Researchers and scientists at the University College London Great Ormond Street Institute of Child Health (UCL GOS ICH) have developed a pair of human eyes to easily study and understand a rare genetic disorder called Usher syndrome.
Usher syndrome causes the slow development of blindness and scientists at UCL wanted to study the disorder's progression. It is impossible to do so in actual humans. They report that they have been able to grow miniature eyes in the laboratory from stem cells.
The 3D "mini eyes" called organoids were created using skin samples donated by some patients at the Great Ormond Street Hospital for Children (GOSH).
Usher syndrome is present in children at birth. Children with the disorder are usually deaf. However, blindness develops gradually in adulthood and there is no treatment for the condition. One of the main reasons why scientists have not been able to find a cure is that it is nearly impossible to study the core of the issue.
Typically, light-detecting rod cells are located in the back of the eye within the retina. These rods process images for the brain. In the latest study, experts were able to develop these rod cells in the mini eye. The rod cells "organised themselves into layers mimicking how they would be organised in the retina."
Previous efforts to create a miniature model of the eye in the lab failed because scientists used animal cells. A similar loss of sight was not observed in those mini eyes as Usher syndrome presents.
While it is a rare genetic condition, Usher syndrome is the most common cause of deafness and blindness, affecting a record 100,000 people across the planet. Children with Type 1 are born deaf and lose sight over time as they enter adulthood. The rest do have the ability to hear but their sight deteriorates eventually.
While hearing loss is easier to manage with hearing aids and cochlear implants, retinitis pigmentosa, the cause of vision loss, has no cure. The new work by researchers opens doors for deeper analysis and a better understanding of the genetic disorder.
Eventually, a stronger understanding can lead to designing treatments that could help people protect their vision.
With these mini eyes, scientists will be able to observe the light-sensing cells in the human eye closely. Such a detailed analysis of the human eye on an individual level has not been done before.
For example, the authors of the study published in Stem Cell Reports found that Muller cells might have a role to play in the development of Usher syndromes. They are the cells responsible for the structural and metabolic support of the retina.
Interestingly, the mini eyes that the scientists developed in the lab were grown using cells donated both by patients who had the genetic fault and those who had healthy eyes. This helped them compare the two and accurately understand where the syndrome comes from.
“It’s difficult to study the inaccessible tiny nerve cells of the patient’s retina as they are so intricately connected and delicately positioned at the back of the eye. By using a small biopsy of skin, we now have the technology to reprogram the cells into stem cells and then create lab-grown retina with the same DNA, and therefore same genetic conditions, as our patients,” said the first study author Dr Yeh Chwan Leong in a media release.
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