Lab-grown Sperm Cells
Sexual reproduction occurs when sperm cells fertilize egg cells. But a research lab in Massachusetts has put a new twist on this universal form of reproduction. George Daly, and his colleagues from the Whitehead Institute for Biomedical Research, successfully fertilized mouse eggs with sperm grown from stem cells. These sperm cells did not come from an adult male mouse, but rather were grown from embryonic stem cells (Geijsen, et al., 2003). Commenting on the newly created sperm cells, Daley noted: “They look like normal sperm but without the tail” (Pilcher, 2003). These lab-grown reproductive cells were created using stem cells derived from male mouse embryos. The embryos were allowed to grow to a specific stage, at which point the sperm-like cells were teased out.
Some are hailing this new development as an alternative treatment for infertility. Yet, as Helen Pilcher reported, only “one in five of the resulting embryos began to develop normally” (2003). Azim Surani of the University of Cambridge in England, who studies sex-cell development, cautioned that the “method’s low success rate may indicate a problem” (Pilcher, 2003). I certainly would hope that a one-in-five success rate would be considered somewhat indicative of a problem! Pilcher noted: “Normally, as sperm and eggs develop, their genetic material is reprogrammed. This switches on the correct genes so that fertilization can proceed. This process may have gone awry in the mouse sperm, Surani speculates—similar problems are thought to occur during animal cloning.” While some may tend to view this as an acceptable alternative, techniques that bypass natural and biological processes are often later deemed impractical and even harmful.
So what will happen as researchers move toward working with humans? We can be assured that human sperm will be much more difficult to create than mouse sperm—but that is not likely to stop investigators from trying. This bold new technology will require researchers to make their stem cells using therapeutic cloning. To do so, DNA from an adult cell would be inserted into an egg that had been emptied of its DNA, and stem cells then would be isolated from the resulting early embryo. Once the stem cells had been teased out, they would be cultured to form these sperm.
While all of this may sound like an easy process, it is not. For instance, look at all of the problems researchers have with reproductive cloning (see “Cloning—Not the Big Bad Wolf—Killed the Three Little Pigs”). Experiments utilizing adult genetic material are risky, warns Hans Schöler of the University of Pennsylvania in Philadelphia. Earlier this year, Schöler was the first to produce lab-grown eggs. He observed: “The DNA in our body is of low quality,” (Pilcher, 2003). He contends that any disease-causing mutation that occurred during aging would be passed on to the offspring.
In September 2003, Japanese researchers were the first to report that embryonic stem cells could form in vitro into germ cells (Toyooka, et al., 2003). This latest study is the first to show that such sperm actually are fertile. In October 2003, at the 59th annual meeting of the American Society for Reproductive Medicine, James Grifo and colleagues at Sun Yat Sen University Medical Science in China created the first human pregnancy using techniques related to cloning (see “Pregnancy and Death Resulting from Human Nuclear Transfer”). Researchers continue to “push the envelope,” and yet success rates continue to be dismal at best. Has anyone stopped to consider that we are spending literally millions of dollars (and animal and human lives) to create a technique that bypasses sexual reproduction—something that routinely works to create healthy offspring? Unfortunately, as we move closer toward human cloning, the cries of the human embryos that will be sacrificed will fall upon the deaf ears of those who now believe they are more than capable of creating and manipulating life.
Geijsen, Niels, Melissa Horoschak, Kitai Kim, Joost Gribnau, Kevin Eggan, and George Q. Daley (2003), “Derivation of Embryonic Germ Cells and Male Gametes from Embryonic Stem Cells,” Nature, [On-line], URL: http://www.nature.com/cgi-taf/DynaPage.taf?file=/nature/journal/vaop/ncurrent/abs/nature02247_fs.html&dynoptions=doi1071606361.
Pilcher, Helen R. (2003), “Sperm From Stem Cells Fertilize Egg,” Nature, Science Update, [On-line], URL: http://www.nature.com/nsu/031208/031208-11.html.
Toyooka, Yayoi, Naoki Tsunekawa, Ryuko Akasu, and Toshiaki Noce (2003), “Embryonic Stem Cells Can Form Germ Cells in Vitro,” Proceedings of the National Academy of Science, 100:11457-11462, September 30.