Understanding Biotechnology

What is Biotechnology

Overview of Biotechnology

History of Biotechnology

Why do we do biotechnology?

Biotechnology for the environment

Biotechnology for food and agriculture

When an egg is fertilised by a sperm to make a human embryo, the single fertilised egg cell divides millions of times to form the six billion or more cells that make up our bodies. Most of these cells have undergone a process called differentiation, which leads to them becoming specialised for a certain function. For example, neurons (nerve cells) are specialised to convey electrical messages around the body.

Stem cells play a critical role in normal growth and development by providing new cells for growth and for replacing and repairing used and damaged tissues. Stem cells differ from other cells in the body in three main ways.

1. Stem cells are unspecialised. They have not developed into cells that perform a specific function (differentiation).
2. Stem cells are capable of self-renewal. Once a cell has become specialised, it has a very limited capacity to produce new cells, and then only cells of the same type. Thus, if a muscle or blood cell is damaged, it cannot replace itself. Stem cells, however, are able to divide and produce copies of themselves and lead to self-renewal.
3. Stem cells can differentiate. They can divide and produce cells that have the potential to become other more specialised cell types. These new cells and tissues are used to repair or replace damaged or diseased cells in the body. Stem cells from different tissues and from different stages of development can give rise to varying numbers and types of cells

Types of stem cells

In humans:

1. 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.
2. Embryonic germ cells are derived from the part of a human embryo or foetus that will ultimately produce gametes (eggs or sperm).
3. Adult stem cells are undifferentiated cells found among specialised (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.
4. Umbilical cord blood stem cells are used to treat a range of blood disorders and immune system conditions

Stem cells that have the potential to develop into any of the cell types found in an adult organism are called pluripotent. Embryonic stem cells are pluripotent.

Stems cells that only have the potential to make a few cell types in the body are called multipotent. Adult stem cells appear to be multipotent.

Cells that are capable of forming a completely new embryo that can develop into a new organism are called totipotent. A fertilised egg is totipotent. None of the stem cells used in research appear to have this capacity.

More basic research is required to find out how stem cells can be:

• located and extracted
• kept alive in the laboratory
• multiplied for extended periods of time
• directed to form specific types of specialised cells

Embryonic stem cells

At this stage of development, the embryo is a hollow ball of about 200 to 250 cells, no bigger than a pinhead. It is called a blastocyst.

Within the blastocyst is a small group of 30 to 34 cells, called the inner cell mass. These cells are pluripotent (able to develop into any type of cell) and are the source of all the highly specialised cells found in an adult organism. The remaining cells generate all other tissues such as the foetal membranes and placenta.

Once the inner mass cells are obtained, they may be used to create pluripotent stem cell lines – cell cultures that can be grown indefinitely in the laboratory. Stem cell lines are important tools for scientists, as the cells are all the same, and new cells do not need to be isolated for every new experiment.

In Australia, it is illegal to conduct any type of research on embryos that are conceived naturally. Embryonic stem (ES) cells are taken from embryos that come from eggs fertilised in an IVF (in vitro fertilisation) clinic. Only embryos not required for implantation are used. They are donated for research purposes only, with informed consent from the donors. They are not derived from eggs fertilised within a woman’s body, and embryos are not created specifically for research purposes.

Because ES cells can become any cell type of the body, they can be used to develop different tissues for cell-based therapies.

Large numbers of ES cells can be grown in the laboratory relatively easily. ES cell lines are sometimes referred to as immortal due to their ability to keep dividing (self-renewing) over many generations. Established cell lines can be maintained in laboratories for further research and generation of cells for cell-based therapies for many years.

Human embryonic stem cells could be used to seek out and destroy a fatal form of brain cancer. Experiments using mice with brain tumours show that ES cells migrate across the brain and can deliver an anti-cancer drug.

