FREQUENTLY ASKED QUESTIONS ABOUT STEM CELLS
Much of the information below is described in-depth in the National Institutes of Health, Stem Cell Information
What is a stem cell?
They are in a sense, the cells from which all else “stems”. Bioethicist Alexander Capron of the World Health Organization described a stem cell as, “the foundation of organisms, the stalk from which everything buds and branches.” Stem cells may be either embryonic or adult (somatic). As a fertilized egg divides, the multiplying embryonic stem cells differentiate into or become all of the diverse tissues of the body, such as lungs, liver, brain, hair, heart.
Stem cells have the potential to:
- Replace cell tissue that has been damaged or destroyed by illness,
- Replicate themselves over and over for a very long time,
- Help scientists understand the origin of human biological development,
- Help scientists understand healthy and diseased cells in hope of creating treatments and cures for many diseases.
The National Institutes for Health (NIH) notes that 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 for as long as the person or animal is still alive. When a stem cell divides, each ‘daughter’ 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. A more detailed primer on stem cells can be found at http://stemcells.nih.gov/info/basics.”
What role do stem cells play in human biology?
Stem cells regenerate lost or damaged cells. For example, when a person gives or loses blood, stem cells will replenish the supply. If the skin is damaged, it generates new skin cells as it heals. Since stem cells have the ability to generate new tissue specific cells, this area of medicine is often called “regenerative medicine”.
All animals, including humans, start from one cell, which results from fertilization of an egg by a sperm. The resulting one cell contains all of the animal's genetic material or DNA and is capable of developing into a complete organism. As the cell divides, the resulting cells or daughter cells, will still contain all of the DNA, while at the same time becoming specialized, and more restricted in their ability to become all types of organs and tissues.
Are stem cells currently used to treat disease?
Yes, adult or somatic stem cells have been used for some time to treat disease. For example, blood stem cells created in the bone-marrow are used in “bone-marrow transplant" as a common therapy for various blood based diseases such as leukemia and aplastic anemia. Organ transplantation also uses stem cell technology.
What are the stages of human development?
The National Bioethics Advisory Commission (NBAC) provided a simple outline of human development:
1. the developing organism is a zygote during the first week after fertilization,
2. the organism is an embryo during the 2nd – 8th weeks of development
3. the organism is a fetus from the 9th week of development until the time of birth.
A zygote could be created without implantation of the fertilized egg in a woman’s uterus. This is commonly done through Assisted Reproductive Technology (ART) using in-vitro fertilization (IVF) procedures (please see below). The zygote is essentially a group of cells called a “blastocyst”. Embryonic stem cells are obtained from zygotes (blastocysts) or a fertilized egg within six to 12 days after fertilization.
What is an embryonic stem cell?
Embryonic stem cells come from the “inner cell mass” of a group of cells called a blastocyst. The blastocyst is an early stage of development known as the “zygote” that occurs within the first 4-6 days after fertilization. Once the “inner cell mass” or embryonic stem cells are removed from the blastocyst, the cells may be kept alive in a petri dish under specific laboratory conditions. Such cells are multi-potent meaning they may become any cell in the body.
What is an adult or somatic stem cell?
They are stem cells found in the tissue and organs of organisms that have the potential to become their tissue of origin. Essentially, adult or somatic stem cells are stem cells that will have a specific occupation within the organism, for example, embryonic stem cells that differentiate or become heart stem cells will form heart tissue. Such cells have the ability to replenish or maintain tissues that have a limited life span, such as skin and intestines. For example, the human intestine sheds and replaces 100 billion cells daily by dividing stem cells that generate replacements for the short-lived cells. Thus, adult or somatic stem cells are “differentiated” or specifically assigned to the creation or replenishing of cells in specific tissues or organs.
The NIH notes, “One important point to understand about adult stem cells is that there are a very small number of stem cells in each tissue. Stem cells are thought to reside in a specific area of each tissue where they may remain quiescent (non-dividing) for many years until they are activated by disease or tissue injury. The adult tissues reported to contain stem cells include brain, bone marrow, peripheral blood, blood vessels, skeletal muscle, skin and liver.”
To date, there is no proven technique to turn adult stem cells into any other cell other than their tissue of origin. For example, there is no proven method to turn blood stem cells into brain stem cells. On the other hand, embryonic stem cells have the ability to turn into any type of cell and therefore, have more potential scientific utility.
What is differentiation?
Differentiation is the process in which a cell, such as a stem cell, specializes in the creation or replenishing of cells in specific tissues or organs in the body. The process occurs through the activation (“turning on”) or inactivation (“turning off”) of specific genes in the cells. The turning on/turning off process results in the development of cells that are assigned specific tasks such as creating the heart or replenishing the lining of the intestine.
What are the sources for embryonic stem cells?
1. Excess fertilized eggs from in-vitro ferilization clinics,
2. Using IVF procedures with donated oocytes and sperm to make blastocysts for research, or
3. Somatic Cell Nuclear Transfer (SCNT)
What is Assisted Reproductive Technology (ART)?
