Imagine that lost, degenerated, or diseased parts of the brain could be regrown in the lab and transplanted for a new lease of life. Scientists at the University of California San Diego have brought us closer to this reality.
Human cortical organoids (or ‘mini-brains’) not only connected to the host’s vasculature, but also responded to pulses of light shining into the test subjects’ eyes in ways similar to the surrounding brain tissue.
For several months, the researchers used an innovative imaging system to measure electrical activity in the organoid, which shows an integrated response to visual stimuli.
It’s the first time scientists have been able to confirm functional connections in a transplanted human brain organoid in real time, largely thanks to advances in implants that can measure subtle neurological signals on a fine scale.
«Further down the road, this combination stem cells and neuro-registration technologies will be used to model disease at the level of neuronal circuits under physiological conditions, to study candidate treatments on a patient-specific genetic background, and to evaluate the potential of organoids to restore certain lost, degenerated or damaged brain regions upon integration. » Writers write.
Led by neuroengineer Duygu Kuzum, a team of engineers and neuroscientists developed new recording systems to simultaneously measure brain wave activity at both macro and micro levels.
The setup uses flexible and transparent microelectrodes. graphene It can be implanted in certain areas of the brain. This highly tuned technology accurately displays spikes in neural activity from both the transplanted organoid and surrounding brain tissue as they arise.
Less than a month after transplantation, the researchers discovered that human organoids formed functional synaptic connections with the rest of the mouse visual cortex.
Two months later, the foreign tissue had become more integrated with the host’s brains.
Previous studies, some conducted by the same authors at UCSDshowed that human mini-brains implanted in mice can connect to blood vessels that supply oxygen and nutrients. Neurons also begin to mature and self-organize.
For example, in 2019 scientists have become versatile stem cells into two million organized neurons the size of a pea researching its surroundings for neighborhood connections.
Pluripotent stem cells also form the basis of human brain organoids. They have the potential to differentiate into a wide variety of tissues and organs, but for this they need to be washed with the right cocktail of molecules. But this mix is incredibly complex and based on a very specific timing that scientists are still working on.
A brain organoid in 2021 began to develop primitive eye structuresand yet the feasibility of achieving functional ‘sight’ in a lab-grown brain is still a long way off.
Placing a human brain tissue made from stem cells into an advanced visual cortex may be a more realistic goal. There are studies has done this before in rodentshowever, determining whether the foreign vaccine was actively receiving functional input from the rest of the brain was more difficult.
Conventional metal electrodes don’t give the brain a clear field of view, meaning that scientists have to remove the electrodes to properly view the sensory cortex, and this can negatively impact the success of a tissue transplant.
Transparent electrodes help solve this problem. Using a fluorescent imaging technique under the microscope, researchers at UCSD have shown that pulses of light can stimulate human organoids transplanted in a mouse brain.
«More down the road, we envision this combination of stem cells and neural recording technologies will be used to model disease under physiological conditions, to study candidate treatments on patient-specific organoids, and to evaluate the potential of organoids to restore certain lost, degenerated or damaged ones.» brain regions» says my lamb.
Study published Nature Communication.
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