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Thread: "Axon Jumper Cables"

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    Senior Member artsyguy1954's Avatar
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    "Axon Jumper Cables"

    Dear Dr. Young, I came across this article about interesting work being done by Dr. Douglas H. Smith at the University of Pennsilvania School of Medicine. www.sciencedaily.com/releases/2006/02/060216232219.htm will link you to it. What I found particularly intriguing was the fact that they were growing the axon bundles from nerve cells found just outside the spinal cord that are said to have retained a natural ability to regenerate. I was wondering if you could comment on this research as it relates to a possible cure for complete chronic injuries such as myself (bridging large lesions, making the right connections at each end). I was fascinated by this somewhat unorthodox work( to my mind), so I was wondering, Dr Young, how significant this work really was in the larger cure picture? ARTSYGUY 1954.

  2. #2
    Quote Originally Posted by artsyguy1954
    Dear Dr. Young, I came across this article about interesting work being done by Dr. Douglas H. Smith at the University of Pennsilvania School of Medicine. www.sciencedaily.com/releases/2006/02/060216232219.htm will link you to it. What I found particularly intriguing was the fact that they were growing the axon bundles from nerve cells found just outside the spinal cord that are said to have retained a natural ability to regenerate. I was wondering if you could comment on this research as it relates to a possible cure for complete chronic injuries such as myself (bridging large lesions, making the right connections at each end). I was fascinated by this somewhat unorthodox work( to my mind), so I was wondering, Dr Young, how significant this work really was in the larger cure picture? ARTSYGUY 1954.
    artsguy,

    Doug Smith has been working on this for several years. For example, here is a topic from January 2002
    http://carecure.org/forum/showthread...ght=doug+smith
    where I commented that i liked the idea. I continue to think that this is a good idea for regrowing outside of the peripheral nerves that can be used to replace damaged peripheral nerves. Actually, I am fascinated by Doug Smith's discovery that it is possible to accelerate axonal growth by stretching them.

    I, however, have trouble envisioning how it might be applied in the way that you suggest, for reconnecting the spinal cord, no matter how long the lesion site. Presumably what Doug Smith is doing is creating an artificial peripheral nerve with cell bodies on one end. I can't really see how these would be transplanted in the lesion site. The axons have to connect to neurons and axons from the spinal have to connect with the cell bodies.

    Several groups have used peripheral nerves to bridge the injury site. This is what Henreich Cheng used. But it is important to remember that these so-called peripheral nerves no longer have axons. When you cut a peripheral nerve out, all the axons in the nerve die and what you have remaining is the scaffolding of the peripheral nerve, through which new axons will grow.

    Regeneration requires axons to grow all the way from the place where they retract to from the injury site, through the injury site, down (or up) the spinal cord until they get to neurons far below or above the injury site. That regeneration path has several major obstacles:

    • Loss of cell adhesion molecules at the injury site. Axons like to grow on surfaces that contain certain cell adhesion molecules, such as L1. These molecules attract axons and the injury site often lacks cells expressing these molecules.
    • Chondroitin-6-sulfate proteoglycan (CSPG). The lesion site has chondroitin-6-sulfate proteoglycan (CSPG) which will stop axonal growth. CSPG demarcate tissues that are "outside" the nervous system and axons stop when they encounter this extracellular matrix protein made by macrophages.
    • Growth inhibitors on glia and oligodendroglia. The spinal cord around the injury site also have various inhibitors to axonal growth, and myelin-associated inhibitors such as Nogo. Recent studies suggest that astrocytes express ephrin. These are present in the spinal cord around the injury site.
    • Growth factors. Axons grow at fastest about a mm a day, usually slower if they encounter various growth inhibitors. Therefore, they need sustained growth factors.


    To overcome these obstacles, most scientists now believe combination therapies are necessary. To overcome the problem of cell adhesion molecules at the injury site, cells can be transplanted into the injury site. For example, olfactory ensheathing glia express L1, a cellular adhesion molecule that we recently showed will stimulate regeneration across the injury site. To overcome the problem of CSPG, we can use a enzyme called chondroitinase. To overcome the growth inhibitors, we can block Nogo or the nogo receptor. To provide growth factors, transplanted cells can be stimulated to produce growth factors. These combinational approaches are what we need to study in animal models and in clinical trial.

    Wise.
    Last edited by Wise Young; 04-13-2006 at 11:14 PM.

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