ES cells may have great potential in forming the basis of long-term therapies, but issues regarding their safety must be overcome first. It is not yet known how transplanted ES cells would behave inside the body, but scientists are particularly worried that the transferred ES cells might not stop dividing. This uncontrolled growth may generate tumours, and this has already been shown to occur in laboratory cultures. While the cells in these tumours are benign, scientists do not know how they might behave in the body. However, cells differentiated from ES cells have been used in a number of studies and have developed normally. This issue must be fully explored before clinical trials can proceed in people.

Another issue with the use of ES cells in regenerative medicine is that they may trigger immune rejection by the patient’s immune system. Alternatives are being investigated to overcome this, including combining stem cell technology with cloning methods in a process called somatic cell nuclear transfer. This is discussed in the section on stem cells in cloning.

The community has a range of opinions about ES cell research. The overwhelming issue for most people who are opposed to ES cell research is that taking inner mass cells inevitably leads to the destruction of the embryo. For those that view a fertilised egg as a human life, this is most distressing. Others consider the blastocyst to be nothing more than a ball of cells with the potential to become a human. Debate on this issue remains considerable and controversial.

Embryonic germ cells

While embryonic stem (ES) cells are similar to EG cells in many ways — such as being able to develop into any cell type — they are grown in different ways in the laboratory.

ES cell cultures have been grown for more than two years in the laboratory as immortal cell lines, but embryonic germ cell cultures can only survive about 70 to 80 cell divisions. This makes them less suitable for establishing cell lines for research.

However, one advantage of EG cells is that they do not appear to generate tumours when transferred into the body, as embryonic stem cells do. This may make them potentially useful sources of transplant tissue and cell-based therapies.

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.

Only mouse EG cells are being studied in Australia.

Adult stem cells

The main role of adult stem cells is to maintain and repair the tissue in which they are found. Skin stem cells, for example, give rise to new skin cells, ensuring that old or damaged skin cells are replenished.

It now appears that probably all tissues contain adult stem cells, but only in very small numbers. Scientists think the cells remain dormant until activated by disease or injury to that tissue. Because of their small numbers, adult stem cells have proven difficult to isolate. However, to date, adult stem cells have been derived from tissues such as the brain, bone marrow, blood, muscle, skin, pancreas and liver. Most research has been done on haematopoietic (blood forming) stem cells isolated from bone marrow and blood.

Adult stem cells appear to only generate the cell types of the tissue in which they are found. Haematopoietic stem cells, for example, are found in the bone marrow and give rise to the many types of cells found in the blood, including red and white blood cells and platelets. Bone marrow transplants have been used for more than 30 years to treat people with life-threatening blood disorders such as leukaemia and thalassaemia.

Adult stem cells are attractive as research tools and for treating disease, as they do not involve the destruction of embryos. It may also be possible to use a patient’s own stem cells to generate tissue for transplant, thus avoiding problems with immune rejection common to other types of transplantation.

However, one of the potential hurdles for the use of adult stem cells for transplants is their limited ability to generate different cell types. Recent experiments, however, have revealed that certain types of adult stem cells from one tissue may be able to generate cell types of a completely different tissue if exposed to the right conditions. This phenomenon is called plasticity. Some researchers believe that adult stem cells may be as potentially useful as embryonic stem cells in generating tissue for transplants. Research into the factors and conditions that control the differentiation of adult stem cells is proceeding.

Researchers in the UK have reported success in using adult bone marrow stem cells to reverse the effects of cirrhosis of the liver, negating the need for a transplant of rarely available organs. The experiment involved separating blood from the patient into its components, isolating stem cells from white blood cells and injecting them into the liver’s hepatic artery, thereby returning red blood cells to the body.

Babies saving lives – umbilical cord blood stem cells

Blood stem cells can be used to treat a range of blood disorders and immune system conditions such as leukaemia and sickle cell anaemia.

Once collected, cord blood can be stored in a ‘cord blood bank’ for use as a potential source of tissue for transplant for that baby should it ever be required. As this blood originated from the person receiving it, there would be no problem with rejection of the transplanted tissue.

