Artificial sperm a reality in China

In a first, a team of researchers has created functioning sperm from mice in a lab, raising the prospect of women never needing men again.

Researchers from China coaxed mouse embryonic stem cells to turn into functional sperm-like cells, which were then injected into egg cells to produce fertile mouse offspring. The work provides a platform for generating sperm cells that could one day be used to treat male infertility in humans.

Reproducing germ cell development in vitro has remained a central goal in both reproductive biology and reproductive medicine, says co-senior author Jiahao Sha from Nanjing Medical University, adding that they established a robust, stepwise approach that recapitulates the formation of functional sperm-like cells in a dish. Their method fully complies with the gold standards recently proposed by a consensus panel of reproductive biologists, so they think that it holds tremendous promise for treating male infertility.

Sha teamed up with co-senior study authors Qi Zhou and Xiao-Yang Zhao of the Institute of Zoology at the Chinese Academy of Sciences to develop a stem cell-based method that fully recapitulates meiosis and produces functional sperm-like cells.

The first step was to expose mouse embryonic stem cells (ESCs) to a chemical cocktail, which coaxed the ESCs to turn into primordial germ cells. Next, the researchers mimicked the natural tissue environment of these precursor germ cells by exposing them to testicular cells as well as sex hormones such as testosterone.

Under these biologically relevant conditions, the ESC-derived primordial germ cells underwent complete meiosis, resulting in sperm-like cells with correct nuclear DNA and chromosomal content. To provide final gold-standard proof of meiosis, the researchers injected these sperm-like cells into mouse egg cells and transferred the embryos into female mice. Remarkably, these embryos developed normally and gave rise to healthy, fertile offspring, which gave birth to the next generation.

If proven to be safe and effective in humans, this platform could potentially generate fully functional sperm for artificial insemination or in vitro fertilization techniques, Sha says, adding "Because currently available treatments do not work for many couples, we hope that our approach could substantially improve success rates for male infertility."

The study appears in Cell Stem Cell.