The researchers first created retinal tissue from human embryonic stem cells in the laboratory. They then surgically transplanted this tissue into the eye of a monkey that had a macular hole. The monkey's vision was tested before and after the procedure using eye-tracking tests and electrical recordings of retinal activity. The researchers also performed detailed microscopic examinations of the eye tissue after the study period to see how well the transplanted cells had integrated and developed.
The transplanted tissue successfully filled the macular hole and showed signs of developing into various types of retinal cells, including photoreceptors. The monkey's ability to focus on visual targets improved significantly after the treatment. Electrical recordings showed increased retinal activity in the treated area. However, there was a mild rejection response to the transplanted tissue, which was controlled with medication.
This study was performed on only one monkey, so the results need to be replicated in larger studies. The follow-up period was relatively short at seven months, so longer-term effects are unknown. The use of human embryonic stem cells may raise ethical concerns for some. There was a mild rejection response, indicating that immune suppression might be necessary for this treatment.
The successful integration of lab-grown retinal tissue and the improvement in visual function are very promising. This approach could potentially overcome limitations of current treatments for macular holes, particularly for difficult cases. The development of different retinal cell types in the transplanted tissue suggests this method could have applications beyond just macular holes. However, more research is needed to refine the technique, address the immune response, and ensure long-term safety before human trials can begin.
The study was supported by several Japanese research institutions and government agencies, including the Japan Agency for Medical Research and Development and the Japan Science and Technology Agency. The researchers declared no competing interests related to this study.