The properties and potential of
adult and embryonic stem cells:
Stem cell are the most primitive of human cells:
The most useful stem cells are found in embryos. William Walker has
"In an embryo,
cells form an outer layer which later become [sic] the placenta. but
cells located in the inner layer have not determined what they will
eventually be. These 'pluripotent' cells could become many of the 220 types of
cells in the human body." 1
There are also adult stem cells that can be removed from a baby, child
or adult. Examples include:
Hematopoietic stem cells are found in bone marrow.
Neural stem cells are found in nervous tissues.
Adult stem cells from bone marrow and nervous tissues appear to be severely limited
in potential. But cells removed from embryos have two extremely
They can divide for long periods of time in the lab to produce
more stem cells.
They can transform themselves into any of the cells present in the human body (e.g. skin
cells, liver cells, heart cells, etc.).
The potential of stem cell research can now only be guessed at:
Methods may be found whereby they could be formed into replacement
tissue and even entire organs. They may eventually be used to repair
injured or poorly functioning brains and nervous systems. New, more
effective treatments may be developed for a wide range of injuries,
disorders and diseases. To date, preliminary research looks very encouraging:
James Thompson at the University of Wisconsin
was able to make stem cells grow into human heart cells. (In order to avoid violating
congressional ban, he took extreme precautions do do his research in a room in which not a
single piece of equipment -- not even an electrical extension cord -- had been
John Gearhart of Johns Hopkins University has been able to grow nerve
cells from stem cells. 2
Researchers have been
able to implant heart muscle cells grown from stem cells into the hearts of
mice and observe them "successfully repopulate the heart tissue and
integrate with the host cells."
Researchers have coaxed stem cells to develop into a urinary
sphincter muscle for a pig. This has the potential to help people
regain bladder control -- a common problem which limits mobility and
the quality of life of the elderly.
Dr. McKay and colleagues of the National Institute of Neurological
Disorders and Stroke (NINDS), was able to take a special type of
stem cell from rat embryos and successfully treat a Parkinson's-like disease in rats.
They used neural stem cells that can only develop into nervous system
cells. Most of the test rats showed "about a 75% improvement in
motor function 80 days after they received the transplants."
In 1998, according to Focus on the Family, a fundamentalist Christian group:
"More than 50 disease advocates and scientific societies,
representing such concerns as diabetes, blindness, Parkinson's disease, glaucoma, AIDS,
Down Syndrome, cystic fibrosis, stroke, lymphoma, infertility and cancer--as well as
professional groups that focus on such issues as cell biology, aging, microbiology,
ophthalmology, cardiology, pediatrics and reproductive medicine--... sent a letter to
members of Congress urging them to support federal funding for...[stem cell] research."
If researchers can decode how cells develop into tissue and organs, then
they will begin to understand the mechanisms of "abnormal growth and
development which, in turn, could lead to the discovery of new ways to
prevent and treat birth defects and even cancer." 4
Researchers might be able to develop specific cell types, tissues, organs,
etc. from embryonic stem cells. The former could then be used to study the effects of
new drugs. This should reduce the numbers of animal studies and human
clinical trials that are required before new drugs are approved.
It is important to realize that adult stem cells derived from bone marrow
and neural tissue have very limited potential for differentiation.
"Embryonic stems cells...appear to be able to give rise to many more,
possibly all, cell types and tissues. It is this pluripotentiality that
makes the embryonic cell so promising for both a basic understanding of
differentiation and for the development of cell therapies." This
information is rarely published in articles which condemn embryo stem cell research,
but is important to remember. 5
Ethical problems with harvesting embryonic stem cells:
Harvesting stem cells from a living blastocyst in order to conduct research is strongly opposed by many people who believe that human personhood starts at conception when an ovum is fertilized and becomes a blastocyst. On the other hand, others regard the transition of human life, in the form of an ovum and spermatozoon, into a human person as happening later in gestation, -- perhaps:
when the embryo's heart begins to beat, or
the embryo first looks human, or
when the higher brain functions of a fetus become operational and the fetus becomes sentient,
For them, harvesting stem cells do not involve a major ethical conflict.
Fortunately, in early 2006, Shinya Yamanaka, a Japanese researcher and the director of Center for iPS Cell Research and Application, found a way to convert any cell in a human body into Induced pluripotent stem cells (also known as iPS cells or iPSCs). These are a type of cell which can be coaxed to develop into a wide variety of cell types, much like stem cells are able to do. The potential of this discovery may take a couple of decades to develop.
References used in the above essay:
William Walker, "Stem cell research row splits U.S.," Toronto Star, 2001-JUL-5, Page A1 & A11
"Berg leads advocacy for stem cell research." Dr Berg is Cahill Professor of Biochemistry, Emeritus, and Director of the Beckman Center for
Molecular and Genetic Medicine at Stanford University Medical Center. He is also Chairman of the American Society of Cell Biology Public Policy
Committee and Co-Chairman of the National Research Councilís Commission on Life Sciences and the Board on Biology. See: