Can same-sex partners have biological kids? What studies say

Hayashi presented the findings at the Third International Summit on Human Genome Editing at the Francis Crick Institute in London, adding that he believed that the same technology could be used for humans within the next decade. The discovery could revolutionise how reproduction is seen, possibly allowing same-sex male couples to have biological children together.

Before understanding why the discovery is monumental, it is important to know about the biology of reproduction.

Humans have 23 pairs of chromosomes, for a total of 46 chromosomes. One member of each pair is inherited from the mother, and the other is inherited from the father. This includes two sex chromosomes, which determine the biological sex of an individual. Females have two X chromosomes, while males have one X and one Y chromosome.

Every cell in the human body contains 23 pairs of chromosomes. Every cell except the gametes, or the specialised cells in the human body responsible for reproduction. These are the sperms in the case of biologically male individuals and ova or eggs in the case of biologically female individuals. The gametes contain 23 chromosomes and only one set of dissimilar chromosomes. While the sperm can contain either X or Y chromosomes, the eggs always only contain the X chromosome. When these 23 chromosome-containing cells meet, during the process of the sperm fertilising the egg, they form a single cell called the zygote which contains the full 46 chromosomes. Through the process of cell division, the zygote goes on to become the embryo which then becomes the foetus.

For same-sex couples, outside the issue of physiology, the barrier to having a biological child that shares both of their DNA is the fact that the body only produces one kind of gamete. Biological females produce the ova while biological males produce the sperm, and one of each gamete is needed for babies to be born. The gametes are different from other cells in the body as they only contain half the genetic material which can then combine with their counterpart. Taking other cells and splitting them in half to induce fertilisation doesn’t work either since the gametes are split through a special process called meiosis.

The Japanese researchers were able to overcome this limiting factor by creating new gametes using stem cells. Stem cells are a type of cell that has the unique ability to develop into different types of specialised cells in the body. They are unspecialised cells that have the potential to divide and differentiate into various cell types that make up different tissues and organs in the body. The scientists extracted stem cells by transforming skin cells. These stem cells were then turned into an ova or egg. The process involved the careful deletion of the Y chromosome present in the cell and an addition of an identical X chromosome from another cell.

“The trick of this, the biggest trick, is the duplication of the X chromosome,” said Hayashi. “We really tried to establish a system to duplicate the X chromosome.”

The newly formed gametes were then cultivated, fertilised and implanted into surrogate mice. The procedure resulted in a 1 percent success rate with the mice born as a result completely healthy, normal and able to reproduce on their own.

This is not the first time that mice have been born using artificial sperm or eggs. In 2018, Chinese researchers created mice with two biological mothers and later recreated the same experiment with two biological fathers. The experiments were done using the CRISPR gene editing tool. Hayashi’s process, called in vitro gametogenesis (IVG), is more promising in terms of stability.

But taking the leap to perform the same process in humans may take much longer. Human gametes are far more complex and as a result, are more complicated to reproduce. While researchers have been able to create human egg precursors using stem cells extracted from blood, the egg precursors are unable to undergo meiosis, which is a necessary critical step.

Apart from the technical boundaries which are currently preventing same-sex parents from having biological kids together, there are other concerns that will be more prominent as the technology becomes more and more achievable. Religious, legal and ethical considerations might still be unsurmountable roadblocks for same-sex couples looking to have children using IVG. In case even those hurdles are crossed, expenses for such a procedure can be a big hurdle for same-sex couples.