The benefits and disadvantages of stem cell research
Do the benefits of using embryonic stem cells for medical and research purposes outweigh the disadvantages associated with loss of life?
Problem: Embryonic stem cells result in loss of life
Embryonic stem cells are unspecialised cells that have the ability under certain conditions to create any of the different types of tissue in early human growth and can renew themselves through cell division1. The ability of stem cells to specialise into over 220 types of cells in the adult human body is what interests scientists and provides potential to create a variety of clinical therapies to cure disease2.
Embryonic stem cells are harvested from fertilised human embryos that have either been donated or have been created artificially in a laboratory. Embryos are created by in vitro fertilisation and donated for research with the donor's consent2. The embryoblast, the inner cell mass, of the blastocyst is removed and is placed into a culture dish containing a controlled culture of nutrients that allow the cells to divide and create stem cell lines that are managed and shared amongst researchers3.
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Fig. 1 - A microphotograph of human embryonic stem cells4.
Scientists are studying the use of stem cells in medical research to harness how they differentiate into specialised cells that make up the tissues of the human body2. Many diseases occur due to problems associated with cell differentiation so better knowledge about what happens in cells can help prevent these problems in the future2. In addition creating new tissues can help to repair damage caused by disease or the creation of new cells can assist patients who have deficiencies such as the inability to create insulin in the case of diabetes patients or have damaged or diseased organs. Such therapies could also reduce the demand on transplant organs and loss of life as many people die waiting for a transplant. Stem cell therapies hope to reduce morbidity for such people in the future. Stem cells are also used to test drugs before testing on live animals and humans2.
In order to use embryonic stem cells, in researching and developing such therapies, a living human embryo, which would otherwise have the potential to develop into a baby in the right conditions, is destroyed by removing stem cells when it is about 4 to 6 days old. Destroying embryos in this manner has resulted in controversy over the sanctity of human life versus the potential to treat a number of human diseases.
The sanctity of human life in arguments about embryonic stem cell research follows similar rationale to those that oppose abortion. Various religious groups see life as sacrosanct and hold that life is precious and the harvesting of embryonic stem cells and the resulting destruction of the embryo brings life to an end albeit to a collection of cells with potential to develop into a person4.
Research using embryonic stem cells is still fairly recent. A few clinical trials are currently underway that are investigating the safety of the use of the techniques and stem cells in restoring spinal cord function and others in retinal stem cells being used to treat eye disease2.
Solution: Use Animal Embryos and Human Cells
Using human embryonic stem cells means destroying human embryos so alternatives should be considered that do not involve using human embryos. Research into the use of animal embryos instead has been successful in creating embryonic stems cells that could be used for human medical therapies. For example in 2003, human cells were fused with rabbit eggs to create an embryonic chimera (a mixture of two animals in one body) that was then used to harvest embryonic stem cells5. For many years animal tissue has been used in humans with pig and cow heart valves serving as a replacement for faulty human heart valvies5.
Ethical - Mixing human and animal cellular material
Ethical issues centre on artificially creating embryos containing both animal and human tissues. This creates moral issues concerned with tampering with animals and using animals in research as well thoughts of such science being immoral or lacking sufficient knowledge on the consequences of mixing animal and human genetic material. Animal welfare organisations will also be concerned about any harm that comes to animals as a result of research.
These ethical issues fall within the four main principles of biomedical ethics: autonomy, nonmaleficence, beneficence and justice which underpin the moral obligations of health professionals and society on meeting the needs of the sick to improve health, prolong life and cure diseases as well as the extent at which scientists can progress medical interventions to do so6.
Social - Chimeras Are Unnatural
Creating chimeras is seen as unnatural as it interferes with natural boundaries between different species. Various chimera combinations have been created to understand more about human diseases, including mice with some human brain structure to assist with understanding more about Parkinson's Disease or Alzheimer's Disease5. However, society is still unable to comprehend how such interference is of benefit to humankind.
Religious objections are also made by humans playing God and interfering with the natural order of life as it was divinely created. The bases of religion and morals have taught us that the value of a human life is different to that of an animal and this has become the socially accepted norm in many cultures. Arguably we already interfere with nature in other ways, like organ transplantation, so why should developing alternative stem cell cultures from animal embryos with human cells be any different? The answer appears to lie in what is deemed to be ethical acceptable and confusion as to what constitutes a human being and an animal.
