Scientists have grown stem cell ‘mini brains’ and then developed something like developed eyes from the brains: ScienceAlert

Lab-grown mini-brains from Stem cells spontaneously developed rudimentary eye structures, scientists announced in a fascinating 2021 paper.

On tiny brain organoids of human origin grown in dishes, two bilaterally symmetrical optic cups were seen to grow, mirroring the development of eye structures in human embryos. This amazing result could help us better understand the process of differentiation and development of the eye, as well as eye diseases.

“Our work highlights the remarkable ability of brain organoids to generate primitive sensory structures that are sensitive to light and contain cell types similar to those found in the body,” said neuroscientist Jay Gopalakrishnan University Hospitals Düsseldorf in Germany in their statement for 2021.

“These organoids can help study brain-eye interactions during embryonic development, model congenital retinal disorders, and generate patient-specific retinal cell types for personalized drug testing and transplant therapy.”

Brain organoids are not real brains, as you may think of them. These are small, three-dimensional structures grown from induced pluripotent stem cells – cells harvested from adult humans and reverse-engineered into stem cells, which have the potential to grow into many different types of tissue.

In this case, those stem cells are coaxed into growing into clumps of brain tissue, devoid of anything resembling thoughts, emotions or awareness. Such ‘mini-brains’ are used for research purposes where using actual living brains would be impossible, or at the very least, ethically tricky – testing responses to drugs, for example, or observing cell development under certain adverse conditions.

This time, Gopalakrishnan and his colleagues sought to observe the development of the eye.

In previous research, other scientists have used embryonic stem cells to grow optic cups, the structures that develop in the almost the entire eyeball during embryonic development. Other studies have also developed optical cup-like structures from induced pluripotent stem cells.

Instead of growing these structures directly, Gopalakrishnan’s team wanted to see if they could be grown as an integrated part of brain organoids. This would add the advantage of seeing how two types of tissue can grow together, rather than just growing optical structures in isolation.

“Eye development is a complex process, and understanding it could provide insight into the molecular basis of early retinal diseases,” the researchers said they wrote in their paper.

“Therefore, it is crucial to study the optic vesicles, which are the primordium of the eye whose proximal end is attached to the forebrain, which is essential for proper eye formation.”

Previous work on developing organoids had shown evidence of retinal cells, but they had not developed optical structures, so the team changed their protocols.

They did not try to force the development of purely neural cells in the early stages of neural differentiation and added retinol acetate to the culture medium to aid eye development.

Their carefully nurtured baby brains formed optic cups after only 30 days of development, and the structures were clearly visible after 50 days. This is in accordance with the time of eye development in the human embryomeaning that these organoids could be useful for studying the intricacies of this process.

There are other implications as well. The optic cups contained different types of retinal cells, which were organized into neural networks that responded to light, and even contained tissue from the lens and cornea. Finally, the structures showed the connectivity of the retina with regions of brain tissue.

“In the mammalian brain, retinal ganglion cell nerve fibers reach connections with their targets in the brain, an aspect never before demonstrated in an in vitro system,” said Gopalakrishnan.

And it’s repeatable. Of the 314 brain organoids the team cultured, 73 percent developed optic cups. The team hopes to develop strategies to maintain the viability of these structures over longer periods of time to perform deeper research with enormous potential, the researchers said.

“Brain organoids containing optic vesicles displaying highly specialized neuronal cell types can be developed, paving the way for the generation of personalized organoids and retinal pigment epithelial layers for transplantation,” they said. they wrote in their paper.

“We believe in it [these] are next-generation organoids that help model retinopathies arising from early neurodevelopmental disorders.”

The research was published in Cell stem cells.

A version of this article was first published in August 2021.