One of the challenges to studying and treating AMD is that it is difficult to observe the progression of the condition in human beings without a physiological model.
This new research developed a biodegradable model through 3D printing that allows researchers to study what is known as the blood-retinal barrier. The blood-retinal barrier is involved in the delivery of nutrients and removal of wastes from retinal pigment epithelial cells, which themselves are important for the health of photoreceptors in your eyes.
“By recreating that barrier, what they did is they created a cellular surface on both sides of the model,” said Dr. Mark Fromer, an ophthalmologist at Manhattan Eye, Ear and Throat Hospital.
This model recreates components of the blood-retinal barrier, which includes the retinal pigment epithelium, Bruch’s membrane, and choriocapillaris, all of which are important when studying AMD. Typically, Bruch’s membrane helps to regulate the exchange of nutrients and waste between the blood vessel-rich choriocapillaris and the retinal pigment epithelium. However, the effects of AMD can disrupt this process, damaging the retinal pigment epithelium and eventually impacting vision
“By creating this 3D image, all of these components can begin to help researchers study the process [of AMD]. The researchers created a system to study the disease process in vitro, versus in vivo, which is a huge difference.”
First, the researchers printed a combination of stem cells for three different cell types (endothelial cells, pericytes, and fibroblasts) onto a 3D scaffold. Then, they seeded retinal pigment epithelial cells onto the other side of the scaffold. The cells then began to create actual layers that resemble structures you would find in the anatomy of a human eye.
The hope would then be that scientists can eventually use this model to study AMD and potentially develop more effective treatments that can help to treat or cure the condition.
Macular degeneration, or age-related macular degeneration, is a problem with the eye’s retina. It happens when a part of the retina, called the macula, is damaged. The damage to the macula
There are two types of macular degeneration: dry and wet. Dry AMD is the most common, affecting about 80% of people who have AMD. Dry AMD happens when the macula thins out with age and starts to produce protein growths, which begin to break down the retina pigment epithelium, as well as disturb blood vessels behind the eye. Ultimately this leads to the destruction of the blood vessels and can cause blindness.
Wet AMD is less common, but more serious. This occurs when abnormal blood vessels grow underneath the retina, which may leak blood or other fluids, and causes scarring of the macula, again leading to blindness.
Currently, there is no way to treat the dry form of AMD. To treat wet AMD, medications called anti-VEGF injections can help to reduce the number of abnormal blood vessels in the retina. VEGF, or vascular endothelial growth factor, is what causes the growth of blood vessels behind the retina. The increase in VEGF is part of what causes wet AMD.
“Those injections limit the [protein] growth factors by blocking the VEGF on the retina, which inhibits bleeding underneath the retina.”
That is for wet AMD. Dry AMD does not have any official treatments, though, according to Fromer, injectables are coming out designed to inhibit retinal degeneration for dry AMD.
That’s why this new research could be potentially a game-changer, as it allows researchers to study the entire picture of how the outer blood retinal barrier is affected in AMD. The 3D model can create both dry and wet AMD scenarios.
“You can look at how different drugs might affect that outer blood-retinal barrier. You can look at the complex interactions between the different types of cells within that region. It’s much more difficult to do that in a live setting. It may even allow in the future a genetically engineered retina that could be transplanted,” added Fromer. “That’s way down the road. But that would be the hope.”
This research is still in its early days and the study did have a few limitations. What researchers created is not exactly the same as what you’d see in an actual blood retinal barrier. The blood supply is also not the same and some of the cell types that are naturally in that barrier cannot be produced in this model.
Fromer said, “But they certainly have a strong foundation for examining the site where the disease occurs, which affects hundreds of millions of people.”