What are Stem Cells?
the stem cell type
Why are stem cells important?
Can doctors use stem cells to treat patients?
Advantages and disadvantages of using stem cells
- are stem cellsnot specializedcells that have not yet 'decided' what type of mature cell they will be.
- They can renew themselves and produce two new stem cells
- They can differentiate to produce multiple cell types.
- Ultimately, they are enhanced by expanding the number of differentiated and mature cells.
There are different types of stem cells that are produced and maintained in our system throughout life. Depending on the conditions and stages of the life cycle, these cells have different properties and functions. There are even stem cells created in the lab that could help us learn more about how stem cells differ and work. Some important things to remember about stem cells before diving deeper into this:
- Stem cells are NOT new to science
- The definition is relatively simple (see above)
- Stem cells are not all the same. There are different types of stem cells:
- Adult Stem Cells (ASCs)
- Embryonic Stem Cells (ESC)
- Induced Pluripotent Stem Cells (iPS)
- Stem cells are important in tissue homeostasis (maintenance), repair and regeneration.
- SomeStem cells (adults) are clinically useful NOW
- OtherStem cells (ESC, iPS) MAY one day be clinically useful; are already useful in fundamental research
- atStem cell types are important in research
- There are both ethical and political issues with the use of some types of stem cells. UNMC continues to work closely with federal and state legislatures, as well as the International Society for Stem Cell Research (ISSCR) to promote responsible, transparent, and uniform practices consistent with federal and state guidelines.
Stem cells are the fundamental cells of every organ and tissue in our body. The highly specialized cells that make up these tissues originally came from an initial set of stem cells formed shortly after fertilization. Throughout our lives, we continue to rely on stem cells to replace damaged tissues and cells that are lost every day, such as skin, hair, blood and the lining of the gut.
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History of stem cells
Until recently, scientists mainly worked with two types of stem cells from animals and humans: embryonic stem cells and non-embryonic "somatic" or "adult" stem cells. Scientists discovered ways to obtain embryonic stem cells from early mouse embryos nearly thirty years ago, in 1981. A detailed study of mouse stem cell biology led to the discovery in 1998 of a method of obtaining stem cells from human embryos and culturing them. cells in the laboratory. These cells are called human embryonic stem cells. The embryos used in these studies were created for reproductive purposes through in vitro fertilization procedures. When they were no longer needed for that purpose, they were donated for research with the informed consent of the donor. In 2006, researchers made another breakthrough by identifying conditions that would allow some specialized adult cells to be genetically "reprogrammed" to assume a stem cell-like state. This new type of stem cell is now known as induced pluripotent stem cells (iPSCs).
The stem cell type
Adult Stem Cells (ASCs):
ASCs are undifferentiated cells that live in specific differentiated tissues of our body and can renew or generate new cells that can replace dead or damaged tissue. You may also see the term "somatic stem cell" used to refer to adult stem cells. The term "somatic" refers to non-reproductive cells of the body (egg or sperm). ASCs are typically scarce in native tissues, making them difficult to study and extract for research purposes.
Distinct populations of ASCs reside in most tissues of the human body and generate cells to replace those lost due to normal repair, disease or injury. ASCs are found throughout life in tissues such as the umbilical cord, placenta, bone marrow, muscle, brain, adipose tissue, skin, intestines, etc. The first ASCs were collected and used for blood production in 1948. This procedure was expanded in 1968, when the first mature bone marrow cells were used in clinical therapies for blood disorders.
Studies demonstrating the specificity of ASC development are controversial; some show that ASCs can generate only the cell types of their resident tissue, while others have shown that ASCs can generate tissue types other than those in which they reside. More studies are needed to confirm the dispute.
Types of adult stem cells
- Hematopoietic stem cells (blood stem cells)
- Mesenchymal stem cells
- neural stem cells
- epithelial stem cells
- stem cells of the skin
Embryonic Stem Cells (ESC):
During days 3 to 5 after fertilization and before implantation, the embryo (called a blastocyst at this stage) contains an internal cell mass capable of generating all of the specialized tissues that make up the human body. ESCs are derived from the inner cell mass of an embryo that has been fertilized.in vitroand donated for research purposes with prior informed consent. ESCs areNeeOriginating from fertilized eggs in a woman's body.
