Erythroid cells in vitro: from developmental biology to blood transfusion products

Purpose of review Red blood cells (RBCs) transfusion plays a critical role in numerous therapies. Disruption of blood collection by political unrest, natural disasters and emerging infections and implementation of restrictions on the use of erythropoiesis-stimulating agents in cancer may impact blood availability in the near future. These considerations highlight the importance of developing alternative blood products. Recent findings Knowledge about the processes that control RBC production has been applied to the establishment of culture conditions allowing ex-vivo generation of RBCs in numbers close to those (2.5 x 10(12) cells/ml) present in a transfusion, from cord blood, donated blood units or embryonic stem cells. In addition, experimental studies demonstrate that such cells protect mice from lethal bleeding. Therefore, erythroid cells generated ex vivo may be suitable for transfusion provided they can be produced safely in adequate numbers. However, much remains to be done to translate a theoretical production of approximately 2.5 x 10(12) RBCs in the laboratory into a 'clinical grade production process'. Summary This review summarizes the state-of-the-art in establishing ex-vivo culture conditions for erythroid cells and discusses the most compelling issues to be addressed to translate this progress into a clinical grade transfusion product.