Generation of Retinal Progenitor Cells from Human Induced Pluripotent Stem Cell-Derived Spherical Neural Mass

Spherical neural mass (SNM) is a mass of neural precursors that have been used to generate neuronal cells with advantages of long-term passaging capability with high yield, easy storage, and thawing. In this study, we differentiated neural retinal progenitor cells (RPCs) from human induced pluripotent stem cells (hiPSC)-derived SNMs. RPCs were differentiated from SNMs with a noggin/fibroblast growth factor-basic/Dickkopf-1/Insulin-like growth factor-1/fibroblast growth factor-9 protocol for three weeks. Human RPCs expressed eye field markers (Paired box 6) and early neural retinal markers (Ceh-10 homeodomain containing homolog), but did not photoreceptor marker (Opsin 1 short-wave-sensitive). Reverse transcription polymerase chain reaction revealed that early neural retinal markers (Mammalian achaete-scute complex homolog 1, mouse atonal homolog 5, neurogenic differentiation 1) and retinal fate markers (brain-specific homeobox/POU domain transcription factor 3B and recoverin) were upregulated, while the marker of retinal pigment epithelium (microphthalmia-associated transcription factor) only showed slight upregulation. Human RPCs were transplanted into mouse (adult 8 weeks old C57BL/6) retina. Cells transplanted into the mouse retina matured and expressed markers of mature retinal cells (Opsin 1 short-wave-sensitive) and human nuclei on immunohistochemistry three months after transplantation. Development of RPCs using SNMs may offer a fast and useful method for neural retinal cell differentiation.