Figure 2. Changes in retinal progenitor cell morphology under different culture conditions. Retinal progenitor cell s were cultured in the same serum-free base media, but under four different treatment conditions defined by the presence or absence of added growth factors, as follows: 1) no growth factor (A-C), 2) glial cell line-derived neurotrophic factor (GDNF) alone (D-F), 3) epidermal growth factor (EGF) alone (G-I), and 4) EGF+GDNF (J-L). In each case, EGF was used at a final concentration of 20 ng/ml and GDNF at 10 ng/ml. The morphology of cells in each condition was assessed on day 1, 3, and 5. Increased extension of processes appeared in the “no growth factor” group (A-C; D-F), with similar changes observed in the “GDNF alone” group (A-C; D-F). Cells grown in EGF+GDNF appeared to form more and larger spherical cellular aggregates (spheres) over the course of 5 days. Magnification was ×100. Scale bars: 100 μm.