PARIS: Immature sperm cells have been created from stem cells in human bone marrow – they might one day lead to treatments for male infertility.
The study, outlined Last week in the journal Reproduction: Gamete Biology, was however unable to produce mature sperm and experts caution that much more research would be required before the method could be used to produce viable sperm for fertility treatments.
Last year German biologist Karim Nayernia successfully used sperm cells created from mouse embryonic stem cells to fertilise mice eggs, resulting in seven live births.
Nayernia – currently with the North-east England Stem Cell Institute at Newcastle University – has now led a team that had translated that discovery to human trials.
The researchers took bone marrow from human volunteers and isolated a type of adult stem cell that usually turns into muscle – stem cells are able to turn into many different types of tissue.
They then cultured the cells in the laboratory in such a way that they became male reproductive cells, bearing genetic markers specific to partly-developed sperm. In most men, these “proto-sperm” develop into mature, functioning sperm, but in the experiment the growth stopped at the most preliminary stage.
“We’re very excited about this discovery, particularly as our earlier work in mice suggests that we could develop this work even further,” said Nayernia. “Our next goal is to see if we can get the spermatagonial stem cells to progress in mature sperm in the laboratory,” he said.
But some independent experts argued that it is too soon to conclude that therapies could evolve directly out of these experiments.
“The observations are interesting but one must be cautious about drawing conclusions based purely on the expression of a few [genetic] markers, without supporting functional data,” said Peter Andrews, a bio-medical scientist and co-director of the Centre for Stem Cell Biology at the University of Sheffield in England. In general, manipulating stems cells, can cause lasting genetic changes with unpredictable results, warned Andrews.
Stem cell research faces not only scientific barriers, but legal and ethical ones as well. Many countries – including the United States and France – have placed very strict limitations on stem cell research, especially when the cells originate from human embryos.
The British government has recently proposed a ban on using artificially created sperm or eggs in human reproduction – meaning that is these results did lead to a fertility treatment it might not be legal to use it in the U.K..
Earlier this month, researchers at the Imperial College in London, announced that they had succeeded in growing human heart valve-like tissue from bone marrow stem cells, opening up the possibility that the replacement tissue could be used in transplants for heart disease patients.
Growing replacement tissue from a patients own stem cells has been a key goal of scientists, as damaged body parts replaced by genetically-matched tissue would be much less likely to be rejected than current transplants.
To date, scientists have grown tendons, cartilage and bladders from stem cells, but not complex organs.