Stem cell factor and erythropoietin-independent production of cultured reticulocytes

Cultured reticulocytes can supplement transfusion needs and offer promise for drug delivery and immune tolerization. They can be produced from induced pluripotent stem cells (iPSC), but the 45-day culture time and cytokine costs make largescale production prohibitive. To overcome these limitations, we have generated iPSC that express constitutive stem cell factor (SCF) receptor and jak2 adaptor alleles. We show that iPSC lines carrying these alleles can differentiate into self-renewing erythroblasts that can proliferate for up to 70 cell-doubling in a cost-effective, chemically-defined, albumin- and cytokine-free medium. These kitjak2 self-renewing erythroblasts retain the ability to enucleate at a high rate up to senescence. Kitjak2-derived cultured reticulocytes should be safe for transfusion because they can be irradiated to eliminate residual nucleated cells. The kitjak2 cells express blood group 0 and test negative for RhD and other clinically significant red blood cell antigens and have sufficient proliferation capacity to meet global red blood cell needs.