It's amazing how the field of stem cell research has advanced so much in such a short amount of time. Today, just a little over a decade after the first stem cell line was produced, scientists announced another breakthrough - turning stem cells into sperm.
In a paper published in the journal Stem Cells And Development (PDF), British scientists from England’s Newcastle University detail a technique for turning stem cells with male chromosomes into reproductive germline cells and prompt them to divide into sperm.
Like non-stem derived sperm, the in vitro versions have 1/2 the amount of genetic material of a regular cell, have a head and a tail, and are capable of swimming and activating an egg for fertilization.
And, interestingly enough, they were only able to produce them with male-derived cells. Female stem cells could begin the process, but stopped at an early stage, suggesting that genes on the Y chromosome are absolutely essential for sperm development.
While this step is a huge one, it's important to note that these sperm are not the same as the normal, mature sperm which are created in the testes, and cannot be used to produce fertilized embryos and offspring. There are other external structural differences which make these man-made sperm unable to act like normal sperm. So while it's an amazing discovery, it isn't a cure for male infertility - yet.
The sperm do, however, give us valuable insights into the origins of sperm and perhaps the underlying causes of infertility. The team is now trying the same trick using skin cells of infertile men and studying the differences between how those sperm and their embryo-derived ones develop, with the hopes of understanding more about the root causes of infertility. These studies may lead to new treatments for infertility, although at the moment, British law forbids the implantation of such sperm into humans, and any lab-grown embryos (if they could get the sperm to successfully fertilize an egg) can only be grown for 14 days, at which point they must be destroyed.
Even if a cure for impotence isn't in the near future, this new technique allows us to speed up nature's clock and see sperm development in a way that we have never been able to before. In the human body, it takes 15 years for the cells which develop into sperm-producing cells to develop and mature before they produce sperm - a process we have never been able to witness step-by-step. Now, it takes only 3 months, granting scientists the unique opportunity to learn even more about human development.
Nayernia, K., Lee, J., Lako, M., Armstrong, L., Herbert, M., Li, M., Engel, W., Elliott, D., Stojkovic, M., Parrington, J., Murdoch, A., Strachan, T., & Zhang, X. (2009). In Vitro Derivation of Human Sperm from Embryonic Stem Cells Stem Cells and Development DOI: 10.1089/scd.2009.0063
Thursday, July 9, 2009