Scientists are able to bring human retinas back to life after they have died
Brain death is one of the few biological realities that seems unchangeable. It has long been believed that our neurons pass away when we do. However, a recent study on the eye’s neuron-rich tissue is starting to cast doubt on that conventional thinking.
The light-sensitive neural tissue at the back of our eyes that communicates with our brains was restored in the current study’s human retinas, which were obtained from recently dead organ donors. This accomplishment, which was published in Nature, provides a better method for researching eye conditions including age-related macular degeneration, which is a major contributor to vision loss and blindness. Additionally, it might pave the way for transplanting retinas in the future as well as the revival of other varieties of brain tissue.
Animals, primarily mice, are used in the majority of retina investigations. However, mouse retinas are not a perfect model because they lack the macula, a crucial part of human vision that picks out small details. It sometimes takes hours to get human eye tissue from autopsies, and by the time scientists can investigate its function, the eye is already dead. What if you could bring it back to life?
Frans Vinberg, a vision scientist at the University of Utah, Anne Hanneken, a retina surgeon at Scripps Research, and their colleagues were motivated to investigate whether retinal epithelium could also be restored postmortem after Yale University researchers demonstrated in 2019 that basic electrical activity could be restored in pig brains after death.
In order to conduct the study, the scientists first examined how long after the mice were put to death, their retinas could still transmit electrical signals. They discovered that oxygen deprivation was the primary cause of permanent loss of function and were able to restore this activity up to three hours later. The researchers then looked into human eyes that were retrieved from organ donors just after cardiac or brain death. The retinal tissue was subjected to low light, and the electrical signals produced by the tissue were measured after the scientists carried the eyeballs to the lab in a container that supplied oxygen and nutrition. If the donor eyes were retrieved less than 20 minutes after death, they were able to restore electrical activity in the light-sensitive cells known as photoreceptors as well as in the neurons these cells connect to. Hanneken observes that since the eyes were not attached to a brain, they could not, of course, “see.” However, the outcomes demonstrated that not only could retinal cell connectivity be restored, but also individual retinal cell functionality.
The most interesting aspect of the new research, according to Joan Miller, chief of ophthalmology at Mass Eye and Ear and chair of ophthalmology at Harvard Medical School, is that it could serve as a model for researching the visual physiology of human retinas in both healthy and diseased states. For instance, it has been difficult to investigate macular degeneration since it is impossible to obtain living human eye tissue. Scientists might examine both healthy and sick donor eyes using this new method to learn how they function and test remedies.
The research team’s findings also imply that other kinds of neural tissue might potentially be capable of regeneration. The retina serves as a window to the brain, therefore if communication can be recovered in the retina after death, it raises the possibility of recovering communication in the brain, according to Hanneken. Although retinal transplants are probably still a long way ahead, the study also raises the possibility of them.
The significance of donor tissue to basic science is demonstrated in this recent work. The researchers are really appreciative of the donors and their families, says Vinberg. They believe that by doing this, more people will check the appropriate box on their driver’s license and agree to donate tissue for scientific research.
Abbas, F., Becker, S., Jones, B. W., Mure, L. S., Panda, S., Hanneken, A., & Vinberg, F. (2022). Revival of light signalling in the postmortem mouse and human retina. Nature, 606(7913), 351–357. https://doi.org/10.1038/s41586-022-04709-x
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