Research using stem cells is probably the most controversial area of scientific research today. The ethical controversy has resulted in delay of treatments. Stem Cells are so early in development; all uses are still experimental and will continue to be so for some time.
Researchers have since found new methods of acquiring stem cells that would not require the use of the initial controversial method. In fact the newer uncontroversial methods are proving better methods for obtaining stem cells.
Information here is to help explain as much about the subject matter as possible, to help with clarification. Topics explained will include:
Stem cells are embryonic or what is known as primitive cells. They are found in three to five day old embryonic blastocysts. At this stage of development, the blastocyst consists of 100-150 cells. Most of these cells develop into placental and supporting tissues for the embryo. The rest of these cells make up what is called the inner cell mass which will eventually develop into embryonic tissues. The inner cell mass consists of 30-40 pluripotent stem cells. In order to create stem cells that grow in cell culture dishes the inner cell mass is taken out which destroys the blastocyst at day 3 - 5 after fertilization.(Klug, 2012) The embryos are usually procured through in vitro fertilization centers where they are no longer needed and donated to research with full donor consent. They are not gotten by removing a fertilized ovum from a woman's body.(NIH, 2009)
There are three things that make stem cells. different from regular somatic cells. They are able to replicate (divide) for long periods of time, they are able to turn into specialized cells (NIH, 2009) such as cells of the muscle tissue, brain, liver and heart (Klug, 2012) and they are unspecialized.(NIH, 2009) Humans have about 200 different cell types in their adult bodies all of which are descended from stem cells.
There are different kinds of stem cells. Totipotent stem cells have the ability to develop into any mature kind of cell or tissue in the body. Pluripotent stem cells can develop into a smaller number of mature cell types. Contrast these abilities of stem cells with mature cells in the body. Cells that have already differentiated (changed) into a cell type in a tissue do not replicate indefinitely nor do they change into other cell types (Klug, 2012), and they are not unspecialized; they have very specific functions.
Several research teams in the past few years have isolated and learned how to culture pluripotent stem cells in culture dishes in the lab. These cells remain stem cells and grow indefinitely. But when scientists treat these pluripotent stem cells with different growth factors or hormones they differentiate or begin to change into cells that have the characteristics of neural, bone, kidney, liver, heart or pancreatic cells. (Klug, 2012)
Adult stem cells are also called somatic stem cells because they are found among already differentiated cells in tissues and organs that are fully mature. Scientists are still investigating the origin of somatic stem cells. Somatic stems cells are thought to be undifferentiated cells (not matured into a specific cell type). They have been located in many different tissues such as brain, bone marrow, peripheral blood, blood vessels, skeletal muscle, skin, teeth, heart, gut, liver, ovarian epithelium, and testis.(NIH, 2009)
Their role in these tissues is thought to be to differentiate into the tissue or organ they are in to repair damage to the tissue by dividing and to replace the damaged cells or to fight disease in these tissues.
Where are somatic stem cells found? They are in what scientists call a "stem cell niche" or specific area in the tissues and organs in which they are found. Some believe they comprise the outer layer of certain small blood vessels in organs or tissues. It is typical to find only a very small number of stem cells in tissues. Once somatic stem cells are removed from the body their ability to divide in the lab is limited. An active area of research is to figure out how to culture somatic stem cells in culture dishes for long periods of time so that many, many cells can be produced. In addition, figuring out how to make specific cell types from somatic stem cells in order to treat injury or disease is also very active area of research. (NIH, 2009) Indeed the whole subject of developmental molecular biology is fascinating as well.
In very recent years, scientists have made several different stem cell types without the use of embryos. Induced pluripotent stem cells (iPS) are one of the most promising. They are made using human somatic cells as the source of pluripotent stem cell lines.
To make iPS cells in the lab, scientists first isolated some somatic cells from tissue such as skin for example. Next the cells are infected with what is known as specially engineered or genetically programmed retroviruses. These retroviruses are pre-programmed to go into the cells and into the cell nucleus where the cell's DNA is and to integrate or fit into the cell's DNA according to the retrovirus's genetic instructions. In addition, the retrovirus has had several human genes added to them. When the retrovirus fits into the cell's DNA, these human genes are turned on, and the instructions they contain are carried out. The genes from the retrovirus are pre-programmed to tell the cell to make several proteins that carry instructions for turning adult somatic cells into pluripotent stem cells with the ability to divide indefinitely. These cells have been induced by retroviruses to become stem cells, so they are iPS cells. Sometimes cells that divide indefinitely in tissue culture dishes in the lab are called immortal. (Klug, 2012)
To establish embryonic stem cell lines in the lab, that fact that early embryos are destroyed in the process disturbs some people. They believe that blastocysts which are pre-implantation embryos at day 3 - 5 after fertilization in the lab or in vitro are persons and therefore have rights. On the other side of the debate are people who believe that blastocysts are too primitive, having only 100 - 50 cells and not even implanted into the uterine wall yet, to have the status of a human being with rights. This debate raises the fundamental question of what makes a human being.
The development of iPS stem cells from somatic cells has renewed the interest in stem cell research. Because these cells are developed from somatic cells and not embryos the ethical debate over their use is bypassed. In addition to making the use of human embryos to create pluripotent stem cells obsolete, the development of iPS cells may become patient specific so they can be used for transplantation without the problem of immune system rejection. Because the initial somatic cells would be harvested from the patient in the first place; they would not be rejected.
Research is still needed, but in time there will be many things Stem Cell treatments will be good for including:
A possible treatment for stem cells under Regenerative Medicine would be the regeneration of bone using cells gotten from bone marrow called stromal stem cells or skeletal stem cells. Another example is the repairing of the heart muscle following a heart attack with cardiac muscle cells. (Klug, 2012)
Cell based therapies is probably the most important prospective use of human stem cells where the generation of cells and tissues would be relatively easy. Today, we rely on donated organs and tissues to replace damaged or destroyed tissue. But unfortunately the need for donated organs and tissues outnumbers the supply. Stem cells offer a renewable supply of cells and tissues that could be used to treat many degenerative diseases by directing them to differentiate into a specific cell type. Some of the diseases that could be treated include Alzheimer's diseases, spinal cord injury, stroke, burns, heart disease, diabetes, osteoarthritis, and rheumatoid arthritis. For example, it may become conceivable to produce healthy heart muscle cells in the lab.(NIH, 2009)
The use of embryonic stem cells in the lab to study the development and differentiation of cells involved in human development could be very important. We already know that this process involves turning genes on and off. Cancer and birth defects are due to abnormal cell division and differentiation. If there were a more complete understanding of genetic and molecular processes that controlled human development it might provide insight into how cancers and birth defects arise. This in turn could suggest new therapies.
Another use of human stem cells is medication screening. New medications might be assayed for safety using pluripotent cell lines as the source of differentiated cells. The availability of pluripotent cell lines could mean the availability of a wider range of cell types than is currently in use.
NF2 is not a Cancer in that the tumors which grow as result of NF2 are generally Benign (Noncancerous), with only a chance they can become Malignant (Cancerous). However, they are similar in that NF2 like Cancers where tumors are always Malignant, are the result of repression of a tumor suppressor gene.(Kasinski, 2011)
Cell death is a normal event necessary to eliminate unwanted and potentially dangerous cells, but a missing tumor suppressor gene slows down or might stop cell death and promote tumor development.
Since encouragement of cell death is needed when a tumor suppressor gene is not working properly, stem cell treatments to fix damage done by tumors, it would be dangerous in that these treatments are more likely to result in tumor growth instead of the desired results of healing.(Garcia, 2010)
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