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    Sunday, August 07, 2005

    From the Land of the Ever Young:: Is the
    placenta going to turn out to be the salvation of mankind? (An argument could be made that it already is, since none of us would be here without it):

    Scientists looking for easier and less-controversial alternatives to stem cells from human embryos said on Friday they found a potential source in placentas saved during childbirth.

    They described primitive cells found in a part of the placenta called the amnion, which they coaxed into forming a variety of cell types and which look very similar to sought-after embryonic stem cells.

    In addition to being researchers at the University of Pittsburgh, the researchers are also shareholders in a company called Stemnion, a biotechnology company that runs the business side of their research. Nothing wrong with that, except that it puts added pressure on them to succeed - or at least give the appearance of succeeding.

    The news reports say that the team got their placenta cells to transform into liver, pancreas, heart, and nerve cells, but the abstract of their paper suggests they merely hypothesize this could happen. (I could be wrong. The paper may go into more detail, but it's only available at a price.) What they did do, according to the abstract and the substance of their interviews, is analyze the contents and gene expression of the cells that make up the inside lining of the amnion, the transparent sac that surrounds the developing baby. (what is sometimes called the caul.)

    What they found is rather fascinating, and certainly has the potential to be a stem cell substitute. They found two genes switched on in the amniotic epithelial cells that heretofor were believed to only be expressed in embryonic stem cells. The first is the utiltarian named octamer-binding protein 4, a protein that plays a key role in controlling the expression of other genes, such as the second gene the researchers found switched on in their epithelial cells - the more imaginatively named nanog. It is this nanog gene, or so science assumes, that is the key to a stem cell's ability to turn into just about any type of tissue cell. It is also the gene that allows the embryonic stem cell to divide in perpetuity, hence its name, derived from Tir Nan Og, the land of the Ever Young in Celtic mythology.

    However, embryonic stem cells have something else going for them that keeps them ever young, an enzyme called telomerase, which repairs a cell's chromosomes as it divides into new cells. Ominously, telomerase, although absent in most adult cells, is also present in cancer cells. It may, in fact, be the key to what turns a normal cell into a cancer cell and sends it into an out of control cycle of propagation, growing and spreading throughout the body. Thus the concern that embryonic stem cells will have the unwanted complication of causing cancer. Amniotic epithelial cells, to their credit, do not have telomerase. They would thus appear to have the best of both worlds - the genes that allow embryonic cells to differentiate into different types of tissue cells, but no association with cancer.

    There's great potential there. In fact, amniotic epithelial cells have already repaired guinea pig ears and transformed into skin. The key word, though, as in all stem cell research, is potential. There is much about the inner workings of our cells that we have yet to discover. We won't truly understand their true potential until we completely understand their biology. Until that day, their therapeutic promise remains just as ephemeral as Tir-Nan-Og.

    UPDATE: Dr. Potato emails from the Phillipines to share another superstition about the caul - that it's associated with a sixth sense. She also shares a ghost story.

    posted by sydney on 8/07/2005 11:20:00 AM 0 comments


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