P>Objective To study the cultivation of retinal progenitor cells of different ages. Methods Retinal progenitor cells of E14 and E18 SD rats were isolated,cultivated in suspension in modified DMEM/F12 serum-free medium and then differentiation was induced in vitro. Cells were observed under phase-contrast microscopy daily and identified by immunocytochemistry, scanning electron microscopy and transmission electron microscopy. Results Cultivated in DMEM/F12 serum-free medium,retinal progenitor cells formed cell spheres.After being plated,isolated cells migrated outwards and differentiated.Scanning electron microscopy demonstrated the morphology of the cell spheres and differentiated cells.Transmission electron microscopy demonstrated that there were stem cell-like cells in cell spheres and neuron- and glia-like cells after the plating.Immunocytochemistry demonstrated that most cells in spheres expressed neural stem cell marker nestin and cell division marker BrdU.After the plating, retinal progenitor cells could be induced to differentiate into various retinal cells,including Thy1 1-positive retinal ganglion cells.The percentage of retinal ganglion cells was 16.91%±4.05% at E14 and 4.65%±1.88% at E18.The differences were statistically significant(t=15.04,P<0.001).Conclusion Retinal progenitor cells can be cultivated successfully in modified DMEM/F12 serum-free medium.The cultivated retinal progenitor cells have the potential to proliferate freely and multi-differentiate.Early retinal progenitor cells are inclined to differentiate in