If further research is able to create fully developed sperm based on this latest study then it could provide hope for fertility treatments.
Researchers led by Professor Karim Nayernia of the North-East England Stem Cell
Institute (Nesci) created the cells by taking bone marrow from male volunteers and isolating the mesenchymal stem cells (MSC), which are cells that exist in bone marrow but can form a variety of other cells.
In a laboratory the scientists then coaxed the MSC into becoming male reproductive
cells, known as 'germ cells'.
After analysing genetic markers they discovered the presence of partly-developed sperm cells, 'spermatagonial stem cells' (SSC), which are an early phase of the male germ cell development.
In most men SSC eventually develop into fully-grown, functional sperm but the researchers were not able to achieve this in the experiment.
"We're very excited about this discovery, particularly as our earlier work in mice suggests that we could develop this work even further," Professor Nayernia said.
"Our next goal is to see if we can get the spermatagonial stem cells to progress to mature sperm in the laboratory and this should take around three to five years of experiments."
He added that he will be collaborating with Nesci colleagues "to take this work forward".
The study is published today in the journal Reproduction: Gamete Biology.
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