Efficient expansion of erythroblasts in plasma/serum-free GMP-grade medium. (A) PBMC were cultured toward erythroblasts in GMP-grade medium supplemented with EPO, SCF, and Dex (EM) for 26 days. Medium was prepared using either cHA, dHA, rHA, Albuman, or plasma. Cell counts at day 0 were normalized to 1 PBMC at the start of culture. Cultures were kept at 0.7 to 2 × 10⁶ by dilution. Symbols indicate mean fold-change at any day compared with 1 PBMC seeded, error bars indicate standard deviation (SD) (n = 4). (B) PBMC from 4 independent donors were cultured from PBMC in Cellquin medium (cHA) supplemented with EPO (2 U/mL), SCF (100 ng/mL), and Dex (1 μM) in culture dishes until a pure erythroblast population was obtained (at day 7). Erythroblasts were further expanded in a G-Rex bioreactor or in culture dishes. Mean fold-change (± SD) was calculated and compared (2-way analysis of variance, *P < .05; n = 4). (C) Representative density plots indicating cell surface expression levels of CD71 and CD235 in cultures as described in panel B. Quadrants are labeled (P1-P4) and relative cell numbers per quadrant indicated as (D-E) percentage quantification of percentages per quadrant in dot blots similar to those shown in panel C. Error bars indicate SD (n = 4). (D) Cells cultured in dishes. (E) Cells cultured in G-Rex.