Fig. 1

Schematic image of the human eye and therapeutic scheme of retinal transplantation. a Anatomical structure of the human eye and retina, which has three layers of neurons. Photoreceptor cells respond to light and are composed of rods and cones, which contain inner segments (ISs) and outer segments (OSs). b Retinal transplantation scheme. Retinitis pigmentosa (RP) is a group of diseases that cause progressive photoreceptor degeneration. It is hoped that retinal tissue differentiated from human ES/iPS cells could be transplanted into RP patients with a degenerative retina without photoreceptors. Although a transplanted retina contains more or less of INL components, the structured layers of photoreceptors will be in direct contact with the INL of the host retina where graft INLs had been stripped off from graft ONLs