Transplanting RPE cells grown from stem cells, Lanza reasoned when he began this research almost a decade ago, might rejuvenate the eye’s rods and cones, restoring lost vision.

To produce RPE cells, Lanza and his colleagues arranged to obtain days-old embryos created by in vitro fertilization. The parents, who no longer wanted the embryos, donated them for research. The scientists then removed a single stem cell from one embryo, grew it in the lab to obtain millions of cells, and differentiated them into RPE cells.

The primary purpose of the clinical trial was to determine whether the implanted cells caused any harm. So far, neither patient has experienced inflammation, an indication that their immune system is not attacking the foreign cells.

And there is no evidence that a teratoma formed in either patient. Researchers also found that the RPE cells still survive after being implanted four months ago.

NOT A CURE FOR THE BLIND

The goal of the study was to determine safety and, at most, see whether the therapy can slow down or arrest vision loss, not restore it. “The fact that we’re seeing measurable improvements in their vision, persisting for more than four months, is a bonus,” Lanza said in an interview.

Although rods and cones cannot be brought back from the dead, he explains, “until you lose them completely you can rescue them.” He believes that the transplanted RPE cells both bathed the deteriorating rods and cones in nourishing growth factors and gobbled up fragments of dead rods and cones, keeping the retinal environment healthier for the survivors.

The UCLA physicians plan to enroll a total of 12 Stargardt’s patients and 12 macular degeneration patients in the ongoing clinical trial, with groups of three patients each receiving a different number of retinal epithelial cells.

The two patients being reported on Monday each received the smallest dose, 50,000 cells. Other patients will receive at least twice that many. The trial is also expanding across the Atlantic: the first patient was treated at Moorfields Eye Hospital in London last Friday. In a later trial, they hope to treat patients with earlier-stage disease, before so much of their vision has been lost.

David Prentice of the Family Research Council, a pro-life group that has opposed the use of human embryos for research, says the results will require more scrutiny.

“You have to follow the patients longer to know if it’s safe,” he told Reuters. “People will also want to know if there are other routes to the same end,” using sources of stem cells other than human embryos.

Lanza is planning just that. He believes that skin cells “re-programmed” to revert to embryonic status might prove just as good a source or RPE and other specialized cells as human embryonic stem cells. Called IPS (for “induced pluripotent stem”) cells, they can be derived from a patient’s own skin cells and pose no risk of immune rejection.

“I think we can be up and running in the clinic with IPS cells in one or two years,” Lanza says.

SOURCE: The Lancet, online January 23, 2012.