Scientists in Sweden have innovated a method of treating blindness using embryonic stem cells to produce retinal cells. The team at Karolinska Institutet and St Erik Eye Hospital reported this week in the paper published in the journal Nature Communications, their approach of using CRISPR/Cas9 gene editing to amend retinal cell production so the generated cells can hide from the body’s immune system, protecting them from becoming rejected.
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Age-related macular degeneration impacts a third of over 65s
By the age of just 65, roughly a third of people have developed some kind of eye disease that impairs vision. The most common cause of blindness in this age group is age-related macular degeneration which causes sufferers to gradually lose central vision.
The condition currently impacts around 11 million people in the US, a figure which is expected to rise to 22 million by 2050. Around the world, as many as 196 million are living with the condition, which is predicted to grow to 288 million by 2040.
With age-related macular degeneration, the rods and cones of the eye (known as the photoreceptors), begin to die following the death and degeneration of the retinal pigment epithelial (RPE cells) that provide nourishment to the photoreceptors.
Scientists regard the transplantation of new RPE cells generated from embryonic stem cells as a potential future treatment for the condition, which could improve the quality of life of millions.
Preventing transplant rejection
Scientists at the Karolinska Institutet teamed up with those at St Erik Eye Hospital to develop a new way to combat age-related macular degeneration of the eye. They identified markers on the RPE cells’ surface, which they demonstrated can be used to isolate and purify the RPE cells.
The team used their findings to create a robust, new protocol which sees embryonic stem cells differentiating into RPE cells. They showed their method to be effective, and importantly, free of contamination of any other cell types.
The team is now planning a clinical study in which they will investigate the efficacy of the method, to prepare for this, the scientists have started to produce RPE cells using their established protocol.
One challenge the team is up against is in preventing the RPE cells produced by stem cells from being rejected. This happens when antigens present in the donor tissue differ to that of the patient, triggering an immune system response. To tackle this, a number of research teams have been working on developing universal cells that do not generate an immune system response.
The Swedish team has also been successful in developing a method to overcome this limitation by creating embryonic stem cells that go undetected by the immune system. To do this, the scientists used the CRISPR/Cas9 gene-editing technique to remove certain molecules from the cell surface, preventing the immune system from recognizing them. These stem cells were then observed to successfully differentiate into RPE cells.
Further to this, the team also demonstrated that the RPE cells produced using their approach retained their character and did not go on to develop mutations. They also proved that their modified stem cells were significantly less likely to trigger a rejection response than regular RPE cells.
A new therapeutic approach
While the research is still in the preliminary stages, the evidence that has initially been collected demonstrates the potential method the team has developed for generating universal RPE cells that could be used to effectively treat age-related macular degeneration of the eye.
Given that there is currently no cure to the condition, and the only treatments available are those that slow down the progression of the disease, this work is significant in that it potentially provides a new, more effective therapeutic approach.
Advances in production of retinal cells for treating blindness. Eurekalert. Available at: https://www.eurekalert.org/pub_releases/2020-03/ki-aip032620.php
Plaza Reyes, A., Petrus-Reurer, S., Padrell Sánchez, S. et al. Identification of cell surface markers and establishment of monolayer differentiation to retinal pigment epithelial cells. Nature Communications (2020). https://doi.org/10.1038/s41467-020-15326-5