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Thread: Neural Stem Cells Are Not Rejected When Transplanted

  1. #1
    Senior Member Max's Avatar
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    Neural Stem Cells Are Not Rejected When Transplanted

    Neural Stem Cells Are Not Rejected When Transplanted
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    NEURAL STEM CELLS TRANSPLANTED
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    For the first time scientists have shown that brain stem cells are immune privileged, which means that they are invisible to a transplant recipient's immune system and do not trigger the immune system to reject them.



    For the first time scientists have shown that brain stem cells are immune privileged, which means that they are invisible to a transplant recipient's immune system and do not trigger the immune system to reject them. These results, published in the July issue of Stem Cells, indicate that using brain stem cells in transplants for diseases of the eye (which is part of the brain), brain, and nervous system, may eliminate the need for tissue typing before and immunosuppressive drugs after transplants. Ultimately these findings promise to improve the success of retinal transplantations to regenerate vision for millions with macular degeneration, retinitis pigmentosa and diabetic retinopathy and brain tissue transplants to restore functioning for patients with brain disorders such as Parkinson's disease.

    "These findings are very exciting," says Michael Young, PhD, the lead author of the study and an assistant scientist at Schepens Eye Research Institute and instructor at Harvard Medical School. "Though we suspected brain stem cells might be protected in this way, this is the first documented evidence."

    Most tissues when transplanted from one body to another are seen by the recipient body as foreign and attacked by the immune system. This is because the transplanted tissue has molecules on its surface called antigens that are recognized by the immune system as "not self." If the immune response goes unchecked by drugs to inhibit the attack, it will eventually kill the transplanted tissue and reject it.

    There are sites in the body that do not mount attacks against foreign tissue because to do so would be too self-destructive. For instance, in the eye an all out immune attack would cause inflammation that would destroy delicate tissue and, with it, vision. These sites, which are known as "immune privileged," include the eye, the brain, the digestive system, and the reproductive system.

    Young, who in previous research found that brain and retinal stem cells transplanted into the eyes of mice and rats seemed to survive longer and integrate more easily into damaged retinas than other cells, suspected that these "neural stem cells" might be immune privileged. The only way for him to learn the true nature of their immune properties was to transplant these neural stem cells to a part of the recipients body that, unlike the eye, was not immune privileged already.

    He and his colleagues chose a part of the body that always rejects transplanted tissue without immunosuppressant drugs and without close tissue typing - the kidney capsule, the pouch in which the kidney is located. This pouch is commonly used to determine whether transplants can survive. Over the years scientists have tested skin, cornea and other tissues in the kidney capsule to evaluate their transplant potential.

    Young and his colleagues took brain stem cells from green mice (normal mice bred to be the color green) and placed them under the kidney capsule in other normal non-green mice. After ___ weeks/days, the team examined the mice and found that the stem cells had not been rejected in any of the mice, and, in fact, had grown into retinal tissue.

    They concluded that these neural; stems cells, did not induce the immune response and must be invisible to the immune system, at least initially. The next step was to determine if the cells possessed the antigens that most other tissues had. To test this theory, the team took other cells - specifically skin cells -- from the green mice and implanted them in the normal non-green mice. These cells were rejected, and when brain stem cells were then again implanted in the normal non-green mice, they, too were rejected. The team concluded, therefore, that the brain stem cells did possess antigens, but unless the recipient was primed or pre-immunized, the antigens were not visible to the immune system of the recipient and not rejected.

    "Understanding the immune properties of these stem cells could have an enormous effect on how we continue to look at transplantations in the future. Stem cells already have the advantage of being able to transform or differentiate into various types of cells and can be reproduced endlessly outside the body. Now we know that at least brain stem cells are immune privileged and can be used without the same worry about tissue matching that is true for other types of tissue.
    .
    Young is the director of Schepens Eye Research Institute's Minda de Gunzburg Retinal Transplantation Research Center. The center is committed, with a focus on retinal regeneration, to unlocking the mysteries of vision and finding the cures for blinding eye diseases that devastate millions in the United States and around the world.

