- Stem cells function to replenish dead or lost cells in areas of the body,
as needed. This could occur in the organ where the stem cell resides or in other
organs. For example, bone marrow stem cells (also referred to as hematopoietic
stem cells) would be able to replenish lost blood and provide new immune cells
during infection. At the same time, these stem cells might have the capacity to
detect damaged organs and migrate to repair the injured tissues. Another example
is neural stem cells (brain). The exact role of these stem cells is not known.
It is suspected that they may play a role in brain repair following injury and
also in the replacement of dying neurons (brain cells). These subjects are the
focus of active research in labs around the world.
- In some cases,
the function of a stem cell is linked to the organ where it resides. For
example, a cardiac stem cell is considered to be a stem cell that repairs and/or
replaces only cells of the heart. Other organs are irrelevant to the cardiac
(Rosenthal N, N Engl J Med 2003;349:267; Nat Med
2002;8:647; Stewart et al, Blood 2001;98:1246; Burt et al, Blood 2002;99:768;
Myers LA et al., Blood 2002;99:872)
Cloning is a procedure where the genetic material (DNA) of an individual is
taken from an adult cell (for example, a skin cell) and then transferred into an
oocyte (an egg). Before the adult cell DNA is placed into the egg, the scientist
removes the egg's existing DNA. Thus, after the adult DNA is transferred into
the egg, the new egg has the DNA of the skin cell. To put what would occur in
perspective, if the skin cell is from Mr. Jones and the egg is from Ms. Smith,
the egg is now converted into the DNA blueprint of Mr. Jones. The eggs are then
treated chemically in the dish to develop into clones (exact replicas) of
embryonic stem cells.
Therapeutic cloning is the same as cloning, except that it is designed only
for the purpose of clinical treatment. For example, if a patient has liver
damage, it is theoretically possible to manipulate the environment in which a
cloned cell is growing so that it becomes a liver cell. If the cells are allowed
to replicate, they can then regenerate the liver.
|Why is cloning associated with stem cell research? What is
At times it is assumed that stem cell research is exclusively cloning. This
is a misconception since stem cell research covers a wide range of topics –
partly described in this FAQ section. At times it is difficult to separate stem
cell research from cloning, since the latter might generate embryonic stem
cells. To reiterate, the majority of stem cell research is exclusive of cloning.
In general, most of the research studies aim to find cures for diseases with
existing embryonic stem cells and also adult stem cells. In cases of therapeutic
cloning and embryonic stem cell research, ethical considerations and current
legal restrictions are always primary concerns of the investigator.
(Gurdon JB et al, PNAS 2003;100:11819; Mombaerts P, PNAS 2003;100:11924)
|What do we know about the ability of adult stem cells to
Some research studies show rare events by some adult stem cells to repair
tissue. Tissue repair by hematopoietic stem cells is controversial, due to
questions of cell fusion. However, hematopoietic stem cells have been
successfully used in bone marrow transplants to repopulate the immune and blood
systems. Research is ongoing to determine if adult stem cells can help repair
the damaged heart and brain, among other tissues.
(Morigi M et al, Blood
2001;98:1828; Ruggeri ZM, Blood 98:1644; Brummendorf TH et al, Exp Hematol
2003;31:475; Abedi M et al, Exp Hematol 2004;32:426; Simard AR & Rivest S,
FASEB J 2004;18:998; Sigurjonsson OE et al, PNAS 2005;102:5227)
EMBRYONIC STEM CELLS
|What is the relationship between the embryo and embryonic
The embryo is formed in early stages of fetal development and contains the
embryonic stem cell. During development, the embryonic stem cells begin the
process of forming tissues that will eventually compose the organs of the fetus.
Embryonic stem cells give rise to all of the tissues of the embryo, excluding
(Gilbert DM, Med Sci Monit 2004;10:RA99; Rossant J, Stem
Cells 2001;19:477; Nature 2001;414:122-8; Yamazaki Y et al., PNAS
|What is an “embryonic stem cell-line”? How does this
differ from a primary embryonic stem cell?