Economic - Profitable Research
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Countries, such as Canada, have banned the creation of animal chimeras through the Assisted Human Reproduction Act, which prohibits transferring a nonhuman cell into a human embryo and putting human cells into a nonhuman embryo5. There are also concerns that this diminishes human dignity or violates either human or animal integrity as chimeras cannot be distinguished as human or not human. However, such is the demand in research that other countries carry out this research instead. Success in creating sustainable and suitable stem cell therapies could be very beneficial in terms of trademarks and pharmaceutical control that it may also be very profitable for those involved. Under the Obama administration the USA is set to reverse restrictions in stem cell policies to enable researchers to develop stem cell therapies and competition amongst scientists has meant that other countries are trying to ensure that funding and expertise is in place to develop therapies to become leaders in stem cell research2.
Impacts on humans:
Embryonic stem cells offer the opportunity to develop clinical therapies that can be used to treat a range of serious, life threatening diseases including heart disease. For example stem cells can be triggered to develop into cardiomyocytes1 (cardiac muscle cells) that can be injected into the damaged hearts of patients to treat heart failure.
The main benefit chimeras have is that they can use cells taken from the patient involved in the treatment, which reduces issues with transplant rejection.
In developing stem cell therapies scientists can also learn more about human development and appreciate how undifferentiated stem cells differentiate to form the tissues and organs found in the human body1. This knowledge will help to understand more about cellular processes, which in turn will assist scientists with learning about diseases, such as cancer, and birth defects that caused by abnormal cell division.
The use of embryonic stem cells includes problems with the impact of using human tissues created using animals, ethics on animal research, potential side effects.
Stem cells must be implanted into patients. The patients' body must accept these cells for transplantation to be successful. Stem cells need to specialise in sync with the patient's cells, for example, neural cells must be able to communicate with the complex network of neural cells within the body to function properly. Immunological rejection is a potential barrier to successful transplantation as a patient's immune system may view the stem cells as foreign in the same way as traditional organ transplants require strong immunosuppressive drugs to reduce the chances of rejection2. It is not known if implanted stem cells would cause secondary problems later in the patient's life, such as cancers or tumours.
Use of animals and human/animal embryos requires ethical guidance and legal frameworks to be established. Embryos need to be harvested or created in an appropriate manner that is socially or morally acceptable. Lack of understanding and the controversy associated with this research are also seen as risks to developing treatments.
Adult stem cells do not involve human or animal embryos at all. Adult stem cells can replenish specialised cells from just a few unspecialised cells. Adult stem cell therapy aims to create healthy cell lines in a laboratory and then use these to replace dysfunctional cells in the patient. The use of adult stem cells appears to be more socially acceptable as it does not involve the destruction of a human embryo. Adult or somatic stem cells most readily create cell types of the organ they are harvested from including the brain, bone marrow, blood and blood vessels, skeletal muscles, skin and the liver3 (see Fig. 1).
Fig. 2 - Potential types of cell and tissues derived from bone marrow stem cells1.
Adult stem cells can be created using a patient's own cells which are re-programmed by forcing them to express genes that make them behave like embryonic stem cells. This creates induced pluripotent stem cells that can create the same cell layers as an embryo1.
Adult stem cells were first extracted from bone marrow in the 1960s4. Scientists, in 2007, have genetically engineered adult stem cells to mirror the attributes of embryonic stem cells that could be used to create any cell or tissue type, for example human liver cells from bone marrow cells8.
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Stem cells can be extracted from umbilical cord blood, placenta and also from fetal tissues4. Research found that stem cells from human umbilical cord blood were transplanted into the brains damaged rats caused by a stroke7.
There is a concern that adult stem cells are present in small quantities and this makes it difficult to get them in sufficient numbers to use them therapeutically2. Scientists have found that adult stem cells are not as successful as embryonic stem cells nor do they proliferate as well. Due to being adult cells they are older than embryonic cells and contain more DNA abnormalities which may restrict their suitability for clinical use2.
Adult stem cells are already being used for creating drug therapies and can be used for trialling new drugs as well.
Adult stem cells can be extracted from human umbilical cord blood. Cord blood stem cells are currently used to treat around 70 blood-derived diseases, such as anaemia, leukaemia and lymphomas7. Umbilical cords are regarded as medical waste but these scientific developments mean that they can now be put to use as a potentially life-saving resource and research continues to see if other cell types can be created.
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