Alternatively, the cord blood may be donated to a general cord blood bank for use by other people in need of a transplant. It is hoped that over time, a store of cord blood samples from people of different tissue types may be established. Someone requiring a transplant would be treated with stem cells from the sample most closely matching their own tissue type, thus minimising complications associated with tissue rejection.

Potential uses of stem cells

Replacing damaged tissue

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.

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.

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.

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.

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 for gene therapy that may help people suffering from genetic illnesses.

Stem cell research in Australia

Researchers around the world are focusing on investigating the molecular characteristics of all stem cell types and improving culturing methods. This includes growing cells without using animal products, which may be a source of new viruses and infections that could limit the use of stem cells in transplants.

Scientists are now beginning to succeed in making stem cells differentiate into particular types of cells, and identifying whether these specialised cells function normally. Australian scientists have been at the forefront of this research. For example, scientists at the Walter and Eliza Hall Institute of Medical Research in Melbourne and at the University of Queensland are looking at brain stem cells, with a long-term view of treating patients with brain injuries or degenerative diseases. Others are studying the capacity for stem cells to produce a complex organ, by making scaffolding for cells to grow on or around.

In 2000, a group of scientists from the Monash Institute of Reproduction and Development reported the development of nerve stem cells from embryonic stem cells. Their work made the front page of the scientific journal Nature, which is the science equivalent to having your photo on the cover of Rolling Stone magazine!

Today, much of Australian stem cell research is directed through the Australian Stem Cell Centre, a Biotechnology Centre of Excellence established by the Australian Government in 2003. The Centre brings together scientists from around Australia to research both embryonic and adult stem cells.

The main areas of research for stem cell therapies target:

• regenerating damaged cardiac (heart) tissue
• blood and bone marrow regeneration to
  • improve bone marrow transplantation techniques
  • generate safer blood cell products for patients needing transfusion
• kidney and lung disease
• neural (brain) diseases such as Alzheimer’s and multiple sclerosis

For more information, go to:
Australian Stem Cell Centre: http://www.stemcellcentre.edu.au

University of Queensland’s Neural Stem Cell Laboratory: http://www.qbi.uq.edu.au/index.html?page=13987

Walter and Eliza Hall Institute of Medical Research: http://www.wehi.edu.au/research/overview/dnb.html

Stem cells and cloning

A major problem with the use of embryonic stem (ES) cells to generate tissue for transplant is that the immune system of the patient would detect them as foreign and attack. Immune rejection is a major problem in all transplant therapies.

Cells in our body display a set of markers known as MHC (major histocompatibility complex), which the immune system recognises ans uses to work out what is meant to be in the body (self), and what is foreign (non-self). Invading pathogens and transplant tissue display different patterns of MHC, which the body recognises as foreign and attacks using the immune system.

One strategy for overcoming this could involve the use of somatic cell nuclear transfer (note: this technology is not legal in Australia).

Nuclear transfer involves replacing the nucleus of an egg cell with that from a cell from the patient’s body, and allowing it to develop to form a blastocyst. Cells from the interior of the ES cell would then be harvested and used to establish an ES cell line that has the genetic makeup of the patient. These cells would then be directed to develop into the tissue needed for transplant. This tissue would display the same antigen markers as the patient’s, and therefore would not be rejected.

This potential application of cloning technology would not result in the formation or development of a new foetus or adult human. However, there has been considerable opposition to this research, as it involves the generation of embryos specifically for research. Many people consider this as unethical. Additionally, the embryos are genetic clones of the patient, and thus could, in theory, be used to generate a new human. Reproductive cloning is widely regarded as unethical by the medical and scientific community.

Alternative strategies for overcoming immune rejection

An alternative strategy for overcoming immune rejection is to use adult stem cells from the patients that require the transplant. These cells would display the MHC markers that the patient recognises as self, so that the immune system would not reject them.

Researchers are also working to establish stem cell banks that contain tissue of many different types. Cells from those that most closely match the patient would then be used for transplant.

