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Good stem cell article in the New York Times tomorrow

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  • Good stem cell article in the New York Times tomorrow

    Boston is a true powerhouse of stem cell research. The story includes Diana Bianchi, Leonard Zon, and Doug Melton. Tomorrow's New York Times has a great article by Gina Kolada.

  • #2
    Dr. Young-

    A fine article indeed but, I have a couple of (3) questions:

    The other line of research with stem cells from embryos, has a different obstacle [versus ASCR], . Although, in theory, the cells could be coaxed into developing into any of the body's specialized cells, so far scientists are still working on ways to direct their growth in the laboratory and they have not yet effectively cured diseases, even in animals.
    Is this to say that ASCs have cured diseases in humans?

    "When you are trying to do research, you look for every advantage you can," he [Zon] said. "Some embryonic stem cell lines make particular tissues better than others."

    Some, for example, might more easily turn into blood cells, and others might more easily grow into nerve cells, but there is no way to know whether there is a better stem cell line for a particular cell type without trying as many as possible, Dr. Zon said. "You would want to find the line that makes the tissue you are studying."
    Why is this? Doesn't "pluripotent" mean pluripotent?

    The challenge for scientists in the midst of a fierce political debate, many say, is to be realistic about how hard it is to develop treatments.

    Dr. Battey lists some of the challenges ahead: getting the cells to develop into exactly the adult cells that are needed, demonstrating that the adult cells can survive, preventing rejection and controlling cell growth.

    Such issues, Dr. Battey said, "need to be addressed in animal models before any thoughtful person would go into humans."
    James Battey seems a reluctant warrior - how was he chosen to head the NIH stem cell task force?



    [This message was edited by harris on 08-24-04 at 05:01 PM.]


    • #3

      Hematopoietic stem cells (i.e. bone marrow and umbilical cord blood stem cells) have been used for over 20 years to treat leukemia, autoimmune diseases, and other problems of the hematopoietic system. Neuropoiesis (the production of neural cells) has not yet achieved in after transplantation of bone marrow or other adult stem cells. Human embryonic stem cells were first isolated and successfully cultured in 1997. To my knowledge, no person has yet to be treated with embryonic stem cells.

      Pluripotent in vitro is not the same as pluripotent in vivo. When cells are grown in culture, they can be bathed in high concentrations of insulin, steroids, growth factors, and other factors that can push them to produce different types of cells. When cells are placed in tissue, they are exposed to the environment of the tissue and they may not respond that environment by producing the desired cells. In fact, most studies suggest that when bone marrow stem cells are placed in the brain or spinal cord, they are not pluripotent.

      Stem cells are almost unique in their ability to make many different kinds of cells in response to different types of signals from their environment. They must be very tightly regulated and very rarely produce inappropriate cells. For example, you would be very astonished indeed if your shoulder grew an eyeball. Note that cells can lose their growth controls of course and engage in inappropriate growth of tissues are called tumors. These growth controls and also the ability of cells to age and die (yes, aging and dying are essential abilities of cells) are among the most highly regulated and evolved functions of cells.

      The signals that the tissue produce are important. Ira Black recently showed that bone marrow stem cells will produce organ-specific cells when they are transplanted into developing fetal brain. So, they possess the ability to respond to fetal tissue signals. However, when transplanted into injured adult brain and spinal cord, they do not tend to produce neurons and glia. In contrast, McDonald, et al. showed that embryonic stem cells will produce neurons and glia when transplanted into injured spinal cord. So, embryonic stem cells are responding to some signals in injured spinal cords that bone marrow stem cells are not.

      One of the major controversies that now exist in the field is whether stem cells can "transdifferentiate". For example, Irv Weissman said in his Senate testimony that he has yet to see convincing evidence of transdifferentiation of adult stem cells. Many scientists would disagree with Weissman in this remark. For example, Angelo Vescovi in Italy reported several years ago that he is able to get bone marrow stem cells to produce neural cells. Also, several years ago, Mayer-Proschel, Mahendra Rao, and colleagues isolated cells called linear restricted neuronal precursors from multipotent neuroepithelial stem cells by sorting fetal bone marrow cells for a neural marker called nCAM. When Whittemore, et al. (2002) transplanted these cells into injured spinal cord, they produce exclusively neurons

      Diana Bianchi's results are of interest in this regard as well. What she has discovered is that fetal cells escape from the fetus into the mother during pregnancy, migrate into different organs, and produce organ-specific cells. Although some scientists have suggested that this could occur if the fetal cells simply "fused" with cells in the mother's organ and then divided, producing the same kind of cells, I think that it is very unlikely that fusion explains what she has found. She has looked at a number of these cells and find that they express only the genes of the fetus and not the genes of the mother, arguing against fusion. Note, however, that these are fetal stem cells from the fetus.

      In order for these findings to be translated to therapy, it is important that techniques for culturing stem cells are made more reliable and scaleable. A problem right now in the field is that some of the findings cannot be replicated by other laboratories, or at least not readily. This may be due to differences in stem cells isolated from bone marrow. We usually assume that all "stem cells" from bone marrow must be the same. This assumption may be wrong. In fact, if you grow bone marrow cells, you often end up with very different looking and behaving cells from batch to batch. There is a company that is focussing on this work (Neuronyx). I am hopeful that this will be achieved.