    The study, titled "Neural progenitor cells lack immunogenicity and resist destruction as allografts" can be obtained at the Stems Cells website at http://stemcells.alphamedpress.org/

    Other members of the research team include Junko Hori, Tat Fong Ng, Marie Shatos, and J. Wayne Streilein of Schepens Eye Research Institute of Boston and Henry Klassen of the Stem Cell Research Program at Children's Hospital of Orange County in Orange, California.

    Schepens Eye Research Institute is an affiliate of Harvard Medical School and is the largest independent eye research institute in the world.



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    テつゥ 2003 Newswise. All Rights Reserved.

  2. #2
    Max

    Member posted Jul 14, 2003 02:04 PM テつ*
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    Neural Stem Cells Are Not Rejected When Transplanted
    Libraries
    Medical News Keywords
    NEURAL STEM CELLS TRANSPLANTED
    Contact Information

    Available for logged-in reporters only
    Description

    For the first time scientists have shown that brain stem cells are immune privileged, which means that they are invisible to a transplant recipient's immune system and do not trigger the immune system to reject them.



    For the first time scientists have shown that brain stem cells are immune privileged, which means that they are invisible to a transplant recipient's immune system and do not trigger the immune system to reject them. These results, published in the July issue of Stem Cells, indicate that using central nervous system stem cells in transplants for diseases of the eye (which is part of the brain), brain, and spinal cord, may eliminate the need for tissue typing before, and immunosuppressive drugs after, transplantation. Ultimately these findings promise to improve the success of retinal transplantation to regenerate vision for millions with macular degeneration, retinitis pigmentosa and diabetic retinopathy and brain transplants to restore functioning for patients with disorders such as Parkinson's disease.

    "These findings are very exciting," says Michael Young, PhD, the lead author of the study and an assistant scientist at Schepens Eye Research Institute and assistant professor at Harvard Medical School. "Though we suspected brain stem cells might be protected in this way, this is the first documented evidence."

    Most tissues when transplanted from one body to another are seen by the recipient as foreign and attacked by the immune system. This is because the transplanted tissue has molecules on its surface called antigens that are recognized by the immune system as "not self." If the immune response goes unchecked by drugs to inhibit the attack, it will eventually destroy the transplanted tissue and reject it.

    There are sites in the body that do not mount attacks against foreign tissue because to do so would be too self-destructive. For instance, in the eye an all out immune attack would cause inflammation that would destroy delicate tissue and, with it, vision. These sites, which are known as "immune privileged," include the eye, the brain, the digestive system, and the reproductive system.

    Young, who in previous research found that brain and retinal stem cells transplanted into the eyes of mice and rats seemed to survive longer and integrate more easily into damaged retinas than other cells, suspected that these "neural stem cells" might be immune privileged. The only way for him to learn the true nature of their immune properties was to transplant these neural stem cells to a part of the recipients body that, unlike the eye, was not immune privileged already.

    He and his colleagues chose a part of the body that always rejects transplanted tissue without immunosuppressant drugs and without close tissue typing -- the kidney capsule, the pouch in which the kidney is located. This pouch is commonly used to determine whether transplants can survive. Over the years scientists have tested skin, cornea and other tissues in the kidney capsule to evaluate their transplant potential.

    Young and his colleagues took brain stem cells from green mice (mice in which the gene for green protein found in jellyfish has been inserted) and placed them under the kidney capsule in other normal non-green mice.t After 4 weeks, the team examined the mice and found that the stem cells had not been rejected in any of the mice, and, in fact, had grown into neural tissue.

    They concluded that these neural stems cells did not induce an immune response and must be invisible to the immune system, at least initially. The next step was to determine if the cells possessed the antigens that most other tissues had. To test this theory, the team took other brain cells (not stem cells) from the green mice and implanted them in the normal non-green mice. These cells were rejected, and when brain stem cells were then again implanted in the normal non-green mice, they, too were rejected. The team concluded, therefore, that the brain stem cells did possess antigens, but unless the recipient was primed or pre-immunized, the antigens were not visible to the immune system of the recipient and not rejected.

