Human neurons implanted into a rat’s brain respond to flashing lights

Lab-grown neurons were transplanted into rat brains with damaged visual cortex. Two months later, neurons responded when rats saw flashes of light

To Jason Arunn Murugesu

Human neurons are integrated into the brains of adult rats with damaged visual cortex, taking over some of the functions of the organ’s visual system.

Isaac Chen of the University of Pennsylvania and his colleagues wondered whether transplanting lab-grown clusters of neurons called organoids into the brains of rats with damaged visual cortex would restore function in that region. rice field.

They first cultured human stem cells, which develop into many different cell types, for 80 days to form a three-dimensional tissue culture of brain cortical cells. They make up the outer layer of the brain and play important roles in several functions such as vision.

The team then removed sections of the visual cortex from 46 rats before transplanting organoids into these damaged cortices.

Rats were studied for 3 months. After two months, the organoids began to show neuronal responses. This was measured by inserting electrodes into the implanted organoids while the rat watched a series of images on a screen.

One set of images consisted of flashing lights, while another set had alternating black and white lines in various directions, such as horizontal and diagonal.

Neuronal responses in the organoids varied with the flashing lights and according to the orientation of the black and white lines. This suggests that neurons have integrated into the rat brain and taken over some of the functions of the visual system, Chen says.

In another part of the experiment, researchers compared organoid-implanted rats to rats without visual cortex damage. Although the neuronal responses were relatively similar, the organoid-implanted rats had fewer neurons that responded to light than the uninjured rats, Chen says.

The researchers did not measure whether organoid implantation improved the rats’ vision.

“There is definitely still work to be done in terms of understanding what factors control this integration and how this integration can be optimized,” says Chen.

The next step would be to remove other cortices in the rat’s brain, such as the motor cortex, and repeat the experiment, he says. “We hope that this research will move us toward using these organoids to restore function, and ultimately, in the long-term, transplantation of organoids into brain-injured patients.”

“This study shows that transplanted organoids can not only integrate into host tissues, but also restore complex lost functions,” said Laura Feraiuolo of the University of Sheffield, UK.