Sperm in Space: Unlike Astronauts, It Can Survive if Frozen

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A space probe falls towards the surface of Titan in this artist's conception of one of Saturn's moons. Space scientists hope that in the upcoming generations probes can be sent to explore the oceans of the large, icy satellites orbiting the outer planets.
Touchdown on Titan, illustration: Live astronauts might not survive protracted space travel but their frozen gametes might.Credit: AP

Happy news for aspiring fathers fantasizing of flying to Mars: Frozen sperm retains its viability in outer space conditions, researchers announced Tuesday at a conference of the European Society of Human Reproduction and Embryology.

The viability of frozen gametes aside, there are other reasons to suspect that protracted long-distance space travel isn’t in our future. The astronauts themselves might not survive the trip. But at least their frozen sperm will, according to the results presented by Dr. Montserrat Boada from Dexeus Women’s Health in Barcelona. Whoopee.

What about sperm that goes into space still inside the astronauts? Apparently, live sperm loses some motility in conditions of microgravity, the scientists explain, hence the investigation into the frozen version.

No, the team didn’t send frozen sperm into space, appealing as that thought may be. Boada’s group sent frozen sperm up in a plane that executed a series of 20 parabolic maneuvers, providing eight seconds of microgravity for each parabola. So not exactly a trip to Mars.

What on earth is all this worth if radiation will kill anything in space except, presumably, cockroaches? “Radiation impairs the quality and viability of human sperm,” Boada said. “These effects are expected to be greater on fresh sperm than on frozen samples.”

In other words, we don’t know that freezing spares sperm the vagaries of radiation poisoning, but maybe it does. And even if the astronauts fry, their cryogenically frozen sperm could be okay.

On the upside for future Martian ventures, in a completely unrelated report delivered at the same conference, scientists from China reported that the duration of freezing sperm makes no difference to live birth rates.

Many countries have clapped limits on how long sperm banks may keep sperm. Intuitively, that’s understandable. You might shrink from steak that’s been in your freezer for 15 years.

But sperm is kept in profoundly different and colder conditions than your freezer, and even the most enthusiastic of housekeepers don’t keep sausages in sterile conditions.

As befits the Chinese, the study was vast, encompassing 119,558 semen samples. The analysis split the samples into three groups: sperm kept in cryostorage for up to five years; six to 10 years; and 11 to 15 years.

The 15-year-old sperm did lose a little viability, dropping from 85 percent to 74 percent survival. But, reports Dr. Chuan Huang of the Changsha-Hunan Sperm Bank in China, the pregnancy and live birth rate in women using these samples barely changed: Cumulative live birth rates came to 82.17 percent, 80.21 percent and exactly 80 percent in the three groups respectively.

If Dad smokes, Son may have fertility issues.Credit: \ JAIME SALDARRIAGA/REUTERS

But if the men smoked before bequeathing their boys to the space freezer, sperm bank or had sex for procreational purposes (that still happens) — all bets are off. Cigarettes may accomplish what microgravity and cryostorage do not: Cause damage that reverberates down the generations, based on yet another study presented at the very same conference, this one based on Danish data.

We already knew that maternal smoking may be associated with low birth weight, premature birth and other problems. We also knew that a pregnant woman smoking may impair the quality of her son’s semen.

Now, the Danish report, based on analyzing the sperm of 778 19-year-old teens born between 1996 and 2002, finds that paternal smoking is associated with lower sperm counts and sperm concentrations in their sons, independent of maternal smoking and other confounding factors such as age, alcohol consumption or obesity. Or caffeine consumption.

The results are statistically significant: Results showed that, in the adjusted analyses, the sons of fathers who smoked daily (whose moms didn’t smoke) had an eight percent lower sperm concentration and nine percent lower total sperm count than the sons of paternal nonsmokers.

It bears noting there are other toxins that can have a much more dramatic effect on sons’ fertility, such as exposure to certain pesticides. These pesticides emulate hormones, which can have devastating effects on developing males. Witness the micropenises in the Floridan alligator population, which scientists believe are the result of pesticides and fertilizers contaminating the Everglades. The unfortunate reptiles would have been better off if their parents had a smoking habit in outer space.

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