Stem cells found in human skin can be turned into sperm precursor cells, US researchers have found. The findings could help restore fertility to cancer patients, and could provide a new way of studying the development of sperm cells in the lab.
'Sperm can be banked for future artificial insemination procedures, but that does not help some patients, such as pre-pubertal boys', said Dr Charles Easley, who led the study at the University of Pittsburgh, Pennsylvania. 'There are procedures to store testicular tissue prior to cancer therapy, but men who didn't have the opportunity to save tissue are permanently sterile, and so far there are no cures for their sterility'.
Men with other causes of infertility, such as Sertoli-cell-only (SCO) syndrome, would also stand to benefit from the treatment. However, the US team has not succeeded in forming mature sperm cells just yet. 'No one has been able to make human sperm from pluripotent stem cells in the lab, but this research indicates it might be possible', said Dr Easley.
Dr Easley and his team have taken in vitro spermatogenesis, the creation of sperm cells in a lab, further than any team of scientists have before. 'It is good work, there is no doubt about that', said Dr Allan Pacey, a male fertility expert at the University of Sheffield.
Pluripotent stem cells taken from skin samples and human embryonic stem cells were both converted into round spermatids, which are one of the final stages of spermatogenesis. The researchers tried the same approach with cells from female skin samples in an attempt to create egg cell precursors, however they were unsuccessful.
Initial results from the spermatids showed they contained the right amount of genes, and even the father's unique epigenetic marks. Dr Easley emphasises that the process of creating spermatids from stem cells can be used as a model to study what leads some men to become infertile, or even the creation of new contraceptives. The use of sperm cells produced in this manner is likely to raise several ethical issues that may first need to be addressed.
'This model gives us a unique opportunity to study the molecular signals that govern the process [spermatogenesis], allowing us to learn much more about how sperm are made. Perhaps one day this will lead to new ways of diagnosing and treating male infertility', said Dr Easley.
Around one in six couples have problems with infertility and in around 40 to 60% (percent) of cases this is due to male infertility.