Skip to comments.ADULT Cell Transplants Restore Vision in Mice
Posted on 11/09/2006 6:51:31 PM PST by Coleus
Scientists say they've restored the vision of blind mice by introducing light-sensitive cells into the rodents' retinas. These "photoreceptor precursor cells" are not undifferentiated stem cells but come from a later stage of cell development when stem cells have already "committed" to being a particular cell type -- in this case the rod-and-cone photoreceptors the eye uses to sense light.
The study invigorates the search for cell transplants that might someday restore the vision of millions of people who suffer from a loss of these photoreceptors. "We think this is a major breakthrough because it shows what can be achieved," said study lead researcher Dr. Robert MacLaren, a consultant vitreoretinal surgeon at Moorfields Eye Hospital and a clinician scientist at the University of London, in England. The finding also gets around the thorny ethical question of using embryonic stem cells. In fact, MacLaren said, "we do not want embryonic stem cells because they are too undifferentiated."
One expert had high praise for the study. "MacLaren's stunning report will re-rejuvenate photoreceptor transplantation research, and may even transform our clinical practice and restore activities of daily living in individuals with retinal degeneration," said Dr. Steven Tsang, assistant professor of clinical ophthalmology at the Columbia University Medical Center in New York City. The findings were published in the Nov. 9 issue of Nature.
Stem cells continue to intrigue scientists because of their ability to develop into any cell type in the body. The tantalizing promise of stem-cell therapy lies in its potential to replace cells or tissues damaged by disease or injury. The millions of photoreceptors in the eye act as the retina's "pixels," interpreting incoming light and hooking up with nerve cells to transmit that information to the brain. But myriad illnesses -- everything from diabetes to age-related macular degeneration -- can kill off these cells, triggering partial or full vision loss.
Scientists have tried introducing embryonic or adult stem cells into the retina before, in the hope they might develop into photoreceptors and make the connections needed to restore sight. Those experiments failed to work, however. According to MacLaren, the problem may have been in the timing. He explained that prior stem cell efforts used cells that had not yet reached that stage where they were committed to develop into a particular cell type. In contrast, "we are transplanting cells at the exact time that they are destined to become photoreceptors -- i.e., they are past the point of no return," MacLaren explained.
In the experiment, his team harvested these photoreceptor precursor cells from the retinas of newborn mice, whose eyes were still developing. They then transplanted these cells into the "subretinal space" of the eyes of blind mice. These mice had certain gene defects that left them with few working photoreceptors. "These cells were transplanted extremely quickly (i.e., 30 minutes out of their normal environment)," MacLaren said. This rapid transfer, plus their positioning in a conducive retinal environment, means that the cells "were able to form quick connections with host cells," he said. It's those connections that allowed progenitor cells to develop into working photoreceptors and then form tangible, functioning neural connections with the rodents' brains. The result: The pupils of these formerly blind mice began to react to even low levels of light in their environment, the researchers reported. Light stimuli also began to spark new activity in brain cells associated with vision.
MacLaren's group had also attached a green fluorescent genetic "tag" to the transplanted cells. This allowed the scientists to observe the cells' progress as they started making connections to other cells within the eye. While this study used photoreceptor precursor cells extracted from the eyes of newborn mice, MacLaren is confident that adult stem cells could also be genetically manipulated to produce high numbers of precursor cells in the lab. In fact, the next step in this research focuses on getting "more photoreceptor progenitor cells from in vitro gene transfer," he said. "We might need stem cell biologists to get these cells for us, or we might be able to find them within the adult human eye." Tsang is optimistic that the research presented by MacLaren's group "will pave the way for clinical use of stem cell derived photoreceptors. Their exciting results will revive interest in photoreceptor transplantation."
Learn more about the human eye at the U.S. National Eye Institute (www.nei.nih.gov).
SOURCES: Robert MacLaren, M.B., Ch.B., F.R.C.S.; clinician scientist, Institute of Ophthalmology, University of London, and consultant vitreoretinal surgeon, Moorfields Eye Hospital, London; Steven Tsang, M.D., assistant professor of clinical ophthalmology, Columbia University Medical Center, New York City; Nov. 9, 2006, Nature
Actual development is directed towards harvesting the patient's own blood marrow, processing blood marrow in the operating room to extract the patient's own stem cells. These cells will be injected into the target joint. This all will take place in one procedure within the confines of the O.R.
Any clinical material either entering or leaving the O.R., triggers massive regulatory requirements. A device entering the O.R. that rearranges the patient's own cells is to the FDA only a device, which incurs a mere fraction of the regulatory burden.
"So this is an cure/therapy with embryonic stem cells?
If so, wow!"
No...here is the important factoid from the article....
"In the experiment, his team harvested these photoreceptor precursor cells from the retinas of newborn mice, whose eyes were still developing."
These were not embryonic stem cells.
"The above title has the word "ADULT" when in fact the cells were not taken from an adult nor are they adult stem cells. Seems the poster wants to imply something that is not true."
The term "adult stem cells" does not mean the cells have to come from an adult.
The term is used to refer to sources of stem cells that do not come from embryos.
Lately however, I've noticed that umbilical cord cells are being referred to as "cord cells" - but I've also seen them be referred to as adult stem cells as well.
The cells in this experiment did not come from an embryonic source.
"I just wanted to be fair and let one of the forum's ESC promoters
gloat...if indeed some ESCs had finally been tamed."
If cancerous tumors produced by embryonic stem cells don't tame them, I don't know what will.
--Wikipedia's definition seems to be leading you to believe that embryonic and adult stem cells are identical in form and nature. They are not.--
You keep making statements about me that are incorrect. Please stay with the facts.
-The cells in this experiment did not come from an embryonic source.--
They are not adult stem cells. Over and out.
"They are not adult stem cells. Over and out."
According to you.
Somehow I think I'll rely on the scientists definitions.
""They are not adult stem cells. Over and out."
I found this site gave helpful info...
The article posted for this thread suggests that stem cells later reach a stage where they have "committed" themselves to particular type of growth.
Is this what you are disputing? That once the cells became receptive to light they no longer fit the definition?
Correct. Once cells have 'differentiated' they are no longer stem cells. The cells in the title article are no longer stem cells. In fact, the authors mention that they will need a source for these cells from humans and they may possibly use either embryonic or adult stem cells for that source depending on future testing.
Please read these few sentences from the second paragraph:
"We think this is a major breakthrough because it shows what can be achieved," said study lead researcher Dr. Robert MacLaren, a consultant vitreoretinal surgeon at Moorfields Eye Hospital and a clinician scientist at the University of London, in England. The finding also gets around the thorny ethical question of using embryonic stem cells. In fact, MacLaren said, "we do not want embryonic stem cells because they are too undifferentiated."
So, UpAllNight, are you saying that the vitreoretinal surgeon is wrong?
By the way we started planting Coleus all over our yards a year ago, but I didn't know that's what it was named.
We've got one that's deep red almost burgundy. And I just learned you can snap a branch off and plant it and it will grow.
Nice going, Coleus.
--So, UpAllNight, are you saying that the vitreoretinal surgeon is wrong?--
No. You are confused. Read more from the surgeon. He says that it may soon be possible to grow the RETINAL CELLS from adult stem cells or embryonic stem cells. They are NOT adult stem cells. They are RETINAL CELLS!!!!!!!!!''
--It's not only wrong but a waste of our money.--
Many said that about the airplane and our military. History has proven them wrong.
It's a black and white, right and wrong, moral absolute thing.
I'm guessing that's where we differ?
--It's wrong because life and personhood begins at conception and we should not create and kill embryos for their parts--
Please insert 'some believe' into your above statement.