The Recipe for Man Made Sperm

Stem cells rock. While the stock market tumbles, stem cell science is sizzling. I know, you’re thinking: what is he talking about? No diseases have been cured with new stem cell technologies. But, from what’s being discovered almost weekly now, I can tell you that male infertility is likely to be one of the earliest boxes ticked on the “Diseases to Cure” list for stem cells.

Sperm from Stem Cells

Honestly, stem cells appear to be great to use to create sperm. Just a few posts ago, I shared the exciting findings from a group in Japan who took stem cells from newborn mouse testicles, placed them in an “organ culture” system (basically Jell-O), and grew mature, fertile sperm in the laboratory. Over the past 2 years, my colleagues at Stanford have also shown that human embryonic stem cells can be pushed along the path toward sperm in a dish. They also showed that adult stem cells from places like skin can also be driven in the same direction. Not all the way to mature sperm, but certainly more than half the way.

Overcoming Sterility in Mice

Last week, researchers at Kyoto University in Japan brought man made sperm closer to reality…at least in mice. I know many of you aren’t really worried about infertility in mice, but we have to start somewhere.
In a study published this past week, they took embryonic stem cells from mice, the mother of all cells, and watched them closely as they began to develop into other cell types (i.e. differentiate) in a dish. After several days, they plucked out rare and transient downstream stem cells called the primordial germ cells and transplanted these cells back into sterile baby mouse testicles. And sperm were made. Good sperm. Genetically intact and fertile sperm. Sperm that led to offspring that were also naturally fertile. And they did the same experiments with adult stem cells and got the same result, eliminating the need to use embryos at the start.
Please realize that this success did not happen overnight, but was the result of good, wholesome science and lots of sweat equity. And not all the results were rosy: primordial germ cells are rare, short lived and inefficient. In addition, when slightly different cells were injected into testicles, benign tumors formed, the scourge of stem cell science. So now you understand why mice experiments come first.

Stem Cells and Human Male Infertility

Imagine this: A boy has cancer and gets cured by being pounded with chemotherapy. Easily enough treatment to sterilize him for life. After that, his testicles could make sperm, but the “seeds” (early germ cells) that develop into sperm have been wiped out. Solution? A skin biopsy. Turn it into an adult stem cell and inject it right back into his testicles. And ta da! Sperm. I can’t stop thinking about how possible all of this is, as stem cell recipes are perfected. As Ted Allen, The Iron Chef once said: “There are two words to improve any dish: Ba-Con.”