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In life, we often hear people say that sperm will “heatstroke” and affect male fertility. We must keep sperm in a cool and comfortable environment and so on.

Of course, this is not a rumor. Previously, a large number of studies have indeed found that high temperature is closely related to the decline in sperm quality and quantity. However, for a long time, people have not been clear why high temperature has such a big impact on sperm.

Recently, a research team from the Institute of Molecular Biology at the University of Oregon in the United States found that even if the temperature rises briefly by 2°C, the DNA damage of sperm during meiosis will increase by 25 times, and male fertility Ability will decrease accordingly.

Related work was published in Current Biology with the title “Elevated Temperatures Cause Transposon-Associated DNA Damage in C. elegans Spermatocytes”.

(Source: Current Biology)

In this regard, Professor Hawley of the National Academy of Sciences of the United States said, “This is a landmark study that clearly shows how heat stress changes sperm at the molecular level, leading to a decline in fertility.”

Why do the fragile testicles grow outside the body cavity?

The majority of male friends have more or less experience of being violently beaten in the process of growing up. This feeling is believed to be unforgettable for many male friends, and female friends may alsoThe painful expression on the male’s face gives me a taste of it.

There is a joke circulating on the Internet: a person can bear the pain of 45 dol (unit) at the limit. But when a woman gives birth, she has to endure the pain of 57dol. Probably it looks like 20 broken bones. However, if a man is kicked into an egg, the pain will reach 9000 dol, which means that 160 children will be delivered at the same time, or 3200 bones will be broken.

Although, this is just a joke, a bit exaggerated, but when a man’s ball is suddenly “critically hit”, the pain will never be less than having a child. This can be seen very clearly from the football game.

Whenever faced with a football that volleyed, these stars would not cover their handsome faces, nor would they cover their proud heads, instead they would meet and cover their own balls regardless of their image. Because they clearly know that if the ball is kicked to the ball, then they may not be able to continue the game throughout the season.

Previously, there were even case reports of a 17-year-old man fighting with a worker, and after being kicked violently, he immediately hugged his belly and fell to the ground. He was unconscious and died without rescue. The hospital identified it as “sudden death from neurogenic shock”, which is simply a painful death.

Speaking of this, everyone might think, since men’s balls are so fragile, why not grow inside the body, but grow outside the body?

Currently, it is generally believed that the reason why men’s eggs grow outside the body is to maintain a lower temperature and ensure a normal environment for sperm. The temperature of male testicles is between 34°C and 35.5°C to produce a lot of healthy sperm. If the temperature of the testicles reaches or exceeds 36°C, the sperm will “heatstroke”, which will affect the quality of the sperm and even cause male infertility. Therefore, the eggs will grow outside and play a role in ventilation and cooling.

But why can sperm only tolerate 35°C? Take the human body as an example. Almost all cells can tolerate 37°C-normal body temperature is so high, even precious eggs are no exception. Why should the steady stream of sperm be specialized?

A brief temperature increase can also seriously damage the quality of sperm

In order to find the reasons why the temperature rise affects the ability of sperm, the research team led by Professor Libuda used microscope and second-generation genome sequencing to observe and analyze the sperm under normal conditions and the sperm after heat treatment.

It was found that the positions of a large number of transposons in the sperm after heat treatment were changed. Transposon is a genetic material that can replicate itself and move between chromosomes of organisms. They have the potential to disrupt the structure of the involved genes, disrupt the expression of genetic information by inserting themselves into other positions in the genome, and cause DNA damage at the same time.

Previous studies have found that under normal circumstances, whether in sperm or ordinary cells, transposons are generally silent, especially during sperm development. In order to protect the genetic stability of offspring, transposons are generally Will be suppressed.

Further research found that after the sperm is heated, a large number of transposons (a type of DNA sequence that can be transcribed or reverse transcribed in the genome, and appear on other loci under the action of endonuclease) Activate to cause DNA damage. In this study, they found that sperm DNA damage increased by 25 times after the temperature increased by only 2°C, resulting in a double decrease in sperm quantity and quality.

In this regard, one of the authors of the paper, Nicole A. Kurhanewicz, said, “We all know that sperm is very sensitive to temperature, but we have not been clear about the reason. Now we have found that after the temperature rises, the transposon in the sperm genome Will become active and affect the stability of chromosomes, leading to a decline in sperm quality.”

Finally, the researchers also said that at present, around 36°C is the most suitable temperature for human sperm. Infertility caused by temperature rise is also our current consensus. This study directly found the reason. Therefore, for the health of your sperm, try not to take a long bath, wear tights, drive, etc.

Reference materials:
https://www.cell.com/current-biology/fulltext/S0960-9822(20)31420-2< br>https://www.sciencedaily.com/releases/2020/10/201023095855.htm