United States: The Promise of Stem Cell Research

The development and application of human stem cells offers a vast number of potential applications, including the prevention, diagnosis and treatment of human diseases. While the very nature of this science raises ethical, legal, religious and policy issues, continued dialogue on this subject must be maintained. The potential applications of the science of stem cells has the ability to cure disease, enhance the quality of life and to prolong life among those suffering from a host of human diseases.

Stem cell research is controversial from an ethical standpoint, partly because critics are concerned that the cells will come from embryos. Further, some fear that this use of stem cells in order to treat disease will inevitably lead to the use of cloning to produce humans (reproductive cloning).

So what are legal considerations or ramifications of stem cell research? Although everyone is keeping an eye on the U.S. Senate, the states have been ahead of the federal government on the cloning issue for some time. Currently, 23 states have cloning legislation pending in their legislatures. Despite bans at state levels, there have been no legal challenges, probably because cloning technology has not been fully proven to be operable in human beings. However, a ban on cloning at the federal level is bound to attract a challenge.

There are other legal considerations – a bill that has passed in the House and parts of a Senate bill prohibits the importation into the United States of medical treatments developed abroad using this technology. A ban on the importation of any proven human therapies developed outside the United States because of the technology employed will inevitably create complex legal and political dynamics.

Stem cells have the ability to literally develop into every cell of the body- kidney cells, spinal cord cells, retinal cells, and the like, and thereby have the potential to replace damaged or diseased tissues, and to treat disease. Stem cells are considered to have tremendous potential in repairing damaged organs, including the spinal cord, which normally does not undergo regeneration. This ability to repair human tissue and to someday provide actual organ systems would provide hope to many with debilitating diseases.

Stem cells may be classified as embryonic or adult stem cells. Embryonic stem cells are classified as such because they are present in and derived from the developing embryo, while adult stem cells are present in the adult animal. The use of adult stem cells does not carry with it the same controversial issues as the use of embryonic stem cells. One difference between these two classes of cells is that the embryonic stem cells appear to posses a greater ability to become other cell types than that possessed by adult stem cells. However, it has recently been found that adult stem cells may also possess these same properties. It is this feature that would allow the use of a patient's own stem cells or those stem cells received from a donor to be used in therapeutic treatment.

The most obvious application of human stem cells and the one that receives the most attention is in cell–replacement therapies: to replace diseased or degenerating tissues, or to replace cell populations, such as those of the hematopoietic system (e.g. blood), that have been destroyed by chemotherapy. In theory, stem cells could additionally provide an unlimited supply of specific cell types for transplantation. To date, stem cell–derived cardiomyocytes (heart cells), neural precursors and hematopoietic precursors have been transplanted into recipient animals. Although the analyses of the long–term outcome of such experiments are limited, the findings suggest that the transplanted cells were able to function in the host animal.

To appreciate the potential importance of stem cell therapy, consider the following applications in the treatment of human disease: the use of stem cell therapy to repair damaged spinal cords; cure Crohn's disease, Alzheimer's and Parkinson's; re-grow arteries around a blockage; re-grow limbs; replace failed kidneys and hearts; cure diabetes by replacing non-functional cells in the pancreas; restore vision and hearing; treat leukemia and lymphoma that are non-responsive to normal therapy; and treat brain cancer. These are merely a few of the potential applications of this phenomenal science. In fact most of the treatments listed above have already been studied, and with promising results.

Other applications of stem cells are in the study of development in both human and animal model systems. This approach includes the identification and isolation of novel precursor cells and of medically important genes. Such genes might encode proteins that have direct therapeutic applications, such as novel growth factors, or genes that would be important targets for drug development.

Human stem cells will also be valuable as a test system for evaluating the toxicity and efficacy of new medicines or chemicals. The wide range of cell types and tissues that may develop from stem cells represent a biological system that mimics many of the complex interactions of the cells and tissues of the body, and as such, provides an attractive and valuable screening tool. This type of assay could have wide applications in the pharmaceutical, chemical, cosmetics and agrochemical industries. It has the potential to reduce the need for animal testing and to increase efficiency and safety reduce the costs of developing safe and effective drugs and chemicals.

It is clear that stem cell technology continues to revolutionize modern biology and provide unique opportunities in the understanding of both the mechanisms that control basic biological processes and in the treatment of diseases. Additional research will be necessary to apply the full therapeutic potential of this technology, but the resulting novel therapies and approaches should more than justify the effort.