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
--In fact, it seems to me he's SPECIFICALLY saying that earlier efforts using ES cells were problematic and that that's why they're NOT doing that, this time 'round.
--What exactly do you think is misleading? Be more specific.---
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" indicates the cells were not taken from embryos. the term "adult" is also used to indicate cells from umbilical cord blood, placenta and amniotic fluid. From under what rock did you just craw out? I did not say these were stem cells. Many freepers have requested from me that I use the term Adult in titles when referring to non-embryoic cells. I have yet to see you post any threads of value on the free republic, just comments that have no substance. You are being very silly and pathetic and have not contributed to this cause.
I see you did not challenge the accuracy of my post.
--Did you perhaps think that "fetal stem cells" were different from "adult stem cells"?--
I do not know what you are referring to.
The researchers said they wanted to pick them up a little bit earlier in the life cycle and then work them through to what amounts to an adult status ~ just as it happens.
They are attempting to avoid working with celltypes (embryonic stem cells) that cause cancer.
Because he just signed up 6 days ago.
--The stem cells --
They weren't stem cells.
You can call them what you want, but there they were ~ doing what stem cells do.
--You can call them what you want, but there they were ~ doing what stem cells do.--
No. Stem cells are undifferentiated.
Embryonic "stem cells" are undifferentiated, and to a degree they can do anything they wish, and no one seems to be able to do anything about it.
You go injecting embryonic stem cells into the brains of the handicapped they are going to develop into cancer.
You know that.
--Stem cells are NOT undifferentiated ~ --
Perhaps you should check your references ...
--Those cells really can't be differentiated from "adult stem cells". --
They can easily be differientiated from "adult stem cells" as these were differentiated and adult stem cells are NOT differentiated.
There's a continuum of development in stemcells, and various terms have been invented to more or less indicate the level of development.
Might be better to use those terms than to mess around with "differentiate" ~ particularly since that term has a quite ordinary meaning related to how I or you might see different things.
I am using NIH definitions.
--Just being consistent with the definitions posted at Wikipedia, I think you are trying to use "differentiate" in place of several other terms.--
Stem cells are primal cells that retain the ability to renew themselves through cell division and can differentiate into a wide range of specialized cell types.
Adult stem cells are undifferentiated cells found throughout the body that divide to replenish dying cells and regenerate damaged tissues.
She's already two faced...
They are not.
Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.