Study: Mouse Sperm Stored in Space Produces Baby Mice on Earth

 

Japanese researchers have successfully produced healthy mice from frozen sperm¹ that was stored on the International Space Station (ISS) for almost six years.

The sperm was freeze-dried and sent to the ISS in 2013. Freeze-drying is a process that removes water from frozen substances in an effort to make them last for a long time.

Once the sperm was brought back to Earth and unfrozen, it resulted in the birth of 168 healthy baby mice. The researchers said there was little difference between the mice produced by space sperm and those made with usual sperm.

Teruhiko Wakayama is a developmental biologist at Japan's University of Yamanashi. He was the lead writer of a study reporting the results in Science Advances.

"All pups had normal appearance," Wakayama told the French news agency AFP about the experiment. When researchers examined genes² of the mice "no abnormalities were found," he said.

The team launched three containers, each carrying 48 samples of freeze-dried sperm, to the ISS in 2013. Freeze-drying permits substances to survive at room temperature for up to a year so no freezer was needed on the launch rocket. On board the ISS, the samples were kept inside a freezer at minus 95 degrees Celsius³.

Samples were returned to Earth at different times. The first were flown back after nine months and the second after two years. When the last container returned to Earth in June 2019, it had spent 5 years and 10 months in space. The returned samples were injected into egg cells, which were put inside female mice.

The experiment aimed to find out whether taking in radiation for long periods in space would damage DNA⁴ in reproductive cells or pass on mutations to babies. This same issue could be a problem for humans in the future if space exploration greatly expands, with large populations possibly living on other planets.

Deep space is filled with high radiation produced by solar particles and cosmic rays from outside our solar system.

The researchers said the sperm cells experienced radiation levels 170 times greater than sperm kept in ground storage for comparative purposes. The researchers reported that the space radiation did not damage the sperm's DNA or reduce its fertilization ability compared to the sperm kept on Earth.

"In the future, when the time comes to migrate to other planets, we will need to maintain the diversity of genetic⁶ resources," Wakayama wrote in a paper on the experiment. He added that such diversity -- both in humans and animals – can protect against increases in harmful mutations seen in inbreeding.

Wakayama said carrying freeze-dried reproductive cells from large numbers of individuals would be easier and less costly⁷ than transporting people or animals themselves to space. This method could permit space colonies to develop that include animals, he added.

The researchers say their results suggest that freeze-dried sperm could be effectively stored on the ISS for up to 200 years.

Words in This Story

sperm – n. a small cell produced by a male animal that joins an egg from a female animal to create a baby

pup – n. a young dog or other kind of baby animal

sample – n. a small amount of something that shows what the thing is like

mutate – v. to cause (a gene) to change and create an unusual characteristic in a plant or animal : to cause mutation⁵ in (a gene)

cosmic rays – n. high-energy particles that move through space at nearly the speed of light

maintain – v. to make something continue in the same way

diversity – n. a situation in which many different kinds of things or people are included in something

inbreeding – n. a situation in which plants, animals or people are produced by breeding between closely related plants, animals or humans 

1 sperm   

n.精子，精液

参考例句：

• Only one sperm fertilises an egg.只有一个精子使卵子受精。
• In human reproduction,one female egg is usually fertilized by one sperm.在人体生殖过程中，一个精子使一个卵子受精。

2 genes   

n.基因( gene的名词复数 )

参考例句：

• You have good genes from your parents, so you should live a long time. 你从父母那儿获得优良的基因，所以能够活得很长。 来自《简明英汉词典》
• Differences will help to reveal the functions of the genes. 它们间的差异将会帮助我们揭开基因多种功能。 来自英汉非文学 - 生命科学 - 生物技术的世纪

3 Celsius   

adj.摄氏温度计的，摄氏的

参考例句：

• The temperature tonight will fall to seven degrees Celsius.今晚气温将下降到七摄氏度。
• The maximum temperature in July may be 36 degrees Celsius.七月份最高温度可能达到36摄氏度。

4 DNA   

(缩)deoxyribonucleic acid 脱氧核糖核酸

参考例句：

• DNA is stored in the nucleus of a cell.脱氧核糖核酸储存于细胞的细胞核里。
• Gene mutations are alterations in the DNA code.基因突变是指DNA密码的改变。

5 mutation   

n.变化，变异，转变

参考例句：

• People who have this mutation need less sleep than others.有这种突变的人需要的睡眠比其他人少。
• So far the discussion has centered entirely around mutation in the strict sense.到目前为止，严格来讲，讨论完全集中于围绕突变问题上。

6 genetic   

adj.遗传的，遗传学的

参考例句：

• It's very difficult to treat genetic diseases.遗传性疾病治疗起来很困难。
• Each daughter cell can receive a full complement of the genetic information.每个子细胞可以收到遗传信息的一个完全补偿物。

7 costly   

adj.昂贵的，价值高的，豪华的

参考例句：

• It must be very costly to keep up a house like this.维修这么一幢房子一定很昂贵。
• This dictionary is very useful,only it is a bit costly.这本词典很有用，左不过贵了些。