Blood Generation from Stem Cells: An Overview

Blood transfusions are the mainstay in modern clinical modalities. The worldwide spread blood banks secure the supply of various blood components which solely depend upon voluntary paid/unpaid donor. According to the WHO reports present collections and supply of safe/adequate blood is inadequately distributed among economically developed and developing countries. Further, blood transfusions are prone to a number of risks/ adverse reactions that may be imposed due to inefficient blood screening and processing methods and put extreme supply constraints, especially in the underdeveloped countries. In past few years stem cells from different sources are demonstrated to give rise to the significant amount of functionally mature erythrocytes, platelets and neutrophils by using a cocktail of growth factors under standard culture conditions. Therefore, a logistic approach to ex vivo manufacturing of erythrocytes ( & other blood components) through modern tissue culture techniques has surfaced in the past few years. Ex vivo expansion of erythrocytes to generate transfusable units of clinical grade RBCs from a single dose of starting material (e. g. umbilical cord blood) has been well established. More and more information is coming from the various research groups showing the use of other potential sources (e. g. embryonic stem cells, induced pluripotent stem cells, and stress induced erythroid progenitors), different cocktails of growth factors, methodologies to get optimal yields of the functional RBCs/ blood cells. One can imagine that with the advent of more defined methods for large-scale production of blood cells the existing system of donor derived blood supplies could be replaced in future. However, various regulating factors should essentially control the fate of large-scale production of RBCs including issues related to the quantity/ quality and per unit cost of these products. These issues would be solved with the invention of more automated culture techniques such as the use of bioreactors and identification of more direct molecular agents regulating all phases of their ex vivo generation such as stem cell proliferation, differentiation, and maturation of final products. Recent studies have shown the possibilities of generating several hundred units of erythrocytes by using continuously feeding hollow fiber bioreactors along with other types of bioreactors. Even more, the functionality and acceptability of ex vivo cultured RBCs is demonstrated by their in-human transfusion which provides essential motivation to develop more sophisticated methods/culturing techniques to pave the way for commercial production of blood components at a feasible cost. s