Human ‘mini brain’ implanted in mice reacts to light for the first time in science!
Imagine if missing or diseased parts of the brain could be re-grown in the lab and transplanted into new life. It seems that scientists at the University of California at San Diego have come close to this reality.
The scientists showed that human cortical organelles (mini-brains) transplanted into mice were not only connected to the host’s vascular system, but also responded to light pulses entering the subjects’ eyes in the same way as the surrounding brain tissue.
Over the course of several months, the researchers used the innovative imaging system to measure the electrical activity in the organelle, which is indicative of an integrated response to visual stimuli. This is the first time that scientists have been able to confirm functional connections in implanted brain organelles in real time, thanks in large part to improvements in implants that can measure subtle nerve signals at the micro level.
“We foresee 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 neural circuits, to select possible treatments against the patient’s genetic background, and to evaluate organoids and the ability to restore certain areas of the brain,” researchers write. “Missing, degraded, or broken integration.”
A team of engineers and neuroscientists led by neuroengineer Duygo Kuzum has developed a new recording system to simultaneously measure brain wave activity at both macro and micro levels.
The device uses flexible transparent graphene microelectrodes that can be implanted in certain areas of the brain. This well-tuned technology accurately maps bursts of neural activity in both the transplanted organ and the surrounding brain tissue as they occur.
Less than a month after the transplant, the researchers found that human organelles form functional synapses with the rest of the mouse visual cortex.
Two months later, the foreign tissue was even more integrated into the host’s brain.
Previous research by authors at the University of California, San Francisco has shown that miniature human brains implanted in mice can 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 cluster of two million pea-sized organized neurons that search for neighboring connections in their environment.
Pluripotent stem cells also form the basis of human brain organelles. They have the ability to differentiate into different tissues and organs, but only if they are immersed in the right mixture of molecules. But this combination is incredibly complex and very time specific, 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, which could ruin the success of tissue culture.
Transparent electrodes help solve this problem. Using fluorescence imaging technology under a microscope, researchers at the University of California, San Francisco have shown that pulses of light can stimulate the transplantation of human organs into mouse brains.
The study was published in the journal Nature Communications.
Source: Science Alert