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Neildez-Nguyen et al., 2002, in their studies demonstrated a method to amplify/expand hematopoietic stem cells (HSCs) from cord blood in a serum free culture medium.Human nucleated erythroid cells produced by this method when injected into nonobese diabetic, severe combined immunodeficient (NOD/SCID) mice showed proliferation and terminal differentiated into mature enucleated red blood cells (RBCs) .Therefore, it can be assumed that ex vivo erythropoiesis can be carried out utilizing various sources, namely, embryonic stem cells (ESCs), induced pluripotent stem cells (i PSCs), and hematopoietic stem cells (HSCs), from various sources, for example, embryo, bone marrow, peripheral blood, or umbilical cord blood.
As per their findings, sequential supply of specific combinations of cytokines in a stepwise manner helped them to obtain large scale ex vivo differentiated enucleated RBCs.
In first step Flt3-L, SCF, and TPO stimulated proliferation of HSCs, which was then followed by SCF, EPO, and IGF-1 aiding in the proliferation of erythroid progenitors and finally terminal erythroid differentiation was promoted by EPO and IGF-1. 2005, described an ex vivo methodology for producing fully mature human RBCs from hematopoietic stem/progenitor cells by applying G-CSF, IL-3, SCF, and EPO . demonstrated a method in which they cultured CD34 cells in a serum free medium supplemented with two cytokine sets SCF IL-3 EPO and SCF IL-3 EPO TPO Flt3 for one week, followed by coculture upon mesenchymal cells derived from cord blood for two weeks to generate an almost pure clinical grade .
There is extreme unavailability of suitable donor due to rare phenotypic blood groups and other related complications like hemoglobinopathies, polytransfusion patients, and polyimmunization.
Looking at the worldwide scarcity of blood, especially in low income countries and the battlefield, mimicking erythropoiesis using ex vivo methods can provide an efficient answer to various problems associated with present donor derived blood supply system.
Fortunately, there are many ex vivo erythropoiesis methodologies being developed by various research groups using stem cells as the major source material for large scale blood production.
Most of these ex vivo protocols use a cocktail of similar growth factors under overlapping growth conditions.in which they used CD34 cells (from bone marrow, umbilical cord blood, and peripheral blood mobilized with G-CSF to isolate) to culture them in modified serum free media in the presence of SCF, IL-3, and erythropoietin . 2008 demonstrated a method with 100% enucleated RBCs by employing SCF, Flt-3/Flk-2 TPO in first phase followed by SCF, IL-3 EPO in the second phase . in 2011 developed a robust method to obtain ultra-high-yield of erythrocytes, with the expansion process having the capability of producing over 500 units of erythrocytes per umbilical cord blood donation using fully defined culture medium with the help of bioreactor .As described by different research groups, all the ex vivo expansion measure would revolve around systemic and orderly use of different growth factors at various phases of ex vivo culture. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.Erythropoiesis is a vital process governed through various factors.The present paper focuses on the molecular mechanism and significance of various growth factors in these protocols that shall remain helpful for large scale production.According to a report by the World Health Organization (WHO), blood donation rate in high-income countries is 39.2 donations per 1000 population, whereas it is just 12.6 donations in middle-income and 4.0 donations in low-income countries out of which more than 50% of blood is being supplied by either family/replacement or paid donors.The same group in 2009 reported up to 95% of enucleation of in vitro generated RBCs by the addition of Poloxamer 188 as an RBC survival enhancer.This enhancer increases the stability of the RBC membrane and decreases the fragility .These precursors finally differentiate into specific cell types.In order to utilize/exploit these growth factors to copy or mimic nature in terms of generation of clinical grade red blood cells, we need to understand their role and how these growth factors are regulated in vivo.