Stage-Specific Regulation of Erythropoiesis and Its Implications in Ex-Vivo RBCs Generation.

Ex vivo erythropoiesis methods are being developed for more than a decade now, and all the distinct types of stem cells (such as CD34⁺ HSCs, ESCs, IPSCs, and extensively proliferating erythropoietic progenitor cells) are defined to bear the potential for large scale RBC production shortly. The various regulating factors at different levels of RBCs production are being explored. Since most of the ex-vivo erythropoiesis protocols mimic the dogma followed by hematopoietic stem cells in vivo to give rise to mature RBCs which essentially deals with the intermediate stages of erythropoiesis such as burst forming unit-erythroid (BFU-E) and committed erythroid colony forming unit-erythroid (CFU-E). In vivo generation of erythroid progenitors (BFU-E/CFU-E) is essentially controlled by several factors including glucocorticoids, inflammation, and stress. Furthermore, regular production of functionally mature /transfusable units of RBCs is possible only through the coordinated regulation of terminal proliferation and differentiation of erythroid progenitors by external signals, such as erythropoietin, SCF, IL-3 and interaction to extracellular matrix protein(s) in a 3D culture system. We discuss these complex intracellular networks of coordinated factors and try to understand their molecular mechanism through gene regulation by transcription factors, and miRNAs that might be helpful in developing the optimal RBCs production protocols for commercial production.