Improvement of Red Blood Cell Maturation In Vitro by Serum-Free Medium Optimization

Despite recent studies on media additives, the low viability and dysplastic features of terminally mature erythroid cells are still major problems in enhancing erythroid cell yields in vitro. Moreover, research on enhancing terminal erythropoiesis has been focused on the immature stage of erythroid cells such as burst forming unit-erythroid and colony forming unit-erythroid. Here, we tested many commercially available serum-free culture media and developed a superior culture media formulation compared with the conventional control for higher expansion-fold, higher viability, and therefore enhanced red cell productivity. The addition of the specific medium to the previously known best media at a specific ratio, whose effects were not dose-dependent, enabled the generation of significantly higher erythrocyte products with over 1.3 million-fold proliferation of erythroid cells after maintenance for 21 days throughout the maturation stages from CD34+ cells. The cells cultured in this condition expressed maturation markers and were significantly superior in differentiation and enucleation. Comparative mRNA profiling revealed that erythroid cells in this medium showed more efficient maturation in mRNA levels. The cultured cells showed comparable erythroblast survival and also restored better red blood cell (RBC) functions of oxygen saturation profile with expression of adult globin up to 99%. However, to develop chemically defined media, the well-known supplements including hormones, cytokines, and serum-replacement reagents were not sufficient to replace the optimized media in producing mature RBCs. Taken together, our optimized medium formulation under serum-free culture conditions produced the best reproducible results on productivity and maturation in erythroid cells with economic benefits. These culture conditions may thus serve as a useful platform for further investigation of in vitro erythropoiesis and to develop defined serum-free media for clinical trials.