Delta-globin gene expression improves sickle cell disease in a humanised mouse model.

Sickle cell disease (SCD) is a widespread genetic disease associated with severe disability and multi-organ damage, resulting in a reduced life expectancy. None of the existing clinical treatments provide a solution for all patients. Gene therapy and fetal haemoglobin (HbF) reactivation through genetic approaches have obtained promising, but early, results in patients. Furthermore, the search for active molecules to increase HbF is still ongoing. The delta-globin gene produces the delta-globin of haemoglobin A2 (HbA2). Although expressed at a low level, HbA2 is fully functional and could be a valid anti-sickling agent in SCD. To evaluate the therapeutic potential of a strategy aimed to over-express the delta-globin gene in vivo, we crossed transgenic mice carrying a single copy of the delta-globin gene, genetically modified to be expressed at a higher level (activated), with a humanised mouse model of SCD. The activated delta-globin gene gives rise to a consistent production of HbA2, effectively improving the SCD phenotype. For the first time in vivo, these results demonstrate the therapeutic potential of delta-globin, which could lead to novel approaches to the cure of SCD.

High-level embryonic globin production with efficient erythroid differentiation from a K562 erythroleukemia cell line.

A reliable cell line capable of robust in vitro erythroid differentiation would be useful to investigate red blood cell (RBC) biology and genetic strategies for RBC diseases. K562 cells are widely utilized for erythroid differentiation; however, current differentiation methods are insufficient to analyze globin proteins. In this study, we sought to improve erythroid differentiation from K562 cells to enable protein-level globin analysis. K562 cells were exposed to a variety of reagents, including hemin, rapamycin, imatinib, and/or decitabine (known erythroid inducers), and cultured in a basic culture medium or erythropoietin-based differentiation medium. All single reagents induced observable erythroid differentiation with higher glycophorin A (GPA) expression but were insufficient to produce detectable globin proteins. We then evaluated various combinations of these reagents and developed a method incorporating imatinib preexposure and an erythropoietin-based differentiation culture containing both rapamycin and decitabine capable of efficient erythroid differentiation, high-level GPA expression (>90%), and high-level globin production at protein levels detectable by hemoglobin electrophoresis and high performance liquid chromatography. In addition, ß-globin gene transfer resulted in detectable adult hemoglobin. In summary, we developed an in vitro K562 erythroid differentiation model with high-level globin production. This model provides a practical evaluation tool for hemoglobin production in human erythroid cells.