by Sara Lerman, MPH
In the last few months, the controversy over stem cell research has been brought into the spotlight by the presidential campaign and by the passing of Christopher Reeve, a leading advocate for increased funding of stem cell research. Most medical scientists say that stem cell research and therapy hold promise for treatment, and possibly the cure, of a wide range of diseases that affect millions of people. This is a controversial subject, however, that raises ethical, religious, and legal questions.
Stem cell research explores the fundamental and basic mechanisms of the cell and how tissues develop, specialize, and differentiate. Information from basic research may then be used to further explore the causes of diseases that result from cell damage or degeneration and from cell death. The final step in this process, stem cell therapy, is the translation of this information into medically useful interventions. Stem cell therapy attempts to replace cell loss and induce repair mechanisms by having the healthy cells become integrated into a patient’s body and begin to function like the patient’s own cells.
What Are Stem Cells?
Stem cells are defined as the “primitive cells,” the “building blocks” of life which give rise to different kinds of tissues, or other cells in the body. They are of particular value because they are self-renewing in the body, as well as in the laboratory, so that large quantities can be reproduced. Through the isolation and direct manipulation of cells, scientists are identifying and regenerating cells that can be transplanted in the body to replace damaged or dead cells in diseased organs. It is hoped that stem cells can generate specific tissues in the body, such as heart or kidney tissues, which could then repair damaged or diseased organs. This process is similar to the procedure of organ transplant. Stem cell therapy, however, consists of the transplantation of cells, rather than organs. Scientists primarily work with two kinds of stem cells from animals and humans: adult stem cells and embryonic stem cells.
Adult stem cells renew themselves continuously in some organs of the body, such as blood stem cells, thereby providing a source of new cells for those organs. Historically, they have been successfully used to treat some diseases. For example, bone marrow stem cells are used to replace the blood cells of patients with leukemia and other cancers. Although there has been some success with the use of adult stem cells to treat disease, there are some produce a stem cell “line.” Studies using embryonic cells transplanted from animals have been conducted over the last 20 years and have provided some important research breakthroughs. Research that has used human embryonic cells, however, has become available only recently and provides the most rapid route to finding results.
Embryonic stem cells have the versatility and potential to become almost any type of cell or tissue and they are easy to isolate and grow in laboratories. For this reason, scientists believe that embryonic stem cells significant limitations. Adult stem cells are present in very small quantities; isolating them is difficult; multiplying them outside the body has not yet been possible in most cases; and they may only be able to develop into a limited number of cell types. The general consensus is that adult stem cells seem to be less versatile than embryonic stem cells.
Embryonic stem cells are found in embryos 5 or 6 days after fertilization when the embryo becomes a hollow sphere called a “blastocyst,” which contains about 200 stem cells. Stem cells that are removed from the blastocyst are placed into a culture dish to have a much greater value and potential than adult stem cells.
Nuclear Transplantation
Another area of research involving stem cells relates to nuclear transplantation. This technique involves the process of replacing the DNA of an unfertilized egg cell with the DNA from a patient’s somatic cell, and then triggering the egg to divide to form a blastocyst. The stem cell that would be derived from such a blastocyst would thus contain the patient’s own DNA. This technique would genetically match stem cells to a patient’s DNA, replace or repair damaged tissue, and avoid the often common result of tissue incompatibility and the body’s rejection of transplanted tissues generated from stem cells.
The Controversy
Human embryonic stem cell research has spurred a great deal of controversy and heated debate about age-old ethical and legal issues, such as when life begins and the rights of an embryo. Controversy is also specifically related to the source of embryonic cells. Some will only accept, or oppose, the use of stem cells derived from embryos created specifically for research from eggs and sperm donated by volunteers who have no reproductive intent. Others may only accept, or oppose, the use of cells derived from embryos produced in fertility clinics that are no longer needed for reproductive purposes.
In August 2001, President Bush announced that he would approve federal financial support for research that uses embryonic stem cells already being cultured in laboratories, but would prevent funding for the development of new lines that involve the creation or destruction of additional embryos. Before the August 2001 announcement, there were about 60 stem cell lines identified by the National Institutes of Health (NIH) as having been derived from excess human embryos. Although the NIH is considered a vital funding source, there is no federal law that prohibits the private sector from creating stem cells by in vitro fertilization or by nuclear transplantation for the purpose of research. Most states do not prohibit private funding for the development and use of human embryonic stem cells.
Advocates and stem cell researchers believe that federal funding of basic research on stem cells would hasten progress in this field more than private funding. Funding from the private sector is often tied in to commercial applications, such as new drugs, and therefore, companies in the private sector may not fund studies in basic stem cell research.
While there is much that is being learned from using existing stem cell lines, there are still many obstacles that need to be overcome. For example, there is concern about potential change in the genetic and biological properties of these stem cell lines, as over time, all cell lines in tissue culture change. And when the cells are implanted into an individual, the cells must be made to function in accord with the body’s natural cells and avoid rejection. These are just a few of the challenges that lie ahead.
Stem cell research, and the eventual therapies it will hopefully result in, are still in their infancy. While there are numerous challenges, many in the scientific community believe that stem cell therapy will revolutionize medicine and make the possibility of cures for devastating diseases such as cancer, Parkinson’s disease—and even spinal cord injury—a reality.
Sara Lerman, MPH, is Program Manager for American Association of Spinal Cord Injury Nurses.
