"There are many different ways of getting autism, but we found that they all have the same downstream effect," says Prof. Dan Arking regarding his research team's finding that brains affected by autism share a pattern of inflammation as a result of increased immune responses.
Prof. Arking and his colleagues at the Johns Hopkins University School of Medicine in Baltimore, MD - along with researchers from the University of Alabama at Birmingham - publish their findings in the journal Nature Communications.
Autism spectrum disorder (ASD) is a neurodevelopmental disorder that affects social interactions and communicative development, and is characterized by restrictive interests and repetitive behaviors.
According to the Centers for Disease Control and Prevention (CDC), around 1 in 68 children in the US have ASD.
In most cases, the cause of the disease is unknown, and the researchers note that despite a strong genetic component, progression on identifying genes implicated in the disease has been slow, leading to a "limited understanding of the molecular basis of autism."
Prof. Arking observed that studies into autism and gene expression - whether and how much genes are used - have involved little data and were unable to draw useful results. This is because gene expression testing must be performed on the specific tissue itself, and in this case, that would be the brain, which can only be acquired through an autopsy.
Inflammation response genes perpetually switched on in autistic brains
In order to perform a more in-depth investigation, the researchers analyzed gene expression data from 104 brain samples from 72 individuals - some with autism and some healthy controls - which they say is the largest data set so far used in a gene expression and autism study.
- ASD is almost five times more common among boys than girls
- The condition occurs more often in people with certain genetic or chromosomal conditions
- Nearly half of children with ASD have average to above average intellectual ability.
Prof. Arking explains that previous studies have identified abnormalities in cells that are linked to autism, which support brain and spinal cord neurons. As such, he and his team were able to identify a specific type of one of these support cells, called a microglial cell.
Microglial cells "police" the brain for threats and pathogens, the researchers say.
After analyzing the brains, the researchers discovered that in the brains of individuals with autism, the microglia were constantly activated and their inflammation response genes were turned on.
Though this type of inflammation is not yet well understood, the researchers say it shines a light on the current lack of understanding regarding how immunity affects neural circuits.
"What we don't know is whether this immune response is making things better in the short term and worse in the long term," says Prof. Arking, who adds that this is "a downstream consequence of upstream gene mutation."
By that, he means that given what they already know about genetic contributions to autism, inflammation is unlikely to be the root cause of the condition.
For further research, the team now wants to determine whether treating the inflammation could mitigate autism symptoms.
In August of this year, Medical News Today reported on a study from researchers at Columbia University Medical Center, which found that children with autism have too many synapses in their brain. The findings revealed that children with autism have brains with neurons consisting of old and damaged components, and the researchers found a potential pathway to help treat the condition.