Sperm from Stem Cells
Sperm from Stem Cells
You’ve probably already heard by now, but a researcher originally based in Germany and now relocated to the UK has succeeded in growing sperm from mouse embryonic stem cells and fertilizing eggs with the new sperm. The story is widely being reported as a health story on the issue of male infertility, although at least one headline says that it’s a way for women to have babies without men. (Hello—don’t sperm banks already do that?) The mice that were born from the fertilized eggs had some major abnormalities, however.
The BBC originally reported this on Sunday (the scientific paper will appear in the journal Developmental Cell). Here’s a summary description of the procedure as described by the BBC:
The scientists isolated from embryonic cells some specialized cells called spermatogonial progenitor cells; these are stem cells that have begun to differentiate into sperm-producing cells. They grew them in culture until sperm were produced, then injected the sperm into mouse eggs. The fertilized eggs were then transplanted into female mice.
The idea of this as a fertility treatment is that men with low or non-existent sperm counts could have some of their own stem cells extracted and sperm grown in the lab from those. However, scientists are urging caution—there are many technical difficulties with the procedure, and the chance of defective offspring is high. Also, the experiment needs to be duplicated with existing stem cells from an adult male to show that it doesn’t require the existence of an embryonic stem cell somewhere in the process. And with embryonic stem cells, it seems to me that right now it would require cloning procedures to get one’s own DNA in the progenitor sperm cells, which is another big hurdle. After all, the mouse sperm cells came from embryonic stem cells, not from adult male mice who wanted to pass their genetic code on.
There is also a cultural/ethical issue with the idea of lab-created sperm; the BBC quoted a scientist who said,
“However, sperm and eggs play a unique role in our understanding of kinship and parenthood, and being able to create these cells in the laboratory will pose a serious conceptual challenge for our society."
The Guardian reports that all seven of the baby mice were infertile, had severe breathing or walking difficulties, and were either abnormally large or had stunted growth. The longest any of them lived was five months, far short of the normal 2 years for a mouse. It also reports that the sperm that developed from the progenitor cells were insufficiently developed to swim to an egg themselves, which is why they were instead injected into the egg. Of 210 eggs that the team tried this on, only 65 were fertilized and only seven of those had live offspring.
In theory, a woman or a man could produce stem cells which could be developed into either an egg or sperm. One could produce one’s own child in that case—which would seem like a big risk to me, given the likelihood of duplicative genetic errors. But perhaps more significantly, gay couples or infertile heterosexual couples could have children that are biologically theirs instead of relying on donor eggs or sperm.
The child you get still depends a lot on the parent that you are, however. There are a lot of loved adopted children and neglected biological children in this world. Adoption is a better option right now than test-tube sperm.
One other thing interests me—these are being called artificial sperm, and there’s a lot of emphasis in the media on the idea of having babies without men. But this is not something from nothing. This is the development of cells that were already on their way to being sperm in a laboratory instead of naturally in vivo. It isn’t exactly astonishing that cells that were beginning to differentiate into sperm could continue to do so, given all the other kinds of differentiation that have been successfully done. It would be far more startling to me if the scientists had derived the sperm from bone marrow or skin stem cells. Yes, sperm and egg are very specialized and very special cells—but they are ultimately cells, subject to the same things other cells are. It’s not magic here, and it’s not synthetic either. It’s enhanced (or, given the results, disrupted) biology.