The potential of stem cells came to light with the findings of Ernest A. McCulloch and James E. in the 1960s. These cells are found in most multicellular organisms throughout the various developmental stages of their lives. They are often referred to as 'miracle cells' due to their ability to divide and give rise to almost any of the various specialized cell lines found in organisms. It is this fact that holds promise to revolutionize the way we view and treat certain diseases.
Where do they come from?
They are present is organisms throughout their various stages of development. However, broadly they have three sources:
Embryonic Stem Cells: These cells have the maximum potential to develop into other lines of cell types. After a zygote is formed due to fertilization of an egg by a sperm, it undergoes cell division. Within 4 to 5 days, the human embryo enters the blastocyst stage, during which the cells are differentiated to form two distinct layers. The outer cell mass is called the trophoblast, which gives rise to the placenta while the inner mass of cells is called the embryoblast, which forms the fetus. It is the embryoblast which is the source of embryonic stem cells.
Adult Stem Cells: As an embryo becomes a fetus and fetal development continues, cells become more and more specialized. The number of cell types that stem cells may develop into gets narrowed down. However, even adults retain some of these in certain tissues like those in the brain, bone marrow, blood vessels, skin, liver, and skeletal muscles. These cells differentiate to give rise to specific tissues within the organ and in some cases, the whole organ itself.
Cord Blood Stem Cells: As the name suggests, they are obtained from the cord blood and hold a lot of promise in the field of research.
Their versatility has produced an entire field of study called regenerative medicine. The greatest benefit of stem cell research is that, it holds promise for those who suffer from diseases like Parkinson's disease, diabetes, cancer and genetic disorders that have no cure. This comes from the fact that, most of these diseases are caused due to some defect that occurs during the various stages of specialization of the totipotent stem cells into specialized lines of cells. With the help of research, scientists are trying to understand the phenomenon of how organisms develop from a mass of undifferentiated cells to a dazzling array of tissues and organs. This understanding will help them to detect birth defects and also find a cure for them.
Another benefit accrues directly from the ability of these cells to develop into various types of specialized cells. This property is being researched to gauge their application to repair and regenerate lost or damaged tissue. This might solve the risks of organ transplant on the whole, as the organ would be developed from the stem cells of the individual himself.
Research in this arena is considered a boost to the field of genetic engineering by many experts. It is also viewed as bringing the fields of genetic engineering, gene therapy, and cloning closer. However, it is this very fact that has many up against it. As per its opponents, this research is the slippery slope to reproductive cloning (cloning whole organisms). Secondly, its ethics are also questioned due to the fact that, they are obtained from embryos. This is done in the blastocyst stage. Critics point that, although the cells may be used for medical purposes, it leads to the destruction of the embryo that otherwise would have developed into an individual. Hence, it is tantamount to homicide! Lack of funds, a preliminary stage of research that pose threats like unpredictable and uncontrolled cell specialization, organ transplant complications, and risks of tumors are some other aspects that add to the controversy.
Despite the controversy, the facts point to the immense benefits that these entities hold for the cure of a large number of diseases that plague mankind. It seems that the ethical issue surrounding this field will take some time to resolve. However, let us hope that the immense promise that this research holds in the field of medicines is not lost in the controversy.