Last week the science onboard the International Space Station got a little sticky when astronauts began experiments with their latest cargo from Earth—samples of human and bull semen.
The material is the centerpiece of a biological study investigating whether sperm can accomplish their reproductive job in space. The study is officially called NASA’s ISS Program Science Office’s brief on the Spaceflight-Altered Motility Activation and Fertility-Dependent Responses in Sperm (Micro-11). Its purpose: If humanity is to spread to other planets, then we might need to make more humans in space.
“The survival of multiple generations of organisms beyond the Earth requires proper function of normal sperm and eggs cells,” the program brief says. “There exists a significant knowledge gap on impacts of spaceflight conditions on the fertility-dependent functions of sperm.”
Sperm in Spaaaaaace
NASA calls this “the first rigorous test” of how spaceflight affects the sperm’s ability to function, bit it’s not the first. Scientists in 1988 put bull sperm into sounding rockets — shooting them high into the air and using the long free fall to study the swimmers’ behavior in microgravity (it turns out the sperm swam faster).
Joint investigations by Russia and the U.S. (flown on the shuttle and tested on the Mir space station) also found that sea urchin sperm enjoyed some faster tail movement. This data seemed to indicate that spaceflight could help fertility — but that’s not the whole picture.
Those Shuttle-Mir experiments also found sperm’s timing was off when it came to egg fertilization. The more researchers looked, the more obstacles seemed to emerge. An unmanned Russian space biology mission called BION-M1 took various animals into space, including mice and gerbils, for a month. (Some died when the automatic food dispenser failed. Ugh.) An examination showed that the animals’ time in space disrupted the formation of sperm and hormones.
More recent microgravity experiments have determined enzymes that control the sperm’s movement suffered delays, suggesting that the lack of gravity was biochemically changing the little guys’ behavior. Even after all of these experiments, we’re not really sure whether sperm can get the job done in space. That set the stage for last week’s experiment, Micro 11.
Motility in Microgravity
The sperm flew to the space station cryogenically frozen and needed to be thawed. The astronauts did this on July 12 using the Commercial Generic Bioprocessing Apparatus, and all-purpose heater/chiller used for various biological experiments.
When the sperm reached room temperature, Flight Engineer Serena Auñón-Chancellor and Commander Drew Feustel introduced them into a fluid designed to trigger their reproductive mandate. The sperm didn’t have any actual eggs to aim for—there are no space embryos up there. NASA says there will be 13 runs for the Micro-11 investigation.
The astronauts put the mixture in the Microgravity Sciences Glovebox, a microscope with video cameras that recorded the sperm’s motility. Those video files will be downlinked for Micro 11’s investigator study. They will show if the sperm are activated more slowly and swim more quickly, as earlier studies indicated.
This study will also be the closest off-planet look at the acrosome, which develops inside the head and acts like an organ. This is the part of the sperm that produces an enzyme that breaks down the outer edge of the ovum, enabling pregnancy. Mirco 11 will study how the space influences the shape of this organelle, the behavior of which is of keen interest to fertility specialists. That’s one way that the things learned in space can also help understand reproduction on Earth.
“In space, scientists can learn more about biochemical changes in various cells and organisms that the force of gravity on Earth may be masking,” says Louis Stodieck, director of BioServe, the company that designed Micro 11.
Stay tuned for the results of the experiment. And in the future, when an interstellar voyager bounces a toddler on their knee, they will look back on last week and say thanks.
Previously published by: Popular Mechanics USA