Assisted Reproductive Technology or ART includes all treatments or procedures that involve the laboratory handling of human eggs and sperm for the purpose of fertilizing an egg and helping a woman become pregnant.
What is In Vitro Fertilization (IVF)?
Human IVF occurs through assisted reproductive technology (ART) by extracting a woman’s egg (oocyte) from her body and fertilizing it in a laboratory, such as a test tube or in a petri dish, and then transferring a resulting fertilized egg into the woman’s uterus. Commonly, ten eggs are extracted and fertilized for an IVF procedure. The fertilized eggs are typically frozen before possible uterine implantation. The Society for Assisted Reproductive Technology estimates 35% of stored embryos likely would not survive the thawing process. Some women may undergo multiple IVF extractions of eggs.
What happens to unused fertilized eggs that result from IVF?
There are approximately 400,000 stored fertilized eggs in IVF clinics. Tens of thousands of fertilized eggs are routinely destroyed when couples finish IVF treatment or because of defects in the fertilized eggs.
Many people who undergo IVF treatment voluntarily donate the residual fertilized eggs for research after appropriate informed consent. According to the NIH, 20% of eggs fertilized using IVF result in a successful pregnancy. In comparison, approximately 30% of normally conceived fertilized human eggs result in successful pregnancies. Fertilized eggs created through IVF that are not transferred to a woman are frozen and stored indefinitely or ultimately destroyed after the individuals using IVF no longer want or need the fertilized eggs. These surplus or unuseable fertilized eggs could be used for research.
What is somatic cell nuclear transfer (SCNT)?
The nucleus of an unfertilized egg (oocyte) is removed in a laboratory and replaced by, for example, a donated somatic cell, such as a skin cell. The process results in a “fertilized” egg but not in an embryo to be implanted in a woman’s womb.
After five days, scientists remove the “inner cell mass” as they would to obtain embryonic stem cells as described above. The resulting stem cells can potentially develop into specialized cells under appropriate laboratory conditions. The cells could help scientists understand human biology and disease as well as serve an important role in drug testing. Because the nucleus would have the same genetic material of the somatic cell (ex: skin cell) donor, this technology could overcome the problems associated with rejection of foreign tissue that is not recognized by the recipient’s immune system.
What is reproductive cloning?
Reproductive cloning uses the same technology as SCNT but with a goal of creating a fetus. The technology was used to create “Dolly” the sheep. Reproductive cloning of humans is against the law in California and many other States.
Is there oversight of stem cell research at UCLA?
Yes. There are several committees that oversee stem cell research at UCLA. The UCLA Institutional Review Board (IRB) www.oprs.ucla.edu is required by California law to review all stem cell research with human subjects. The IRBs are composed of faculty, community representatives and consultants representing special subject populations. The Boards ensure informed consent for voluntary participation in research is obtained, when required, that risks to subjects are minimized and benefits maximized to the extent possible, and that there is justice in the identification and recruitment of subject populations. The IRBs are governed by Federal and State regulations and UCLA policy.
UCLA also convenes a special embryonic stem cell review committee called the Embryonic Stem Cell Research Oversight (ESCRO) committee to provide oversight of human embryonic stem cell (hESC) research and other stem cell research as required by California law and the California Institute for Regenerative Medicine (CIRM) regulations in order to ensure that UCLA research meets the highest scientific and ethical standards. The goals are achieved in collaboration with the UCLA Administration, the UCLA Institutional Review Boards (IRBs), other applicable compliance committees, and the participation of the research community.
What is Proposition 71?
Proposition 71 is the California initiative approved by 59% of voters in the November 2004 election. The initiative:
- Established the California Institute for Regenerative Medicine (CIRM) http://www.cirm.ca.gov/ to regulate stem cell research and provide funding, through grants and loans, for such research and research facilities
- Established a constitutional right to conduct stem cell research; prohibits Institute's funding of human reproductive cloning research
- Established an oversight committee (Independent Citizens Oversight Committee [ICOC]) to govern the CIRM
- Provided a General Fund loan up to $3 million for the CIRM's initial administration/implementation costs
- Authorized issuance of general obligation bonds to finance CIRM activities up to $3 billion subject to annual limit of $350 million
- Appropriated monies from the State General Fund to pay for bonds.
Additional reading:
1. National Bioethics Advisory Commission, Volume 1, Ethical Issues in Human Stem Cell Research: Report and Recommendations, September 1999.
Volume 2, Religious Perspectives, June 2000.
Volume 3, Commissioned Papers, January 2000. http://www.georgetown.edu/research/nrcbl/nbac/pubs.html
2. National Institutes of Health, Stem Cells: Scientific Progress and Future Research Directions, June 2001; http://stemcells.nih.gov/info/scireport/
3. Committee on Guidelines for Human Embryonic Stem Cell Research, Guidelines for Human Embryonic Stem Cell Research, National Research Council, Institute of Medicine of the National Academies, Washington DC, 2005; www.nap.edu
4. International Society for Stem Cell Research, http://www.isscr.org/
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