Lab-Grown Stem Cell 'Mini Brains' Just Developed Eyes

The growth of the "optic cups" mirrored the process that occurs in the embryo.
Ameya Paleja
Brain organoid with optic cupsElke Gabriel

Researchers at the University Hospital Dusseldorf in Germany have grown primitive eye structures on brain organoids that they had made in their lab. The growth of eye structures in the lab mirrored the one that occurs in the embryo and will help us understand how eyes develop. 

The human brain is a fascinating organ and an inspiration for computer processor developers too. However, studying the human brain is not that easy. It is locked up inside the skull for its active period and available for analysis only after its stops to function. Most brain development also occurs quite early in life, leaving little scope for an investigation into its development and workings. Scientists have, therefore, turned to organoids, three-dimensional tissues that can be observed in the petri-dish, to improve our understanding of the brain. 

Modern research methods allow us to extract skin or blood cells from an individual and then reprogram them into stem cells. Called induced pluripotent stem cells (iPSCs), these stem cells are capable of developing into any cell type in the body. Scientists carefully modify the nutritional medium they grow in to convert them into desired cell types, even making miniaturized brain cells, if needed. 

Neuroscientist Jay Gopalakrishnan at University Hospital Dusseldorf and his team of researchers are interested in studying diseases of the eye. To understand, how these diseases occur in the first place, they need to understand the process of eye development. Other researchers had previously, used iPSCs to develop optic cups, structures that lead to the development of the retina - the light-sensitive layer of cells in the eye. 

The retina plays an important role in the eye. It converts the light it receives into neural signals that it transmits to the brain using the optical nerve. The brain then analyses the signals, which in common terms is called 'sight'. Since the retina works closely with the brain, Gopalkrishnan and his team decided to grow the optic cups on brain cells, that were sourced from iPSCs. 

Using samples from four iPSC donors, the team first made the brain organoids and then modified its growth media to induce the formation of optic cups. These cups on mini brains not only contained retinal cells but also developed lens and corneal tissue and demonstrated connections to the brain cells. During embryonic development, the retinal cells reach out to the brain but this was never demonstrated in the lab before, until this work. 

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Development of brain organoid with optic cups
Source: University Hospital Dusseldorf in Germany

The optic cups appeared as early as 30 days into the brain development and became distinctly visible by 50 days. The timeline of the development mimicked the one that occurs inside the human embryo. Out of the 314 brain organoids that the team made, almost 73 percent developed optic cups. The study was published in 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,” Gopalkrishnan said in a press release. For future studies, the team wants to increase the viability of the optic cups to help them study diseases of the retina.  

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