If you know just one thing about embryonic stem cells, it’s probably that they have the potential to grow into any type of cell in the body. That, of course, is why scientists find them so valuable.
But having the potential to become any type of cell is not the end game -- research groups around the world are trying to figure out the precise recipe for turning those stem cells into specific types of cells that would be useful for studying or treating various diseases.
This week, a group of Japanese researchers from Kyoto University said they had figured out a way to turn embryonic stem cells into the more specific type of stem cell that makes sperm. Their findings were published online Thursday in the journal Cell.
How did they know they got it right? They took those sperm progenitor cells and injected them into the testes of infertile mice. Those mice went on to father healthy mouse pups that were able to reproduce themselves.
These experiments offer hope to men who struggle with infertility issues. But there’s a long way to go before this work can be translated into people.
For starters, the recipe used to transform the mouse stem cells into sperm will need to be modified to work with human embryonic stem cells. But infertile men who want to pass their own DNA to their children won’t be helped much by this, at least not directly. By the time a person is of reproductive age -- let alone gets past the first several days of embryonic development -- it’s too late to make embryonic stem cells with one’s matching DNA.
So the second step will be to figure out a way to make the sperm precursor cells out of induced pluripotent stem cells, or iPS cells. These are the cells taken from skin or another adult tissue and rewound to an early state where they are flexible enough to -- say it with me -- become any type of cell in the body. The Japanese researchers were able to make sperm progenitor cells out of iPS cells, and some mouse pups were born as a result, but the entire process worked less well than with embryonic stem cells. If these technical hurdles can be overcome, a man with fertility issues theoretically could donate a patch of skin and let scientists use that to produce sperm that contains his DNA.
A summary of the study is available here.