Can humans have babies in space? It may be harder than expected

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Humanity is doomed to become a spacefaring species, expanding beyond the limits of Mother Earth, just as it spread millions of years ago from its cradle in Africa.

At least that’s what space exploration leaders, like the world’s richest man, think. Elon Musk I would like you to believe. However, there may be biological obstacles that could forever confine this vision to the realm of science fiction and human civilization to our earthly soil. A new study has found that sperm from mammalian species, including humans, mice and pigs, have difficulty making their way through the female reproductive tract in microgravity to reach and fertilize an egg. Even when the sperm reach their destination, the study revealed that embryos formed under these conditions develop poorly compared to those that develop normally. gravity.

The study, carried out by researchers at the University of Adelaide in Australia, is just the latest addition to a growing pile of evidence suggesting that mammal reproduction in space could be quite complicated, if not impossible.

There have been previous studies with titles stating baby mice were born from stem cells subjected to a space flight lasting several months, but most previous research, carried out either in space or in microgravity simulators on Earthrevealed a multitude of negative effects of the space environment on reproductive cells and embryos.

“When you think about the future of space exploration and space colonies, this is happening. It’s happening now,” Nicole McPherson, a reproductive biologist at the University of Adelaide, Australia, and lead author of the paper, told Space.com. “I think people forget that in order to maintain these colonies without having to continually colonize them from Earth, we need to be able to reproduce in space.”

McPherson, whose previous work focused on the effects of obesity and diet on successful conception, became intrigued by the question of the possibility of reproduction in space after watching a documentary hosted by British physicist Brian Cox. A discussion with his partner then gave rise to the idea of ​​a unique research experiment.

A chance meeting with the founder of space medicine company Firefly Biotech a week later allowed him to acquire a 3D clinostat for his laboratory. This device is a high-tech centrifuge that simulates microgravity by rotating vials containing samples around two axes, effectively confusing the cells inside as to their position in space. In his experiment, McPherson and his colleagues created a device containing human, mouse and pig sperm in one part of the compartment and eggs in the other, divided by a thin channel simulating the female reproductive tract. The researchers observed that 30% fewer sperm reached the egg compared to those with normal gravity.

Scientists know that sperm rely on a complex set of signals to navigate their way to an egg. Some of this navigation is determined by chemical signals, such as concentrations of the female hormone progesterone, but gravity also appears to play an important role, McPherson said.

“We know that sperm respond to chemical signals, but we also know that they like to swim near surfaces,” she said. “Obviously, to know where the surfaces are you need to understand your position in time and for that you need gravity.”

The sperm’s struggle to reach the egg is only part of the findings. When the sperm successfully reached the eggs, the early-stage embryos, called blastocysts, initially appeared stronger than their gravity-conceived counterparts. However, when exposure to microgravity continued, the superior quality of microgravity-engineered blastocysts deteriorated and the embryos began to lag behind their normal counterparts.

McPherson believes that the initial quality gain seen in embryos formed after just four hours of exposure to microgravity was due to the natural selection process that had occurred, allowing only the fittest sperm to reach the eggs. The subsequent deterioration of embryos left in microgravity for 24 hours was likely due to the negative effects of the absence of gravity on the processes taking place in rapidly dividing embryonic cells.

“So many changes occur in the first 24 hours of embryo development,” McPherson said. “You have maternal and paternal DNA coming together. You have a lot of epigenetic remodeling that determines early fetal development. And being exposed to zero gravity is actually very detrimental.”

McPherson said researchers would, in the future, want to conduct similar experiments in reduced gravity, such as those on the Moon or Mars, to see if partial gravity could alleviate the problem. She thinks the findings have implications not only for visions of space colonies, but also for commercial space tourism and babies potentially conceived on lunar and orbital honeymoons. In contrast, natural selection leading to the formation of stronger embryos after short exposures to microgravity could lead to advances in human IVF technologies that help treat infertility on Earth.

In the future, researchers would like to expose embryos to longer periods of microgravity to better understand the processes that take place in space-like conditions.

The study was published in the journal Communications Biology on Thursday March 26.