Towards manufactured red blood cells for the treatment of inherited anemia

Abstract

Patients with inherited anemia and hemoglobinopathies (such as sickle cell disease and β-thalassemia) are treated with red blood cell (RBC) transfusions to alleviate their symptoms. Some of these patients may have rare blood group types or go on to develop alloimmune reactions, which can make it difficult to source compatible blood in the donor population. Laboratory-grown RBC represent a particularly attractive alternative which could satisfy an unmet clinical need. The challenge, however, is to produce - from a limited number of stem cells - the 2x1012 RBC required for a standard adult therapeutic dose. Encouraging progress has been made in RBC production from adult stem cells under good manufacturing practice. In 2011, the Douay group conducted a successful proof-of-principle mini-transfusion of autologous manufactured RBC in a single volunteer. In the UK, a trial is planned to assess whether manufactured RBC are equivalent to RBC produced naturally in donors, by testing an allogeneic mini-dose of laboratory-grown manufactured RBC in multiple volunteers. This review discusses recent progress in the erythroid culture field as well as opportunities for further scaling up of manufactured RBC production for transfusion practice.

Figure 1.

Overview of the erythroid culture process.Ex vivo culture systems require the isolation of peripheral blood mononuclear cells (PBMNC) or magnetic sorting of the CD34⁺ cells as starting material. Culture systems then employ either flasks, spinner flasks or a bioreactor system depending on scale. The volume of the culture will increase dramatically as the cells expand and differentiate through days 7-14. Upon generation of a mixed population of reticulocytes, nucleated cells and pyrenocytes at day 21, cells then require filtration using either a syringe (small scale) or multiple leukocyte filters (large scale) depending on volume to give a pure reticulocyte population. Diagram made using biorender.com.