#brain organoids
Brain organoids provide insight into the mechanism of a difficult-to-treat seizure disorder
Brain cells, or neurons, communicate through organized electrical bursts to control body processes like walking, talking and breathing. Sometimes, those electrical bursts can become disorganized and cause seizures, or epilepsy if the seizures are recurring. Focal cortical dysplasia — a brain disease characterized by abnormal balloon cells in the outer layer of the brain — is the leading cause of medication-resistant epilepsy. Some cases are caused by spontaneous genetic mutations, but the majority have an unknown cause. Treatment options are limited to invasive brain surgery, which may be ineffective.
In a new study, published online December 27, 2021 in Brain, an international collaboration between teams of researchers led by senior authors Alysson Muotri, PhD, director of the Stem Cell Program at the University of California San Diego School of Medicine and Iscia Lopes Cendes, PhD, professor in the Department of Translational Medicine at the University of Campinas, Brazil, describe a new laboratory model for focal cortical dysplasia using small floating balls of human brain cells called brain organoids.
Using a method called “reprogramming,” researchers are able to take skin cells from a skin biopsy and turn them into pluripotent stem cells. These stem cells can transform into any cell in the body — even tissues like brain organoids — and retain the same genetic material as the patient that received the skin biopsy, making it easier to personalize medicine.
The lead author of the study, Simoni Avancini, PhD, generated brain organoids from stem cells derived from patients with focal cortical dysplasia and compared them to brain organoids derived from healthy patients.
The researchers mimicked several aspects of the disease using the new model. They observed abnormal neurons, abnormal balloon cells, less actively dividing cells and more electrical bursts between the neurons. The results suggested that, at least in these patients, spontaneous genetic mutations do not cause focal cortical dysplasia, and it may be caused by unknown inherited mutations.
Inside brain organoids are sunflower-shaped areas called neural rosettes. where cells divide and mature into neurons. Precursor cells divide and fill the inner circle. Maturing neurons grow out of that circle like the petals of a sunflower. To investigate why brain organoids from patients with focal cortical dysplasia had less actively dividing cells, the researchers zoomed in on those neural rosettes and discovered differences in the expression of ZO-1 — a protein that helps cells stick together.
Unlike brain organoids from healthy patients where ZO-1 forms a smooth outline around the inner circle, brain organoids from patients with focal cortical dysplasia show ZO-1 as disorganized points within the inner circle. This led the researchers to investigate RHOA — a gene that regulates ZO-1 — in diseased brain organoids, and they discovered decreased expression of this gene compared to healthy brain organoids, suggesting that the decrease in actively dividing cells is caused by abnormal RHOA regulation.
Overall, these findings offer new insights into the mechanisms underlying focal cortical dysplasia, write the authors.
“We hope that this model will be useful to test and screen new theories and new ideas regarding focal cortical dysplasia, as well as finding novel treatments for this condition,” said Muotri.
— Gabriela Goldberg, graduate student
Brain organoids derived from a healthy person (left) compared to a person with focal cortical dysplasia (right).
Click to watch a video with Professor Lopes Cendes.
