It’s a fascinating experiment. Who did it? Scientists at Stanford University in the United States. They achieved a transplantation of human neurons into mice. They were human neurons from a patient with Timothy syndrome. They tested new drugs to treat this rare congenital disease.
“We will study the effects of drugs on transplanted human neurons.” Said Sergiu Pasca, Romanian physician who headed the study. It was published in the prestigious journal Nature. The experiment was not without controversy. The results influenced the behavior of the animals.
Treatment of disorders
Using cells from volunteers, millions of brain neurons were converted into brain neurons. They condensed into tiny spheres a few millimeters in diameter, known as ‘brain organoids’. A sort of ‘mini-human brain’. They were transplanted into the brains of a group of genetically modified rats. They were deprived of their immune system so that they would not reject the grafts.
The animals were between 3 and 7 days old. They were being trained to lick a tube when they needed to drink water. It was found that their behavior and learning could be controlled at will. After activating human neurons by laser bursts, the rodents instantly came to the device to quench their thirst.
The main application of this experiment would be research on psychiatric and neurodegenerative diseases. They started with Timothy syndrome, a rare disorder that causes severe neurological and cardiac problems in children. In future experiments, they promise to extend their study to other disorders. For example, autism and schizophrenia.
“To understand psychiatric disorders we need better models. And, the more human these models are, the more we will have to address these ethical issues.” The Romanian physician, advises against using this strategy on monkeys or apes.
“We need to seek a balance. Weighing potential benefits of avoiding some of the suffering caused by these disorders and the risks of generating models that are too similar to humans.” Transplantation of human neurons into mice is highly controversial. However, the benefits in humans could be very important.