What Are Stem Cells?
Stem cells are how we all begin: undifferentiated cells that go on to develop into any of the more than 200 types of cell the adult human body holds.
Few quarrel with predictions of the awesome potential that stem cell research holds.
One day, scientists say, stem cells may be used to replace or repair damaged cells,
and have the potential to drastically change the treatment of conditions like cancer,
Alzheimer's and Parkinson's disease and even paralysis.
But the divisions over how to conduct that research have been deep and bitter.
Most research has been conducted on embryonic stem cell lines --
cultures of cells derived from four- or five-day-old embryos, or fertilized cells.
Stem cells have the remarkable potential to develop into many different cell types in the body during early life and growth.
In addition, in many tissues they serve as a sort of internal repair system,
dividing essentially without limit to replenish other cells as long as the person or animal is still alive.
When a stem cell divides, each new cell has the potential either to 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.
Stem cells are distinguished from other cell types by two important characteristics.
First, they are unspecialized cells capable of renewing themselves through cell division, sometimes after long periods of inactivity.
Second, under certain physiologic or experimental conditions, they can be induced to become tissue- or organ-specific cells with special functions.
In some organs, such as the gut and bone marrow, stem cells regularly divide to repair and replace worn out or damaged tissues.
In other organs, however, such as the pancreas and the heart, stem cells only divide under special conditions.
Stem cells are important for living organisms for many reasons.
In the 3- to 5-day-old embryo, called a blastocyst, the inner cells give rise to the entire body of the organism,
including all of the many specialized cell types and organs such as the heart, lung, skin, sperm, eggs and other tissues.
In some adult tissues, such as bone marrow, muscle, and brain,
discrete populations of adult stem cells generate replacements for cells that are lost through normal wear and tear, injury, or disease.
Given their unique regenerative abilities, stem cells offer new potentials for treating diseases such as diabetes, and heart disease.
However, much work remains to be done in the laboratory and the clinic to understand how to use these cells for cell-based therapies to treat disease,
which is also referred to as regenerative or reparative medicine.
Laboratory studies of stem cells enable scientists to learn about the cells’ essential properties and what makes them different from specialized cell types.
Scientists are already using stem cells in the laboratory to screen new drugs and to develop model systems to study normal growth and identify the causes of birth defects.
Research on stem cells continues to advance knowledge about how an organism develops from a single cell and how healthy cells
replace damaged cells in adult organisms.
Adult Stem cell research is one of the most fascinating areas of contemporary biology,
but, as with many expanding fields of scientific inquiry, research on stem cells raises scientific questions as rapidly as it generates new discoveries.
What Are Adult Stem Cells?
An adult stem cell is thought to be an undifferentiated cell, found among differentiated cells in a tissue or organ that can renew itself and can differentiate
to yield some or all of the major specialized cell types of the tissue or organ.
The primary roles of adult stem cells in a living organism are to maintain and repair the tissue in which they are found.
Scientists also use the term somatic stem cell instead of adult stem cell, where somatic refers to cells of the body (not the germ cells, sperm or eggs).
Unlike embryonic stem cells, which are defined by their origin (the inner cell mass of the blastocyst),
the origin of adult stem cells in some mature tissues is still under investigation.
Adult stem cell research has generated a great deal of excitement.
Scientists have found adult stem cells in many more tissues than they once thought possible.
This finding has led researchers and clinicians to ask whether adult stem cells could be used for transplants.
In fact, adult hematopoietic, or blood-forming, stem cells from bone marrow have been used in transplants for 40 years.
Scientists now have evidence that stem cells exist in the brain and the heart.
If the differentiation of adult stem cells can be controlled in the laboratory, these cells may become the basis of transplantation-based therapies.
The history of adult stem cell research began about 50 years ago.
In the 1950s, researchers discovered that the bone marrow contains at least two kinds of stem cells.
One population, called hematopoietic stem cells, forms all the types of blood cells in the body.
A second population, called bone marrow stromal stem cells (also called mesenchymal stem cells, or skeletal stem cells by some), were discovered a few years later.
These non-hematopoietic stem cells make up a small proportion of the stromal cell population in the bone marrow, and can generate bone,
cartilage, fat, cells that support the formation of blood, and fibrous connective tissue.
History Of The Research
Stem cells have an interesting history that has been somewhat tainted with debate and controversy.
In the mid 1800s it was discovered that cells were basically the building blocks of life and that some cells had the ability to produce other cells.
Attempts were made to fertilise mammalian eggs outside of the human body and in the early 1900s,
it was discovered that some cells had the ability to generate blood cells.
In 1968, the first bone marrow transplant was performed to successfully treat two siblings with severe combined immunodeficiency.
Other key events in stem cell research include:
- 1978: Stem cells were discovered in human cord blood
- 1981: First in vitro stem cell line developed from mice
- 1988: Embryonic stem cell lines created from a hamster
- 1995: First embryonic stem cell line derived from a primate
- 1997: Cloned lamb from stem cells
- 1997: Leukaemia origin found as haematopoietic stem cell, indicating possible proof of cancer stem cells
In 1998, Thompson, from the University of Wisconsin, isolated cells from the inner cell mass of early embryos and developed the first embryonic stem cell lines.
During that exact same year, Gearhart, from Johns Hopkins University, derived germ cells from cells in foetal gonad tissue;
pluripotent stem cell lines were developed from both sources.
Then, in 1999 and 2000, scientists discovered that manipulating adult mouse tissues could produce different cell types.
This meant that cells from bone marrow could produce nerve or liver cells and cells in the brain could also yield other cell types.
These discoveries were exciting for the field of stem cell research, with the promise of greater scientific control over stem cell differentiation and proliferation.
