Scientists grow human brain cells in rats — influencing rodents’ behavior

Move over Stuart Little — there may be a new anthropomorphic pest in town.

For the first time ever, scientists have managed to successfully transplant human brain tissue into the brains of newborn rats, which reportedly changed the rodents’ behavior. An article detailing the Frankenstein-esque study was published Wednesday in the journal “Nature.”

“We found that human neurons respond very quickly after we stimulated the whiskers,” Sergiu P. Pasca, a Stanford psychiatry professor who co-authored the study, told NBC news.

The team had engineered the cerebral experiment in an effort to shed light on human brain development and neurological diseases, AP News reported. Unfortunately, while “disorders such as autism and schizophrenia are likely uniquely human” the human noodle has not been very “accessible” to this point, according to Pasca.

To circumvent this hurdle, the Stanford brain trust decided to create organoids — miniature replicas of human organs — by transforming skin cells into stem cells, which they then manipulated into becoming several types of brain cells. These cells multiplied to create an organoid of the human cortex, which is responsible for various functions ranging from memory to reasoning and emotions.

In other words, they created human brain tissue from “concentrate.”

Finally, the scientists injected the synthetic human brain tissue into the somatosensory cortexes — regions involved in processing sensations like touch or pain — of two- to three-day-old rats, whose brain connections are still forming.

The neurological connection was instantaneous. “More than 70% of the human neurons are engaged in some form of activity within a second or so of that stimulation, so that tells us that they’re probably connected,” Pascal told the outlet. He added that the human neurons were “sparkling with electricity under a microscope,” indicating that they’d “become part of the rat circuitry.”

Within eight months, the human neurons sextupled in size, until they encompassed one third of a single hemisphere of the rats’ brains à la the smart sharks in “Deep Blue Sea.”

This interspecies brain transfusion also influenced the Frankenrats’ behavior. While they didn’t become Michelin chefs like in “Ratatouille,” the lab rats would lick spouts in search of water whenever their human neurons were activated.

Pasca deemed the creation “the most advanced human brain circuitry ever built from human skin cells and a demonstration that implanted human neurons can influence an animal’s behavior.”

As an added ethical bonus, the neurologically-enhanced rodents didn’t exhibit health problems like seizures, while more than 70% were alive following the brain splicing.

To test out the neurological speedball’s practical applications, scientists transplanted organoids into both hemisphere’s of a rat’s brain. One was generated from a healthy person’s cells while other came from a person with Timothy syndrome, a rare genetic affliction similar to autism.

They found stark differences in the amount of electrical activity between the two hemisphere’s. Meanwhile, the neurons from the Timothy syndrome patient were much smaller and didn’t form as many connections as they healthy ones.

In the future, scientists hope to perform these same experiments with organoids created from the cells of people with autism or schizophrenia.