In vitro gametogenesis involves making human eggs and sperm in the laboratory from any cell in a person's body. Photo: 123rf.com
We've all heard of IVF - in vitro fertilisation - but what about IVG ?
In vitro gametogenesis involves making human eggs and sperm in the laboratory from any cell in a person's body. This means IVG could see same-sex couples have genetically related children.
The prospect opens the door to a myriad of other possibilities and potential ethical dilemmas, such as a person having a child… with themselves.
Hank Greely - professor of genetics at the Stanford University School of Medicine, director of the university's Center for Law and the Biosciences and chair of its Steering Committee of the Center for Biomedical Ethics - says science will soon support the creation of life without the need for sex.
People will be choosing this form of reproduction in the not-too-distant future, Greely forecast in his 2016 book, The End of Sex and the Future of Human Reproduction.
"What this is about is an offshoot of stem cell research," he told RNZ's Nine to Noon on Friday.
"About 25 years ago people figured out how to make human embryonic stem cells, cells taken from human embryos at day five, six or seven that could form every cell type in the human body.
"Now, scientists disagree whether there are 300 cell types in the human body or 300,000 cell types in the human body, but we know that embryonic stem cells can make all of them because they make us, and we have all the cell types.
"About 10 years later, a Japanese scientist named Shinya Yamanaka figured out how to take skin cells - a particular kind of cell called a fibroblast skin in other places - and turn it into something that looks an awful lot like a human embryonic stem cell. These are called induced pluripotent stem cells (IPSCs), and they too can form any kind of cell in your body…
"The idea here is one could take skin cells from a person, turn them into these IPSCs, feed them the right ingredients to make them decide to become eggs or sperm, use that egg or sperm to fertilise a sperm or egg. And from there on, it's just in vitro fertilisation - you make the embryo and after a few days you transfer it into a woman's uterus for potential pregnancy."
Perhaps surprisingly, this might be an easier process than using stem cells to replace a damaged organ, Greely said.
"Organs have all sorts of cell types in them, you know - blood nerves, as well as the liver cells or kidney cells or heart muscle cells - whereas you're just making one cell type here, either a sperm or an egg."
Predictions for the future of human reproduction
So far no one has managed to make a human sperm or egg cell this way however, but it is getting closer by the day. Greely said progress was perhaps a bit slower than he forecast in 2016, but it was a field prone to progressing in fits and starts - and the breakthrough could happen today, next week, next year or perhaps not for another decade.
How it differs from cloning
IVG differs from cloning, Greely said, because it uses a DNA mix from a sperm and egg - at least it has been shown to be that way in mice.
"We don't know yet whether it will be in humans. There's no reason to think it will be different, but we haven't gotten far enough in making the eggs in the sperm to be sure - we don't even know for sure that we can make human eggs and sperm, although there's no obvious reason why we shouldn't be able to, and people are working on it."
Scenarios in which IVG could be useful include when one of the partners is sterile - perhaps from having mumps, Greely said.
"You could take the woman's egg harvested in the normal in vitro fertilization protocol. You could take a skin sample from the man, you could turn that into an induced pluripotent stem cell, you could turn that into a sperm, you could turn that into hundreds thousands or millions of sperm and you could use some of that sperm to fertilise the woman's egg.
Hank Greely. Photo: Stanford School of Medicine
"The resulting embryo would have half of its genes from the man and half of its genes from the woman. It certainly wouldn't be a clone… which half of the genes it had from the man and which half of the genes it had from the woman would be the same kind of random situation that you see in regular reproduction."
Another possibility is allowing gay couples to have a child with genetic input from them both - Japanese scientists have already achieved this in mice, Greely said, using eggs created from a male mouse (they were yet to create a successful sperm from a female mouse, he said, but were working on it).
"And if you really want to to rock your Friday morning, let's say that we take a skin cell from you and we turn it into sperm and we take a skin cell from you and we turn it into eggs, and we fertilise your eggs with your sperm and we put it in your body and you give birth to, what?
"I call it a 'una baby'. It's not a clone exactly, but it is a baby with one parent - you. Would anybody want to do that? I can't see a good reason to do that, but there are 8 billion people on this earth and some of them are crazy."
The biggest roadblock to research at present was safety, Greely said.
"We often don't think of safety as an ethical issue, but it is the overwhelming ethical issue. And here it's not safety to the man or woman whose skin cell is being turned into an egg or a sperm - it's safety for the baby that you're making.
"So I think at any moment anytime in the next two days or two years or 10 years, someone is going to announce that they've made a mature human egg or a mature human sperm from skin cells. That will be the start of what I think has to be about a decade-long effort to see whether that's safe enough to try to make babies from.
"The hard, long slog is going to be figuring out whether it's safe enough to be ethical to use."
A curious ethical dilemma society might face one day is harvesting sperm or egg cells from the unwilling - for example, celebrities.
"In theory, somebody could try to steal sperm or eggs, but it's really hard to steal eggs and, you know, pretty hard to steal sperm too. But… you can get living cells out of hair. You'd be better off with spit or a Kleenex, you know - you blew your nose, they're gonna be living human cells in that; you drank out of a bottle, there are going to be some living cells from your mouth or your cheek that are on that bottle when you throw it away.
"Stealing somebody's cells is not going to be that hard."
While his book's title included the phrase 'the end of sex', Greely admitted that was unlikely to come to pass.
"People will still have sex - they just won't have sex to make their babies."
As for whether this meant humans would evolve to not even desire sex, he was not so sure.
"I and probably you both have a vermiform appendix which as far as we could tell only serves to kill off about one person in 1000 by causing appendicitis. Evolution is not very streamlined. I think people, most people, like sex enough that I think it will stay around."