Under experimental conditions, a stem cell line is created when a single stem
cell is allowed to divide (expand). These dividing cells, if maintained
properly, will maintain their stem cell properties for a long period of time.
Primary embryonic stem cells are those cells that have been directly obtained
from the donor embryo. The expansion of primary embryonic stem cells is not
generated from a single cell, but from all that were initially obtained from the
|Why is the use of stem cells a political issue?
The use of embryonic stem cells in research is controversial because some
individuals consider a stem cell as the earliest form of human life, and they
believe they should not be tampered with. The use of adult stem cells, which are
derived at birth, is not ethically controversial.
(Vogel G, Science 2003;302:1875)
|Is embryonic stem cell research going on now?
With respect to federal funding for research, only the embryonic stem cell
lines approved for research by President Bush in 2001 may be used. Detailed
information on these cells can be found at: http://escr.nih.gov. Several laboratories around the country
also conduct embryonic stem cell research using private funding. This research
is monitored by an Institutional Review Board (IRB) within a privately funded
|Why not use adult stem cells for research and stay away
from the whole embryonic stem cell issue?
Although there are many ethical and scientific issues with embryonic stem
cells, these cells have the greatest capacity to make new tissues. To date,
adult stem cells have not been shown to give rise to the variety of tissues that
embryonic stem cells potentially can. Additionally, under certain conditions,
embryonic stem cells can form cancerous cells. For this reason, embryonic stem
cells have the potential to be studied as a model of cancer development.
USE OF STEM CELLS TO TREAT DISEASE
|How could stem cells be used to treat spinal cord injury
or Parkinson's disease?
In spinal cord injury and Parkinson’s disease, the body is unable to
naturally heal the damaged axons and dopamine-producing neurons of the spinal
cord and brain, respectively. In spinal cord injury, loss of muscle and sensory
function is seen below the site of the injury. In Parkinson’s disease,
involuntary movements and tremors result from the damaged neurons in the brain.
Current research is examining how stem cells can be used to make specific types
of nerve cells to help promote repair and regenerate new neurons within these
|What about cancer? Can stem cells be used to combat
Using stem cells to combat cancer is an interesting prospect. Research into
this area is very new and novel. One research group found that they could use
mesenchymal stem cells to deliver a cancer-toxic protein to developing tumors.
Studies like this combine stem cells and gene therapy. In this study, the
scientists engineered the mesenchymal stem cells to produce a specific protein
(gene therapy), and made use of the migrating properties of the stem cell to
deliver the “knock-out” blow.
(Nakamura K et al, Gene Ther 2004;11:1155)
|Can scientists use animal stem cells in humans and vice
We are unaware of experiments that place animal stem cells into humans.
Research studies are ongoing where human stem cells are placed into animals.
However, the studies are only experimental and they are performed under strict
regulation by the participating institution. The facts gained from these
experiments will provide valuable information for future therapies using stems
cells. Hopefully, these experiments will pave the way for getting stem cells to
the bedside of patients. It should be noted that animals undergoing these types
of studies are not allowed to survive, but are euthanized using humane methods.
(Inzunza J et al, Stem Cells 2005;23:544)
|Are there side effects following treatment with stem
There are issues that have to be considered as a person undergoes stem cell
therapy. An obvious concern is the development of unwanted tissue types in the
region undergoing treatment. For example, we would not want bone to be formed in
the liver if the goal was to regenerate the liver. Rejection is another concern,
even though current clinical practice ensures a match between donor and host.
Some adult stem cells appear to be resistant to rejection. These adult stem
cells are seriously considered for treatment. The formation of cancer cells
(teratomas) from embryonic stem cells is another major potential side effect of
any embryonic stem cell-based therapy.
