Patients with macular degeneration are having their sight partially restored using human embryonic stem cells. This marks the first medium-term demonstration of the safety of embryonic stem cells, with implications for a host of other conditions.
Stem cell science is promising to replace everything from hearts to kidneys, with some hopes for diseases like MS as well. However, debate has raged over whether treatments should involve human embryonic stem cells (hESCs) or adult pluripotent stem cells from the patient themselves. The debate is partly about whether the use of hESCs is ethical, but there are also questions of safety.
Many attempts to use ESCs in animals have produced tumours, and rejection by the immune system can also be a problem. So the fact that 18 patients have had hESCs implanted without negative effects an average of 22 months later is big news.
Half the patients have Stargardt’s macular dystrophy and the other half have atrophic age-related macular degeneration, two of the most common causes of blindness in the developed world. Doses of 50,000-150,000 cells were applied. By treating one eye in each patient and leaving the other untouched, the researchers had the perfect control to establish the extent to which any changes were the result of the transplanted cells.
Ten of the patients experienced noticeable improvement in the visual acuity of their treated eye, while seven remained the same and only one got worse. On the other hand, none of the untreated eyes showed any improvement, although the researchers admit that one cannot rule out placebo effects since “both examiner and patient were aware of [which] eye underwent surgery.”