(RxWiki News) Two women going blind from two different conditions are seeing better after the first known transplant of human embryonic stem cells into human patients.
Human embryonic stem cells have been the source of much political controversy since first discovered 13 years ago, but until now, the potential for their use in humans has not been demonstrated beyond animals in the laboratory.
"Get an eye exam if you experience changes in your vision."
Dr. Steven Schwartz, of the Jules Stein Eye Institute Retina Division at UCLA's David Geffen School of Medicine, and colleagues have begun two clinical trials to investigate the safety and effectiveness of transplanting retina cells grown from embryonic stem cells into two female patients.
One woman has Stargardt's macular dystrophy, a genetic form of progressive blindness that usually begins in childhood or adolescence and affects approximately one in 10,000 children.
The other woman has dry age-related macular degeneration, the most common cause of blindness in developed countries.
Neither condition is currently treatable, but studies in mice and rats had previously shown potential to prevent vision loss with transplants of eye cells grown from stem cells.
To grow the retinal cells needed for the transplant, the scientists controlled the differentiation of the embryonic stem cells, directing them what kind of cells they developed into. Researchers reported that the experimental cells were 99 percent pure retinal once fully grown.
During the first four months following the patients' surgeries, researchers did not note any problems with the transplanted cells or the host eyes, such as abnormal growth or a transplant rejection from the host's immune system.
Although no post-transplant problems have occurred so far, the authors state that it is too early to tell whether the cells might eventually be rejected if the women stop taking immunosuppressive drugs.
It is also too early to note any other adverse events or side effects, and the authors did not discuss the possible cost of the surgery.
During the study, neither patients' vision further worsened, but each woman appeared to experience improvement in the eye that received the new cells.
The patient with Stargardt's macular dystrophy was able to see five letters on the eye chart in the eye that received the new retinal cells after the transplant, up from zero before the transplant.
The patient with dry age-related macular degeneration was able to see seven additional letters on the chart, from 21 before surgery to 28 afterward.
The scientists caution that they cannot state with certainty that it was the transplants that caused the improvement in both patients' vision rather than a placebo effect or the immunosuppressive drugs.
However, they are cautiously optimistic that the apparent success of these transplants may pave the way for doing similar transplants in other patients with forms of macular degeneration.
"Continued follow-up and further study is needed," they wrote in their conclusion. "The ultimate therapeutic goal will be to treat patients earlier in the disease processes, potentially increasing the likelihood of photoreceptor and central vision rescue."
The study appeared online January 23 in the journal The Lancet.
Four of the authors are employees of Advanced Cell Technology, the biotechnology company that funded the study. The other authors stated they have no conflicts of interest.