Posted on 09/22/2006 9:12:17 AM PDT by neverdem
In an experiment that boosts hopes for regenerative medicine, scientists have used stem cells from human embryos to save the sight of lab rats going blind.
The genetically engineered rodents suffered from an eye disease similar to macular degeneration, the leading cause of vision loss in people older than 55. But after receiving injections of retinal tissue generated from human embryonic stem cells, the rodents' vision did not deteriorate and, researchers say, proved to be 100 per cent better than untreated rats.
The work not only represents a new possibility for treating an incurable condition on the rise, but also a strategic bit of ammunition for those fighting for the potential medical value of human embryonic stem cells.
"People are saying this stuff [stem-cell therapies] is decades away and with this we're saying, 'No, we've shown you can do this sooner, with large numbers of cells that are reliable and look to clinical trials,' " said study leader Robert Lanza, who is scientific director at the U.S. biotech firm Advanced Cell Technology. "We rescued the visual function in these rats, rats that would have otherwise gone blind."
Related to this article Latest Comments Start a conversation on this story Macular degeneration involves the deterioration of retinal tissue crucial for central vision tasks such as reading and driving. Light-sensitive cells in the macula, known as photoreceptors, transmit signals to the brain and losing them can result in blind spots and blurred vision. More than a third of Canadians older than 55 will develop the condition that already affects 30 million people worldwide.
A key challenge for any therapy that would rely on stem cells is being able to produce enough of the tissue needed for a given treatment. But the researchers report in this week's issue of the journal Cloning and Stem Cells that they succeeded in growing 67 good-quality batches of retinal cells from 18 different human embryonic stem-cell lines.
While animal studies are continuing, Dr. Lanza's group is now generating large numbers of particular retinal cells with the hope of applying next year to test them in vision-impaired patients.
"We're in the process of creating these cells under Good Manufacturing Practices and getting ready to supply them for human clinical trials," he said. (Good Manufacturing Practices are regulations set up by the U.S. and Canadian governments for the manufacture of medicines.)
A great gap lies between treating rats and treating people and Dr. Lanza acknowledged certain safety questions must still be answered. For one, rats in this study received the implants not long after birth and it is unclear how well older human eyes would accept new tissues.
There was no evidence of serious side effects or abnormal tissue growths -- a particular concern with any stem-cell therapy because stem cells are prized for their power to multiply indefinitely and mature into the various tissue types that make up the human body. But the rats were followed for only 100 days. Dr. Lanza said ongoing studies are expected to follow the animals for about a year.
Mick Bhatia, scientific director of the Stem Cell and Cancer Research Institute at McMaster University in Hamilton, applauded the work for being one of few that has made the leap of "getting [stem cells] out of the dish and into a living animal."
However, Dr. Bhatia cautioned that the paper does not make clear that there is a real therapy here. He noted that the researchers transplanted only one type of retinal cell, even though they generated various retinal-cell types. He also noted that other research has shown that any cell implanted at an injury site might improve conditions and so it cannot be certain that the benefits reported in this experiment are due specifically to the tissue from embryonic stem cells.
Advanced Cell Technology has often made headlines in the controversial field of embryonic stem-cell research. Last month, the company reported it had found a method to derive stem cells without destroying an embryo -- the key concern of those morally opposed to the work.
But the field's opponents, the U.S. Conference of Catholic Bishops in particular, rejected the report because the donated lab-dish embryos had been destroyed in the ACT experiment. As the ethical debate continues, the field's proponents are anxiously investigating ways stem cells could be used to generate replacement tissues for patients -- be they retinal cells, neurons or arteries. Researchers at the California-based Geron Corp. and the University of California, for example, also plan to apply next year for U.S. government approval to test an embryonic stem-cell therapy in patients with acute spinal-cord injuries. Studies in rats have found that using the cells to generate a particular kind of nerve cell can significantly improve movement.
Dr. Lanza said it's no surprise that stem-cell treatments for the eyes and central nervous system may be the first "out of the gates." These tissue types are the most easy to generate from stem cells, he said. As well, tissues transplanted into the eye or nervous system are less likely to be rejected than cells implanted in other areas.
The eye, in particular, Dr. Lanza noted, is "an immune-privileged site . . . If there is rejection, the [immune] response is less aggressive."
