Mini Brains Grown From Stem Cells Developed Light-Sensitive, Eye-Like Features

Understanding how eyes develop can help researchers pinpoint how to treat early retinal diseases

An image of a brain organoid with optic cups. The mini brain looks like  a small yellow blob with two pitch black eyes
After the cells developed into mini-brains, the optic cups formed 30 days later and fully matured at 50 days. Elke Gabriel

In a new study, researchers remarkably grew miniature brains with a set of eye-like formations called optic cups. The optic cups are precursors to the retina, and its development within the mini organoids resembled the emergence of eye structures in human embryos.

The research could help scientists understand eye diseases, eye development, and differentiation processes, reports Michelle Starr for Science Alert. The study was published this week in the journal Cell Stem Cell.

Organoids are small, three-dimensional tissue cultures that can replicate organs. Researchers grow tiny organoids from stem cells, or cells that have the potential to mature into any cell in the body, reports Yasemin Saplakoglu for Live Science. Growing organoids allows researchers to peer into how organs develop and provide valuable insights into how organs could react to specific drugs or treatments.

There are two types of stem cells: adult stem cells and embryonic stem cells. Human-induced pluripotent stem cells (iPSCs) are a type of adult stem cell, which are derived from human embryos. Instead, iPSCs are taken from adult human cells, usually from a skin or blood sample, and converted into an embryonic-like state. Instead of remaining a skin or blood cell, these iPSC cells can now develop into any cell in the body.

In previous studies, only pure retinal cells or optic cups were grown in the lab individually. Jay Gopalakrishnan, an organoid expert at University Hospital Düsseldorf, and his colleagues used iPSC-grown mini brains to see if eye structures could develop as an integrated part of the organoid—instead of growing the two parts separately, Science Alert reports.

A series of images of brain organoids with optic cups/eyes. The images look like white/yellow blobs floating against a black background. Each blob has a pair of black hamster-like beady eyes.
At 60 days, the brain organoids had developed a pair of black optic cups. Gabriel et al., Cell Stem Cell, 2021

Per Live Science, the team modified a technique used to turn stem cells into neural tissue to create the brain organoids with the optic cups. After the cells developed into mini-brains, the optic cups formed 30 days later and fully matured at 50 days. The timing was on target with eye development in a human embryo, meaning the process could be used to study how eyes develop in utero.

Out of the 314 created mini-brains, 72 percent grew optic cups. The team also found that the structures responded to light and developed different retinal cell types connected to neuron tissue. The eyes on the organoids even had a lens and corneal tissue, Live Science reports.

“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,” Gopalakrishnan says in a statement. “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.”

Scientists are now looking into how to keep the optic cups functioning longer to use for studying retinal disorders, Futurism’s Victor Tangermann reports.

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