9. Are some kinds of stem cells better than others?
The field of stem cell research involves the study of these cells for many reasons. Some scientists are examining stem cells to better understand the process of development to learn how specific cell types and specific tissues and organs are formed. Some scientists are looking at stem cells to understand what goes wrong in cells to cause various diseases. For these purposes, valuable information can be gained by studying any of the stem cell types that are currently available.

The most publicized use for stem cells, however, is their ability to form different types of cells that can be used to restore or replace damaged tissue in patients with disease or injury. From studies using mice, it was found that mouse embryonic stem cells could contribute to every tissue in the adult mouse. It is believed that human embryonic stem cells have this property, and are called pluripotent stem cells. Scientists now need to compare human embryonic stem cell lines for their potential in tissue repair to that which can be accomplished from adult stem cells.

Currently, it is not clear whether stem cells from adult tissues or umbilical cord blood are pluripotent. The comparison of human ES cells to adult stem cells is currently a very active area in research, and one that will hopefully lead to cures for tissue degenerative diseases in the future.

10. Do stem cells come from aborted fetuses?
One potential source of stem cells comes from early fetal tissue recovered during a narrow window of development. In development, an embryo is called a fetus at about 7-8 weeks following fertilization. At about 4-5 weeks of development, embryonic germ cells, the precursors to the egg and sperm cells, are found in the developing ovary or testis, structures only about 2 mm long.  In 1998, the isolation, culture and partial characterization of embryonic germ cells were reported. The cells were derived from human aborted tissue. When isolated and cultured, these germ cells were shown to have properties similar to stem cells isolated from the inner cell mass of blastocysts.

However, some evidence has suggested that embryonic germ cells may be more limited in their ability to become many different cell types because they are isolated from tissue that is further along in development (several weeks as opposed to only 4-5 days). More research will be required to understand the properties and behavior of these cells to determine their usefulness for future cell therapies. Because of various discrepancies in federal regulations, stem cells taken from fetuses are subject to different rules that stem cells derived from embryos.

11. What diseases can be cured by using stem cells?
The most promising use of stem cells is due to their ability to be modified into different Functional adult cell types and serve as a potential source of replacement cells to treat numerous diseases. Thus, any disease in which there is tissue degeneration can be a potential candidate for stem cell therapies, including conditions and disabilities as Parkinson's and Alzheimer's diseases, spinal cord injury, stroke, burns, heart disease, Type 1 diabetes, osteoarthritis, rheumatoid arthritis, muscular dystrophies and liver diseases.

In addition, retinal Regeneration with stem cells isolated from the eyes can lead to a possible cure for damaged or diseased eyes and may one day help reverse blindness. Hair stem cells have also been isolated and could help people with hair loss by allowing hair cell regeneration.

Embryonic stem cells, which can form all types of functional adult cells, provide the hope that one day such cells can produce the cells or tissues to grow entire hearts, liver and even kidneys, thus solving the problem of the shortfall of organ donors.

Adult stem cell replacement, through bone marrow transplantation with a matched donor, has been a well-established treatment for blood cancers and other blood disorders. However, significant toxicity and donor availability limit this approach to a minority of affected individuals. It is hoped that genetic alteration a patient's own bone marrow stem cells, and subsequent transplantation, will provide a viable alternative; however, these techniques for genetic manipulation must be improved before this is ready for clinical application.

Recently, new possibilities for the use of adult stem cells have emerged when researchers showed that cells from the bone marrow can give rise to specialized cells in a variety of tissues as different as blood, brain, muscle, kidney, pancreas and liver. One can imagine that one day, we will be able to isolate our own bone marrow cells, treat them and reintroduce them back into the body to renew or repair cells in a number of different organs.

12. Are stem cells currently used in therapies today?
Hematopoietic stem cells (HSCs), present in the bone marrow and precursors to all blood cells, are currently the only type of stem cells commonly used for therapy. Doctors have been transferring HSCs in bone marrow transplants for more than 40 years. Advanced techniques for collecting or "harvesting" HSCs are now used to treat leukemia, lymphoma and several inherited blood disorders.

The clinical potential of stem cells has also been demonstrated in the treatment of other human diseases, including diabetes and advanced kidney cancer. However, these new therapies have been offered only to a very limited number of patients using adult stem cells.

New clinical applications for stem cells are currently being tested therapeutically for the treatment of liver diseases, coronary diseases, autoimmune and metabolic disorders (amyloidosis), chronic inflammatory diseases (lupus) and other advanced cancers.