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20th January 2023

The National Eye Institute steps towards treating retinal diseases

Did you know that researchers at the National Eye Institute (NEI), a part of the National Institutes of Health (NIH), are printing cells to make tissues look and act like tissue in the back of the eye?

They start by creating 3 types of cells from patient stem cells and combine and print them in a gel. Tissue grows over several weeks. These tissues can then be used for research and, someday, treatment, helping millions regain their vision.

National Eye Institute scientists have developed a method to bioprint eye tissue that forms the outer blood-retina barrier, the interface between the retina and the choroid, including the choriocapillaris and Bruch’s membrane.

They combined different cell types primarily derived from patient stem cells in a hydrogel carrier that is suitable for bioprinting and created a tissue structure similar in features to the native tissue.

Currently, many diseases do not have useful in vitro models and, asides ethical concerns, in many cases, experimental animals may not accurately mimic human physiology. Therefore, there’s an apparent need to develop more advanced in vitro systems that enable accurate mimicking of human tissues and study disease.

The researchers hope that this new technology will help with the creation of an unlimited supply of eye tissue with which they can study various eye diseases.

The outer blood-retina barrier supports the photoreceptors in the retina and is involved in the initiation of age-related macular degeneration. Kapil Bharti, one of the researchers involved in the study revealed their concern, “We know that age-related macular degeneration starts in the outer blood-retina barrier.

However, mechanisms of age-related macular degeneration initiation and progression to advanced dry and wet stages remain poorly understood due to the lack of physiologically relevant human models.”

The researchers therefore created a 3D bioprinted model of the tissue. In age-related macular degeneration, the retinal pigment epithelium of the outer blood-retina barrier breaks down, resulting in degeneration of photoreceptor and eventual vision impairment.

The three cell types combined together in the creation of the printed constructs were pericytes, fibroblasts, and endothelial cells – all of which had been derived from patient stem cells. These cells were mixed with a hydrogel after which the mixture is bioprinted onto a biodegradable frame.

The tissue constructs were cultured, and they grew under observation, reaching maturity within 6 weeks, and showing features of the native outer blood-retina barrier.

To model age-related macular degeneration, the researchers then expose the tissue to low oxygen, and they tested the effects of drugs that are used to treat the condition in humans.


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