A team of British scientists claimed Wednesday to have created human sperm using embryonic stem cells, in a medical first that they say will lead to a better understanding of fertility.
Researchers led by Professor Karim Nayernia at Newcastle University and the NorthEast England Stem Cell Institute (NESCI) developed a new technique that allows the creation of human sperm in the laboratory.
They stressed that the sperm, developed from stem cells with XY chromosomes (male), would not be used for fertility treatment, as this is prohibited by British law and in any case is not their main interest.
"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," said Nayernia.
"This understanding could help us develop new ways to help couples suffering infertility so they can have a child which is genetically their own."
He said more investigation was needed to decide whether the so-called in-vitro derived (IVD) sperm, could be used as a fertility treatment, for example for boys who became infertile after receiving chemotherapy for cancer.
While such a treatment would not likely be developed for at least a decade, Nayernia said legislation should be put in place "sooner rather than later" to allow the technique to be licensed.
The team's work involved developing stem cells that had XY chromosomes into germline cells -- cells that can can pass their genetic material to future generations.
These were then prompted to complete meiosis, or cell division, which then produced "fully mature, functional sperm."
Stem cells are immature cells that can develop into different cell types.
The scientists tried to develop cells with XX chromosomes (female) in the same way but they did not progress beyond early stage sperm, called spermatagonia. The team concluded that the genes on a Y chromosome are essential for sperm maturation.
The research, published in the journal Stem Cells and Development, could also lead to a better understanding of how genetic diseases are passed on.
However, other scientists expressed doubt about the work.
"As a sperm biologist of 20 years' experience, I am unconvinced from the data presented in this paper that the cells produced by Professor Nayernia's group from embryonic stem cells can be accurately called 'spermatozoa'," said Dr Allen Pacey, senior lecturer in andrology at the University of Sheffield.
"While the cells produced may possess some of the distinctive genetic features and molecular markers seen in sperm, fully differentiated human spermatozoa have specific cellular morphology, behaviour and function that are not described here."