US researchers have managed to grow mouse sperm stem cells in the laboratory. They have also transplanted these cells into infertile mice, which have then produced mature sperm and fathered offspring. The scientists, based at the University of Pennsylvania School of Veterinary Medicine, say their achievement opens up research into possible new treatments for male infertility. It also provides a way in which the genetic information of the sperm could be potentially be altered, prior to fertilisation. The study appears in the early online edition of the Proceedings of the National Academy of Sciences.
Spermatogonial stem cells, which give rise to sperm cells, have proved difficult to grow outside the body. In the latest study, the scientists developed a culture solution that contained the precise combination of cellular growth factors required by the stem cells. The researchers say that by manipulating the growth conditions, they might also be able to get the stem cells to grow into mature sperm in the laboratory. This could lead to new treatments for male infertility in humans, say the team, especially since the factors needed to grow the mouse stem cells would probably also foster the growth of human sperm.
The research could also help male cancer patients who are too young to store semen before undergoing treatment that could leave them infertile. The ability to grow sperm stem cells in the laboratory could also provide an alternative method for growing embryonic stem cells (ES cell). Team leader Ralph Brinster thinks that it might be possible to turn the sperm stem cells into ES cells, which could then be used to produce all the different types of body cell. Other groups have already shown it is possible to use mouse ES cells to grow sperm, which have been used to fertilise an egg.
The study also opens up the possibility of altering the genetic material of sperm before fertilisation, providing a new method of creating genetically altered animals and, potentially, humans. 'If each parent in a couple carries a similar defective recessive gene for a disease, for example, it should be possible in the future to harvest the male spermatogenic stem cells, correct the gene in culture and implant the stem cells back into the male to produce normal sperm', says Brinster, adding 'the couple could then conceive a healthy child'.