After enucleation, the retinas of 8-day-old normal-sighted C57B1/6 mice were placed in CO2-free Dulbecco’s modified Eagle’s medium (DMEM; Life Technologies, Cergy Pontoise, France), dissected free of pigment epithelium and cut into small fragments. Fragments from six retinas were rinsed twice in Ringer’s solution without Ca2+, supplemented with 0.1 EDTA, and incubated in 1 mL papain (2.8 U/mL, Worthington Biochemicals, Freehold, NJ) during 20 minutes at 37°C with gentle agitation. The enzymatic reaction was stopped by adding an equal volume of medium M199 containing 10% fetal bovine serum (FBS). The resultant cell suspension was gently mechanically dissociated with a flame-constricted Pasteur pipette. Retinal cells were seeded into poly-d-lysine (8 μg/mL)-coated 12-well plates at 2 to 3 × 106 cells/cm2 in M199+10% FBS, left to attach overnight, rinsed twice, and then incubated in chemically defined medium (CDM), containing M199 medium supplemented with insulin (5.0 μg/mL), transferrin (5.0 μg/mL), sodium selenite (5.0 μg/mL), putrescine (16.1 μg/mL), progesterone (0.63 μg/mL), prostaglandin F2α (100 ng/mL), taurine (375 μg/mL), cytidine 5′diphosphatidyl-choline (2.56 μg/mL), cytidine-5′diphosphatidyl-ethanolamine (1.28 μg/mL), hydrocortisone (0.2 μg/mL), tri-iodotyrosine (0.02 μg/mL), and sodium pyruvate (110 μg/mL; all from Sigma-Aldrich, Lyon, France).