The effects of macular degeneration could soon be a thing of the past (Image: Garo/Phanie/Rex Features)

For the first time since they were discovered 13 years ago, human embryonic stem cells (hESCs) have shown medical promise.

Two people with eye degeneration both say their vision improved in the four months after they received implants of retinal pigment epithelial cells made from hESCs. The treatments were also safe, with no sign that the cells triggered aggressive tumours called teratomas, no sign of immune rejection of the cells, and no inflammation.

Discovered in 1998, hESCs had previously failed to deliver on their medical promise. The new procedures, performed by Robert Lanza of Advanced Cell Technology of Marlborough, Massachusetts, and colleagues, could represent a turning point for hESC therapies.


One of the women in the trial had Stargardt disease, an inherited form of eye degeneration in which the pigment cells wither and die. She had replacement cells made from hESCs injected into one of her eyes.

Before the treatment she could only make out hand movements, but afterwards her vision in the treated eye had improved enough to discern finger movements too. She could also read five letters on a standard visual acuity chart – beforehand she could not make out any letters.

“That doesn’t really capture the difference it’s made in her life,” says Lanza. “She reports she can see more colour and has better contrast and dark adaptation out of the treated eye. She started using her computer and could even read her watch. Little things like that, which we all take for granted, can make a huge difference in the quality of people’s lives.”

Stem cell boost

The second woman in the trial, who has age-related macular degeneration, also reported improved vision. She expanded the number of letters she could read on a visual acuity chart from 21 to 28.

Although modest, the vision improvements represent a huge boost for researchers developing treatments based on hESCs.

From the outset, these studies have been opposed by anti-abortion groups on the grounds that the cells can be obtained only by destroying human embryos. Consequently, most progress so far with stem cells has been with adult stem cells extracted from tissue such as fat or skin.

Former US president George W. Bush impeded progress in federally funded US labs by restricting researchers’ access to hESCs in 2001. The move was reversed by Barack Obama in 2009, paving the way for treatments to enter trials in 2010, including the eye trials that have now been completed.

“The goal of this therapy is not to cure blindness, but to slow down or prevent its onset,” says Lanza. However, with evidence now that the stem cells are safe they could be used earlier in treatment, where they might have a greater impact.

Other researchers welcomed the developments. “At last we’re seeing the fruits of hESC research entering clinical trials, and I am immensely happy this has happened in the eye,” says Pete Coffey of University College London, who is head of a team developing tiny patches of retinal pigment epithelial cells from embryonic stem cells to treat age-related macular degeneration. “Hopefully, we will be able to enter our own clinical trials using hESC therapy soon,” he says.

The results “move us much closer to the future of regenerative medicine for vision disorders”, says Paul Sieving, director of the US National Eye Institute in Bethesda, Maryland. He adds that the institute is also working with hESCs to combat retinal diseases and cataracts.

Journal reference: The Lancet, DOI: 10.1016/S0140-6736(12)60028-2