    "Understanding the immune properties of these stem cells could have an enormous effect on how we perform brain or retinal transplantations in the future. Stem cells already have the advantage of being able to transform or differentiate into various types of cells and can be reproduced endlessly outside the body. Now we know that at least brain stem cells are immune privileged and can be used without the same worry about tissue matching or immunosuppression that is true for other types of tissue. . Young is the director of Schepens Eye Research Institute's Minda de Gunzburg Retinal Transplantation Research Center. The center is committed, with a focus on retinal regeneration, to unlocking the mysteries of vision and finding the cures for blinding eye diseases that devastate millions in the United States and around the world.

    The study, titled "Neural progenitor cells lack immunogenicity and resist destruction as allografts" can be obtained at the Stems Cells website at http://stemcells.alphamedpress.org/.

    Other members of the research team include Junko Hori, Tat Fong Ng, Marie Shatos, and J. Wayne Streilein of Schepens Eye Research Institute of Boston and Henry Klassen of the Stem Cell Research Program at Children's Hospital of Orange County in Orange, California.

    Schepens Eye Research Institute is an affiliate of Harvard Medical School and is the largest independent eye research institute in the world.



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    テつゥ 2003 Newswise. All Rights Reserved.
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    Posts: 5661テつ*|テつ*From: Montreal,Province of Quebec, CANADAテつ*|テつ*Registered: 07-25-01

  3. #3
    Senior Member Max's Avatar
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    Immune 'invisibility' of brain stem cells proven

    Immune 'invisibility' of brain stem cells proven


    17:10 18 July 03

    NewScientist.com news service

    Stem cells from the brain do not provoke an immune response when transplanted to different parts of another individual's body, suggests a study in mice.

    The finding could help overcome immune rejection, one of the most difficult obstacles to developing therapies to treat people with central nervous system problems such as spinal cord injuries and Parkinson's disease.

    Michael Young, at the Schepens Eye Research Institute, Harvard, and US and Japanese colleagues have shown that stem cells from the brain have a special "immune privilege" even when they are transplanted to places outside their normal location in the central nervous system.

    The team found that stem cells transplanted from the brains of mice to the kidney capsules of mice of a different strain not only survived, but developed into mature tissue.

    "These findings are very exciting," says Young. "Though we suspected brain stem cells might be protected in this way, this is the first documented evidence."

    The study is "encouraging" says Douglas Kerr, a neurobiologist at Johns Hopkins University in Baltimore, Maryland, who is researching applications of embryonic stem cells in spinal cord injury. If the results are reproducible "it would certainly make a human application more likely", he told New Scientist.


    Stern test


    Special sites within the body are known to have "immune privilege". The body's immune system does not mount an attack against foreign invaders in these areas - which includes the eye, brain and reproductive system - as these tissues are so delicate that inflammation caused by a response would destroy their function.

    As a stern test of the immune properties of stem cells from the brain, the team transplanted the cells to a part of the body - the kidney capsule - known to always reject foreign tissue unless the tissue is closely matched or immunosuppressant drugs are given.

    Stem cells were taken from the brains of so-called "green mice" which have a jellyfish gene for a green protein inserted in their DNA. These were then transplanted to the kidney capsules of normal mice.

    The green cells were not rejected in any of the mice after four weeks, and in fact had grown into neural tissue. But Young told New Scientist that the team were not surprised at this: "We really anticipated that these were going to be really cool cells from an immunological perspective."


    Identity tag


    What did surprise the team was that further tests revealed that even though the stem cells had antigens on their surface - molecules which should have identified them as foreign - they appeared to be invisible to the immune system.




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    Weblinks


    Michael Young, Schepens Eye Research Institute

    Cloning and stem cells, New Scientist

    Stem Cells




    "These really have important implications for the ultimate success of stem cell transplantation," Young says.

    Kerr agrees that tackling immunosuppression is key. He says that people with CNS disorders like stroke or spinal injury are already more susceptible to infection. "This is a high risk population to immunosuppress, so it's really been a barrier in terms of human trials," he told New Scientist.

    Another type of immune privileged stem cell is being investigated by Osiris Therapeutics in Baltimore and others (New Scientist print edition, 15 December 2001). These are called "mesenchymal stem cells" (MSCs) and are taken from bone marrow. These cells have been shown to develop into six kinds of tissue, including bone, cartilage, tendon and muscle but not the neural cells that Young's team studied.

