Transduction of recombinant human erythropoietin receptor cDNA into daughter progenitors derived from single CD34(3+) cord blood cells changes the differentiation profile of daughter progenitors

Erythropoietin surprises: an immune saga

Erythropoietin (EPO) an erythropoietic stimulating agent also exerts effects on other cell systems. Nairz et al. (2011) now link EPO and intracellular signaling through the EPO receptor (EPOR) to innate immune cell activity via macrophages.

Enhancement of proliferation and differentiation of erythroid progenitors by co-transduction of erythropoietin receptor and H-ras cDNAS into single CD34(3+) cord blood cells

Our previous studies have demonstrated that retrovirus-mediated gene transduction of either the human erythropoietin receptor (EpoR) or H-ras cDNA into single purified hematopoietic progenitor (HPC), CD34(3+), cells from cord blood (CB) resulted in increased numbers and sizes of erythroid cell containing colonies. We therefore evaluated if there were further effects when H-ras and EpoR genes were co-transduced into the same progenitor cells. Highly purified single sorted CD34(3+) CB cells were transduced with retroviral vectors encoding EpoR or H-ras cDNA. At the single cell level, and in response to stimulation by a combination of growth factors, including Epo, the number of colonies formed by BFU-E and CFU-GEMM was significantly increased in cells transduced with either single H-ras or EpoR cDNA compared to mock virus-transduced cells as previously described. Increased numbers of BFU-E, but not CFU-GEMM, colonies were produced from cells simultaneously co-transduced with both EpoR and Hras genes. Little or no growth was seen in transduced cells without exogenously added cytokines. The size of all types of colonies including CFU-GM was increased in cells transduced with H-ras and/or EpoR cDNAs, and the greatest increase was noticed in cells co-transduced with both genes. Integration and expression of either gene in individual colonies as assessed by PCR and RT-PCR analysis were 45-62% and 48-58%, respectively, with approximately 31% of the cells containing and expressing both genes. These results add to information suggesting an enhancing interacting role of H-ras and EpoR in erythroid proliferation/differentiation.

Enhancing effects of co-transduction of both human erythropoietin receptor and c-kit cDNAs into hematopoietic stem/progenitor cells from cord blood on proliferation and differentiation of erythroid progenitors

Steel factor (SLF) and erythropoietin (Epo) play critical roles in erythropoiesis. To evaluate interactive effects of Epo and SLF receptors (R) in erythropoiesis, CD34+ and CD34 cord blood cells were transduced with human EpoR and c-kit cDNAs by retroviral mediated gene transfer. Erythroid (BFU-E) colonies derived from CD34+ or CD34 cells transduced with either the EpoR or c-kit gene were significantly increased in the presence of interleukin (IL)-3, granulocyte-macrophage colony-stimulating factor (GM-CSF), Epo, and different concentrations of SLF compared with that from mock transduced cells. This number was further enhanced by co-transduction of both genes. Enhancement was more apparent in the absence of SLF. Cell numbers in individual erythroid colonies were also significantly increased in cells transduced with both genes compared with cells transduced with a single gene. Short-term liquid culture showed that ex vivo expansion for five days and numbers of CD34+CD71+ cells in expanded cells from single CD34 cells co-transduced with both EpoR and c-kit genes were increased compared with those of EpoR or c-kit-transduced cells. These results demonstrate that co-transduction of both c-kit and EpoR enhances the proliferative capacity of erythroid progenitors under cytokine stimulation above that of single-gene transduced cells.

Retroviral-Mediated Gene Transduction of c-kit Into Single Hematopoietic Progenitor Cells From Cord Blood Enhances Erythroid Colony Formation and Decreases Sensitivity to Inhibition by Tumor Necrosis Factor- and Transforming Growth Factor-β1

The c-kit receptor and its ligand, steel factor (SLF), are critical for optimal hematopoiesis. We evaluated effects of transducing cord blood (CB) progenitor cells with a retrovirus encoding humanc-kit cDNA. CD34+ cells were sorted as a population or as 1 cell/well for cells expressing high levels of CD34+++ and different levels of c-kit (++, +, Lo/−), transduced and then cultured in the presence of granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin-3 (IL-3), IL-6, erythropoietin (Epo) +/− SLF in the absence of serum. At a single-cell level, transduction with c-kit, but not with control (neo only), virus significantly increased colony formation, especially by erythroid and multipotential progenitors. The enhancing effect of c-kit transduction was inversely correlated with expression of c-kit protein before transduction. The greatest enhancing effects were noted in CD34+++kitLo/− cells transduced with c-kit. The stimulating effect was apparent even in the absence of exogenously added SLF, but in the presence of GM-CSF, IL-3, IL-6, and Epo. Enzyme-linked immunosorbent assay (ELISA) of SLF protein, reverse transcriptase-polymerase chain reaction (RT-PCR) analysis of SLF mRNA expression in CD34+ cells, and use of neutralizing antibodies to SLF and/or c-kit suggested the presence of endogenous, although probably very low level, expression of SLF by these progenitor cells. Transduction of c-kit significantly decreased sensitivity of progenitor cells to the inhibitory effects of transforming growth factor-β1 and tumor necrosis factor-.c-kit–transduced cells had increased expression ofc-kit protein and decreased spontaneous or cytokine-induced apoptosis. Our results suggest that transduced c-kit into selected progenitor cells can enhance proliferation and decrease apoptosis and that endogenous SLF may mediate this effect.