Stem cells are generally very early stage cells that have the ability to turn into other specialised types of cells. A stem cell can turn into liver cells, skin cells, nerve cells etc. These early stage cells can have differing abilities to turn into more specialised cells. What are adult stem cells? An adult stem cell is an undifferentiated cell found among differentiated cells in a tissue or organ, can renew itself, and can differentiate to yield the major specialized cell types of the tissue or organ. The primary roles of adult stem cells in a living organism are to maintain and repair he tissue in which they are found.
Some scientists now use the term somatic stem cell instead of adult stem cell. Unlike embryonic stem cells, which are defined by their origin, the origin of adult stem cells in mature tissues is unknown. Scientists have found adult stem cells in many more tissues than they once thought possible. This finding has led scientists to ask whether adult stem cells could be used for transplants. In fact, adult blood forming stem cells from bone marrow have been used in transplants for 30 years. Certain kinds of adult stem cells seem to have the ability to differentiate into a umber of different cell types, given the right conditions.
If this differentiation of adult stem cells can be controlled in the laboratory, these cells may become the basis of therapies for many serious common diseases. What are embryonic stem cells? Embryonic stem cells, as their name suggests, are derived from embryos. Specifically, embryonic stem cells are derived from embryos that develop from eggs that have been fertilized in vitro (IVF) and then donated for research purposes with informed consent of the donors. They are not derived from eggs fertilized in a woman’s body.
The embryos from which human embryonic stem cells are derived are typically four or five days old and are a hollow microscopic ball of cells called the blastocyst. Growing cells in the laboratory is known as cell culture. Human embryonic stem cells are isolated by transferring the inner cell mass into a plastic laboratory culture dish that contains a nutrient broth known as culture medium. The cells divide and spread over the surface of the dish. The inner surface of the culture dish is typically coated with mouse embryonic skin cells that have been treated so they will not divide. This coating layer of cells is called a feeder layer.
Over the course of several days, the cells of the inner cell mass proliferate and begin to crowd the culture dish. When this occurs, they are removed gently and placed into several fresh culture dishes. The process is repeated many times and for many months, and is called sub culturing. Each cycle of sub culturing the cells is referred to as a passage. After six months or more, the original 30 cells of the inner cell mass yield millions of embryonic stem cells. Once cell lines are established, or even before that stage, batches of them an be frozen and shipped to other laboratories for further culture and experimentation.
Why are embryonic stem cells important? Embryonic stem cells are of great interest to medicine and science because of their ability to develop into virtually any other cell made by the human body. In theory, if stem cells can be grown and their development directed in culture, it would be possible to grow cells of medical importance such as bone marrow, neural tissue or muscle. Stem cell technology, therefore, would permit the rapid screening of hundreds of thousands of chemicals that ust now be tested through much more time-consuming processes.
The study of human development also benefits from embryonic stem cell research. The earliest stages of human development have been difficult or impossible to study. Understanding the events that occur at the first stages of development has potential clinical significance for preventing or treating birth defects, infertility and pregnancy loss. A thorough knowledge of normal development could ultimately allow the prevention or treatment of abnormal human development. For instance, screening drugs by esting them on cultured human embryonic stem cells could help reduce the risk of drug-related birth defects.
The ability to grow human tissue of all kinds opens the door to treating a range of cell-based diseases and to growing medically important tissues that can be used for transplantation purposes. For example, diseases like juvenile onset diabetes mellitus and Parkinson’s disease occur because of defects in one of just a few cells types. Replacing faulty cells with healthy ones offers hope of lifelong treatment. Similarly, injecting ealthy cells to replace damaged or diseased cells could shore failing hearts and other organs, in theory, up.
History of stem cells In the mid 1800s, scientists began to recognize that cells were the basic building blocks of life, and that cells gave rise to other cells. In the early 1900s, European scientists realized that all blood cells came from one particular “stem cell. ” While “bone marrow transplants”-actually a transplant of stem cells-are currently used for a wide variety of diseases, and fetal nerve cells have been transplanted experimentally into the brains f people with Parkinson’s disease for the past ten years, it wasn’t until very recently that sources of cells that might be used to regenerate other organs became available.
In 1998, James Thomson isolated and grew stem cells from human embryos, and John Gearhart did the same for human germ cells. In 1999 and 2000, researchers began to find that manipulation of adult mouse tissues could sometimes yield previously unsuspected cell types; for example, that some bone marrow cells could be turned into nerve or liver cells and that stem cells found in the brain appear to be able to form other kinds of cells.