    Journal reference: Stem Cells (vol 21, p 405)


    Shaoni Bhattacharya

    http://www.newscientist.com/news/news.jsp?id=ns99993953

  4. #4
    Senior Member Max's Avatar
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    Brain Stem Cells Are Invisible to the Immune System

    Brain Stem Cells Are Invisible to the Immune System
    Dwayne Hunter
    Betterhumans Staff
    Wednesday, July 16, 2003, 1:42:07 PM CT


    http://www.betterhumans.com/News/new...D=2003-07-16-3

    The chance of successfully treating brain, spinal cord and eye diseases with stem cells has been greatly increased with a finding that brain stem cells are invisible to the immune system and likely won't be rejected when transplanted.

    Reported in the July issue of the journal Stem Cells (read abstract), the finding suggests that using central nervous system stem cells to treat various conditions wouldn't require tissue typing before a procedure or the use of immunosuppressive drugs after.

    "These findings are very exciting," says Michael Young, lead author of the study, an assistant professor at Harvard Medical School in Boston and an assistant scientist at the Harvard-affiliated Schepens Eye Research Institute. "Though we suspected brain stem cells might be protected in this way, this is the first documented evidence."

    The findings could lead to better treatments for eye diseases such as macular degeneration, retinis pimentosa and diabetic retinopathy, as well as brain diseases such as Parkinson's.

    Immune privileged


    Typically, when cells or tissues are transplanted from one body to another, there is a strong chance that the recipient's immune system will identify them as foreign and proceed to attack them.

    The immune system picks up on molecules on the surface of the foreign cells -- antigens -- and categorizes them as "not self." Without the use of immunosuppressive drugs, the immune system will destroy the cells.

    There are areas in the body in which this doesn't occur, however, because immune system-related inflammation would damage delicate tissue.

    These areas are considered immune privileged, and they include the eye, the brain, the digestive system and the reproductive system.

    Rejection free

    Young suspected that neural stem cells taken from the brain might be immune privileged.

    To test his theory, he took brain stem cells from green mice (mice engineered to produce green jellyfish proteins that are used as a marker) and placed them in a body part of non-green mice that always rejects transplanted tissues -- the kidney capsule, the pouch in which the kidney is located.

    Young and colleagues found that after four weeks the stem cells had not only avoided rejection, but had also grown into neural tissue.

    Antigens?

    From this finding, it appeared that the neural stem cells were indeed invisible to the immune system.

    But before making this conclusion it was necessary to determine if the cells possessed antigens at all.

    To check, the researchers took other non-stem brain cells from the green mice and implanted them in the non-green mice.

    These cells were rejected, and subsequently the brain stem cells were also rejected, indicating that indeed they do have antigens.

    This finding supports the theory that brain stem cells are invisible to the immune system and won't provoke immune rejection unless a recipient is primed or pre-immunized.

  5. #5
    Senior Member bill j.'s Avatar
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    BusinessWeek, July 28

    Scientists have produced evidence that stem cells from the brain may be among the few tissues that can be transplanted from one body to another with minimal risk of rejection. These central nervous system cells lack the ability of embryonic stem cells to transform into almost any kind of tissue. But scientists at the Schepens Eye Research Institute in Boston, a Harvard Medical School affiliate, believe that the cells could be used to repair diseased spinal cords, brain tissue, and eyes, which are biologically part of the brain, without the need for immunosuppressive drugs.

    Usually, transplanted tissue is attacked by the recipient's immune system as a foreign invader. Without drugs holding the attack in check, the donor tissue is eventually destroyed. But neural stem cells appear to be immune-protected by nature -- possibly because intense inflammatory responses in the brain would do too much damage. The Schepens team, led by assistant scientist Michael J. Young, tested this hypothesis by extracting brain-stem cells from mature mice and inserting them into other mice. The transplant site was a pouch surrounding the kidney that is known to mount an aggressive immune response. After four weeks, none of the transplanted stem cells had been rejected. Instead, they grew into neural tissue.

    Young says the discovery could lead to the improvement of retinal transplants for patients with eye diseases and to brain-cell transplants for the treatment of Parkinson's disease. The study was published in the July issue of the journal Stem Cells.
    By Catherine Arnst

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