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Human “mini-brains” transplanted into mice respond to light for the first time

Imagine if missing or diseased parts of the brain could be re-grown in a lab and transplanted for a new life, UC San Diego scientists seem to be getting closer to that reality, RT reported.

The scientists showed that human cortical organoids (mini-brains) transplanted into mice were not only connected to the vascular system of the host, but responded to pulses of light shining into the subjects’ eyes in similar ways to surrounding brain tissue.

Over the course of several months, the researchers used an innovative imaging system to measure the electrical activity in the organelle that indicates an integrated response to visual stimuli. This is the first time that scientists have been able to confirm functional connections in implanted brain organoids in real time, thanks in large part to improvements in implants that are able to measure subtle nerve signals on a microscale.

“We envision that, along the way, this combination of stem cells and neural recording techniques will be used to model disease under physiological conditions at the level of neuronal circuits, screen candidate therapies on a patient’s genetic background, and evaluate organoids and the ability to restore specific brain regions,” the researchers write. missing, degraded, or damaged integration”.

The team of engineers and neuroscientists, led by neuroengineer Duigo Kuzum, developed their new recording system to measure brain wave activity at both the macro and micro levels simultaneously.

The setup uses flexible, transparent microelectrodes made of graphene that can be implanted in specific parts of the brain. This highly-tuned technology accurately displays spikes in neural activity from both the transplanted organ and surrounding brain tissue as they occur.

Less than a month after transplantation, the researchers found that the human organoids formed functional synapses with the rest of the mouse’s visual cortex.

After two months, the foreign tissue was further integrated into the host’s brains.

Previous studies, conducted by the authors at the University of California, San Francisco, showed that human miniature brains implanted in mice could connect to blood vessels that supply oxygen and nutrients. Neurons also begin to mature and self-regulate.

And in 2019, for example, scientists grew pluripotent stem cells into a pea-sized clump of two million organized neurons, which search their surroundings for neighborhood connections.

Pluripotent stem cells also form the basis of human brain organoids. They have the ability to differentiate into a variety of tissues and organs, but only if they are dipped in the right mix of molecules. But this combination is incredibly complex and very specific timing, which scientists are still working on.

Conventional metal electrodes do not give a clear field of view of the brain, which means that scientists have to remove the electrodes to properly see the sensory cortex, and this can spoil the success of tissue culture.

Transparent electrodes help solve this problem, and using fluorescent imaging technology under a microscope, researchers at the University of California, San Francisco, have shown that pulses of light can stimulate human organ transplants inside a mouse brain.



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