Scientists have created early-stage sperm cells from human bone marrow, a development that a researcher says could one day lead to improvements in fertility treatments.

In a study published Friday, Professor Karim Nayernia of the University of Newcastle on Tyne in Britain and a team of researchers said they were able to create spermatagonial cells, which in most men develop into fully functional sperm, from stem cells in the bone marrow of human male volunteers.

However, the spermatagonial cells in the experiment did not turn into sperm cells, a process Nayernia hoped could be reached after more experimentation.

"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," Nayernia said in a statement.

The next step for these early-stage cells to become sperm would be for them to undergo meiosis — or cell division. Earlier experiments were able to achieve this step using cells from bone marrow in mice. These cells also did not develop into fully mature sperm.

The research, published in the journal Reproduction: Gamete Biology, could one day help in fertility treatment for men, Nayernia contends.

And if female bone marrow is also able to produce sperm cells, it raises the possibility that women would be able to pass on their genetic material through manufactured sperm.

Nayernia told the British newspaper the Telegraph that growing sperm from females is possible, based on evidence from testing of mice.

The process could run into legal concerns in the U.K., with a recent government white paper proposing a ban on using artificially created sperm or eggs in assisted reproduction.

Though any advances are likely far off, University of Alberta law professor Tim Caulfield told CBC News Online Canadian regulators should start thinking about where artificially created sperm would fall under the law.

Buying reproductive material not allowed

The Assisted Human Reproduction Act allows the donation of sperm and eggs and their use to assist conception and allows the use of human stem cells in research. But buying or selling sperm, eggs and other human reproductive material is not allowed.

"If these cells are defined as naturally created, they would likely fall under the act and be subject to the same rules," said Caulfield, a Canada Research Chair in Health Law and Policy.

"But if they are found to be outside the normal definition, then we'll need to figure out how they can be used," he said.

Last year, Nayernia and scientists at the University of Gottingen in Germany became the first to produce viable artificial sperm from embryonic mouse stem cells. These sperm were used to fertilize mice eggs, resulting in seven live births.

Stem cells have the unique ability to develop into any type of cell, with embryonic stem cells considered the most versatile kind.