Establishment of immortalized human erythroid progenitor cell lines able to produce enucleated red blood cells

Abstract

Transfusion of red blood cells (RBCs) is a standard and indispensable therapy in current clinical practice. In vitro production of RBCs offers a potential means to overcome a shortage of transfusable RBCs in some clinical situations and also to provide a source of cells free from possible infection or contamination by microorganisms. Thus, in vitro production of RBCs may become a standard procedure in the future. We previously reported the successful establishment of immortalized mouse erythroid progenitor cell lines that were able to produce mature RBCs very efficiently. Here, we have developed a reliable protocol for establishing immortalized human erythroid progenitor cell lines that are able to produce enucleated RBCs. These immortalized cell lines produce functional hemoglobin and express erythroid-specific markers, and these markers are upregulated following induction of differentiation in vitro. Most importantly, these immortalized cell lines all produce enucleated RBCs after induction of differentiation in vitro, although the efficiency of producing enucleated RBCs remains to be improved further. To the best of our knowledge, this is the first demonstration of the feasibility of using immortalized human erythroid progenitor cell lines as an ex vivo source for production of enucleated RBCs.

Figure 1. Schematic outline of the procedures for establishing immortalized human erythroid progenitor cell lines from iPS cells and from hematopoietic stem/progenitor cells in umbilical cord blood.

Figure 2. Effect of enforced expression of a transcription factor, TAL1, on induction of hematopoietic cells from human iPS cells. HiPS, human iPS cells (HiPS-RIKEN-3A).

HiPS-TAL1, HiPS cells expressing TAL1 (HiPS-RIKEN-3A-TAL1). The cells were analyzed after the induction of differentiation of hematopoietic cells for 15 days. (A) Fold increase of production of hematopoietic cells from HiPS-TAL1 cells compared to HiPS cells. (B) Flow cytometer analysis. CD71, transferrin receptor. Glycophorin A (GPA), an erythroid specific marker. Percentages of GPA-positive cells are indicated in the figure. (C) Morphology of the cells derived from HiPS-TAL1 cells. Scale bar indicates 50 µm. The comparison of HiPS-RIKEN-4A and HiPS-RIKEN-4A-TAL1 showed similar results.

Figure 3. Dependency of the established erythroid progenitor cell lines on externally supplied culture factors.

(A) The survival and proliferation of HiDEP-1 cells are dependent on DOX (HPV16-E6/E7) and EPO and partially dependent on DEX. (B) The survival and proliferation of HUDEP-1 cells are dependent on DOX (HPV16-E6/E7) and SCF and partially dependent on EPO. (A, B) DOX, doxycycline; expression of HPV16-E6/E7 is induced by DOX. SCF, stem cell factor. EPO, erythropoietin. DEX, dexamethasone. ALL, cells were cultured in the presence of DOX, SCF, EPO and DEX. –DOX, –SCF, –EPO, –DEX, cells were cultured after deprivation of DOX, SCF, EPO and DEX, respectively. Dependencies of other cell lines on externally supplied culture factors are summarized in Table S1.

Figure 4. Flow cytometer analyses of the established erythroid progenitor cell lines.

(A) Representative results of HiDEP cells. (B) Representative results of HUDEP cells and HUDEP-1 expressing TAL1, HUDEP-1-TAL1. (A, B) GPA, glycophorin A. CD71, transferrin receptor. c-KIT, the receptor of SCF. CD36, a marker of immature erythroid cells.

Figure 5. Cell pellets of the established erythroid progenitor cell lines.

(A) HiDEP-1 cells before the induction of differentiation. (B) HUDEP-1 cells before and after the induction of differentiation. HUDEP-1 cells were cultured in erythroid differentiation medium on OP9 feeder cells to maintain cell viability during the differentiation process. All other cell lines also showed red cell pellets after the induction of differentiation.

Figure 6. Oxygen-carrying abilities of hemoglobin produced in the established erythroid progenitor cell lines.

Oxygen equilibrium curves were determined using an automated apparatus. Following the induction of differentiation, the cells were subjected to the analyses. CB, umbilical cord blood. PB, peripheral blood of adult.

Figure 7. Gene expression profiles of the established erythroid progenitor cell lines estimated by quantitative RT-PCR analysis.

Analyzed genes are indicated. FL, results with cDNA derived from human fetal liver. Relative expression was evaluated compared to that of FL. CB, cord blood. CB 6, 10 and 16, results with cDNA derived from cultured erythroid cells, i.e., CD34-positive cells in CB were induced to differentiate into mature erythroid cells for 6, 10 and 16 days, respectively, using the previously reported method . B and A, Before and 2 days after induction of differentiation of HiDEP and HUDEP cells.

Figure 8. Analyses of cell viability and cell size during the induction of differentiation of the established erythroid progenitor cell lines.

Cell viability and cell size were estimated by an automated cell counter. (A) Results of HiDEP-1 cells. (B) Results of HUDEP-1 cells. (A, B) <10 µm (%), the percentages of cells with a diameter less than 10 µm. Among all HiDEP and HUDEP cell lines, HiDEP-1 cells most efficiently differentiated into more mature cells.

Figure 9. Morphological analyses during the induction of differentiation of the established erythroid progenitor cell lines.

(A) HiDEP-1 cells before (Day 0) and 6, 10 and 12 days after the induction of differentiation (Day 6, 10 and 12). Scale bar in Day 0 indicates 50 µm and other scale bars indicate 10 µm. (B) HUDEP-1 cells before (Day 0) and 2, 6 and 9 days after the induction of differentiation (Day 2, 6 and 9). HUDEP-1 cells were cultured in erythroid differentiation medium on OP9 feeder cells to maintain cell viability during the differentiation process. All scale bars indicate 50 µm. (A, B) Black arrows and arrowheads show enucleated and enucleating cells, respectively. Blue arrows indicate cell debris. Among all HiDEP and HUDEP cell lines, HiDEP-1 cells most efficiently produced enucleated cells.

Figure 10. Confirmation of enucleated cells.

As a representative, the cells induced from HiDEP-1 cells were subjected to the analyses. (A) Supravital staining. Arrows indicate reticulocytes. (B) Immunohistostaining with glycophorin A antibody (pink) 12 days after the induction of differentiation. Nuclei are stained with SYTO16 (green). An arrow shows an enucleated cell. (C) Benzidine staining 10 days after the induction of differentiation (brown, left panel). After benzidine staining, cell nuclei were labeled with DAPI to distinguish nucleated and enucleated cells (blue stained nuclei in right panel). Arrows or arrowheads show enucleated and enucleating cells, respectively. (A–C) Scale bars indicate 10 µm.