Stem cells from human bone marrow can be converted into early-stage sperm, according to a research team based at the North-east England Stem Cell Institute (NESCI), Newcastle. The discovery could improve our understanding of natural sperm cell production and perhaps lead to novel fertility treatments in the long-term.

NESCI's Karim Nayernia and colleagues extracted a tiny sample of bone marrow from male volunteers and then isolated the so-called mesenchymal stem cells from this living tissue. Other researchers have demonstrated previously that these cells can grow into other body tissues such as muscle cells.

The researchers grew the mesenchymal stem cells in the laboratory and used a little chemical trickery to coax these cells to grow into male reproductive cells. More specifically, genetic markers reveal these partly developed sperm cells to be spermatagonial stem cells, which are the early phase of sperm formation. Under natural conditions, spermatagonial stem cells mature into fully fledged sperm cells, although the maturation process was not carried out with the human samples.

Previously, Nayernia and his team had carried out this final step successfully with mouse spermatagonial cells from mouse bone marrow, which could be transplanted into the mouse testis where they undergo early cell division in the next stage before mature sperm cells form. "We're very excited about this discovery, particularly as our earlier work in mice suggests that we could develop this work even further," Nayernia explains.

"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 adds. "I'll be collaborating with other NESCI scientists to take this work forward." The researchers hope to one day be able to restore fertility in young men who have undergone chemotherapy, although it could be several years before clinical trials for that treatment begin.

Nayernia is concerned that government legislation, such as the UK's recent White Paper Review of the Human Fertilisation and Embryology Act, could outlaw such treatments. Even in the short term, the threat of legislation may hinder efforts to gain support and funding for further research, he says.

Reproduction: Gamete Biol, 2007, 69-76; http://dx.doi.org/ http://www.biolreprod.org/collected/gamete_biology.dtl