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02-02-2012 | Surgery | Article

Human embryonic stem cells show promise for treatment of macular degeneration


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MedWire News: Human embryonic stem cells (hESCs) could improve vision in patients with macular degeneration, research suggests.

The study, published in The Lancet, reports on the safety and tolerability of subretinal transplantation of hESC-derived retinal pigment epithelium (RPE) in patients with two forms of macular degeneration.

"Our paper is the first published report using embryonic stem cells in humans for any purpose," co-author of the study Robert Lanza (Advanced Cell Technology, Marlborough, Massachusetts, USA) told MedWire News. "Both patients tolerated the transplant well without signs of postoperative inflammation, rejection, or tumorigenicity at the time of this report."

Furthermore, the researchers observed "functional visual improvements" in both patients.

"These improvements appeared to occur despite the progressive nature of these [visual] conditions," remarked Lanza. "This is particularly important, since the goal of this therapy is not to cure blindness, but rather to slow down or prevent the onset of blindness altogether."

For the study, Steven Schwartz (Jules Stein Eye Institute, Los Angeles, California, USA), Lanza, and co-investigators differentiated hESCs into greater than 99% pure RPE in culture. The cells displayed "typical RPE behavior," and integrated into the host RPE layer forming mature quiescent monolayers after transplantation into mice and rats.

Next, the team injected 50,000 RPE cells generated from hESCs into one eye of two patients: one with Stargardt's macular dystrophy - the most common pediatric macular degeneration - and one with dry age-related macular degeneration (AMD) - the leading cause of blindness in the developed world.

After surgery, Schwartz et al did not identify any signs of hyperproliferation, abnormal growth, or immune-mediated transplant rejection in either patient during the first 4 months.

They also observed functional visual improvements in both patients. For example, the patient with AMD had improvements in best-corrected visual acuity, from 21 Early Treatment Diabetic Retinopathy Study letters (20/500 vision for the patient, with 20/20 being perfect vision) to 28 letters (20/320) by week 6. The patient remained at this level through postoperative month 6.

Lanza said that this patient was able to use her computer again and even read her watch. "Little things like that - which we all take for granted - can make a huge difference in the quality of a person's life."

He added that, since hESCs are among the most versatile stem cells that we know about, "these results have significance for the entire pluripotent stem-cell field."

Indeed, in an accompanying editorial, Anthony Atala (Wake Forest School of Medicine, Winston-Salem, North Carolina) says that the work described by Schwartz et al is "paving the way for clinical use of other pluripotent stem-cell populations."

He concludes: "The ultimate therapeutic goal in patients with visual loss would be to treat them earlier in the disease processes, hopefully increasing the likelihood of visual rescue. Much remains to be seen - literally."

By Nikki Withers

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