Blind World


Hope for retinal transplant success.





Tuesday, July 08, 2003.

By Health Newswire reporters.
Health-News.




LONDON


Glial cells – located in the retina – set up a physical barrier preventing retinal transplants from hooking up to the host retina and restoring sight, US and Swedish researchers suggests.



Retinal transplant hope


Disarming these cells can free transplanted tissue to make the sight-saving connection to the retina and optic nerve and, ultimately, the brain, say a team from the Harvard Medical School and Goteborg University.


The study’s authors say their findings will affect the success of retinal transplantation and have the potential to restore vision to millions of people afflicted by retinal diseases, such as macular degeneration, glaucoma and retinitis pigmentosa.


Such discoveries could also lead to the success of brain tissue transplants for conditions such as Parkinson’s disease, say the authors in the journal Nature Neuroscience.


Glial cells are support cells for nerve cells and, in injured or diseased eyes, they cause an increase of the proteins that help scar formation.


The researchers tested the hypothesis that glial cells may form similar scars in response to the injection of transplanted tissue and that these scars may act as a barrier to transplant survival.


They also hypothesised that transplants might survive and integrate in mice whose glial cells had been disarmed or rendered unable to stimulate the production of the necessary scar-forming proteins.


The team investigated mice which either had normal glial cells or whose glial cells had been manipulated so that the scar-forming proteins had been knocked out.


In the mice with normal glial cells, the transplanted cells remained near the injection site, did not grow or migrate to other areas of the retina and failed to grow the nerve tentacles necessary to wire up to the host retinas and the optic nerves.


In addition, they found that the glial cells surrounded the transplanted tissue, forming a scar and creating a physical barrier that kept the transplanted tissue from integrating into the eye and connecting to the optic nerve.


In contrast, the transplanted cells in mice that were missing the scar-forming proteins survived, migrated to the retina, grew the necessary tentacles and became entwined in the optic nerve. When divested of the proteins the glial cells did not form a physical scar barrier.


Dr Dong Feng Chen, assistant professor of the Harvard Medical School, said the discovery increased the chances that retinal transplants may one day be able to survive in the human eye.


She said, “This is a significant piece of the retinal transplant puzzle. Because it has been so difficult to transplant neurons to retinas and brains, we have long suspected that there are physical barriers preventing donor cells from surviving, migrating and integrating into the host environment of these tissues.


“This study clearly shows us the nature of one major barrier and ways to break it down.”



Source: Nature Neuroscience


© HMG Worldwide 2003.






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