Establishing a murine xenograft-model for long-term analysis of factors inducing chromosomal instability in myelodysplastic syndrome: Pitfalls and successes.

Myelodysplastic syndromes (MDS) are difficult to culture long-term showing the need of a model to study the fate of cells with MDS-abnormalities associated with chromosomal instability (CIN). This approach to establish a xenograft model transplanting human hematopoietic stem cells (HSC) with different independent lentivirally-mediated MDS-related modifications into immunodeficient mice is a long-lasting and tedious experiment with many parameters and every positive as well as non-functioning intermediate step will help the research community. As the establishment of appropriate xenograft models is increasing worldwide we aim to share our experiences to contribute toward minimizing loss of mice and following the "right" approach. Here, modified HSCs were intrafemorally transplanted into NSG and/or NSGS mice: (1) RPS14-haploinsufficiency, (2) TP53-deficiency, (3) TP53 hotspot mutations (R248W, R175H, R273H, R249S). Engraftment was achieved and cytogenetic analyses showed human cells with normal karyotypes. However, in all experiments with NSG mice, mainly control cells or GFP-negative cells were engrafted, not allowing observation of modified HSCs. In NSGS mice, engraftment rate was higher, but mice developed graft-versus-host disease. In summary, engraftment of HSCs is promising and could be used to analyze the induction of CIN. However, the analysis of modified HSCs is limited and further experiments are required to improve this model.