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Stem cell research in the U.S. and the world during the past decade

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    Stem cell research in the U.S. and the world during the past decade

    Seven years ago, the discovery that human embryonic stem cells can be cultured created a great deal of excitement for three reasons. First, embryonic stem cells are robustly pluripotent and can generate all types of cells required for repair of tissues. Second, the cells can be expanded indefinitely and therefore may be used to treat many people. Third, these cells provide a powerful tool to study human diseases, particularly human genetic diseases. Despite all the talk and promise of stem cells, progress in moving stem cell therapies to clinical trials for devastating diseases such as brain and spinal cord injury, neurodegenerative disorders such as Alzheimer's and Parkinson's disease, auto-immune disorders such as diabetes and arthritis, have been intolerably slow.

    In 2000, after three years of protracted discussions with ethicists and religious leaders, the National Institutes of Health (NIH) proposed what they believed was an ethically acceptable approach to studying human embryonic stem cells. By taking stem cells from blastocysts that will be discarded from fertility clinics by their parents, NIH hoped to derive sufficient human embryonic stem cell lines for research and perhaps for therapy. Thousands of these blastocysts are being discarded from fertility clinics, whether or not their stem cells are used. However, several organizations, including the Catholic Church and pro-life groups, have rejected this argument and strongly opposed any research that involves embryonic stem cells. In 2001, President George W. Bush decided to restrict federal funding of human embryonic stem cell research to only those cell lines derived before August 9, 2001.

    President Bush's decision assumed that there was an adequate number of human embryonic stem cell lines for research. Neither proponents or opponents of embryonic stem cell research were satisfied with this decision. Proponents of embryonic stem cell research argued that there are insufficient cell lines for research or therapy while opponents pointed out that private use of embryos continued unrestricted and unmonitored. Unfortunately, the embryonic stem cell issue was mixed up with cloning and abortions. People were further confused by the term cloning of stem cells versus cloning of a human. Senator Brownback and Congressman Weldon proposed legislation to ban transfer of a nucleus from a somatic cell into an egg, one particular technique of cloning. Opponents believed that cloning is tantamount to creating an embryo to use kill it for its stem cells. They claim that embryonic stem cells are unnecessary because umbilical cord blood and adult tissues also have stem cells that may be therapeutically useful.

    Congress has been at a legislative impasse concerning stem cells for nearly four years. While most U.S. voters and many legislators would like to ban human cloning, opponents of embryonic stem cells have insisted on banning both human cloning and cloning of stem cells for therapeutic purposes. Neither side has been able to get their bills passed. Neither side wants the current situation. We currently do not have a federal law regulating private embryonic stem cell research or banning human cloning. While the federal government will not fund human embryonic stem cell research other than on cells derived before August 2001, private use of blastocysts or fetuses is not regulated nor monitored. Meanwhile, embryonic stem cell research is languishing in the United States. NIH funded only $24 million of human embryonic stem cell research in 2003, mostly to characterize old stem cell lines derived before 2001. Surprisngly, the NIH spent less than $300 million on research studying stem cells from all sources. Much of the recent progress in human embryonic stem cell research came from overseas, including the derivation of the first cloned human embryonic stem cell line and development of new methods of culturing human embryonic stem cells without contaminating them with mouse feeder cells.

    Opponents of human embryonic stem cell research claim that it is not necessary to study or use embryonic or fetal stem cells because umbilical cord blood and adult stem cells will be sufficient. Unfortunately Congress has not significantly increased funding for umbilical cord blood or adult stem cell research at NIH at the same time. The debate may have held back stem cell research in the United States. In 2003, the National Institutes of Health (NIH) spent less than $300 million on all human stem cell research. Since the current annual NIH is close to $30 billion, this amounts to about 1% of its budget to study a phenomenon that is widely acknowledged to have the potential to alleviate or cure diseases affecting millions of people. By comparison, NIH spent over US$3 billion on AIDS research. Other countries, such as England, Sweden, China, Japan, and other countries are accelerating their investment in stem cell research. Although the investment by these countries is not well documented, Singapore alone has spent over US$1 billion on stem cell research in the past 3 years. Thus, overseas investment into stem cell research has exceeded that the United States.

    One approach to assessing activity in a field of research is to examine the number of research articles published. I searched the National Library of Medicine Medline for stem cell articles. Table 1 compares the number of publications for all stem cells studies worldwide year-by-year, those that are related to human, trials, embryonic, and human embryonic stem cell studies. I searched only for articles that have abstracts (essentially eliminating news reports) and those that address stem cells as a "major topic". Several interesting trends are apparent.
    1. The number of stem cell articles doubled since 1995 from about 1600 to over 3200.
    2. The U.S. share of all stem cell publications has remained consistently about 34%.
    3. The U.S. share of embryonic stem cell studies fell from 46% in 1995 to 31% in 2004.
    4. The U.S. share of human embryonic stem cell studies fell from 67% in 1995 to 34% in 2004.
    5. U.S. publications of embryonic stem cell research fell precipitously starting in 2001.
    6. Human embryonic stem cell research account for less than 5% of all stem cell publications.
    7. Non-U.S. stem cell clinical trials has fallen from 15-28 in 1995-2000 to 7-19 in 2001-2004.
    8. U.S. clinical trial reports of stem cell therapies fell from 9-14 in 1995-2000 to 2-9 in 2001-2004.
    9. Non-U.S. embryonic stem cell studies increased from 32-71 in 1995-2000 to 90-217 in 2001-2004.
    10. U.S. embryonic stem cell studies increased from 25-32 in 1995-2000 to 43-98 in 2001-2004.

    While I have not done formal statistical analyses of these data, the trends are clear. Scientific research on stem cells doubled worldwide in the past decade. Human studies continue to outpace animal studies. Surprisingly, clinical trials reports of stem cell therapies have declined, not only in the United States but also worldwide. Embryonic stem cell cell research reports still reprsent a small minority of stem cell publications, accounting for less than 10% of the publications in 2004. In 1995, the U.S. dominated the embryonic stem cell field with about 50% of the publications in the field. The number of human embryonic stem cell research studies from non U.S. authors is now more than double that in the U.S. The United States has lost its leadership in embryonic stem cell research, at least in terms of scientific publications. The number of studies is remarkably small considering that stem cells is considered to be the most important advance in biology of the past decade. In 2004, we had less than 1000 scientific articles on stem cells. It seems that President Bush's decision to restrict human embryonic stem cell research has had a significant impact.

    The recent commitment by California, New Jersey, Wisconsin, and other states to fund stem cell research is likely to reverse these trends. This is the first time that the states have stepped in to fund biomedical research. We should see an a doubling or even tripling of U.S. research reports in the coming five years, not only in embryonic but all stem cell research. I think that the whole world will benefit from this investment. On the other hand, U.S. scientists have a huge responsibility to deliver on the promise of stem cell therapies, particularly those in those states that are committing to the research. The hopes of many people in this nation and the world rest on the shoulders of researchers who have taken on this responsibility. It is time to deliver. The ball is in our court and we have to hit as well and as hard as we can.

    [This message was edited by Wise Young on 01-18-05 at 06:19 AM.]
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