(Kuramotot K et al, Blood 2004;103:4070; Kirk AD et al., Nat Med 2002;8:553;
Farag SS et al, Blood 2002;100:1935; Reviewed Exp Hematol 2000;28:479; Takahashi
K et al, Nature 2003;423:541)
|Could stem cells implanted in the brain improve learning
While there is some evidence in animal studies that learning correlates with
the birth of new stem cells, the use of stem cells in humans to improve memory
is not supported by any current research. However, it is true that if neural
stem cell therapy can be used to prevent the death of neurons in Alzheimer's
disease, then the decline in mental ability in those patients could be slowed or
(Schaffer DV and Gage FH, Neuromolecular Med 2004;5:1)
|To date are there any successful treatments of patients
using stem cells?
Yes. Bone marrow stem cell transplantation has been a standard form of care
for immune cell replacement since the late 1960s/early 1970s. Historically
speaking, the first transplant occurred in 1958 to care for a radiation
accident. To date, children with leukemia have been known to survive following
stem cell transplant. One research study showed that children with leukemia
receiving bone marrow stem cell transplantation had a 63% survival rate at 5
years following the transplant.
(Farag SS et al, Blood 2002;100:1935; Baker D et al, J Pediatr Hematol Oncol
2004;26:200; Perry AR and Linch DC, Blood Rev 1996;10:215)
|If I do not have neurological damage or some other stem
cell therapy-associated disease, why should I care about stem cells?
On the surface, stem cells might seem irrelevant to you because you lack any
of the disorders mentioned on TV, such as: spinal cord injury, diabetes etc.
However, stem cells could be important to any disease due to their unique
property of being forever ‘young’ and being responsive to change. An
understanding of these properties would lead to insights into the biology of
other diseases. For example, an individual might have a condition that could
eventually lead to a stem cell disorder such as leukemia. By understanding the
biology of stem cells, drugs could be developed to prevent the dysfunction of
CANCER AND CANCER STEM CELLS
|Is there a relationship between stem cells and
Some researchers believe that cancer is maintained by a few cancer stem
cells, while others believe that it could be a normal stem cell “gone wrong”.
Research on any type of stem cells is likely to lead to a better understanding
of cancer stem cells. Once this information is fully understood, drugs can be
developed to kill the cancer stem cells and thereby improve cancer treatment.
(Pardal R et al. Nature Reviews 2003;3: 895-902; Reya T et al. Nature
2001;414: 105-111; Al-Hajj, M & Clarke MF. Oncogene 2004, 23: 7274-7282
|What is the difference between cancer stem cells and
normal stem cells?
Cancer stem cells share many characteristics with normal stem cells. For
example, a normal stem cell can self-renew, which means the daughter cells
retain their numbers and properties/functions as the mother cells. Cancer stem
cells also maintain the ability to self-renew. A few cancer stem cells could
evade treatment and later give rise to a tumor, referred to as cancer relapse.
The tumors formed are really the progenies of the cancer stem cells. Like all
progenies of stem cells, they multiply rapidly. However, the progenies of cancer
stem cells are not like normal progenies, whose growth are tightly controlled so
that there is never too many or too few. The cancer stem cell could be
considered as a normal stem cell “gone wrong”. A major difference between the
progenies of a normal stem cell and those from a cancer stem cell is that
progenies of normal stem cells eventually form mature cells, whereas progenies
of cancer stem cells form rapidly dividing progenitor cells which do not fully
(Reya T et al. Nature, 2001;414: 105-111; Pardal R et al. Nature Reviews
2003;3:895-902; Reya T et al. Nature 2001;414:105-111)
|Why are cancer stem cells a major health problem?
Scientists are working diligently all over the world to find the signature of
the cancer stem cells. The question is: Do we have to find the signature of stem
cells in different cancers or is there a common signature? Another possibility
is that cancer stem cells and healthy stem cells share common signatures. These
questions can be explained by the infamous vend diagram illustrated here.
Signature— Could be described as an ID-tag. The tag could be on the surface
or inside the cells.
