Mini-Brains The Size of Peas Are Helping Us Study Incurable Neurological Conditions

In the last few years, neuroscientists have gotten much better at growing the beginnings of the human brain in the lab. Now, these 'mini-brains' are growing complex enough for us to study neurological disease in its earliest stages.

Maintaining them isn't easy, either. Brain organoids derived from the stem cells of those with Parkinson's disease have been grown for about 30 days. For Alzheimer's disease, they've been grown for 84 days. Researchers at Cambridge have now grown a pea-sized mini-brain to study amyotrophic lateral sclerosis (ALS) for nearly a year, which is a really big step.

ALS, which often overlaps with frontotemporal dementia (ALS/FTD), is a currently untreatable neurodegenerative disease that leads to rapid cognitive decline and paralysis. Because the neurological symptoms don't show up until later in life, scientists know very little about how it starts.

Enter the lab-grown mini-brain grown using stem cells from patients with ALS/FTD. One of the big hurdles with growing brain-like clumps in a dish is that as the organoid grows, cells in the middle become deprived of nutrients and stop becoming useful models.

To get around this, some researchers a few years ago started slicing the organoids before bathing them in culture, keeping their models alive for longer periods and for better study. Researchers at Cambridge did this with their early model of ALS/FTD. In unpublished work, the team claims to have grown their organoids for a total of 340 days.