Scientists Successfully Made Sperm-Like Cells From Human Skin Cells

Another leap forward in artificial conception.

According to the Centers for Disease Control and Prevention (CDC), about 6 percent of married women in the US are unable to get pregnant, and about 12 percent of women have difficulty getting pregnant or carrying a pregnancy to term, regardless of marital status.

"What to do when someone who wants to have a child lacks gametes [eggs or sperm]?" one of the researchers in a new study, Carlos Simon from the Valencian Infertility Institute, said in a press statement. "This is the problem we want to address: to be able to create gametes in people who do not have them."

To help couples who want to have babies naturally, the researchers in Spain decided to focus on creating a new option for artificial conception, and in a breakthrough, they successfully made sperm-like cells from human skin cells.

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The scientists say they were inspired by the work of Shinya Yamanaka and John Gordon, who won a Nobel prize in 2012 for their groundbreaking discovery that adult cells can be reprogrammed into pluripotent stem cells — meaning they can be transformed into any other type of tissue.

Simon and his colleagues have built upon this work by adding a “cocktail of genes” to skin cells, which then can turn into germ cells in about a month. These germ cells could eventually be developed into sperm or eggs, creating another option for couples who rely on donated sperm and eggs for conception.

However, while the germ cells could indeed be turned into sperm, they wouldn’t have the ability to fertilize until a further mutation phase creates a gamete, according to Simon.

In the study discussion, the researchers offer an explanation for why the sperm cells they made in the lab couldn’t go on to create a gamete.

“The reason for this is intriguing,” they write, “and we hypothesize that it may be due to the fact that cells within the clumps spontaneously enter into a meiotic cell cycle that results in the formation of haploid cells that cannot be further maintained in vitro.”

To break it down, this means that the cells entered the cycle required to produce egg and sperm cells for reproduction (meiosis), in which cell division reduces the number of chromosomes in the parent cell by half and produces four gamete cells. These haploid gametes — cells with half the usual number of chromosomes — couldn’t continue to grow and replicate themselves in the lab. They just died off.

The researchers say that future studies should address this point.

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But this is when the ethical questions come in — if scientists do give us the option to conceive babies using artificial sperm and eggs, do we go through with it? Would children conceived in this way have biological disadvantages, or perhaps some unforeseen health issues?

Although further research is required to turn the sperm into a gamete, this study is an advancement from earlier work carried out by Chinese researchers, in which mouse eggs were fertilized with test-tube sperm cells. Mouse offspring were produced using this technique, but obviously dealing with human embryos is much more complicated.

"With the human species we must do much more testing because we are talking about the birth of [a] child," Simon explains. "We are talking about a long process."

The study results appear in the journal Scientific Reports.

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