The thymus gland is the organ most responsible for programming our immune system to recognise its own cells very early in life. It ceases this function shortly after birth, so that any cells entering the body after that will be rejected. Scientists are researching ways of possibly reactivating the thymus gland, so that it will recognise the transplanted tissue.

This work is still in its early stages and is very complex – treatments such as this are likely not to be available for at least ten years.

Ethics of stem cell research

For many, this constitutes destruction of a potential human, and conflicts with religious and moral views held in our society. For others, the potential for this research to provide treatments and possibly cures for debilitating illnesses that have no cure and significantly impact on our way of life overrides this concern.

Central to any argument on this is what actually constitutes the beginning of life for a human. Opinions on this vary from the moment of conception to a 14 day embryo and a living baby at birth. This issue is highly emotive, and it will always be necessary to consider all opinions and to balance the harm that might be done against the potential good this research may provide for those suffering from debilitating diseases.

In Australia, legislation states that no embryo may be created for the purpose of this research or to generate stem cell lines. The embryonic stem and germ cells are obtained from either donated embryos not required for an IVF procedure that would otherwise be destroyed, or from pregnancies that were terminated for medical or social reasons.

The other major ethical issue associated with stem cell research ties in with the combination of embryonic stem cell and cloning technologies, leading to generation of an embryo that is a genetic clone of the donor of the nucleus (see section on stem cells and cloning). What is critically different in this context is that an embryo is actually created for research or therapeutic purposes. This raises a wider range of objections, in that a potential life is created for a specific purpose.

Also of issue here is the purpose of this type of cloning, which would be done purely for the purpose of generating tissue for transplantation. The embryo generated could be allowed to continue development and could potentially lead to the birth of a new human if implanted into a willing mother. There are serious ethical and medical concerns associated with the use of somatic cell nuclear transfer technologies to reproduce humans and it is illegal in Australia, UK and the USA to conduct any research into reproductive cloning of humans.

The Prohibition of Human Cloning Act 2002 (Cth) prohibits all types of human cloning by any method. The Research Involving Human Embryos Act 2002 (Cth) allows for regulated use of an appropriate number of excess 'assisted reproductive technology' (ART) embryos in approved research programs. State and territory governments are introducing complementary legislation to provide nationally consistent prohibition and regulation of use of excess ART embryos in research.

Some people speculate that allowing any somatic cell nuclear transfer will be the start of a slippery slope into reproductive cloning.

Given these concerns, which stem cell research should be permitted?

There are pluses and minuses associated with the research and use of all types of stem cells. Which ones should research focus on?

The ethical issues surrounding the origin of embryonic stem cells will always be of a sensitive nature. There are strict guidelines and legislation regarding any research involving embryos, but for many, research on adult stem cells is the only acceptable alternative.

Embryonic stem and germ cells can give rise to every cell type in the body. Adult stem cells, however, are multipotent, giving rise to a limited range of cell types. This may limit their use in cell-based therapies, and many researchers believe research using embryonic cells will be more fruitful. However, recent research has revealed that some adult stem cells may be able to generate different tissues under the right conditions and this may increase their therapeutic potential.

Embryonic stem (ES) cells have a greater capacity for self-renewal. ES cell lines will be useful for research into the effects of drugs and toxins, and also into early human development. Their uncontrolled growth also leads to the development of tumours called teratomas, which may restrict their use in cell-based therapies. Research is continuing into ways to control and regulate the growth of ES cells more effectively. Embryonic germ and adult stem cells do not form these tumours in culture, which may make them better alternatives for transplant tissue sources.

Obviously, there are pros and cons to the use of all three types of stem cells. Most scientists agree that it is important to continue to pursue research into embryonic stem and germ cells, and adult stem cells. All scientists are aware that they must undertake their work ethically and within the bounds of the law, and these can vary from country to country. In Australia, all research involving humans must be approved by Human Research Ethics Committees.