September 24, 2004.
By Kristen Philipkoski,
Scientists have derived retinal cells from embryonic stem cells for the first time, in a breakthrough that could lead to the first therapeutic use of the controversial cells.
If animal studies go well, the researchers said they could begin testing the replacement cells in human eyes in as little as two years.
"These cells actually make the cones and rods," said Robert Lanza, chief scientific officer at Advanced Cell Technology and lead author of the paper. "We're in a position to not only maintain vision so you don't get further loss, but these cells appear to want to form entire eyeballs."
The cells could help treat people with macular degeneration, which affects more than 30 million people worldwide. The disease gradually causes complete loss of sight and is the leading cause of blindness in people older than 60 in the United States. The cells could also help people with retinitis pigmentosa, which afflicts about 75,000 people in the United States.
"This ... takes us nearer to being able to treat forms of blindness that affect thousands of people every year for which, at present, there is no effective treatment," said Ian Wilmut, editor in chief of Cloning and Stem Cells and head of gene expression and development at the Roslin Institute, in a statement.
The study, which was published in the Nov. 3 issue of Cloning and Stem Cells (.pdf), demonstrates the potential of embryonic stem cell technology, the researchers said.
Embryonic stem cells are primordial cells that differentiate to become every cell in every organ of the body, and researchers believe they can harness that power to create therapies for disease. President Bush has limited federal funding of stem cell research in the United States because the embryo is destroyed when scientists derive stem cells -- at the point when the embryo is a ball of about 100 cells approximately the size of the period at the end of this sentence. In 2001, Bush declared that no federal funds could be spent on embryonic stem cell lines developed after that date. Presidential candidate Sen. John Kerry (D-Massachusetts) has said he will reverse Bush's policy if he wins the election in November.
While the recent results are a boost for the entire field, the researchers did have a leg up when trying to develop retinal cells, which are a type of neuron.
"Embryonic stem cells like to do what they want to do, and one of the things they like to do is make neurons," Lanza said. "They tend to be much easier to derive."
The challenge to scientists is to guide embryonic stem cells to differentiate into the specific types of cells the scientists want. It will be more difficult for researchers to coax stem cells to become more complicated cell types, like those that produce insulin, since those cells would need to precisely calibrate glucose levels in the blood.
Previous research has shown limited success in transplanting retinal cells derived from fetal or adult stem cells. Lanza and his colleagues are confident that their embryo-derived cells will work even better, because the cells are even more similar to natural retinal cells than those that were tested previously.
© Copyright 2004, Lycos, Inc.
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