Although studying brain cells as a single layer in petri dishes has led to countless ground-breaking discoveries in neurobiology, it’s pretty intuitive that a two-dimensional “lawn” of cells doesn’t fully represent what’s happening in our complex, three-dimensional brain.

In the past few years, researchers have really upped their game with the development of brain organoids, self-organizing balls of cells that more accurately mimic the function of particular parts of the brain’s anatomy. Generating brain organoids from induced pluripotent stem cells (iPSCs) derived from patient skin samples is revolutionizing the study of brain diseases (see our previous blog stories here, here and here.)

Tiny brain organoid spheres in petri dishes. Image: Case Western

This week, Case Western researchers reported in Nature Methods about an important improvement to the organoid technique that includes all the major cell types found in the cerebral cortex, the outer layer of the brain responsible for critical functions like our memory, language, and consciousness. The new method incorporates oliogodendrocytes, a cell type previously missing from the “mini-cortexes”. Oliogodendrocytes make myelin, a mix of proteins and fats that form a protective wrapping around nerve connections. Not unlike the plastic coating around an electrical wire, myelin is crucial for a neuron’s ability to send and receive signals from other neurons. Without the myelin, those signals short-circuit. It’s this breakdown in function that causes paralysis in multiple sclerosis patients and spinal cord injury victims.

With these new and improved organoids in hand, the researchers can now look for novel therapeutic strategies that could boost myelin production. In fact, the researchers generated brain organoids using iPSCs derived from patients with Pelizaeus-Merzbacher disease, a rare but fatal inherited myelin disorder. Each patient had a different mutation and an analysis of each organoid pointed to potential targets for drug treatments.

Dr. Mayur Madhavan, a co-first author on the study, explained the big picture implications of their new method in a press release:

Mayur Madhavan, PhD

“These organoids provide a way to predict the safety and efficacy of new myelin therapeutics on human brain-like tissue in the laboratory prior to clinical testing in humans.”