A lab-grown retina cell is 1 step closer to reality.
In a study published this month, researchers at University of Wisconsin-Madison have shown that retinal cells grown in a lab were able to make synaptic contacts with nerve cells. Which means they functioned just the way actual retinal cells do.
It has been a decade of research and experimentation in which the team has worked step-by-step to get to this point. First the team developed a way to grow organized clusters of cells, called organoids. For this they used human skin cells reprogrammed to act as pluripotent cells – the type of cells that can develop into many different types of cells or body tissues.
The team then needed to find out if the organoids would resemble the form and function of the actual retina. They did.
Next, they tested to find out if lab-grown retinal cells can respond to different wavelengths and intensities of light. They can.
And now, the researchers have shown that these lab-grown cells can connect and communicate with existing nerve cells. The lab-grown photoreceptors responded to light and extended out “cords” or axons towards other retinal cells in the organoid.
The next step is human trials.
The end goal is to restore the visual circuits that were destroyed by disease. “We wanted to use the cells from those organoids as replacement parts for the same types of cells that have been lost in the course of retinal diseases,” said David Gamm, MD, PhD, the UW–Madison ophthalmology professor and director of the McPherson Eye Research Institute whose lab developed.
Diseases that destroy photoreceptors such as retinitis pigmentosa and age-related macular degeneration, as well as eye injuries that destroy photoreceptors, and glaucoma that degenerates the optic nerve could all one day be treated with the introduction of lab-grown cells to replace those that were destroyed.
What are photoreceptors?
Photoreceptors are the retinal cells that respond to light. They consist of rods and cones and they convert visual information into electrical signals. The human retina contains 120 million rod cells and 6 million cone cells, with the latter concentrated in the central or macula region of the retina.
Rod cells are highly sensitive to light and are responsible for our ability to perceive the size, shape, and brightness of visual images. They also provide good vision in low light. They are concentrated in the outer areas of the retina and provide our peripheral vision.
The cone cells detect a wide spectrum of light and provide our color vision.
What is a synapse?
A synapse is the fluid-filled space between the axon end of one neuron and the dendrite tip of the next neuron that serves as a communication junction. It is also called a neuronal junction.
A chemical and an electrical synapse work differently. In a chemical synapse, the nerve impulse is transmitted chemically via neurotransmitters, and in an electrical synapse, the nerve impulse is transmitted electrically via channel proteins.
Electrical synapses are instantaneous, but because chemical synapses depend on the release of neurotransmitter molecules from synaptic vesicles to pass on their signal, there is an approximately one millisecond delay between when the axon potential reaches the presynaptic terminal and when the neurotransmitter leads to the opening of postsynaptic ion channels.
Electrical synapses are present throughout the central nervous system, including the retina.