30 October 2007

Stem cells for dummies

Stem cells are the new black. The hot new accessory.

Stem cell research has been hailed for the potential to revolutionise the future of medicine with the ability to regenerate damaged and diseased organs. On the other hand, stem cell research has been highly controversial — within a large faction of functional lunatics — due to the ethical issues (read: religious issues) concerned with the culture and use of stem cells derived from human embryos.

OK, but what the fuck is a stem cell?

Stem cells have the remarkable potential to develop into many different cell types in the body. Serving as a sort of repair system for the body, they can theoretically divide without limit to replenish other cells as long as the person or animal is still alive. When a stem cell divides, each new cell has the potential to either remain a stem cell or become another type of cell with a more specialized function, such as a muscle cell, a red blood cell, or a brain cell. Stay with me...

There are three classes of stem cells: totipotent, multipotent, and pluripotent.

A fertilized egg is considered totipotent, meaning that its potential is total; it gives rise to all the different types of cells in the body.

Stem cells that can give rise to a small number of different cell types are generally called multipotent.

And pluripotent stem cells can give rise to any type of cell in the body except those needed to develop a fetus.

OK, but where do stem cells come from?
Pluripotent stem cells are isolated from human embryos that are a few days old. Cells from these embryos can be used to create pluripotent stem cell "lines" —cell cultures that can be grown indefinitely in the laboratory. Pluripotent stem cell lines have also been developed from fetal tissue obtained from fetal tissue after 8 weeks.

Once a stem cell line is established from a cell in the body, it is essentially immortal, no matter how it was derived. That is, the researcher using the line will not have to go through the rigorous procedure necessary to isolate stem cells again. Once established, a cell line can be grown in the laboratory indefinitely and cells may be frozen for storage or distribution to other researchers.

Stem cell lines grown in the lab provide scientists with the opportunity to engineer them for use in transplantation or treatment of diseases.

For example, before scientists can use any type of tissue, organ, or cell for transplantation, they must overcome attempts by a patient's immune system to reject the transplant. In the future, scientists may be able to modify human stem cell lines in the laboratory by using gene therapy or other techniques to overcome this immune rejection. Scientists might also be able to replace damaged genes or add new genes to stem cells in order to give them characteristics that can ultimately treat diseases! It's like Inner Space but real and without Dennis Quaid.

So why are doctors and scientists so excited about stem cells?
Stem cells have potential in many different areas of health and medical research. To start with, studying stem cells will help us to understand how they transform into the dazzling array of specialised cells that make us what we are. Some of the most serious medical conditions, such as cancer and birth defects, are due to problems that occur somewhere in this process. A better understanding of normal cell development will allow us to understand and perhaps correct the errors that cause these medical conditions.

Another potential application of stem cells is making cells and tissues for medical therapies. Today, donated organs and tissues are often used to replace those that are diseased or destroyed. Unfortunately, the number of people needing a transplant far exceeds the number of organs available for transplantation. Pluripotent stem cells offer the possibility of a renewable source of replacement cells and tissues to treat a myriad of diseases, conditions, and disabilities including Parkinson's and Alzheimer's diseases, spinal cord injury, stroke, burns, heart disease, diabetes, osteoarthritis and rheumatoid arthritis.

Scientists have only been able to do experiments with human embryonic stem cells since 1998, when a group led by Dr. James Thomson at the University of Wisconsin developed a technique to isolate and grow the cells. Moreover, federal funds to support hESC research have only been available since August 9, 2001, when Bush announced his decision on federal funding for hESC research. Because many academic researchers rely on federal funds to support their laboratories, they are just beginning to learn how to grow and use the cells. Thus, although hESC are thought to offer potential cures and therapies for many devastating diseases, research using them is still in its early stages.

Adult stem cells such as blood-forming stem cells in bone marrow (called hematopoietic stem cells, or HSCs) are currently the only type of stem cell commonly used to treat human diseases.

Doctors have been transferring HSCs in bone marrow transplants for over 40 years. More advanced techniques of collecting, or "harvesting", HSCs are now used in order to treat leukemia, lymphoma and several inherited blood disorders.

The clinical potential of adult stem cells has also been demonstrated in the treatment of other human diseases that include diabetes and advanced kidney cancer. However, these newer uses have involved studies with a very limited number of patients.

Individual states still have the authority to pass laws to permit human embryonic stem cell research using state funds. Unless Congress passes a law that bans it, states may pay for research using human embryonic stem cell lines that are not eligible for federal funding.

"Wrap it up, I'll take it."
Stem cells are unprogrammed cells in the human body that can be described as "shape shifters." These cells have the ability to change into other types of cells. Stem cells are at the center of a new field of science called regenerative medicine. Because stem cells can become bone, muscle, cartilage and other specialized types of cells, they have the potential to treat many diseases, including Parkinson's, Alzheimer's, diabetes and cancer. Eventually, they may also be used to regenerate organs, reducing the need for organ transplants and related surgeries.

Stem cells can typically be broken into four types:
Embryonic stem cells - Stem cells taken from human embryos
Fetal stem cells- ...from aborted fetal tissue
Umbilical stem cells - ...from umbilical cords
Adult stem cells - ...from adult tissue

Embryonic and fetal stem cells have the potential to morph into a greater variety of cells than adult stem cells do.

In April 2001, researchers at UCLA and the University of Pittsburgh found stem cells in fat sucked out of liposuction patients (Mmmmmm.) Previously, stem cells were found only in bone marrow, brain tissue and fetal tissue — sources that have caused both logistical and ethical problems.

Stem cells from fat have the ability to mature into other types of specific cells, including muscle, bone and cartilage, but how many other types is still unknown.

Prior to being transplanted into a person's tissue to begin regeneration of that tissue, stem cells have to go through differentiation. Differentiation is the process by which scientists pre-specialise the stem cells, almost like pre-programming the stem cells to become specific cells.

These cells are then injected into the area of the body being targeted for tissue regeneration. When stem cells come into contact with growth chemicals in the body, the chemicals program the stem cells to grow into the tissue surrounding it.

Stem cells are already being used to treat leukemia and some joint repairs. For example, a bone-marrow transplant is accomplished by injecting stem cells from a donor into the bloodstream of the patient. Stem cells from bone marrow also have the ability to repair the liver. Researchers are studying stem cells to find out if they could correct brain damage resulting from Parkinson's disease.

The next step will be to learn what influences stem cells to change into particular types of cells. Once that's known, it will be possible to grow cells that perfectly match those of the patients.

OK? Enough now, leave me alone.

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