Definitive Erythropoiesis from Pluripotent Stem Cells: Recent Advances and Perspectives.

Derivation of functional and mature red blood cells (RBCs) with adult globin expression from renewable source such as induced pluripotent stem cells (iPSCs) is of importance from the clinical point of view. Definitive RBC generation can only be succeeded through production of true hematopoietic stem cells (HSCs). There has been a great effort to obtain definitive engraftable HSCs from iPSCs but the results were mostly unsatisfactory due to low, short-term and linage-biased engraftment in mouse models. Moreover, ex vivo differentiation approaches ended up with RBCs with mostly embryonic and fetal globin expression. To establish reliable, standardized and effective laboratory protocols, we need to expand our knowledge about developmental hematopoiesis/erythropoiesis and identify critical regulatory signaling pathways and transcription factors. Once we meet these challenges, we could establish differentiation protocols for massive RBC production for transfusion purposes in the clinical setting, performing drug screening and disease modeling in ex vivo conditions, and investigating the embryological cascade of erythropoiesis. More interestingly, with the introduction of relatively efficient and facile genome editing tools, genetic correction for inherited RBC disorders such as sickle cell disease (SCD) would become possible through iPSCs that can subsequently generate definitive HSCs, which then give rise to definitive RBCs producing β-globin after transplantation.