Queer Future Science: Same Sex Couples Could Have a Child Genetically Related to Both Parents
Imagine being in a same sex partnership? (Check for me). Imagine wanting to have a baby? (Check for me). Imagine being able to have a child with genetic contributions from both intended parents, whether they be all male or all female? (Yes, please!).
My husband and I have just gone through the process of selecting an egg donor, which you can read about in a previous BabyMoon Family article (https://www.babymoonfamily.com/original-articles/choosing-egg-donor or https://medium.com/@babymoonfamily/how-to-navigate-picking-an-egg-donor-9f93eeaf003a). However, what if we didn’t even have to do this step to have a biological child? What if one of us could contribute the egg to the other’s sperm? What if the child could genetically match both of us, instead of just one of us?
The science that could one day make this a reality has recently had some incredible advances in preclinical mouse studies that I wanted to discuss in this article.
How can two dads (or two moms) become parents without an additional egg (or sperm)?
The process of making a male produce an egg, or vice versa and having a female produce sperm, is known as in vitro gametogenesis, or IVG.
A bit of background on the cells in the body of a human (or any organism). Each cell contains all the body’s complete genetic information. However, through embryonic development, cells differentiate or become specialized. All embryonic stem cells (ES) further develop into one of three cell lines: Endoderm cells, mesoderm cells, and ectoderm cells. Through further signaling and differentiation, each of these three cell lines expresses specific patterns of genes in order to become one of each specific cell type of the body, some examples of which are shown in the figure here.
(1)
The pathway just described from embryonic stem cell (ES) to intestinal, pancreatic beta, muscle, and all other cell types including gametes such as egg and sperm, is called differentiation. IVG is the reverse of this process, which is shown on the right side of the figure above. IVG induces pluripotency or reverses differentiation, and then allows the creation of an induced pluripotent stem cell (iPS cell). iPS cells are essentially engineered ES cells, and they have the ability to then be directed in a lab to differentiate into egg and sperm cells. While iPS cells do have the potential to also be differentiated into any other bodily cell types, IVG is specific to the creation of gametes or the cells for reproduction i.e. eggs and sperm.
The leading researchers in this field are Katsuhiko Hayashi and Mitinori Saitou in Kyoto, Japan. These scientists were the first to take skin cells from a male mouse’s skin, reprogram them into iPS cells, and then turn those iPS cells into viable mouse eggs. This process of IVG also required the scientists to use genetic engineering to delete the Y-chromosome of these donor skin cells and replace it with a X chromosome that was borrowed from another female donor cell. In order to have the iPS stem cell differentiate into an egg, it requires the female pattern of two X chromosomes, and not the male pattern of an X and a Y chromosome. Finally, the XX engineered cells were cultivated in an ovary organoid, a culture system designed to replicate the conditions inside a mouse ovary in order to produce the gametes, or egg cells (2).
More recently, this Japanese team has taken these engineered egg cells that were developed from a male mouse’s body, and then fertilized them with sperm from another male mouse. These results were described in a recent Nature news article entitled: The mice with two dads: Scientists create eggs from male cells (3).
Katsuhiko Hayashi and Mitinori Saitou were able to obtain about 600 embryos from the sperm and engineered egg fertilization. These embryos were then implanted into a surrogate mouse, resulting in the birth of seven mouse pups. Although the efficiency of about 1% offspring was lower than the efficiency achieved with normal female-derived eggs, where about 5% of embryos went on to produce a live birth, the baby mice that were born were healthy, had normal lifespans, and went on to have healthy offspring of their own through natural reproduction (4).
So when will this technology be ready for experimentation in humans?
While there have been breakthroughs in terms of IVG in mice, the truth is that the ability to place human iPS cells into a medium that induces human egg formation is not yet understood. Human cell differentiation is, understandably, more complex than in mice, and scientists believe that the ability to control the differentiation of human eggs from iPS cells is about a decade or so away.
What does IVG and the future mean for same sex intended parents and rainbow family creation?
Even if human trials and practical work with IVG is not yet a reality, when it does become available, it will revolutionize current assisted reproductive technologies (ART) for same sex couples.
Currently, production of and retrieval of eggs from a donor is a complicated protocol that requires hormonal injections and a surgical procedure, all of which I described in a previous BabyMoon Family article (https://www.babymoonfamily.com/original-articles/egg-donation-procedure or https://medium.com/@babymoonfamily/what-is-it-like-to-undergo-egg-donation-8ecb4a9f3f60). However, IVG will replace this entire process. Instead, one person in the couple will only have to provide a swab of their cheek for a sample of skin cells.
These skin cells can then be de-differentiated into iPS cells and then re-differentiated into egg or sperm cells, depending on the couple’s needs. This would essentially allow for an unlimited number of eggs or sperm. Now, egg retrievals are limited in the number of viable eggs retrieved, and the numbers decrease — sometimes significantly — once those eggs are fertilized. IVG would remove the stress and some of the cost of couples going through this process who run out of viable embryos after failed transfers, or if they want more children.
What IVG does not do is replace the need for a gestational carrier (GC) for male same sex couples. However, science in the area of being able to grow embryos outside of a uterus is also progressing, and it is a topic that I have previously researched and summarized in a BabyMoon Family article (https://www.babymoonfamily.com/original-articles/artificial-womb-pod-generation or https://medium.com/@babymoonfamily/how-close-are-we-to-becoming-the-pod-generation-and-how-would-this-affect-queer-intended-dads-c2dc3f3d29c7).
Speaking personally and from conversations with other gay, bi, queer intended parents, I can say that this is an exciting future prospect. We — like straight couples — choose our partner because we love everything about them. While genetics are not everything, and there is a huge environmental component to making people who they are, it would be great if we could have a child who is the genetic offspring of the couple we have chosen to create.
IVG would also minimize the external factors that are required as part of an IVF process for gay, bi, queer men and women in terms of selecting an outside donor.
Lastly, it could have huge cost and emotional implications for intended queer parents, as they would not have to worry as much about the efficiency of an egg retrieval or the number of embryos they still have in the same way as today as the process of making more would be much less logistically complicated through IVG.
I believe the future of ART for same sex couples using IVG is extremely exciting and cannot wait to continue to see how this field and the science develops over the coming years.
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