For over 50 years, organ transplants has helped people with various diseases get a new lease on life. While retinas can be transplanted, the eye itself can’t be transplanted. That means that persons with retinitis pigmentosa, age-related macular degeneration and certain kinds of eye injuries have to deal with compromised vision or eventually blindness. Of course, researchers at University of California San Diego (UC San Diego) and the Waisman Center at the University of Wisconsin-Madison are studying ways to take lab grown eye cells and implant them in a living organism. Here are the results from their research.
Organoids implanted into mice respond to stimuli
A team of engineers and neuroscientists at UC San Diego showed that brain organoids implanted in mice have both functional connectivity to the animals’ cortex and responded to external sensory stimuli. The organoids were derived from human stem cells and have become promising models in the study of both brain development and neurological conditions.
Until recently, no one was able to show that the organoid implanted in the mouse cortex was able to share the same functional properties as the surrounding tissue. The team solved this problem by developing experiments that combined microelectrode arrays made from transparent graphene, which is a one-atom-thick layer of carbon atoms arranged in a hexagonal lattice that is used in biomedical applications, such as tissue engineering. It also utilized two photon imaging, which is a microscopy technique that can show images of living tissue up to one millimeter thick.
Researchers foresee that this neural recording technology will serve as a way to evaluate organoids as models for brain development and disease. Also, the hope is that they can be used as a prosthetic that can restore function in damaged brain regions. In fact, using both the electrodes and the two-photon imaging, the team was able to record neural activity in the organoid and the cortex in real time and saw that blood vessels grew into the organoid, which provided needed nutrients and oxygen for its survival.
Lab-grown retinal eye cells make successful connections
What if all you want to do is make a retina? Well, a little over ten years ago researchers at the Waisman Center at the University of Wisconsin-Madison developed a way to grow organized groups of cells that resemble the retina.
Starting with human skin cells, they induced those cells to become layers of retinal cells that sense light and transmit it to the brain. The plan was to use those cells as a replacement for the cells lost due to retinal diseases. Of course, what grows in a lab might not work in a living organism.
During 2022, researchers published studies showing that the lab grown retinal cells respond to light like cells in a healthy retina and they reached out to neighboring cells via axons, which are cords attached to the cell. Since cells in the retina and brain communicate by way of gaps, known as synapses, at the tips of their cords, researchers wanted to see if the cords had the ability to “shake hands” with other retinal cells type and communicate with each other.
This was done by using a modified rabies virus to identify pairs of cells that could communicate with each other. Next, the retinal organoids were broken into individual cells and were given a week to see if they would extend their axons and make new connections, as well as exposing them to the rabies virus. After a week, researchers saw that the rabies virus had infected the retinal cell across the synapse that was formed between the cells. After the connections were confirmed, researchers found that the retinal cells that formed the synapses were the photoreceptors. These cells are lost in diseases like age related macular degeneration and retinitis pigmentosa. Of course, the next step for this research are human clinical trials.
While these two research projects haven’t progressed to human trials, cells grown in the lab have the potential to be used as a way to treat various eye diseases. Research projects like these show that in the near future, blindness as a result of disease isn’t inevitable.