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click the first picture to know more basic concepts on stem cells.

In the face of extraordinary advances in the prevention, diagnosis, and treatment of human diseases, devastating illnesses such as heart disease, diabetes, cancer, and diseases of the nervous system, such as Parkinson's Disease and Alzheimer's Disease, continue to deprive people of health, independence, and well-being. Research in human developmental biology has led to the discovery of human stem cells (precursor cells that can give rise to multiple tissue types), including embryonic stem (ES) cells, embryonic germ (EG) cells, fetal stem cells, and adult stem cells. Recently, techniques have been developed for the in vitro culture of stem cells, providing unprecedented opportunities for studying and understanding human embryology. As a result, scientists can now carry out experiments aimed at determining the mechanisms underlying the conversion of a single, undifferentiated cell, the fertilized egg, into the different cells comprising the organs and tissues of the human body. Although it is impossible to predict the outcomes, scientists and the public will gain immense new knowledge in the biology of human development that will likely hold remarkable potential for therapies and cures.

Stem cell cultivation

1) In vitro fertilized egg - made in an artificial environment
outside of a living organism.

2) Blastocyst stage - 5 to 7 days after egg is fertilized,
cells are beginning to multiply.

3) Inner stem cell mass - removal of stem cells.

4) Cultured undifferentiated stem cells - stage when
cells can be directed to what they will become.

5) Specialized cells - what the cells become.
a) blood cells
b) neural cells
c) muscle cells

Similarities and differences between embryonic and adult stem cells
Human embryonic and adult stem cells each have advantages and disadvantages regarding potential use for cell-based regenerative therapies. Of course, adult and embryonic stem cells differ in the number and type of differentiated cells types they can become. Embryonic stem cells can become all cell types of the body because they are pluripotent. Adult stem cells are generally limited to differentiating into different cell types of their tissue of origin. However, some evidence suggests that adult stem cell plasticity may exist, increasing the number of cell types a given adult stem cell can become.

Large numbers of embryonic stem cells can be relatively easily grown in culture, while adult stem cells are rare in mature tissues and methods for expanding their numbers in cell culture have not yet been worked out. This is an important distinction, as large numbers of cells are needed for stem cell replacement therapies.

A potential advantage of using stem cells from an adult is that the patient's own cells could be expanded in culture and then reintroduced into the patient. The use of the patient's own adult stem cells would mean that the cells would not be rejected by the immune system. This represents a significant advantage as immune rejection is a difficult problem that can only be circumvented with immunosuppressive drugs.

Embryonic stem cells from a donor introduced into a patient could cause transplant rejection. However, whether the recipient would reject donor embryonic stem cells has not been determined in human experiments.

(national institute of health)

The unique potential contribution of human embryonic stem cells to therapies is a product of both their longevity and their capacity to produce a wide range of specialised cells in the laboratory. By contrast, adult stem cells that are grown in the laboratory appear to have much shorter lifespans than embryonic stem cells. This reduces their capacity to form new cell types. Stem cells can also be obtained from aborted fetuses and umbilical cord blood, but it is not clear whether the full range of cell types that are required for treatments could eventually be generated from these sources alone.

Stem cell research around the world
Nine of the 15 European Union nations have banned stem cell research on embryos. Here is a list of countries involved in the research and their position on the issue:

In January, Britain became the first country to legalise cloning, which it did in order to allow scientists to create cloned embryos for stem cell research. Scientists can destroy donated fertility clinic embryos for stem cells and other research, and are allowed to create embryos by in vitro fertilization. Now, the new law allows researchers to create stem cells by cloning. All embryos involved in research must be destroyed after 14 days.

The government approved guidelines last week for stem cell research, a move likely to allow Japanese laboratories to start studies on building tissue from embryonic cells by the end of the year.

The guidelines stipulate that embryonic cells used in research would be taken only from those made for fertility treatment that would otherwise be discarded. Research on cloning humans or creating sperm and ova is strictly banned.

There is no law regulating stem cell research in Israel and embryo destruction for stem cell research is allowed. Scientists announced this month that they succeeded for the first time in growing heart cells from human embryonic stem cells.

The heart cells can beat spontaneously, according to a report published in the Journal of Clinical Investigation. In 1999, a law was passed prohibiting cloning humans for five years.

In June, Australian federal and state health ministers agreed to draw up laws banning cloning nationwide, but they could not reach consensus on the issue of stem cell research. As a compromise, they agreed to consult with community and research groups before meeting again to develop a nationwide policy.

There are currently bans on cloning in three of Australia's six states and another two are considering legislation. However, all the legislation differs in its approach to stem cell research, which is legal in parts of the country.

Research on embryonic tissue is generally banned in China, according to the Chinese Health Ministry. However, the study of stem cells drawn from the umbilical cord and afterbirth is permitted. Chinese institutions are very aggressive in many areas of genetic research and regulation is somewhat lax.

Stem cell research is ongoing in Singapore, according to Shirlene Sharmini, a spokeswoman at Singapore's National University Hospital. Earlier this year, the government appointed a panel of experts on philosophy, science and law to study ethical and moral questions regarding biotechnology research.

The government last year earmarked million to promote what it calls "life sciences" research in the private sector.


Stem Cells And Cloning
In theory, embryonic stem cells could be used to replace any part of the body damaged by accident or illness. That could lead to cures for such recalcitrant diseases as Parkinson's, Alzheimer's and diabetes. Some scientists believe the cells might eventually allow those who are paralyzed to walk again.

But many feel such medical miracles would be tainted, because scientists must destroy human embryos to make these cells. To those who believe an embryo has the rights of a person, this is akin to murder.

Embryo-derived cells are only one type of stem cell. Others are found in umbilical cord blood, or even in specific organs like bone marrow or the brain. But these other types do not appear to be as flexible as those taken from embryos. Another advantage for the embryonic cells: Unlike other types of cells, they can probably reproduce forever.

Some researchers believe that the process used to clone animals might be important in stem cell research. Researchers would clone one of the patient's own cells. They would destroy the embryo used in the process, creating stem cells that would not be rejected by the patient's body.

Human stem cells hold out the potential of almost unimaginable medical breakthroughs. That's because they're a kind of universal cell that can develop into most of the specialized cells and tissues of the body. And that means new tissues or entire organs could one day be grown in a lab, then used to treat everything from heart disease to spinal cord injuries.