Embryonic stem cells have been encouraged to grow into sperm cells for the first time, Japanese scientists report.
The work is very preliminary, and was done in the laboratory with mouse stem cells. The next step would be to see if it can be repeated in live animals.
Stem cells are the basic building blocks of animals, forming in the new embryo and later developing into the various organs and tissues as the fetus grows.
Researchers have grown stem cells into many other types of cells, including egg cells, but this is the first time a sperm cell has been developed, the scientists said.
The work was headed by Toshiaki Noce of Mitsubishi Kagaku Institute of Life Science in Japan. The results are reported in this week's online issue of Proceedings of the National Academy of Science.
Noce and his team incubated the stem cells with other cells that produce a protein called BMP4, which is known to stimulate formation of sperm cells during the development of an embryo. In their laboratory, some of the stem cells began developing into sperm cells within one day, a process that takes three days in the embryo.
Bert Vogelstein, a professor at Johns Hopkins University who headed an Academy panel on stem cells, said the work is 'novel and provides a wonderful example of how new technologies can provide diverse cell types in the test tube that may prove useful for biomedical applications in the future.'
Growing stem cells into other tissues has been hailed as a source of major potential therapies in the future. However, the process is controversial because many stem cells are harvested from discarded embryos.
The Bush administration has limited federal funding for stem cell research to lines of cells that already exist, although new stem cell lines can be developed using private funds and in some other countries.
The body's master cells can repair the damage caused by a heart attack, a study suggests.
Tests on rats have shown that stem cells can restore up to 90% of the heart's ability to pump blood around the body, which is often reduced following an attack.
Stem cells, which can be obtained from bone marrow, are unique in that they have the potential to turn into any other cell in the body.
Doctors have injected these cells into a small number of patients with heart disease. However, the results of these trials are not yet known.
This latest study adds to the growing body of evidence that stem cells could provide real hope to patients with heart problems.
Difficult procedure
Up until now, the technique has proved problematic because the stem cells tended to die shortly after being transplanted.
This has meant that the stem cells have not been able to turn into new muscle, replacing tissue that has died as a result of a heart attack.
Dr Victor Dzau and colleagues at Brigham & Women's Hospital in Boston, United States, have tried to get around this problem by engineering these cells to enable them to survive longer.
They added the Akt gene to cells in the laboratory. Akt is a protein that prevents cell death.
These engineered cells were then injected into the hearts of rats, which had had a heart attack.
Tests showed that cells with this gene were much more likely to survive compared to other stem cells.
The treatment restored between 80% and 90% of the heart's volume.
Writing in the journal Nature Medicine, they said it also dramatically improved the heart's ability to pump blood around the body.
'Stem cells genetically enhanced with Akt can repair infracted myocardium, prevent remodelling and nearly normalize cardiac performance,' they said.
Doctors elsewhere in the US announced in April that they had carried out stem cell transplants on 15 patients with advanced heart disease.
One of these patients died 14 weeks later. Doctors at the Texas Heart Institute have yet to reveal how the other patients have fared.
They are also considering carrying out much larger trials. If successful, they could pave the way for stem cell transplants for other patients with heart disease around the world.
The European Commission has said the EU should fund research which involves harvesting stem cells from frozen human embryos - but not in countries where the technique is banned.
However those countries may still oppose the introduction of the new rules on moral grounds.
Sweden, Finland, Greece, the Netherlands and Britain allow stem cells to be harvested from 'spare' IVF embryos.
But taking stem cells from embryos is illegal in countries such as Germany, France, Ireland and Spain and blocked elsewhere.
The European Commission hopes the rules can be introduced by 31 December this year when a moratorium on EU funding for stem cell research ends.
But all member states must approve the rules before they can be introduced.
Laboratory sources
Supporters of stem cell research say it could hold the key to cures for a wide range of serious diseases, including Alzheimer's and Parkinson's.
Stem cells are cells at an early stage of development which have the potential to turn into many different types of tissue.
But critics say existing sources of stem cells - so-called 'lines' which can be grown in laboratories, can supply enough for research and would eradicate the need for embryos to be used in research.
In Germany, the law states research on stem cells is only allowed if they were imported and existed before 1 January 2002.
It is understood Germany wants the EU to introduce similar rules.
The European Commission has set a cut-off date of 27 June 2002 for when embryos must have been created - but it does not set a date for when stem cells should have been created by.
Foresight
EU Research Commissioner Philippe Busquin said the main aim was to stop a 'brain drain' of the brightest scientists leaving Europe to work in countries like the US, Australia and Singapore.
He said: 'Europe is in relatively weak position.
'Obviously there are ethical concerns. But the real question is 'Are we able to have excellence in this field in Europe?'.'
He said countries could continue to choose whether they funded embryonic stem cell research themselves, but that the EU felt it was important to encourage as much research as possible.
Sir George Radda, chief executive of the Medical Research Council, said: 'The decision to set a cut-off date for which embryos can be used is limiting and may mean fewer high-quality embryos available for research, but we recognise compromise was needed given the disparate views of member states.
'Overall we're pleased that the Commission has recognised the importance of granting funding to allow researchers to generate stem cells using freely donated embryos left over from IVF research.
'The MRC sees stem cell research as a key research priority over the coming decades and the UK government has had the foresight to put in place legislation that will enable ethical and beneficial research into heath and human disease to be carried out.
'It's good to see this being echoed in EC policy, as we are on the brink of real medical progress.'
A spokesman for the Parkinson's Disease Society said: 'The use of stem cell research offers real hope that lost dopamine-producing cells can be replaced with new healthy cells.
'This could be the first treatment to reverse the symptoms of Parkinson's and could therefore effectively lead to a cure.
Controversy surrounding stem cell research.
There exists a widespread controversy over stem cell research that emanates from the techniques used in the creation and usage of stem cells. Human embryonic stem cell research is particularly controversial because, with the present state of technology, starting a stem cell line requires the destruction of a human embryo and/or therapeutic cloning. However, recently, it has been shown in principle that embryonic stem cell lines can be generated using a single-cell biopsy similar to that used in preimplantation genetic diagnosis that may allow stem cell creation without embryonic destruction.
Opponents of the research argue that embryonic stem cell technologies are a slippery slope to reproductive cloning and can fundamentally devalue human life. Those in the pro-life movement argue that a human embryo is a human life and is therefore entitled to protection.
Contrarily, supporters of embryonic stem cell research argue that such research should be pursued because the resultant treatments could have significant medical potential. It is also noted that excess embryos created for in vitro fertilisation could be donated with consent and used for the research.
The ensuing debate has prompted authorities around the world to seek regulatory frameworks and highlighted the fact that stem cell research represents a social and ethical challenge.
