Objective: The control of mature erythroid progenitors and precursors' production via erythropoietin (EPO) is the major systemic regulatory mechanism in erythropoiesis. However, hypoxia seems to influence erythropoiesis beyond this well-known mechanism. The aim of our study is to test this hypothesis adapting the oxygenation level to each stage of erythropoiesis.
Materials and methods: We exploited the newly developed ex vivo three-phase protocol for red blood cell (RBC) production starting from the steady-state peripheral blood and cord blood CD34(+) cells exposed to adapted O(2) concentrations. Differentiation and maturation were followed by functional tests, morphology, immunophenotype, and analysis of molecular markers' expression.
Results: We report here an enhancement of total RBC production if low O(2) concentrations (1.5-5%) were applied, instead of 20% O(2), during the first phase of culture. This results from a comprehensive action of low-O(2) concentration on: 1) amplification of erythroid progenitors, 2) acceleration of their proliferation, 3) differentiation, and 4) maturation of erythroid precursors. In addition, arterial blood O(2) concentration (13%) is critical for stromal cells to fully sustain the differentiation of erythroid precursors. These effects were associated with upregulation of erythroid 5-aminolevulinate synthase and gamma-globin gene expression.
Conclusion: These results imply that integral regulation of erythropoiesis is operated by low O(2) concentrations, beyond the EPO/EPO-responsive cells loop and provide a tool to optimize the technology for ex vivo production of RBC.