In July, a Japanese woman in her forties received the first-ever corneal transplant made from induced pluripotent stem cells (iPSCs) — adult skin cells that have been reprogrammed into stem cells — to treat a disease of the cornea. At a press conference on 29 August, doctors reported that over the past month the woman’s cornea has remained clear and her vision has improved. They hope that the one-time procedure will prove effective for the remainder of the patient’s life.
The cornea is the transparent outer layer of the eye and is often referred to as the window to the eye. However, when stem cells of the cornea are damaged by injury or disease, the tissue can become cloudy leading to blurry vision and possibly, blindness. Whereas, a healthy cornea has the ability to regenerate itself naturally. In this case, the patient was suffering from corneal epithelial stem cell deficiency and therefore, lacking the cells the body needs to naturally regenerate the tissue.
The typical treatment for this is replacing the damaged cornea with a new donor one. But in Japan, long waiting lists for corneal tissue mean there are around 1,600 patients currently awaiting transplants. To address these shortages, the team of researchers from Osaka University in Japan, led by ophthalmologist Dr Kohji Nishida, hope thin sheets of ‘reprogrammed’ stem cells can be used instead.
“We have only conducted the first operation and we are continuing to monitor the patient carefully”, Nikida said at the press conference. The Japanese health ministry has given approval for a total of four patients to receive a corneal transplant made from stem cells and the second procedure will be performed later this year.
In theory, stem cells are less prone to immune rejection — a problem typically associated with transplanting any type of tissue from a cadaver. But doctors say they will still cautiously monitor the patient to fully determine to safety and efficacy of the treatment. And importantly, to look out for signs of potential tumour growth, which is one of the main risks associated with stem cell therapies.
Stem cells have the ability to differentiate into any specialised cell type, in this case, corneal cells. The idea is that iPSCs will be able to continuously replenish any damaged or lost cells. For the procedure, skin cells were first taken from another person and used to create the iPSCs. Then, the extremely thin sheets of these ‘reprogrammed’ stem cells — 0.03-0.05 millimetres thick — were transplanted onto the left eye. While skin cells are generally used since they are easy to isolate and grow, any type of body tissue should be able to produce iPSCs.
Japan is leading the way in the clinical use of iPSC. The cells were discovered by another Japanese stem-cell biologist Prof Shinya Yamanaka of Kyoto University and have now been used to treat spinal cord injuries, Parkinson’s disease, and age-related macular degeneration, a disease affecting the retina at the back of the eye. And now, the reprogrammed stem cells are being used for the cornea.