Modelling severe paediatric aplastic anaemia using induced pluripotent stem cell technology

Abstract

Aplastic anaemia (AA) is a disorder resulting in pancytopenia and hypocellular bone marrow. Although the immunological nature of AA pathogenesis is widely accepted, there is an increasing recognition that a significant number of AA patients might present dysfunctional haematopoietic stem or progenitor cells. In this study, induced pluripotent stem cell (iPSC) technology was used to reprogram fibroblasts from four paediatric severe AA (SAA) patients and three unaffected controls. SAA-iPSC lines were successfully differentiated into erythroid and myeloid progenitors and cells. Two key differences were observed in three of the four SAA patients: (1) SAA-iPSC generated a reduced number of erythroid and myeloid cells and (2) SAA-iPSC failed to elongate their telomeres during the reprogramming process. These deficiencies comprise two key features of AA and indicate that the iPSC model closely mimics the disease phenotype. These deficiencies also suggest that some (but not all SAA) may be characterised by an underlying genetic predisposition which impacts the proliferation and/or differentiation of erythroid and myeloid cells. A detailed flow cytometric analysis indicated a significant reduction in the fraction of proliferative iPSC-derived-haematopoietic progenitors in three SAA patients. Likewise, significant levels of replicative stress-associated DNA damage were observed in iPSC-derived-haematopoietic progenitors from one of the SAA patients, which may suggest an impaired DNA damage response in the face of replicative stress. Finally, thrombopoietin-receptor agonist eltrombopag was investigated in the iPSC model system and was shown to have no significant effect on the, proliferation, DNA repair and erythroid/myeloid colony-forming potential of SAA-iPSC derived haematopoietic progenitors under normal or stress conditions. In summary, the data generated from this study highlights the utility of patient specific iPSC in providing a disease model for SAA, in identifying likely constitutional cases for further genetic studies and predicting patient specific responses to available and future drugs.