(Zhou S et al, Nat Med 2001;1028; Schwarzenberger P et al, Can Inves
2002;20:124; Yin AH et al, Blood 1997;90:5002; Murray LJ et al, Exp Hematol
1999;27:1282; Al-Hajj M et al, Curr Opinion Gen Develop 2004;14:43)
|Are cancer stem cells normally present in the body?
At this time no one knows the answer to this question. There may be a few
cancer stem cells that are part of our normal tissues that are not detected by
current clinical methods. If the cells never develop into tumors or spread to
other tissues, then this may be normal for the body. If these cells do lead to
cancer, then they become a medical problem. For this reason, it is necessary to
understand all aspects of stem cell biology. Research into the basic biology and
chemistry of cancer stem cells will allow drug companies to develop the
appropriate medication to rid the body of these few cancer stem
(Reya T et al. Nature 2001;414: 105-111)
|Can research on cancer stem cells help other health
The origin of cancer stem cells is still unclear. An appropriate analogy to
this dilemma would be: Which came first, the chicken or the egg? Just as we do
not know which came first, researchers still are unsure whether cancer stem
cells come from a normal stem cell gone wrong or the progeny of a stem cell
taking on the property of the mother stem cells.
(Reya T et al, Nature 2001;414:105; Pardal R et al, Nature Review 2003;3:895;
Al-Hajj & Clarke MF, Oncogene 2004;23:7274; Al-Hajj et al, Curr Opinion Gen
For additional information regaring cancer and stem cell research, please
visit the New Jersey Medical
School/University Hospital - Cancer Center.
UMBILICAL CORD BLOOD
|What are the current medical uses of umbilical cord blood?
Umbilical cord blood stem cells are mostly used in stem cell transplantation
to replace bone marrow cells. For reasons yet unknown, these cells pose less of
a risk for rejection when compared to bone marrow stem cells. Due to the limited
amount of cord blood, there is generally an insufficient number of cells for
(Ballen KK, Blood 2005;105:3786; Chen BJ et al., Blood
|Why do parents save their children's umbilical cord blood?
Umbilical cord blood is stored because it has a higher number of
hematopoietic stem cells than bone marrow. Mothers generally save their babies'
umbilical cord blood in case something is wrong, such as the baby needing a stem
cell transplant while he or she is still a child. If, for example, the baby
develops leukemia, he or she could be infused with his or her own umbilical cord
blood. Another point to keep in mind is that the use of umbilical cord blood
does not have the controversy associated with it that embryonic stem cells does.
(Ballen KK, Blood 2005;105:3786)
STEM CELL TRANSPLANTATION
|I have heard about stem cell transplants as a standard
treatment for decades. What is this?
Bone marrow stem cell transplants have been commonplace since the late
1960s/early 1970s. The therapy was developed as a method to replace new stem
cells in the bone marrow and has been successfully used in patients with cancer.
Scientists are able to withdraw the patient’s own bone marrow stem cells, treat
the patient for the cancer and then re-infuse the bone marrow stem cells. In
other cases, patients receive bone marrow from a matched donor.
(Parkan P & McQueen KL, Nature Rev Immunol 2003;117:108; Suzuki Y et al,
Stem Cells 2005;23:365; Askenasy N et al., Stem Cells 2003;21:200; Rondelli D et
al, Blood 2005;105:4115 ; Drouet et al, Stem Cells 19:436, 2001; Glimm H et al,
Blood 2003;99:3454; Perry AR and Linch DC, Blood Rev 1996;10:215)
A donor ‘match’ means that the host will not reject the donor's stem cells.
This could only occur if the stem cells from the donor and host have similar
genetic blueprints, as seen in family members or in twins.
|Can stem cells from one person be given to another person?
Yes, if the two people are matched. That is, cells of the host (the person
getting the cells) and donor (the person donating the cells) do not reject each
other. This type of sharing is successful in bone marrow transplantation in
(Spyridonidis A et al, Blood 2005;105:4147; Parkan P & McQueen KL, Nature
Rev Immunol 2003;117:108; Korblin M & Anderlinin P, Blood