STEM CELLs Are a special variety of cells that have been identified in some multicellular organisms. Most of the cells in the body transform into and reproduce only the parent cell type; stem cells, in contrast, have the capacity to transform into multiple cell types throughout their life spans. We also know that stem cells are of two types—adult and embryonic. As the name indicates, adult stem cells are found in adults and serve to replenish cells in certain parts of the body where they are lost because of a continuous turnover for a variety of reasons.
Examples of such tissues include skin, bone marrow, and the lining of gastrointestinal tract, and so forth. Embryonic stem cells, in contrast, are found in the body at a very early stage of its development and play an important role by forming different tissues of the body.
Since the 1960s, when the presence of stem cells was first elucidated in some cancers, these cells have been the center of attention for scientists. However, it was only in 1981 that researchers were able to isolate these cells in tissues derived from mice; since then, murine models have been a major source of our understanding regarding the functioning of these fascinating cells. Mouse stem cells have provided invaluable information regarding how stem cells proliferate and are affected by different external, as well as internal, growth factors during the process of differentiation. These growth factors, which are mainly proteins in nature, affect stem cells’ behavior at different stages. Because there is a lot of similarity between the DNA of mice and that of humans, the two species make excellent candidates for research and help us appreciate the ways they might work in human beings. Furthermore, mice offer the advantage of being raised at a lower cost with relative ease and do not need any special environment when compared with other animal models. They also have a short generation time, thus enabling researchers to study successive generations with respect to a particular trait or disease without having to wait for long periods of time.
The photo shows a human embryonic stem cell colony on a mouse embryonic fibroblast feeder layer.
There has been a lot of debate regarding ethical issues surrounding human stem cell research, especially when it involves embryonic stem cells, because embryos need to be killed at a very early stage of their development to extract them. This approach raises the question of taking a human life and at the same time offers the prospect of providing researchers with the material that might one day be used as a treatment for many diseases. The gray area between the two doctrines has been the source of a big dilemma for the scientific world. Under the present legislation, the National Institutes of Health does not fund studies that involve human embryonic stem cell lines derived after August 2001, and that is where mouse stem cells come in.
They have played a pivotal role by being free of such controversies. Mouse stem cells have not only provided insight into some of the core principles regarding human development but have also shed light on novel ways to scrutinize the pathology of various medical disorders. They also offer hope for innovative modalities of treatment for diseases with significant morbidity and mortality despite currently available therapies.
The most exciting prospect in futuristic therapies involving stem cells is in the treatment of Parkinson’s disease, a condition in which dopamine-producing neurons at a specific area of the brain degenerate. Scientists have shown from experiments in mice that stem cells could be made to differentiate into nerve cells and that these cells, when transplanted into the brains of mice lacking the dopamine-producing neurons, started producing dopamine and hence produced improvement in the severity of the disease. Other researchers have shown that stem cells improved cardiac function in mice that underwent myocardial infarction experimentally, by forming new muscle tissue and vessels.
If such techniques were perfected for humans, they would revolutionize the lives of many patients who suffer because of the lack of availability of suitable modalities of treatment. Stem cell therapy thus offers a ray of hope for such people and would have a significant effect on their lifestyle. Scientists have also been successful in transforming embryonic stem cells into corneal cells in mice, which could then be transplanted and thus used to treat corneal injuries.
In the past, it was indicated that the skin contains stem cells that could be used to regenerate new skin cells that could be used for skin grafting and to treat baldness; recently, however, scientists have gone a step farther and have transformed skin cells in mice into embryonic stem cells. This technique, if perfected for humans, would open new arenas for stem cell research because it does not involve the loss of life on the part of human embryos.
There have also been reports of successful studies using mice models in which stem cells grew into muscle cells that could be used to replace diseased skeletal muscle. Similarly, insulin-producing pancreatic cells have been regenerated that could open a new avenue into how we can treat diabetes mellitus. All these prospective treatments could eventually materialize and potentially be used in the future to treat a variety of disorders. Furthermore, advances in gene therapy and stem cell research have enabled scientists to make disease models in mice that, in turn, have greatly enhanced our ability to understand the disease process.
Mouse stem cells can also prove useful in comprehending the difficulties that we might encounter in the future. One such example would be that of immune intolerance resulting from a mismatch between the donor and the recipient genes. In addition, stem cells have also shown aberrant growth and a potential to transform into cancerous tissue. Such problems would limit their clinical applications; further research on mouse stem cells would permit us to analyze the intricate physiological processes that govern their behavior, helping us in finding solutions to these dilemmas.
Although modern science has taken big strides in stem cell research by studying mouse models, there are still hurdles in the process of identification, growth, and differentiation of stem cells that need to be overcome to achieve much-needed progress in this field. Mouse stem cells, however, have given us clues about ways to approach similar cells found in human tissue and thus have laid the basis for research that might one day change the principles and practice of medicine.
