Figure 5. Viability of murine retinal progenitor cells (RPCs) in different culture media. A: Murine RPCs exhibited exponential growth in the presence of epidermal growth factor (EGF) alone (20 ng/ml), as well as with EGF+Glial cell line-derived neurotrophic factor (GDNF; 20 and 10 ng/ml, respectively), but diminished from day 1 in the absence of both factors, or with GDNF alone. A difference in the surviving cell number between the EGF-containing groups was observed, with the addition of GDNF to the medium conferring a statistically significant advantage over EGF alone at day 5. This effect was not evident at earlier time points. The y-axis shows absorbance at 450 nm. All experiments were performed in 96-well plates (ten wells/condition). Error bars show standard deviation (SD), * indicates p<0.03. B: Growth of RPCs over a one-month period in EGF or EGF+GDNF was monitored by manual cell counts (with a hemocytometer). The growth curves thus obtained confirmed that the addition of GDNF (10 ng/ml) to standard EGF-containing medium does not impair the proliferation of murine RPCs and in fact provides a detectible advantage.