Abstract
Purpose: :
Transplantation of photoreceptor cells has been reported to restore retinal functions. Despite of many studies using fetal retinal tissues and tissue stem cells, ideal cell source has not been devised. We previously reported the differentiation of mouse embryonic stem (ES) cells into retinal progenitors in floating aggregate culture. However, the differentiation of these progenitors into photoreceptors occurs only infrequently unless they are co-cultured with embryonic retinal tissues. In the present study, we examined in vitro generation of photoreceptors from human ES cells.
Methods: :
For induction of retinal differentiation, monkey and human ES cells were treated with several factors that regulate retinal differentiation during development, in feeder- and serum-free suspension culture. Induced cells were analyzed by immunocytochemistry, RT-PCR and electronmicroscopy.
Results: :
Feeder- and serum-free suspension culture combined with Wnt and Nodal inhibitors (SFEB/DL culture) induces differentiation of Rx+ or Mitf+ retinal progenitors. In SFEB/DL culture, these progenitors differentiate into retinal pigment epithelial cells with characteristic morphology and phagocytic function. However, photoreceptor differentiation occurs only infrequently under these conditions. In contrast, additional treatment with retinoic acid and taurine (RA/T) significantly promotes differentiation of ES cell-derived progenitors into rhodopsin+/recoverin+ rod photoreceptors. In SFEB/DL + RA/T culture, human ES cells also differentiate into blue opsin+ or red/green opsin+ cone photoreceptors. These SFEB/DL + RA/T-treated cells express phototransduction genes.
Conclusions: :
We can obtain rod and cone photoreceptors from human ES cells under defined culture conditions. For transplantation studies, we need to purify these photoreceptors and analyze their functions.
Keywords: regeneration • differentiation • photoreceptors