Establishment of immortalized human erythroid progenitor cell lines able to produce enucleated red blood cells
Authors: Nakamura Y. 
Published: June 2012

Background  In many countries, the available supply of transfusable red blood cells (RBCs) is often inadequate. This problem has stimulated considerable research around the world into the development of a robust method for in vitro production of transfusable RBCs. Some possible methods are under active investigation such as the production of RBCs from hematopoietic stem/progenitor cells and from embryonic stem (ES) or induced Pluripotent Stem (iPS) cells. Although it may be feasible to produce RBCs from their immediate precursor cells, it is not easy to obtain sufficient numbers of these precursor cells. One solution to the latter problem may be to establish immortalized erythroid progenitor cell lines able to produce transfusable RBCs in vitro; these immortalized cells would form a very valuable resource. We previously developed a robust method for generating immortalized erythroid progenitor cell lines following the induction of hematopoietic differentiation of mouse ES cells, and successfully established several immortalized erythroid progenitor cell lines that we designated Mouse ES cell Derived‐Erythroid Progenitor (MEDEP) cell lines. Although the precise characteristics of these cell lines varied, each of them could differentiate in vitro into more mature erythroid cells, including enucleated RBCs. Transplantation of MEDEP cells into mice suffering from acute anemia resulted in transient proliferation of the cells, which subsequently differentiated into functional RBCs and significantly ameliorated the acute anemia.Aims  Establishment of immortalized human erythroid progenitor cell lines able to produce enucleated RBCs.Methods  We sought to establish immortalized erythroid progenitor cell lines following the induction of hematopoietic differentiation of human ES cells and iPS cells using a similar method as for establishment of MEDEP cell lines (Hiroyama et al., PLoS ONE 3: e1544, 2008).Results  Using the original method developed in mice, we failed to establish immortalized human erythroid progenitor cell lines. This may have been due to the low efficiency of inducing erythroid cells from ES and iPS cells. It was previously reported that enforced expression of the transcription factor TAL1, which plays essential roles in early hematopoiesis and differentiation of erythroid cells and megakaryocytes, improved the efficiency of induction of hematopoietic cells from ES cells of the common marmoset. We therefore enforced expression of TAL1 in human iPS cells and found that this resulted in a significant improvement in the rate of production of hematopoietic cells, in particular of erythroid cells. However, our attempts to establish immortalized human erythroid progenitor cell lines from iPS cells expressing Tal1 were unsuccessful. Recently, it was reported that enforced expression of HPV16‐E6/E7 in CD36‐positive erythroid cells aided the establishment of immortalized human erythroid progenitor cell lines. We decided to adopt this strategy with some modifications and succeeded in establishing immortalized human erythroid progenitor cell lines able to produce enucleated RBCs.Summary/Conclusions  We have successfully established immortalized Human Umbilical Cord Blood Derived‐Erythroid Progenitor (HUDEP) cell lines and Human iPS cell Derived‐Erythroid Progenitor (HiDEP) cell lines that are able to produce enucleated RBCs.