UK scientists have created human sperm cells in the laboratory for the first time. The sperm, called in vitro-derived (IVD) sperm, were grown from embryonic stem (ES) cells. The researchers hope that the IVD sperm will provide a useful model for studying the development of sperm cells and the causes of male infertility.
The research team, from the North-East England Stem Cell Institute (NESCI) in Newcastle, UK, treated human ES cells with a chemical to prompt them into becoming germline stem cells – stem cells that are found in the reproductive organs and give rise to eggs and sperm. They then selected out these germline stem cells and continued to grow them in the presence of chemicals to encourage them to develop further into mature sperm cells. The IVD sperm, like normal sperm, grew tails and were highly mobile. They also contained only 23 chromosomes, compared to the 46 chromosomes found in all other human cells (apart from egg cells which also contain only 23 chromosomes - when a sperm fertilises an egg they merge to form a single cell with a total of 46 chromosomes).
Professor Karim Nayernia, who led the study, said: ‘This is an important development as it will allow researchers to study in detail how sperm forms and lead to a better understanding of infertility in men – why it happens and what is causing it. This understanding could help us develop new ways to help couples suffering infertility so they can have a child which is genetically their own. It will also allow scientists to study how cells involved in reproduction are affected by toxins, for example, why young boys with leukaemia who undergo chemotherapy can become infertile for life – and possibly lead us to a solution'.
The research has sparked much controversy, however, with suggestions in the media that this work could lead to men becoming unnecessary for human reproduction. Professor Nayernia answered such claims, saying: ‘While we can understand that some people may have concerns, this does not mean that humans can be produced ‘in a dish' and we have no intention of doing this. This work is a way of investigating why some people are infertile and the reasons behind it. If we have a better understanding of what's going on it could lead to new ways of treating infertility.'
It is illegal to use IVD sperm for human reproduction in the UK. Laboratories can be granted a licence by the UK's Human Fertilisation and Embryology Authority (HFEA) to grow IVD sperm, and can use them to fertilise eggs, but the resulting embryos must be destroyed 14 days after fertilisation. The researchers are calling for the laws to be debated and reconsidered, as they feel that the technique has the potential to one day be used as a way for infertile men to father children. This would be a long way in the future, however, as much more would need to be known about the IVD sperm first and safety issues would need to be addressed. Previous studies in mice found that IVD sperm could be used to fertilise eggs but the resulting offspring had major health problems and died within five months, indicating an inherent defect in the IVD sperm.
The technique could only be performed using male ES cells that have an X and a Y chromosome. Female ES cells with two X chromosomes could not form mature sperm cells, because male genes found on the Y chromosome are essential for sperm development - further dispelling notions that the research could mean ‘the end of man'.
Other members of the scientific community have cast doubts on how significant this study of the creation of IVD sperm is. They have suggested that the data, published in the journal Stem Cells and Development, is insufficient to prove the IVD sperm are equivalent to normal sperm. Professor Azim Surani, from Cambridge University, believes they were ‘sperm-like cells' but ‘a long way from being authentic sperm cells.'