Mouse xenograft assays to assess the functionality of hESC and iPSC-derived CD34+ cells (transfer to Tromsø)

The in vitro derivation of functional hematopoietic stem cells (HSC) from pluripotent stem cells (iPSC) and subsequent analysis using xenograft assays will allow in the future the use of these cells for bone marrow transplantations. It will also allow targeted gene alterations to study human hematopoiesis in the physiologic setting and in disease. It further will be of great interest to determine whether blood malignancies can be recapitulated using in vivo xenograft models with genetically modified hESC-derived CD34+ cells. Along the same line, such model systems can be used to study iPSC-derived CD34+ cells that harbor the disease causing mutation with iPSC-derived CD34+ where the mutation has been repaired. The function of reprogrammed HSC can only be studied in vivo. Prior to transplantation, animals (NSG-SGM3, 400; 350 in Tromsø, 50 in Oslo) need to be preconditioned through irradiation. Total Whole body irradiation is used in the field of blood stem cell function and cancer (for more information: http://www.bu.edu/orccommittees/iacuc/policies-and-guidelines/irradiation-of-rodents/). It allows to kill proliferating blood cells without significant damage of tissues. In this study, mice will receive a single 2Gy dose (sublethal). This low level of irradiation does not induce bone marrow depletion, thus no adverse symtoms are expected. This sublethal dose increases the amount of factors released by the bone marrow niche allowing the engrafment of transplanted cells and their proliferation. Mice will be transplanted after irradiation and will be monitored over time to check blood cell subsets reconstitution. Mice will be used in the most efficient way and numbers are kept to minimum.