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Scientists Grew a Brain-Like Blob With Primitive Eyes

The brain organoids developed optic structures that reacted to light, but they're not conscious.

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A brain organoid with developed optic cups.
A brain organoid with developed optic cups.
Image: Elke Gabriel (CC BY-NC-SA)

Now the stem cells are just showing off. An international team of researchers say they’ve developed a lab-grown mass of tissue that mimicked a brain and was able to spontaneously produce two symmetrical optic cups, eye-like structures sensitive to light. But don’t worry—these rudimentary organoids are not conscious.

The researchers used pluripotent stem cells—so named for their ability to create a multitude of cells that occur naturally in the human body—to better understand how the body develops; the brain is especially useful as arguably the most important organ in shaping our species. Stem cell therapies have previously restored the olfactory system in mice and given the animals part-human brains. The recent mini-brain, which modeled the way eyes develop in human embryos, was described in a study published last week in the journal Cell Stem Cell.


“Our work highlights the remarkable ability of brain organoids to generate primitive sensory structures that are light sensitive and harbor cell types similar to those found in the body,” said Jay Gopalakrishnan, a biologist at the University Hospital Dusseldorf and a co-author of the paper, in a Cell press release. “These organoids can help to study brain-eye interactions during embryo development, model congenital retinal disorders, and generate patient-specific retinal cell types for personalized drug testing and transplantation therapies.”

A graphic showing the cells' development.
The cells grew from a bunch of uncollected cells to a complex mass of tissue.
Graphic: Gabriel et al./Cell Stem Cell 2021

On the first day of the team’s research, the stem cells were a disconnected bunch of dots. By day 10, they had formed a neurosphere, a cluster of cellular tissue. By the end of the month, the organoid had formed with a primordial eye field, or a group of retinal cells that lay the foreground for more complex eye structures. And at the two-month mark, full optic vesicles had formed, which are the foundation of eyes and are connected to the brain.

A little over 70% of the brain organoids the team generated formed optic cups, and the structures formed electrically active networks of neurons that were light sensitive. The optic cups in the organoids had lens and corneal cells, too.

The ability to grow such eye structures has implications for studying eye diseases and better understanding how the brain and eye structures “talk” to each other in an embryo. That’s the wonder of stem cells: They allow scientists to study biological processes up close and understand why they sometimes go awry.

More: Scientists Use Lab-Grown Brains to Study What Makes Us Human