Other research has tested the potential of implanting retinal tissue from human fetuses in patients. But in those cases, Dr. Lanza said, there had been some rejection issues and not nearly enough tissue to conduct large studies. But he estimates that banking stem-cell lines from 100 different embryos should be enough to generate retinal tissue with the potential to match anyone in the ethnically diverse U.S. population.
In this study, Dr. Lanza and colleagues grew the retinal tissue from stem cells harvested from 18 different human embryos. The stem cells were cultured in the lab and matured into different cell types spontaneously.
After about six to eight weeks, scientists were able to hand-pick under a microscope those cells that were turning into retinal pigment epithelial cells, or human RPE cells. These retinal cells were then cultured separately in a special medium to encourage their growth.
Fourteen young rats, which carried a gene defect that would lead to blindness, received two injections of about 10,000 human RPE cells each in the retinal areas of their eyes before their vision had deteriorated. Another eight rats, serving as the control group, received injections of a solution that did not contain the cells.
Tests were then conducted to determine how well the rats could see. These included measuring the retinal response to a flashing light and tracking the rats' reaction to a virtual three-dimensional pattern. Rats that had received the cell transplants out-performed those that did not.
Post-mortem tests showed rats that received the transplants grew the needed photoreceptor cells five to seven cells deep in the outer nuclear layer of the eye. Those that did not showed only one cell. Normal rats have a layer 10 to 12 cells deep.
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Growing the cells
In an experiment that boosts hopes for regenerative medicine, scientists have used stem cells from human embryos to save the sight of rats going blind.
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Retinal tissue was grown from stem cells harvested from 18 different human embryos. The stem cells were cultured in the lab and matured into different cell types spontaneously.
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After about six to eight weeks, scientists were able to hand-pick under a microscope those cells that were turning into retinal pigment epithelial cells, or RPE cells.
***
These retinal cells were then cultured separately in a special medium to encourage their growth. From the original 18 stem cell lines, 67 batches of RPE cells were grown.
***
Fourteen young rats, which carried a gene defect that would lead to blindness, received two injections of about 10,000 human RPE cells each in the retinal areas of their eyes before their vision had deteriorated. Another eight rats, serving as the control group, received injections without the cells.****
Postmortem tests showed rats that received the transplants grew the needed photoreceptor cells five to seven cells deep in the outer nuclear layer of the eye. Those that did not showed only one cell deep. Normal rats have a layer 10 to 12 cells deep.
SOURCE: ADVANCED CELL TECHNOLOGY
That's interesting. I remember being taught that certain eye injuries require that the injured eye must be removed so that the immune response doesn't attack the remaining good eye. Are there any ophthalmologists available to comment?
The type of rodent used isn't mentioned. IIRC, they have a critter genetically engineered, i.e. "knock out" types, that lack the ability to reject transplants. Somebody correct me if I'm wrong.
'rats have a vision?...huh...go figger...seems they're always on the wrong side of history....coulda swore they were all blind...whodathunk!
I was really worried about rats getting lasic surgery but now I know we can just murder a few babies and they will be able to see again!!
Adult stem cells little or no help to heart repair
FReepmail me if you want on or off my health and science ping list.
Someone needs to post the bug-eyed Nancy Pelosi picture.
But will it help them stay in office?
I'm not enthused about using human embryos to restore rodent vision.
Exactly. Maybe we can get the plague going again.
"the [immune] response is less aggressive."
I wonder how that affects the chances of developing cancer in that particular area of the eye .
Using human cells in animals strikes me as quite creepy, although I want to stay abreast of what the ghouls are doing.
How good is the vision in the eyes of the rats with the transplants?
I realize that some vision is better than none, but "100% better" doesn't mean 100%.
Is the vision in the untreated rats is 2%, then the vision in the rats helped by the sacrificed humans is 4%.
A very good idea.
Why didn't they just use retinal tissue generated from rat retinas? Or, for that matter, from rat embryos? Is there a reason?
I have no idea other than studying any rejection involved in xenografts and chimeras.
Which is a good thing, because the seeing-eye dog usually ends up just eating the rat.
yeah...*sigh*...the Mengele crowd always seems to find another "good" excuse to murder more babies.
moral depravity in the most evil form.
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