Stem Cell Research - Miracles on a Cellular Level

Miracles on a Cellular Level

Medical science has grown by leaps and bounds over the course of the past few years. While some breakthroughs are hailed as tremendous accomplishments, others are seen under a much more scrupulous light. Stem cell research has taken its place at the front lines of the controversy. In past years the term, "stem cell," has appeared frequently in various publications. The practice of stem cell research has come under fire in the recent past, but no one should take a stand without first knowing all the facts. One memorable, highly publicized event is when President Bush addressed the nation on whether stem cell research would be allowed to take place in the United States. The verdict was simply that no further government funding would be permitted for use in research unless an organization has already secured it. Some scientists were offended by this new rule because they understood the immense importance of researching stem cells and feared that without government support the projects will starve in deprivation. "I have concluded that we should allow federal funds to be used for research on these existing stem cell lines, where the life-and-death decision has already been made," stated President Bush, referring to the embryos that must die to be studied. Even with this government-imposed roadblock, many private donors felt the need to help with the research by donating large sums of money. The potential of these cells is beyond what anyone can imagine and their use would be beneficial to the human race.

Everything in the human body came into being by virtue of stem cells. They are unspecialized and have no tissue-specific structures to help them perform designated functions. By the same token, stem cells are incapable of carrying oxygen or nerve messages as specialized cells can do. Although stem cells do not perform specific operations, they alone have the capability to mature into any other type of cell. All stem cells can divide and renew themselves for long periods of time, a process muscle, blood, and nerve cells do not normally posses. If a population of stem cells is allowed to proliferate in a laboratory for many months, then millions of new cells will be created. The parent cells of these proliferated cells are unspecialized, and if the new cells remain unchanged, then they will be capable of long-term self-renewal. This process however is not simple by any standard; it took twenty years of research after understanding how rat stem cells proliferate to understand how to grow stem cells without specifying into certain cells. This was a very crucial step in understanding how to control the differentiation of stem cells. What scientists found was that signals both inside and outside of the cell trigger the differentiation. The cell's genes, on strands of DNA, control the internal signals that carry instructions for all of the structures and functions of a cell. Chemicals secreted by other cells, physical contact with neighboring cells, and molecules make up all of the external signals. Scientists are now working to discover if specific sets of signals cause the stem cell to differentiate for specific uses.

Stem cells are normally derived from one of two different sources, either a four to five day-old embryo or a five to ten week-old fetus. The inner cell mass of an embryo contains three basic embryonic cell types; endoderm, mesoderm, and ectoderm. If the stem cells come from the inner cell mass of the embryo, they are capable of generating an assortment of cell "sub-types" derived from the three basic embryonic cell types. Previously, scientists believed adult stem cells could be used only to generate the cell type of the tissue in which they existed. This hypothesis has since been rejected as scientists have successfully taken hematopoietic stem cells (blood forming cells in bone marrow) which were once considered unable to form neurons and discovered they can, in fact, mature into nerve cells. This conclusion has been proven numerous times with other cell types; liver cells have been manipulated to produce insulin, hematopoietic stem cells have been developed into heart muscle, and muscle stem cells have been developed into neurons. This practice of taking stem cells from one tissue and giving rise to a second is called plasticity. Plasticity has opened the possibility of using adult stem cells for cell-based therapies such as in organ transplants or new drugs.

In order to use stem cells in medicine they must first be cultivated. The most popular way of beginning the cultivation process is to use an "in vitro fertilized egg". An in vitro fertilized egg is an egg that is fertilized with sperm in a laboratory setting. Not long after in vitro fertilization has concluded, the fertilized egg undergoes several cell divisions to produce identical cells that have the potential to develop into an entire human being. After this occurs, each cell undergoes many rounds of cell division. Generally four days after fertilization, the cells begin to specialize and form a blastocyst, or a ball of cells consisting of a hollow outer layer, within which a cluster of cells is found. The outer layer of cells will ultimately become the placenta and other tissues which are needed for the support and development of the fetus. The inner cell mass will develop into the fetus, or human body. Given that it is pluripotent, the medical uses of the inner cell mass are currently under investigation. Once the blastocyst has formed, the inner cell mass will become visible, allowing scientists to extract the cells. To isolate the stem cells, a petri dish with the nutrient medium present is coated with mouse embryonic skin cells. The skin cells act as a feeder layer by releasing nutrients into the medium and also providing the stem cells with a sticky surface with which to adhere. Recently scientists have begun to develop new ways of growing embryonic stem cells without the mouse feeder cells. This is a monumental scientific advancement since it reduces the risk of viruses or other macromolecules originating in the mouse cells from being transmitted to the human cells. Over the next few days, the cells from the inner cell mass start to crowd the petri dish. When this occurs, scientists gently remove and plate the cell mass into several fresh petri dishes. The cells are replated numerous times for many months. After six or more months, the initial 30 cells of the inner mass bear millions of embryonic stem cells. A cell line composed of embryonic stem cells that have proliferated in a cell culture for six or more months without differentiating appears genetically normal. Clearly a surplus of stem cells is produced when they are cultivated. In response, scientists freeze

...