Sperm made from bone marrow cells
By Marlowe Hood PARIS, AFP
The China Post
15th April 2007
Scientists have succeeded in turning human stem cells into immature sperm cells which researchers said could lead to treatments for male infertility in a study published Friday.
The lead scientist, Karim Nayernia, last year succeeded in using sperm cells created from mouse embryonic stem cells to fertilize mice eggs, resulting in seven live births.
Experts in cell biology, however, cautioned that the results must be evaluated with caution and may not lead to the hoped for developments.
The results of the experiment, conducted in Germany, were published in the journal Reproduction: Gamete Biology.
Nayernia and his colleagues took bone marrow from human volunteers and isolated a type of stem cell that normally grows into other body tissue, especially muscle.
They then cultured the cells in a 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" -- known as spermatagonial cells -- 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 in a statement.
"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 other experts suggest 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 molecular markers, without supporting functional data," said Peter Andrews, a bio medical scientist and co-director of the Center for Stem Cell Biology and the University of Sheffield in England.
In general, manipulating stems cells, he warned, can cause lasting genetic changes with unpredictable results.
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.
Earlier this month, researchers at the Imperial College London announced that they had succeeded in growing tissue from stem cells in bone marrow that works in the same way as the valves in human hearts, opening up the possibility that replacement tissue could be used in transplants for heart disease patients.
Growing replacement tissue from stem cells has been a key goal of scientists. Damaged body part replaced by tissue that is genetically matched to the patient cannot be rejected.
To date, scientists have grown tendons, cartilage and bladders, but no complex organs.
