-
Embryonic stem cells – These stem cells have the potential to become anything from skin cells to brain cells. They are usually produced from donated embryos (fertilised eggs) from couples undergoing IVF treatment.
-
Adult stem cells – Although they are found in children as well as adults, they are referred to as adult stem cells to distinguish them from those derived from embryos. Adult stem cells can be found all over the human body, but scientists are finding them difficult to isolate and identify. Unlike embryonic stem cells, it is not yet known whether adult stem cells can become any tissue type or are restricted to a range of different cells related to one tissue type.
-
Foetal stem cell – After 8 weeks of development, a human embryo is then called a foetus. Foetal stem cells can be found in blood from the umbilical cord or the placenta, which are donated after childbirth. They can also be isolated from aborted foetuses. Although many of the foetal stem cells are differentiated, some still retain the ability to be made to change into something else.
The two images below belong to mammals in the animal kingdom. The being a mouse’s embryonic stem cell and the other being a human stem cell.
(Source: Wikipedia, the University of Edinburgh- Website and the National Institute of Health - Website)
Process
A fertilised egg (zygote) divides by the process of mitosis to produce a bundle of cells – the embryo of the new organism. To start with the cells in the embryo are all the same. These embryonic stem cells are undifferentiated. This means they’re able to produce any type of specialised cell. As you can see in the figure. (B.3) the stem cell A differentiates into two different tissue cells B & C. Differentiation results in the formation different cells. This is due to their position in the body. The image shows that to start with all the stem cells were type A, but after differentiation, type A formed type B, and B formed C.
In humans, all the cells in the embryo are undifferentiated up to the eight cell stage. The process of stem cells becoming specialised is called differentiation. As the cells start to differentiate the embryo begins to develop tissues and organs. All cells contain the same genes but not all genes are active in each cell type. What type of cell a stem cell differentiates into depends on what genes are active in that cell.
(Source: OCR- Biology revision guide textbook & Wikipedia)
Properties
The classical definition of a stem cell requires that it possess two properties:
-
Self-renewal - the ability to go through numerous cycles of cell division while maintaining the undifferentiated state.
-
Potency - the capacity to differentiate into specialized cell types. Potency specifies the differentiation potential (the potential to differentiate into different cell types) of the stem cell.
-
Totipotent stem cells can differentiate into embryonic and extra embryonic cell types. Such cells can construct a complete, viable, organism. These cells are produced from the fusion of an egg and sperm cell. Cells produced by the first few divisions of the fertilized egg are also totipotent. As you can see in figure (B.4)
-
Pluripotent stem cells are the descendants of totipotent cells and can differentiate into nearly all cells, i.e. cells derived from any of the three germ layers. As you can see in figure (B.4)
-
Multipotent stem cells can differentiate into a number of cells, but only those of a closely related family of cells (e.g. hematopoietic stem cells differentiate into red blood cells, white blood cells, platelets, etc.).As you can see in figure (B.4).
-
Oligopotent stem cells can differentiate into only a few cells, such as lymphoid or myeloid stem cells. As you can see in figure (B.4).
-
Unipotent cells can produce only one cell type, their own, but have the property of self-renewal which distinguishes them from non-stem cells (e.g. muscle stem cells). As you can see in figure (B.4).
(Source: Wikipedia)
Stem cell controversy
ARUGMENT FOR – STEM CELL RESEARCH
An argument which supports the ‘for’ my big question is that medical researchers believe that stem cell therapy has the potential to dramatically change the treatment of human disease. A number of adult stem cell therapies already exist, particularly bone marrow transplants that are used to treat leukemia. This statement is reliable because bone marrow transplants do take place to treat diseases like leukemia.
Furthermore stem cells play an important role in current research in developing new medical techniques. In one experimental method in regenerative medicine, stem cells are used to stimulate the growth of human tissues.
Another supporting argument is that in the time to come, medical researchers anticipate/ believe being able to use technologies derived from stem cell research to treat a wider variety of diseases including cancer, Parkinson's disease, spinal cord injuries, Amyotrophic lateral sclerosis, multiple sclerosis, and muscle damage, amongst a number of other impairments and conditions. This is a reliable statement as all these diseases are caused due to the mal-functioning of human cell and as stem cell have the ability to change into any type of tissue cell these diseases could be cured.
During chemotherapy, most growing cells are killed by the cytotoxic agents. These agents not only kill the leukemia or neo-plastic cells, but also the haematopoietic stem cells within the bone marrow. It is this unfortunate side effect of the chemotherapy that the Stem Cell Transplant attempts to reverse; the donor's healthy bone marrow reintroduces functional stem cells to replace those lost in the treatment.
The major reason for the promotion or at least by the people who support this project of stem cell research is that the stem cells posses the unique ability or potential which help to cure incurable diseases or problems such as: brain damage, cancer, spinal cord injury, heart damage, haematopoiesis, baldness, missing teeth, deafness, blindness and vision impairment and so on and so forth because all these defects occur in the body due defects in cells and stem cells fix or correct these defects in our bodies.
(Source: Wikipedia)
ARUGMENT AGAINST – STEM CELL RESEARCH
An argument which supports the ‘against’ my big question is that the ethical implications of stem cell research (particularly with regard to embryonic stem cell research) are becoming an increasingly popular – not to mention a hotly contested – topic of debate.
Another supporting argument is that with the present state of technology, starting a stem cell line requires the destruction of a human embryo and/or therapeutic cloning which could have a drastic impact on the environment because it could changes in the human DNA and also create a big issue among the people.
Stem cell transplants – whether autologous or allogeneic transplants – carry potential side effects and complications. Depending on the type of stem cell transplant performed Furthermore, the type of high-dose chemotherapy treatment regimen used, as well as the type of treatable disease and the patient’s medical status, are all factors that may contribute to the risk of certain transplant side effects.
The side effects of stem cell transplant can be really serious. It could cause infections, anaemia, bleeding, veno-occlusive disease, interstitial pneumonia syndrome, graft failure, graft-versus-host disease and a few more.
Furthermore, taking stem cells from the embryo violates the to-be-child or human beings right to live/life. Taking stem cells from the embryo which is going to become a human being in a few months time, taking its life is not right.
(Source: Wikipedia)
CONCLUSION
I claim that the stem cell research should be taken forward; because when its pros and cons are compared the pros outweigh the cons, such as the ability of stem cells to cure diseases which had no remedies, which in turn increase our life span on earth. Further more these experiment can change our current medicines for better results, such as quicker recoveries etc. In addition stem cell research is a very beneficial research which can do well for whole humanity. Yes, surely stem cell research carries a few risks with it, but the knowledge of stem cells can help mankind to find cures for all types of disease which have drastic effect on human lives.
My reason for this claim is that with cures for few hard to cure diseases helps save human lives which in itself is a great achievement for every person that dies, their relatives suffer and the world as such suffers with them. Also, it’s my belief that with advancement in this field would have a good impact on our society and might well change it for the better.
Other/some people might think stem cell research is bad and should not be promoted as it has a few risks with it and prefer taking the precautionary method but the forget that stem cell research could lead to global development, but most importantly we should all remember that the advancement in this field would/might come handy to save someone precious to you.
**** THE END ****