The ultimate goal of gene therapy for sickle cell anemia (SCA) is an improved phenotype for the patient. In this study, we utilized bone marrow from a sickle cell patient as a model of disease in an in vitro setting for the hyperactive Sleeping Beauty transposon gene therapy system. We demonstrated that mature sickle red blood cells containing hemoglobin-S and sickling in response to metabisulfite can be generated in vitro from SCA bone marrow. These cells showed the characteristic morphology and kinetics of hemoglobin-S polymerization, which we quantified using video microscopy and imaging cytometry. Using video assessment, we showed that delivery of an IHK-βT87Q antisickling globin gene by Sleeping Beauty via nucleofection improves metrics of sickling, decreasing percent sickled from 53.2 ± 2.2% to 43.9 ± 2.0%, increasing the median time to sickling from 8.5 to 9.6 min and decreasing the maximum rate of sickling from 2.3 x 10-3 sickling cells/total cells/sec in controls to 1.26 x 10 -3 sickling cells/total cells/sec in the IHK-βT87Q- globin group (p < 0.001). Using imaging cytometry, the percentage of elongated sickled cells decreased from 34.8 ± 4.5% to 29.5 ± 3.0% in control versus treated (p < 0.05). These results support the potential use of Sleeping Beauty as a clinical gene therapy vector and provide a useful tool for studying sickle red blood cells in vitro.
Bibliographical noteFunding Information:
The authors are grateful to Heather Bechtel for assistance in procuring stored patient bone marrow, Alexander Swart and Ryan Johnson for technical assistance, and Robert P. Hebbel for continued support and helpful comments. We would also like to acknowledge the Flow Cytometry Core Facility of the Masonic Cancer Center, an NCI designated Comprehensive Cancer Center funded in part by NIH grant P30 CA77598.