Tiny human brain illuminates path to cure blindness

A new study shows that human ‘mini-brains’ can integrate with damaged rat brains to perform vision-related functions. This is a promising step into the future where lab-grown brain tissue can reverse blindness in humans.

Challenge: if visual cortex —The part of the brain that receives and processes information from the eyes—When damaged by injury or disease, a person can lose the ability to see.

It was not yet known whether organoids implanted in the visual cortex actually functioned like natural brain tissue.

Researchers believe that grafting brain organoid — clump of Cells grown in the lab Mimics the structure of real brain tissue – When applied to damaged visual cortex, people may regain some or all of their vision.

Although this area of ​​research is still very new, research showed that baby rat brains accept and integrate grafts from human minibrains. While this was a promising sign, it was still unclear whether organoids implanted in the visual cortex actually functioned like natural brain tissue.

what’s new? To find out, researchers at the University of Pennsylvania grown brain organoids 80 days in their lab. He then transplanted clumps of cells into the brains of 46 of his rats with damaged visual cortex.

After 3 months, approximately 82% of the grafts were successfully integrated into the rat brain. Cells grown in the laboratory increased in size and number, formed synapses with the rat’s own neurons, and developed healthy vasculature.

To investigate whether the small human brain is actually adapted to function as part of the visual cortex, researchers mapped neural networks using fluorescent viruses that use synapses to travel between neurons. Did.

“By injecting one of these viral tracers into the eyes of animals, we were able to follow neuronal connections downstream from the retina. Said Senior author H. Isaac Chen. “The tracer reached the organoid.”

After finding that these specific connections formed between rat brains and organoids, the researchers connected electrodes to neurons in the transplanted brains. mini brainsThis allowed us to measure organoid activity while the rats were exposed to flashing lights.

“We found that a significant number of neurons within the organoids respond to specific directions of light. This is not only because these organoid neurons are able to integrate with the visual system, but also adopt very specialized functions of the visual system.” It shows that we can, it’s the cortex,” Chen said.

Notes: About 75% of the neurons in the rat’s own visual cortex responded to light stimulation, compared to only 20% in the transplanted human minibrain.

“[T]There were fewer neurons responding to light here than ideal,” Chen said. told Technology Networks“Understanding how to improve this response rate/consolidation is one of our major goals for the future.”

“Nervous tissue has the potential to rebuild damaged areas of the brain.”

H. Isaac Chen

This is another area ripe for future research, as the type of visual impairment the rodents underwent in this study is not exactly the same type that commonly causes blindness in humans.

“[W]The aspiration cavity we created is a kind of brain injury, not a good model for traumatic brain injury or stroke. increase.”

Future plans: As is the case with all rat studies, humans may respond in completely different ways to this procedure, so more research is needed before attempting to use organoids to repair brain damage in humans. is required.

However, researchers believe the potential is very high.

“Neural tissue has the potential to remodel areas of the brain that have been damaged,” Chen said. “We haven’t solved everything, but this is a very solid first step.

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