These pluripotent stem cells have the potential to become virtually any type of cell and are only found during the earliest stages of development. Scientists hope to understand how these cells differentiate during development. As we begin to understand these developmental processes, we will be able to apply them to stem cells grown in vitro and potentially regenerate cells such as nerve, skin, gut, liver, etc. for transplants.
Induced Pluripotent Stem Cells (iPSCs)
Induced pluripotent stem cells are stem cells created in the lab, a middle ground between adult stem cells and embryonic stem cells. iPSCs are made by introducing embryonic genes into a somatic cell (for example, a skin cell), causing it to revert to a "stem cell-like" state. These cells, like ESCs, are considered pluripotent. Discovered in 2007, this method of genetic reprogramming to create embryonic cells is new and will require many years of research before it can be used in clinical therapies.
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Stem cells are important to living organisms for many reasons. In the three to five day old embryo, called a blastocyst, the inner cells make up the entire body of the organism, including all the many types of specialized cells and organs, such as the heart, lungs, skin, sperm, eggs, and other tissues. In some adult tissues, such as bone marrow, muscle and the brain, separate populations of adult stem cells generate replacements for cells lost through normal wear and tear, injury or disease.
Given their unique regenerative properties, stem cells offer new possibilities for the treatment of diseases such as diabetes and heart disease. However, much work remains to be done in the lab and clinic to understand how these cells can be used in cell therapies to treat disease, also known as regenerative or restorative medicine.
Laboratory studies of stem cells allow scientists to learn more about the essential properties of cells and what sets them apart from specialized cell types. Scientists are already using stem cells in the lab to screen for new drugs and develop model systems to study normal growth and identify the causes of birth defects.
Stem cell research continues to advance knowledge about how an organism develops from a single cell and how healthy cells replace damaged cells in mature organisms. Stem cell research is one of the most exciting areas of biology today, but as with many growing areas of scientific research, stem cell research raises scientific questions as quickly as new discoveries.
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Can doctors use stem cells to treat patients?
Some stem cells, such as those from adult bone marrow or peripheral blood stem cells, have been used in clinical therapies for more than 40 years. Other stem cell therapies include skin replacement of adult stem cells extracted from hair follicles grown to produce skin grafts. Other clinical studies on neuronal damage or disease have also been conducted using neural stem cells. There were side effects that accompanied these studies and further research is warranted. While much research remains to be done in the future, these studies give us hope for the future of stem cell research therapy.
Possible therapies using stem cells
Stem cell therapies for adults
Bone marrow and peripheral blood stem cell transplants have been used for more than 40 years as a therapy for blood disorders such as leukemia and lymphoma, among others. Scientists have also shown that stem cells reside in most tissues of the body, and research continues to learn how to identify, extract and distribute these cells for further use in therapy. Scientists hope to develop therapies for diseases such as type 1 diabetes and heart muscle repair after a heart attack.
Scientists have also shown the possibility of reprogramming ASCs so that they transdifferentiate (return to a different cell type than the existing tissue they replaced).
Embryonic stem cell therapies (ESC).
ESCs have the potential to treat certain diseases in the future. Scientists continue to learn how ESCs differentiate, and once this approach is better understood, they hope to apply the knowledge to allow ESCs to differentiate into the cell of choice required for patient therapy. Diseases targeted by ESC therapy include diabetes, spinal cord injury, muscular dystrophy, heart disease, and vision/hearing loss.
Therapies induced with pluripotent stem cells
Therapies using iPSC are interesting because the recipient's somatic cells can be reprogrammed to achieve an "ESC-like" state. Mechanisms can then be applied to differentiate these cells to generate the necessary cells. This is attractive to physicians because it avoids the problem of histocompatibility and lifelong immunosuppression, which is necessary when transplants use stem cells from donors.
iPS cells mimic most of the properties of ESCs in that they are pluripotent cells, but do not currently carry the ethical baggage of ESC research and use because iPS cells cannot be manipulated to form the outer layer of an embryonic cell. growth that is necessary for the development of the cell into a human being.
Advantages and disadvantages of using different stem cells
- Abundant donor somatic cells can be used.
- Histocompatibility problems can be avoided with donor/recipient transplants
- Very useful for drug development and development studies.
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