Definition: A stem cell is a "generic" cell that can
make exact copies of itself indefinitely. In
addition, a stem cell has the ability to produce
specialized cells for various tissues in the body -such as heart muscle, brain tissue, and liver tissue.
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Stem cells can be classified into three broad
categories, based on their ability to differentiate
Totipotent stem cells are found only in early
embryos. Each cell can form a complete
organism
Pluripotent stem cells exist in the
undifferentiated inner cell mass of the
blastocyst and can form any of the over 200
different cell types found in the body.
Multipotent stem cells are derived from fetal
tissue, cord blood, and adult stem cells.
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Embryonic stem cells- these are obtained from
either aborted fetuses or fertilized eggs that are
left over from in vitro fertilization (IVF).
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They are useful for medical and research
purposes because they can produce cells for almost
every tissue in the body.
Adult stem cells - these are not as versatile for
research purposes because they are specific to
certain cell types, such as blood, intestines,
skin, and muscle.
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Both children and adults have them.
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Adult stem cells are found in the human body
and in umbilical cord blood.
The most well known source of adult stem cells
in the body is bone marrow but they are also
found in many organs and tissues; even in the
blood.
Adult stem cells are more specialized since
they are assigned to a specific cell family such
as blood cells, nerve cells, etc.
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Embryonic stem cells come from a five to six-day-old embryo.
They have the ability to form virtually any type of cell found
in the human body.
Embryonic germ cells are derived from the part of a human
embryo or fetus that will ultimately produce gametes (eggs
or sperm).
Adult stem cells are undifferentiated cells found among
specialized (differentiated) cells in a tissue or organ after
birth. Based on current research, adult stem cells appear to
have a more restricted ability to produce different cell types
and to self-renew than embryonic stem cells.
Umbilical cord blood stem cells are used to treat a range of
blood disorders and immune system conditions.
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Human embryonic germ cells (EG cells) normally
develop into eggs and sperm. They are derived from a
specific part of the embryo called the gonad ridge, and
are isolated from fetuses older than 8 weeks of
development.
One advantage of embryonic germ cells cells is that
they do not appear to generate tumors when
transferred into the body, as embryonic stem cells do.
One of the greatest issues facing researchers is that the
derivation of EG cells results from the destruction of a
foetus. EG cells are isolated from terminated
pregnancies and no embryos or foetuses are created for
research purposes.
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Cells found early (less than 2 wks.) in the
development of an embryo
Embryonic stem cells are the most versatile
because they can become any cell in the body
including fetal stem cells and adult stem cells.
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Cloning has brought a revolution in the world
of medical science. This process of creating
embryos to produce stem cells holds great
promise for treating life-threatening diseases
like diabetes, Parkinson’s, and many types of
cancers.
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Step 1- The scientists first isolate the nucleus
from an egg cell, which is unfertilized.
Step 2- The scientists gently push the needle
through the hard shell around the egg cell. This
shell is known as zona pellucida and it
safeguards the egg while it moves down the
fallopian tube and enters the uterus.
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Step 3- After removing the nucleus of the egg
cell, it is discarded.
Step 4- After removing the nucleus of the egg
cell, it is discarded. After several years, this
donor cell can be a skin cell taken from an ill
patient whom doctors wish to treat by making
use of the patient’s own cells that are grown in
culture. Once again, the scientists ease the
needle tip through the zona pellucida and
penetrate deep into the cell without the
nucleus. Here, they inject the donor nucleus.
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Step 5- After completion of the nuclear transfer
process, scientists “stimulate” the unfertilized
egg cell with the help of electrical or chemical
treatment, which activates cellular division.
Step 6-Eighty-four hours after the
commencement of division, the multiplying
cells generate a mass of cells known as
blastocyst, which is similar to the size of egg
cell
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Step 7- When the blastocyst is placed onto a dish that promotes tissue
culture, various types of cells get a favorable condition to grow the following:
embryonic stem cell colonies from the internal cell mass, cells that are
membrane-like, and placental cells. Out of these, the stem cells are the only
one to have the capacity of continuing growth under these conditions. In due
course of time, they are going to multiply to such an extent that scientists can
expand their culture to several dishes. This process is called “passaging.”
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Step 8- The human as well as the mouse embryonic stem cells
produce dense colonies having hundreds of individual cells,
which look amazingly similar and are difficult to distinguish even
by a trained eye. There are “feeder cells” too, which are actually
connective-tissue cells of mouse. The cloning is done. Scientists
use these clones to study the growth of specific tissues and cells.
