lead to unexpected side-effects in muscle precursors. We demonstrated that HO-1-derived carbon monoxide in a cGMP-independent way inhibits the nuclear translocation of cEBPδ, decreases its binding to myoD promoter, and thereby blocks the expression of myoD, the master regulator of myogenesis. In consequence, HO-1 disturbs myoblast maturation and development of myotubes. Furthermore, we showed that transplantation of HO-1 overexpressing myoblasts to the murine gastrocnemius muscle may lead to formation of hyperplastic, undifferentiated tumors. This example illustrates the importance of choosing the cell-specific approaches and indicates that cell therapies should be based on knowledge on cell-specific regulatory pathways. L11.2