Research Fact Sheet ~ Stem Cell Therapy
What is a stem cell?
Many of the cells in our bodies are continually replaced by cell division. Stem cells, are one type of dividing cell, which has the ability to self-renew (generate more stem cells) or to give rise to “daughter cells” that are different from the parent (as seen below). 
Stem cells are present in the embryo where they divide ultimately producing all human cells. In adults, only some parts of the body retain stem cells. Consequently, many cells in our bodies are not replaced if they die - including most brain cells and the light-sensing cells of the eye called photoreceptors.
What is the goal of stem cell research in the retina?
People with retinitis pigmentosa, dry age-related macular degeneration and many other conditions, slowly lose photoreceptors. Stem cell therapy could potentially restore sight to people who have lost much of their vision by replacing the photoreceptors.
Why not transplant the retina?
Unfortunately, this doesn’t work. A donor retina surgically implanted into the eye doesn’t communicate with the brain. However research has shown that stem cells can produce photoreceptor daughters that make connections with the brain when transplanted into a host eye. Unfortunately, the eye does not welcome transplanted cells. In most studies, less than 0.01% of transplanted cells survive.
When will therapies be ready?
Stem cell transplants have restored sight to animals but there are still barriers to success in people. Scientists must be able to direct large numbers of new cells to survive and build connections, while controlling their growth to avoid causing cancers. A partnership between the FFB and the Canadian Institutes of Health Research is funding research in these areas, but it will be 10-15 years before human trials of stem cell therapy to replace photoreceptors can begin.
Where do we get stem cells for research (or therapy)?
Initially all of the cells used in research came from embryos. Today stem cells from several sources are used.
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Could my own cells be used?
Yes, another advantage of using adult stem cells (or induced pluripotent cells) is that these cells can come from the patient. Such cells may be more likely to thrive. However if your condition is genetic, any cells taken from your body will carry the same genetic defect. Transplanted cells will begin to break down, unless other protective treatment can be used.
I have heard I can get stem cells therapy overseas. True?
Stem cell therapies have not been approved in Canada, because there is not yet enough evidence to show they are safe or effective. Treat reports of such “cures” with scepticism.
What about the new embryonic stem cell trials recently approved in the USA?
Small safety trials using embryonic stem cells to treat Stargardt’s macular degeneration (Nov 2010) and dry age-related macular degeneration (Jan 2011) have been approved in the USA. In these trials, stem cells will be used to try and restore the retinal pigment epithelium (RPE). The RPE is a layer of cells that nourishes and protects the photoreceptors in the retina. Restoring the RPE may help damaged photoreceptors survive and function more normally, but it will not replace lost vision cells.
Updated Jan 5, 2011: This text has been reviewed by Dr. Valerie Wallace of the Ottawa Hospital Research Institute and Dr. Carol Schuurmans of the University of Calgary.