These specialized tissues and cells developed from embryonic
stem cells through nuclear transfer hold a tremendous potential to
treat big diseases, hence, this process is also referred to as
“therapeutic cloning.”
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The history of stem cell research had a benign,
embryonic beginning in the mid 1800's with the
discovery that some cells could generate other
cells.
The history of stem cell research includes work
with both animal and human stem cells.
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A prominent application of stem cell research has been
bone marrow transplants using adult stem cells.
The early 1900's physicians administered bone marrow
by mouth to patients with anemia and leukemia.
Although such therapy was unsuccessful, laboratory
experiments eventually demonstrated that mice with
defective marrow could be restored to health with
infusions into the blood stream of marrow taken from
other mice.
This caused physicians to speculate whether it was
feasible to transplant bone marrow from one human to
another (allogeneic transplant). Among early attempts
to do this were several transplants carried out in
France following a radiation accident in the late 1950's.
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Marrow transplants in humans was not attempted
on a larger scale until in 1958 Jean Dausset, a
French medical researcher, identified the first of
many human histocompatibility antigens.
These proteins, found on the surface of most cells
in the body, are called human leukocyte antigens,
or HLA antigens. These HLA antigens give the
body's immune system the ability to determine
what belongs in the body and what does not
belong.
A bone marrow transplant between identical twins
guarantees complete HLA compatibility between
donor and recipient. These were the first kinds of
transplants in humans.
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It was not until the 1960's that physicians knew enough
about HLA compatibility to perform transplants
between siblings who were not identical twins.
1973 a team of physicians performed the first unrelated
bone marrow transplant. It required 7 transplants to be
successful.
In 1984 Congress passed the National Organ
Transplant Act, which among other things, included
language to evaluate unrelated marrow transplantation
and the feasibility of establishing a national donor
registry.
This led ultimately to National Marrow Donor
Program (NDWP) that took over the administration of
the database needed for donors in 1990.
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In 1998, James Thompson (University of Wisconsin
- Madison) isolated cells from the inner cell mass
of early embryos, and developed the first
embryonic stem cell lines.
In the same year, John Gearhart (Johns Hopkins
University) derived germ cells from cells in fetal
gonadal tissue (primordial germ cells).
Pluripotent stem cell "lines" were developed from
both sources. The blastocysts used for human stem
cell research typically come from in vitro
fertilization (IVF) procedures.
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In 1973 a moratorium was placed on
government funding for human embryo
research. In 1988 a NIH panel voted 19 to 2 in
favor of government funding.
In 1990, Congress voted to override the
moratorium on government funding of
embryonic stem cell research, , which was
vetoed by President George Bush.
President Clinton lifted the ban, but changed
his mind the following year after public outcry.
Congress banned federal funding in 1995.
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In 1998 DHHS Secretary Sullivan extended the
moratorium.
In 2000, President Bill Clinton allowed funding of
research on cells derived from aborted human fetuses,
but not from embryonic cells.
On August 9, 2001, President George W. Bush
announced his decision to allow Federal funding of
research only on existing human embryonic stem cell
lines created prior to his announcement.
In the November 2004 election, California had a Stem
Cell Research Funding authorization initiative on the
ballot that won by a 60% to 40% margin. It established
the "California Institute for Regenerative Medicine" to
regulate stem cell research and research facilities..
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Replacing damaged tissue cells - Human stem
cells could be used in the generation of cells
and tissues for cell-based therapies. This
involves treating patients by transplanting
specialised cells that have been grown from
stem cells in the laboratory.
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Due to their ability to replace damaged cells in the
body, stem cells could be used to treat a range of
conditions including heart failure, spinal
injuries, diabetes and Parkinson disease. Scientists
hope that transplantation and growth of
appropriate stem cells in damaged tissue will
regenerate the various cell types of that tissue.
For example, haematopoietic stem cells (stem cells
found in bone marrow) could be transplanted into
patients with leukaemia to generate new blood
cells. Or, neural stem cells may be able to
regenerate nerve tissue damaged by spinal injury.
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Studying human development - Stem cells
could be used to study early events in human
development and find out more about how
cells differentiate and function. This may help
researchers find out why some cells become
cancerous and how some genetic diseases
develop. This knowledge may lead to clues
about how these diseases may be prevented.
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Testing new drugs - Stem cells grown in the
laboratory may be useful for testing drugs and
chemicals before they are trialled in people.
