Stems Cells are the source of all body tissues. Growth and development of the human body arises from the stem cell and is maintained by it. Although all cells can divide or copy themselves, stem cells are unique because they can replicate and create all other types of cells. This ability of the stem cell to develop into any of the 220 cell types that make up the human body makes it a powerful tool for biological research and medicine. Scientists believe that stem cell research has the potential of leading to previously incurable diseases.
How are Stem Cells Formed?
When a sperm cell fertilizes an egg, a zygote (fertilized egg) is formed. The zygote divides itself almost immediately to form stem cells. These unspecialized stem cells have the ability to replicate (to form other stem cells) and to make all other specialized cells that make up the body tissues such as bone cells, blood cells, muscle, and skin cells. Although stem cells are present in every cell of the body even in an adult, they lose some of their ability to make a wider range of cells with age. Hence, the youngest stem cells, i.e., those found in the embryo are most useful for research and medicinal purposes.
Sources of Stem Cells
Stem Cells can be obtained for research purposes through four different methods.
Fertility Clinics: During fertility treatment, a process known as in-vitro fertilization is used in which eggs removed surgically from a female ovary are fertilized with sperms in a lab for subsequent implant in a woman's uterus. Numerous fertility clinics fuse more than one egg with sperm as a routine -- this is done to try another implant if the first one does not work. There are thousands of such "left-over" embryos in liquid nitrogen freezers in the U.S.A. And elsewhere. These embryos are the most common source for scientific research.
Aborted Fetuses: Aborted fetuses donated by women were first used for developing stem cell culture by researchers and could be another source for embryos.
Cloning: Privately funded research companies, e.g., Advanced Cell Technology of Worcester, Mass., are trying to create cloned human embryos as sources for stem cells for commercial purposes.
Made to Order: Some companies have fertilized eggs specially to create stem cell sources for research purposes. These include the Jones Institute in Virginia, USA.
Out of the 4 sources the "left-over" embryos from the in-vitro fertilization clinics are the most ethically acceptable and widely used source for stem cell research.
The methodology for cultivating stem cell lines in the laboratory (usually in vitro fertilization clinics) is briefly described below:
An egg removed surgically from a female ovary is injected with a sperm. A day after its fertilization, the egg splits into a two-celled embryo, which splits into 4 cells the day after and continues to split until, on the 4th or the 5th day, the embryo becomes a multi-celled ball called a blastocyst. At this point the embroyo (blastocyst) is very tiny and its size can be compared to the dot on an "i."
The embryo can then either be implanted into a woman's womb for starting a pregnancy or stored (frozen in liquid nitrogen) for later use; or it can be used for stem cell research. In case the embryo is used for research, the scientists remove stem cells from inside the blastocyst; thus destroying the embryo. The stem cell lines can now be cultivated in the laboratory and can be made to multiply indefinitely. Research scientists are attempting to treat or "coax" the stem cells in developing them into different kinds of cells, such as muscle cells, nerve cells etc.
The Ethical Debate
Because embryos are destroyed when harvested for research, stem cell research has become a controversial issue and become entangled with the abortion debate. The opponents of stem cell research oppose the use of anything for research that is "viable," i.e., able to grow and argue that it is wrong since it destroys human life and. Supporters of the research point out that the frozen embryos kept in the fertility clinics by the thousands would either be eventually discarded or kept frozen indefinitely. They are of the opinion that the cell research holds immense potential for benefiting mankind through development of cures for diseases such as diabetes, Parkinson's and Alzheimer's.
The opponents are in favor of research conducted through "adult" cells, such as the ones derived from bone marrow or umbilical cords instead of embryos. Most researchers, however, are of the opinion that adult cells are not as versatile or flexible as embryonic cells and far less capable of growing into different types of tissues. The development of human embryos specifically for research by a private company has provided further ammunition for the opponents. They argue that a life start at conception and any destroying of the embryo, thereafter, is morally wrong whatever the benefit.
One of the major issues in the stem cell debate is whether to allow federal funding for the research. It must be remembered that federal funding is crucial for the rapid development of stem cell research since only the availability of such funds can widen the scope of research sufficiently to accelerate the rate at which cures are found. Without federal funding most labs which receive such funds (and most big name labs in the country receive fed funds) cannot carry out stem cell research. If research is only carried out in privately funded labs, most of the country's leading scientists would not be involved in the research, lack of sharing information would lead to unnecessary duplication, and commercial pressures would restrict research in areas of high profit only. On the other hand, in federally funded research scientists are able to share findings and the work gets peer-reviewed that immensely enhances the quality of research.
Latest Status firm government position on federal funding was hanging fire when President George W. Bush took over the presidency. Due to conservative pressures and the anti-abortion lobby Bush was opposed to federal funding for stem-cell research during his campaign trail. In August 2001, the President announced the government policy on federal funding. It stipulated that federal funds would be available for research only on existing stem lines, i.e., only stem cells that were already in culture could be used for federally funded research but scientists may not isolate additional sources of stem cells.
The Human Genome complete collection of all the genetic material in an organism is called the genome, i.e., all the DNA including its genes. Genes carry information for making all the proteins required by organisms. These proteins determine, among other things, how the organism looks, how well its body metabolizes food or fights infection, and sometimes even how it behaves.
Human Genome Project - Scientific Collaboration
The Human Genome Project (HGB) is a program of international scientific collaboration that seeks to understand the entire genetic blueprint of a human being. Started in 1990, the program was due to be completed in 15 years but technological innovations and effective resource allocation have reduced the completion time to 13 years. Its main aims are to identify all the genes in the human DNA, determine the sequences of about 3 billion base pairs that make up human DNA, and to store the data in data bases. It also seeks to improve tools for data analysis, transfer genome technology to the private sector, and the ethical, legal, and social issues related to the technology.
Apart from the U.S.A., other countries involved in the Project include Australia, Canada, China, Russia, United Kingdom, France, Germany, and Japan. A rough draft of the human genome sequence was completed in June 2000, and the analyses were published in February 2001. Efforts are underway to complete a high-quality & accurate sequence of the genome by 2003.
The expected benefits of the HGB are immense. Only a few of these can be visualized at present. The project expects to provide future generations of biologists and researchers with detailed DNA information for understanding the structure, organization, and function of DNA in chromosomes. More specifically, many scientists believe that that the project has the potential to revolutionize the fields of therapeutic and preventive medicine by "providing insight into the basic biochemical processes that underlie many human diseases."
The DNA Structure
The most important component of a chromosome is the single continuous molecule of DNA. This molecule is shaped like a twisted ladder and is composed of linked chemical compounds known as nucleotides. Each nucleotide consists of 3 parts -- a sugar, a phosphate, and one of 4 bases (abbreviated A, T, C, and G). The sugar and phosphate form the two parallel sides of the ladder while the bases join in pairs as rungs of the ladder. These bases or rungs of ladder are repeated millions or billions of times throughout a genome. The human genome, for example, has 3 billion pairs of bases.