Until now, patients who suffer from one of the most common causes of vision loss have had little hope for treatment. Age-related macular degeneration, or AMD, typically strikes people older than 60 by thinning a layer of cells at the back of the eye known as the retinal pigment epithelium. This layer of cells eliminates waste from the eye and nourishes photoreceptors, the neurons that absorb and convert the light that creates the images we see. As the disease progresses, photoreceptors die, and patients lose central vision—the ability to see what is directly in front of them; peripheral vision is not affected.

Embryonic stem cells may be able to halt the progress of the disease. When researchers used stem cells to create new retinal pigment cells and injected them under the retinas of rats, the new cells helped restore the epithelium, temporarily stopping the degeneration of the retina and rescuing threatened photoreceptors.

This spring scientists will test this method in patients for the first time. The clinical trial, led by biotech company Advanced Cell Technology, will focus on treating the most common form of macular degeneration, known as atrophic (dry) AMD. “There’s a desperate need to be thinking about cell therapies for blinding diseases because not a lot else is coming down the pike,” says Marie Csete, former chief scientific officer at the California Institute for Regenerative Medicine, a research funding agency (she is not involved in the trial).

Some critics warn that patients’ immune systems could reject the foreign cells, and that undifferentiated stem cells could turn into cancer cells. Robert Lanza, chief scientific officer at Advanced Cell Technology, says his team has addressed both concerns. For one, the eye is immune-privileged, meaning it is less likely than other organs to reject foreign tissue; indeed, rejection was not an issue in trials on rats. The company has also developed a test to detect a single undifferentiated stem cell among the retinal pigment cells they will give to patients.

If trials prove the treatment is safe, Lanza will test it on patients with earlier stages of AMD, the better to prevent the onset of the disease. At best, though, the treatment would spare vision but not restore sight that has already been lost.

6 Comments

1. 1. teddy's cousin 11:46 AM 4/20/11

   I encourage Ms. Collins to re-check her facts as they relate to the last sentence of her article.
   
   "At best, though, the treatment would spare vision but not restore sight that has already been lost."
   
   This is not what ACTC has represented to the world on this matter. In fact just today, April 20, 2011, ACTC issued a press release that included the following statement:
   
   "We are very excited about this European filing, because our preclinical data from various animal models with hESC-derived RPE cells have been tremendously encouraging," said Robert Lanza, M.D., chief scientific officer at ACT. "In rats we have seen 100 percent improvement in visual performance over untreated animals without any adverse effects. Near-normal function was also achieved in a mouse model of Stargardt's disease."
   
   

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2. 2. jgrosay 05:51 AM 5/7/11

   Is it ethically acceptable blocking the development of a zigote into a human being, and using his/her remains as spare parts for ill persons ?

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3. 3. jgrosay 05:55 AM 5/7/11

   Sorry for the mistake: any human zigote is a human being, the development is from a single or small number of cells human to a full body person

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4. 4. Pazuzu 11:31 AM 5/8/11

   Yes, jgrosay, it is ethically acceptable to harvest embryonic stem cells to prevent blindness in sentient adults. A zygote (note spelling!) is simply a fertilized ovum and is totally devoid of sentience and capable of neither joy nor suffering. It normally develops into a human being, but to say that it is already a human being is like saying a lumber yard is already twenty homes.
   
   Let's focus our ethics on the well fare of sentient creatures.

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5. 5. ironjustice 01:35 PM 5/8/11

   Quote: patients who suffer from one of the most common causes of vision loss have had little hope for treatment
   Answer: "Maculas affected by age-related macular degeneration contain increased chelatable iron in the retinal pigment epithelium and Bruch's membrane."

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6. 6. bucketofsquid 04:33 PM 5/12/11

   Since it has been stated repeatedly that adult stem cells are as versatile as embrionic stem cells and are easier to obtain and don't have the ethical conundrum attached, would it not be better to use them instead of embrionic source stem cells?

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