The cells could be directed to differentiate into
the cell types that are important for screening
that drug. These cells may be more likely to
mimic the response of human tissue to the
drug being tested than animal models do. This
may make drug testing safer, cheaper and
more ethically acceptable to those who oppose
the use of animals in pharmaceutical testing.
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Screening toxins - Stem cells may be useful for
screening potential toxins in substances such as
pesticides before they are used in the
environment
Testing gene therapy methods - Stem cells may
prove useful during the development of new
methods forgene therapy that may help people
suffering from genetic illnesses.
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Stem cells are derived from the inner mass of the
blastocyst, which is the early stage in the
development of an embryo.
So first, one must obtain a blastocyst, then isolate
the inner mass cells, then finally grow the stem
cells.
Harvesting, which is when the cells are gathered
from a location in the body, is also a part of the
stem cell process.
Another process of retrieving stem cells requires a
collection of cells from the umbilical cords from
new born babies.
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There are three types of stem cells; pluripotent
stem cell, huam embryonic stem cell, and adult
stem cell.
Pluripotent stem cells, are taken from human
embryos and fetal tissue. Pluripotent stem cells
can form all the body’s cell types.
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Researchers are working to design stem cell
therapies that are more effective and reduce the
risks to patients
Today’s stem cell therapies rely mostly on cells
donated by another person, causing the risk of
rejection by the patient’s immune system. In
the future it may be possible for a person to use
a sample of his/her own stem cell for
regenerate tissue. How?
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Collecting healthy adult
stem cells from a patient
and manipulating them
in the laboratory to
create new tissue.
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Therapeutic cloning
might enable the
creation of embryonic
stem cells that are
genetically identical to
the patient.
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By manipulating the
existing stem cells
within the body to
perform therapeutic
tasks
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The research has evolved to a standard where
the physician-scientists can use regular skin
cells ands and a “chemical cocktail” to create a
INDUCED PLURIPOTENT STEM CELL (iPS)
that can produce genetically perfect copes of
every cell in a human’s body. Perfect solution
for fast recovery!
In reality deriving an iPS cell line takes longer
than a year, however the scientists have made
progress in the research achieving to use stem
cells now as tools, to change the state of cells, to
understand disease mechanisms and speed
drug discovery.
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“Opposition to stem cell research is mainly coming from religious
and social conservatives who are also pro-life. Most of them believe
that a pre-embryo from which embryonic stem cells are removed is
a human person, and that the process of extracting the cells
murders that person.”
The debate centers on "the value of human life" and people who
are against stem cell research generally believe that we are
destroying innocent life and harvesting babies for our own benefit.
These people are not wrong, to obtain an embryonic stem cell an
embryo must be destroyed; however, currently this is prohibited by
the federal law.
“If these stem cells are going to be destroyed anyways, it is best to
use them to possibly help save and improve lives. The benefits for
supporting stem cell research far out way the moral ambiguity of
the source of stem cells.”-Phil B. (philforhumanity.com)
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Are not AS versatile or
available as embryonic stem
cells
No harm done to the human
donor
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Fertilized embryos that aren’t
wanted are sometimes used for
research
More abundant
Attained from a blastocyst
 Egg after it has been
fertilized, but before an
embryo has formed
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Due to different opinions research on human
embryonic stem cells has slowed because of
philosophical qualms, political opposition and
confusion about the science.
On March 9, 2009, President Barack Obama issued
Executive Order (EO) 13505, entitled Removing
Barriers to Responsible Scientific Research
Involving Human Stem Cells
A federal judge then temporarily blocked the
Obama administration form using federal dollars
to fund expanded human embryonic stem cell
research, since it involves the destruction of
embryos.
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The court challenge was brought by adult stem
cell researches who argued that the new rules
would increase competition for limited funds
and violate federal law.
A nonprofit group of Nightlight Christian
Adoptions argued that new guidelines would
decrease the number of human embryos
available for adoption.
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The District Court for the District of Columbia
granted a preliminary injunction on the research.
US District Judge Royce Lamberth ruled that
despite attempts to separate the derivation of
human embryonic stem cells from the research
process that two cannot be separated because
culling those stem cells destroys an embryo.
The new NIH guidelines did not authorize the
explicit creation or destruction of any embryonic
stem cells. At issue were rules for working with
cells that initially were created using private
money.
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The NIH came up with a compromise, saying it
deems those old stem cell lines eligible for
government research dollars if scientists can
prove they met the spirit of the new ethics
standards.
The District Court previously dismissed the
case, saying the plaintiffs did not have legal
standing.
But after an appeals court upheld the suit, the
District Court reversed course and allowed the
case to proceed.