In the new Canadian film The Baby Formula, opening later this week, two lesbians become pregnant using sperm derived from each other's stem cells.
The premise of the mockumentary may be fictional, but with the speed at which stem cell research is evolving, could same-sex human reproduction one day become reality? And should it?
Scientists have already taken the first baby steps toward realizing this brave new, and some would say controversial, world of conception.
Stem cells are like the body's blueprint, giving rise to all the different cells that make up an organism, from the skin and organs to the brain, bone and blood. Harnessing them as factories to produce specialized cells to repair or regrow tissues is the great hope of regenerative medicine.
In 2006, Karim Nayernia of Newcastle University generated sperm from male embryonic stem cells that fertilized female mice and produced offspring. A year later, his team was able to derive primitive sperm from stem cells taken from the bone marrow of human men.
Since then, Dr. Nayernia's group has been working on creating sperm from women's bone marrow stem cells and is expected to report its findings within weeks.
"We are now publishing a paper describing the producing of human sperm in the laboratory," he says. "It is male, but we have had some success with female."
Dr. Nayernia says there are a number of reasons for pursuing the research - to produce lab-based sperm to help scientists better understand the genetics of these "germ" cells and a safe means of testing how they are affected by environmental toxins and drugs.
He says artificially derived sperm and eggs also could help researchers look for ways to protect the fertility of men and women undergoing cancer treatments.
As to the idea of a woman's stem cells giving rise to sperm that could be used to fertilize another woman's egg, "scientifically, in principle, it is possible," says Dr. Nayernia, chair of the Stem Cell Biology Institute of Human Genetics at the university in Newcastle upon Tyne.
But Toronto stem cell scientist Andras Nagy isn't so sure.
There would be several biological hurdles to overcome, he says. First and foremost, women's DNA contains two X chromosomes, but no Y (male) chromosome.
"Without the Y chromosome, it's just simply not possible," Dr. Nagy says. "The other issue here is that females have two X chromosomes and the presence of two X chromosomes in a cell again [blocks]the sperm formation."
Germ cells must also be able to undergo meiosis - the process of cell division that leads to sperm and eggs having just one set of 23 chromosomes, rather than pairs adding to 46, as found in all other cells. It's not clear whether sperm coaxed from female stem cells could do that.
"So the bottom line is as far as the biology is concerned, that film is based on fiction," Dr. Nagy says of The Baby Formula .
Leaving aside the notion of same-sex reproduction, there are some "legitimate scientific reasons" why researchers would want to create both human sperm and eggs from stem cells, says Tim Caulfield, a professor of health science and law at the University of Alberta.
For one, the technology would give scientists an unlimited supply of eggs and sperm for study, he says. At a practical level, it could allow infertile couples to produce offspring containing their own genetic material.
"Let's say a man or a woman could no longer produce sperm or eggs for whatever reason, they could use the technology to grow sperm and eggs and then they could have kids."
Being able to produce numerous eggs and sperm in the lab would also make it easier for couples at risk of passing on genetic mutations, such as those that cause Tay-Sachs or Huntington's disease, to opt for in-vitro fertilization and to test embryos prior to implantation.
The ability to create eggs from stem cells may also allow a woman to conceive at a later age, when her natural supply has run out, he says.
But beyond the scientific feasibility, what of the ethics of bypassing the usual means of making babies?
"The biggest hurdle, I think, is how are you going to test this technology?" Prof. Caulfield says. "At some point, you're actually going to have to start creating embryos."
Those embryos would have to be allowed to develop to a certain point to determine whether they are healthy and do not contain genetic abnormalities as a result of their mode of conception, he says.
"From a research ethics point of view, that's a major challenge."
In Canada, at least, any discussion about spawning life using stem cell-generated sperm or eggs is a moot one. Current laws do not allow scientists to produce embryos by any means for the purpose of research.
Still, the mere idea of lesbian couples (or gay men using a surrogate mother) having a baby with their own genetic material is sure to horrify some people.
As the religious mother of one of the women in The Baby Formula says: "Who do you think you are, God?"
Yet Prof. Caulfield wonders if safety issues could some day be overcome, "is there anything inherently wrong with allowing a lesbian couple to give birth? I don't know that there is. …
"I think we have to move beyond the sort of yuck response," he says. "When we start regulating and curtailing technologies and setting up barriers, I do think we need to do it on a principle basis."
It wasn't that long ago that sperm donation and test-tube babies were thought disgusting by some, he says. Now they're accepted practice.
"I think the yuck response is a good reason for caution and a good reason for reflection, but it's not a justification for prohibition. …
"We do evolve. There is social accommodation that occurs and I think with a lot of these new technologies, that's also going to be the case."
Dr. Nagy, who saw The Baby Formula in a prescreening and "liked it very much," says the film contains an important social message, even if the premise is fictional.
Stem cell research will push the boundaries of what is biologically possible and society will be faced with a host of ethical challenges that this revolution in science will engender, he says.
"It's a very, very rapidly changing world and we really have to be aware of that," Dr. Nagy says.