In the developing embryo, the first step toward a functional eye is the formation of the optic vesicle from the neural tube. This optic vesicle then invaginates to form an optic cup, which in turn develops into the outer pigmented layer of the retina and the inner neurosensory layer.
Normally, this all takes place in the context of the developing organism, next to neighbouring tissues. But, in a paper published in Nature this week, the Sasai lab at the RIKEN institute in Japan describes how they generated an optic cup in culture, from mouse embryonic stem cells.
The lab had previously generated retinal precursors from mouse ES cells in culture, but those did not form three-dimensional structures. In this new study, they changed the cultured medium by adding Matrigel (containing basement-membrane components). This initiated the formation of small, polarized, spheres after six days in culture. These spheres then invaginated to form the optic cup structure, as shown in this video from the study:
The immediate relevance of this paper is the increased understanding it offers in the mechanisms behind eye development. The study suggests that formation of the retina occurs to a large extent via an intrinsic order that does not entirely depend on external forces. That does not mean that neighbouring tissues have no influence at all, but this influence appears smaller than previously believed.
While this does not mean that we can make custom eyes on demand just yet, the study does have some other clinical implications: If we can generate functional retina from induced pluripotent stem cells taken from patients’ tissues, these could be used in drug testing or disease modeling, and help increase our understanding of diseases that cause blindness.
RIKEN press release
Nature News article
Eiraku, M., Takata, N., Ishibashi, H., Kawada, M., Sakakura, E., Okuda, S., Sekiguchi, K., Adachi, T., & Sasai, Y. (2011). Self-organizing optic-cup morphogenesis in three-dimensional culture Nature, 472 (7341), 51-56 DOI: 10.1038/nature09941
Ikeda, H. (2005). Generation of Rx+/Pax6+ neural retinal precursors from embryonic stem cells Proceedings of the National Academy of Sciences, 102 (32), 11331-11336 DOI: 10.1073/pnas.0500010102