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• Posted June 7, 2024

Could Brain 'Overgrowth' Contribute to Autism?

Severe forms of autism could be linked to overgrowth of the brain's outer layer that starts while a baby is in the womb, a new study finds.

Toddlers with autism have cerebral cortexes -- often referred to as "gray matter"-- that are roughly 40% larger than those of children without the developmental disorder, researchers reported recently in the journal Molecular Autism.

Further, the larger a toddler's gray matter size, the more severe their social and language symptoms were later in life.

"The bigger the brain, the better isn't necessarily true,"said researcher Alysson Muotri, director of the stem cell program at the University of California, San Diego.

Results show that in "toddlers with profound autism, there are more cells and sometimes more neurons -- and that's not always for the best,"Muotri noted in a university news release.

One continuing mystery of autism is why some children with the disorder experience profound symptoms like developmental delay, social struggles and an inability to speak, while others have milder symptoms that improve with time.

For this study, researchers used blood stem cells from 10 toddlers ages 1 through 4 to create brain cortical organoids -- 3D models of the children's cortexes, created though laboratory cell cultures.

The gray matter of the cortex lines the outside of the brain, researchers said. It holds tens of billions of nerve cells and is responsible for essential functions like consciousness, thinking, reasoning, learning, memory, emotions and senses.

They compared these organoids to others generated from the stem cells of six toddlers without autism.

The organoids of all children with autism, regardless of severity, grew roughly three times faster than those from children without autism, researchers report.

Some of the largest brain organoids -- from children with the most severe cases of autism -- also experienced an accelerated formation of neurons. 

The more severe a toddler's autism, the quicker their organoid grew, sometimes to the point of developing too many neurons.

Researchers found the size of a toddler's cortical organoid grown in the lab corresponded to a larger brain structure viewed on MRI scans.

Further, toddlers with excessively enlarged cortical organoids had greater-than-typical volume in the social, language and sensory brain regions, compared to children without autism.

This study is "one of a kind"because it's the first to link autism symptoms to a lab-created model of brain development, said researcher Eric Courchesne, co-director of the UC-San Diego Autism Center of Excellence.

"The core symptoms of autism are social affective and communication problems,"Courchesne said. "We need to understand the underlying neurobiological causes of those challenges and when they begin. We are the first to design an autism stem cell study of this specific and central question."

Now that they have established that brain overgrowth occurs in the womb, the researchers next hope to pinpoint why this happens. Once that's uncovered, a therapy that might ease autism symptoms could be possible.

More information

The U.S. Centers for Disease Control and Prevention has more about autism.

SOURCE: University of California, San Diego, news release, June 5, 2024