Thanks to advances in reproductive technology, couples given the same sex at birth may be able to have genetically related offspring.
Scientists have achieved advances with lab mice. Some organizations have used genetic engineering to create a few rats from male and female pairings in the previous decade.
If these cutting-edge technologies are ethically and securely developed for humans, many forms of families may be viable in the far future.
“These researchers have been remarkably creative,” Bedford Research Foundation embryologist David Albertini tells Inverse. “They considered Mother Nature when engineering gametes—sperm or eggs—from stem cells.”
Japanese researchers bred mice with two biological fathers for the first time in a March Nature publication. In vitro gametogenesis (IVG) was employed by Kyushu University’s Katsuhiko Hayashi and co-authors.
IVG genetically reprograms cells from any tissue, such as skin or blood, into induced pluripotent stem cells (iPSCs), which may become any cell type. Chemicals encourage stem cells to become egg or sperm cells.
Recently, the scientists turned male mouse tail skin cells to iPSCs. They next coaxed these cells to lose their Y chromosome and grow a second X, creating eggs. Finally, these eggs were fertilized by another male mouse and implanted into surrogate female mice’s uteri.
Hayashi and colleagues transferred 630 egg cell-derived embryos into surrogate mice. They only produced seven healthy, surviving mouse pups—a success rate of slightly over 1%.
Queer Couples’ new frontier
Hayashi’s breakthroughs inspired the milestone. His team made the first stem cell-derived mouse sperm in 2011. Hayashi and another Tokyo University of Agriculture team became the first to turn mouse skin cells into viable eggs in 2016.
“This is a decade in the making,” adds Albertini, who was not involved in the new research. “Hayashi and his team have been pretty much singular in manipulating stem cells to make eggs and sperm.”
IVG predicts a future when doctors can generate eggs and sperm from a microscopic sliver of skin or blood, allowing same-sex couples to bear children with both parents’ DNA.
However, other methods might improve fertility.
CRISPR-Cas9 technology allows researchers to accurately modify genetic code using molecular scissors. According to a 2018 Cell Stem Cell research, Chinese scientists employed mouse stem cells with one pair of maternal chromosomes to create mice pups with two moms.
They employed CRISPR to remove genetic instructions from these stem cells and transfer them into sex cells from another female mouse to create an embryo with two parental DNAs. They implanted the embryo in a surrogate.
29 of 210 surrogate-born embryos survived. This study generated mice from two dads, but the pups barely lived a few days.
Experts warn that numerous engineering challenges remain before same-sex human couples may bear children.
Kevin Doxzen, a biotechnology expert and World Economic Forum fellow, tells Inverse that human cells need longer to develop an egg.
That might increase the danger of unexpected genetic mutations that could harm a growing baby.
According to recent study, CRISPR may cause damaging gene alterations and render cells malignant. Albertini thinks genetic modification is necessary for these investigations.
IVG-based genetic engineering may potentially raise legal and ethical concerns. One issue is whether cell donors should consent. Many unused embryos have uncertain outcomes.