A team of Japanese researchers has successfully created oogonia, or primitive precursors to human eggs, out of blood cells, marking a significant milestone in the race to manufacture lab-grown eggs and sperm.
The scientists’ findings, newly detailed in the journal Science, build on previous research conducted by Kyoto University biologist Mitinori Saitou, who successfully bred mice using stem cell-generated eggs and sperm in 2012. As Antonio Regalado reports for MIT Technology Review, this landmark step was accomplished with the help of a simulated ovary constructed out of fetal mouse tissue. It’s extremely difficult to retrieve the human fetal tissue needed to create a similar makeshift ovary, so Saitou and his colleagues were forced to explore other options as they shifted focus from mice to men.
Vice Motherboard’s Daniel Oberhaus writes that the scientists eventually turned to human blood cells, which were used to create induced pluripotent (iPS) stem cells. Regalado describes iPS cells as victims of “molecular amnesia,” noting that they have no fixed identity but are instead capable of becoming any type of cell, from blood to liver or bone.
According to The Washington Post’s Carolyn Y. Johnson, the team worked to transform these blank slate cells into “primordial” reproductive ones. The researchers incubated the cells in artificial ovaries created using embryonic mouse cells over a four-month period, and by the end of the testing window, the cells had developed into oogonia—still too immature for fertilization, but a step closer than ever before.
"For the first time, scientists have been able to convincingly demonstrate that we are able to make eggs—very immature eggs," Amander Clark, a developmental biologist at the University of California, Los Angeles, who wasn’t involved in the research, tells NPR’s Rob Stein.
The technology heralded by this new research—as well as similar experimental efforts being undertaken across the world—has the potential to radically reimagine the process of human reproduction.
Although the Japanese study produced immature eggs unfit for fertilization, let alone the eventual development of a full-grown fetus, Johnson writes that scientists believe “it is a matter of when, not if,” researchers create a fully mature, lab-manufactured egg.
Once this happens, individuals facing infertility issues, same-sex couples and others unable to conventionally conceive may be able to have offspring that share their DNA. If existing human cells are the key to producing lab-grown eggs, it would theoretically be possible for scientists to make babies out of another individual’s (say the child’s mother- or father-to-be) blood, hair or skin cells.
Needless to say, “there are some very weird possibilities emerging,” as Dartmouth bioethicist Ronald Green tells NPR’s Stein.
On the far-fetched end of the spectrum, Green notes that eggs could be produced using stolen or questionably acquired cells.
“A woman might want to have George Clooney's baby," he says. "And his hairdresser could start selling his hair follicles online. So we suddenly could see many, many progeny of George Clooney without his consent."
Additional concerns associated with the emerging field revolve around a lack of understanding that could lead to the birth of babies with serious genetic diseases and ethical dilemmas such as allowing embryo DNA analysis—a practice that Stanford bioethicist Hank Greely, author of The End of Sex and the Future of Reproduction, tells Stein could lead to “parents and potentially governments” picking and choosing which embryos are permitted to grow to full maturity.
Moving forward, Motherboard’s Oberhaus reports that the Japanese team hopes to produce human sperm via a similar stem cell process, as well as create egg cells mature enough for fertilization. Regardless of which group of researchers achieves this objective first, the arrival of a new era in reproductive strategies appears imminent.