2024-01-08 18:01:19
A team led by Princess Máxima Pediatric Oncology Center and the Instituto Hubrecht (Netherlands) has generated small 3D brain models – organoids – from human fetal brain tissue. Until now, these brain organoids – which try to resemble real organs on a miniature scale – were grown in the laboratory using pluripotent or embryonic stem cells.
The new technique, published in the magazine ‘Cell‘, allows regions of brain tissue are able to self-organize into three-dimensional brain structures. The authors used these organoids and the CRISPR-Cas9 tool to simulate the development of a type of brain tumor, glioblastoma, and see how it responded to different drugs.
Organoids have characteristics and a level of complexity that allows scientists to closely model the functions of an organ in the laboratory. They can be formed directly from tissue cells. Scientists can also “guide” stem cells (found in embryos or in some adult tissues) so that they develop until they become the organ they intend to study.
Until now, brain organoids were grown in the laboratory by inducing embryonic or pluripotent stem cells to grow until they formed structures that represented different areas of the brain. Using a specific cocktail of molecules, they would try to mimic the natural development of the brain, and develop the «recipe« for each cocktail it would require a lot of research.
The researchers, led by Delilah Hendriks, Hans Clevers and Benedetta Artegianiwere surprised to discover that using small pieces of fetal brain tissue instead of individual cells was vital for growing mini-brains.
The researchers clarify that the human fetal tissue used was derived from healthy abortion material, between gestation weeks 12 and 15, from completely anonymous donors. The anonymous women donated the tissue voluntarily and with prior informed consent. They were informed that the material would be used for research purposes only and that the research included understanding how organs normally develop, including the possibility of growing cells derived from the donated material.
«Until now, we could obtain organoids from most human organs, but not from the brain; “It’s really exciting that we’ve now been able to overcome that hurdle as well,” adds Clevers.
To grow other mini-organs such as the intestine, the original tissue is usually broken down into individual cells. Instead of working with small pieces of fetal brain tissue, the team found that these pieces could self-organize into organoids.
The brain organoids were about the size of a grain of rice.z. The three-dimensional composition of the tissue was complex and contained several different types of brain cells.
Human brain
The scientists highlight that the brain organoids contained many so-called external radial glia, a type of cell found in humans and our evolutionary ancestors. This underlines the close similarity of the organoids to the human brain and their use in the study.
Whole pieces of brain tissue also produced proteins that form the extracellular matrix, a kind of “scaffold” around the cells.
We can now more easily study how the developing brain expands and look at the role of different cell types and their environment.
Benedetta Artegiani
Princess Máxima Pediatric Oncology Center
«Brain organoids obtained from fetal tissue are a valuable new tool for studying human brain development. “Now we can more easily study how the developing brain expands and observe the role of different cell types and their environment,” highlights Benedetta Artegiani.
‘Our new tissue-derived brain model allows us to better understand how the developing brain regulates cell identity. “It could also help understand how errors in that process can lead to neurodevelopmental diseases such as microcephaly, as well as other diseases that can result from derailed development, including childhood brain cancer.”
The team believes that these proteins could be the reason why pieces of brain tissue were able to self-organize into three-dimensional brain structures. The presence of extracellular matrix in organoids will allow further study of the environment of brain cells and what happens when this goes wrong.
Organoids could play an important role in unraveling the network of molecules involved in brain development
The researchers also discovered that the tissue-derived organoids maintained several characteristics of the specific brain region from which they were derived. Thus, they responded to signaling molecules that are known to play an important role in brain development. This finding suggests that tissue-derived organoids could play an important role in unraveling the complex network of molecules involved in brain development.
Given the ability of tissue-derived organoids to expand rapidly, the team next investigated their potential in brain cancer modeling.
Thus, they used the CRISPR-Cas9 gene editing technique to introduce defects in the known cancer-causing gene TP53 into a small number of organoid cells. Within three months, the cells with defective TP53 had completely outcompeted the healthy cells in the organoid, meaning they had gained a growth advantage, a typical characteristic of cancer cells.
Until now, we could obtain organoids from most human organs, but not from the brain
Hans Clevers
Princess Máxima Pediatric Oncology Center and the Hubrecht Institute
They then used CRISPR-Cas9 to deactivate three genes linked to the brain tumor, glioblastoma: TP53, PTEN and NF1. Additionally, they used these mutant organoids to observe their response to existing anti-cancer drugs.
These experiments showed the potential of organoids for cancer drug research by linking certain drugs to specific genetic mutations.
The tissue-derived organoids continued to grow in a dish for more than six months. Importantly, the scientists were able to multiply them, allowing them to grow many similar organoids from one tissue sample.
«These new organoids derived from fetal tissue can offer new knowledge about what shapes different regions of the brain and what creates cellular diversity. Our organoids are an important addition to the field of brain organoids, which can complement existing organoids made from pluripotent stem cells. We hope to learn from both models to decode the complexity of the human brain,” highlights Hendriks.
‘Being able to continue growing and using brain organoids from fetal tissue also means we can learn as much as we can from such valuable material. “We are excited to explore the use of these new tissue organoids for new discoveries about the human brain,” adds Hendriks.
Minitumors with changes in the glioblastoma gene were also capable of multiplying, maintaining the same combination of mutations. This feature means that scientists can perform repeated experiments with tissue-derived organoids, increasing the reliability of their findings.
The researchers aim to further explore the potential of their new tissue-derived brain organoids. They also plan to continue their work with bioethicists, who were already involved in setting up this research, to guide future development and applications of the new brain organoids.
Clevers believes that “this study makes an important contribution to the fields of organoid and brain research. Since we developed the first human intestinal organoids in 2011, it’s been great to see the technology really take off. “Since then, organoids have been developed for almost all tissues in the human body, both healthy and diseased, including an increasing number of childhood tumors.”
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