Where We Are Today?
Adult Stem cell research has now progressed dramatically and there are countless research studies published each year in scientific journals.
Adult stem cells are already being used to treat many conditions such as heart disease and leukaemia.
Researchers still have a long way to go before they completely control the regulation of stem cells.
The potential is overwhelmingly positive and with continued support and research,
scientists will ideally be able to harness the full power of stem cells to treat diseases that you or a loved one may suffer from one day.
Cancer And Stem Cells
Cancer afflicts millions around the world each year and many go through treatment only to relapse years later.
Others die from the disease and often after a great deal of suffering.
It's no surprise that cancer research is at the forefront for current medical studies.
In particular stem cells are being used for cancer treatments today as well as driving current research efforts in the hopes of finding more effective cancer treatments,
including the ultimate goal of a cure.
Current Stem Cell Treatments for Cancer
Adult stem cells have been used for decades to treat certain cancers through bone marrow transplants.
In this therapy, the stem cells that give rise to the different blood cells in the body are transplanted into the bone marrow of the patient,
where they regenerate the blood. This is a vital and often life saving treatment because chemotherapy destroys the bone
marrow alongside cancer cells and the blood cells must be replenished for the patient's treatment to be successful.
It is hoped that the molecular basis for this treatment can lead to similar treatments for other forms of cancer,
allowing for cancerous tissues in areas such as the brain to receive stem cells that replenish those that are damaged through radiation.
Cancer Cell Biology
Treating cancer directly is one aim of stem cell therapy, but understanding actual cancer cell biology is another important one.
In fact, it's particularly crucial because that understanding can then encourage the development of drugs and cancer specific treatments.
Some of the more recent studies have shown that cancers seem to be regularly maintained by a relatively small cluster of cancer stem cells that are able to self-renew.
Scientists are trying to learn more about the genes that regulate the self-renewal feature of stem cells so that drugs can be developed to destroy the cancer stem cells.
Stem Cells and Tumours
Another important focus involves identifying and isolating cancer stem cells from tumours so that researchers can look at how cancer genes are expressed.
The connection between cancer stem cells and healthy ones is also being investigated in research studies.
Stem Cell Development and Cancer
Even when cancers develop in different tissues, they can still have similar genetic abnormalities.
An important scientific focus is to identify all of these genetic abnormalities and develop treatments to combat the effects.
To properly identify all of these abnormalities, however, scientists need to learn more about stem cell characteristics at the various developmental stages.
By examining the developmental process of healthy stem cells, scientists can better gauge how abnormal differentiation occurs
and may then be able to develop treatments to prevent or treat the abnormalities.
An understanding of how stem cell differentiation and specialization are controlled is another fundamental
development process that researchers need to grasp in hopes of creating effective cancer treatments.
Because cancer rates have significantly increased over the last century and the incidence is such that even if you do not suffer from cancer in your lifetime,
you will likely know someone who does, stem cell research must continue in this area.
The chance to save lives and decrease suffering is exactly the sort of motivation that should support further stem cell studies for cancer treatments.
Politics And Stem Cells
Unfortunately, politics have played a relatively large role in stem cells,
which has left many people feeling powerless to influence the progress of this potential therapy.
With politics comes funding – or lack thereof – and religious and other personal views tend to get into the mix as well.
US Policies on Stem Cells
The US has changed over the years in terms of political stem cell views.
In the earlier days of stem cell research, the US played a more active role.
In the last decade, however, the US has significantly fallen behind as stem cell research has continued to forge ahead in Britain and other areas around the world.
Religious Views
A key reason for the US falling 'behind' was due to the Bush administration policies on stem cell research.
Many cited these policies as highly personally charged ones that were mostly impacted by strong religious and anti-abortion views.
As such, funding for embryonic stem cell research – thought to be the most promising – was virtually at a standstill.
Discarded embryos from failed in vitro fertilisation procedures became a challenge to obtain for
research purposes and existing stem cell lines similarly became difficult to access.
Obama and Stem Cell Changes
Obama, the new president in the US is set to reverse the vast majority of stem cell policies that were in effect when Bush was in power.
By removing restrictions on embryonic stem cell research, he hopes to fuel the progress of US researchers into promising therapies using stem cells.
Diseases such as Alzheimer's and Parkinson's will hopefully be closer to a cure or treatments to slow their destruction.
The news has been welcomed by scientists around the world as they are excited to finally access the tools needed
to study stem cells while also obtaining funding to support their research efforts.
Opponents of Stem Cell Research
There are, however, opponents of the policy reversals who cite that it is unethical to use embryonic stem cells.
Instead, they believe that research should focus on adult stem cells, which do not involve the destruction of am embryo
.
Arguments over adult stem cells usually suggest that the quality and potential of adult stem cells is not comparable to embryonic stem cells.
In this way, it is thought that embryonic stem cells are more likely to result in effective stem cell therapies for disease.
Another positive effect of the policy changes is that countries such as Britain – while committed to stem cell research
everywhere in the world – are scrambling to ensure that their funding and expertise are in place to continue being a leader in stem cell research.
Science has always been fraught with competition and will continue to do so, particularly in the area of stem cell research.
Scientists in Britain want to be sure that they don't fall behind in the quest to find effective stem cell therapies.
With the US set to speed ahead now, Britain may ultimately achieve greater progress with a dose of healthy competition.
Future of Stem Cell Research
For now, it looks as though the US may accelerate its stem cell research and if anything,
give other countries in the world a strong challenge to continue their own research and work into advancing stem cell therapies.
Hopefully, ethical progress can continue, which can then bring treatments to the many people around the world who suffer from devastating diseases.
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