Image: Janet Stephens/Wikimedia Commons

Lab rats probably don’t have many deep thoughts. But one of these days, right as a scientist is transplanting a testicle onto a rats’s neck, one of those little furry guys is going to ask itself—what did I do to deserve this? And how will I get my revenge?

Case-in-point, the little guy below. Entire testes have proven especially difficult to transplant back into the same place, at least in lab animals. So, a team of scientists decided to transplant them somewhere else in the case of these rats—onto their necks. And the scientists plan to continue transplanting testes onto rat necks, so that one day, entire testes may be reliably transplanted from person to person.

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Testicles are incredibly special organs, since they’ve got something called immune privilege. That means they’re safe from the body’s immune response, and can survive in another body for a while without being rejected. The testicles’ privileged status serves to protect the sperm cells inside from an attack by the body. In theory, this means doctors should be able to easily transplant them between people—which could be useful in cases where a person undergoes a treatment that would kill all of their sperm. That’s why the researchers are doing the research, so they can study this immune privilege.

According to the paper published today in the journal PLOS One:

Chemotherapy or radiation therapy for malignant cancers often injure the spermatogenesis [sperm making process] of young patients. In particular, prepubertal patients may suffer from permanent infertility because mature spermatozoa in semen cannot be cryopreserved prior to therapy. Thus, transplantation of children’s testes... to their fathers or brothers before receiving medical therapy may be helpful for obtaining mature [sperm cells] from the transplanted testes at a future date. It is also possible that the transplanted testes in recipients are transplanted back into donors after medical treatment.

But researchers are still testing out just how well those transplants would work. They could only find six prior examples of attempts to transplant entire testicles into the place they belong in lab animals. It turns out, transplanting them onto the neck is simply much easier.

How easy, you ask? Watch:

The researchers performed these testes-to-neck transplants, then performed testes-to-crotch transplants, and compared how the two procedures went. The former, on average, took 60 minutes and was successful 100 percent of the time, for the 12 attempts. The latter took 154 minutes, on average, and was successful on five of the seven attempts.

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Several issues arise from putting testes in the wrong place, though. First, testes are highly sensitive to temperature changes—the neck could be the wrong temperature. Secondly, folding the testes and its tubes into the rat’s neck could constrict blood flow. And third, fluids might leak.

Anyway, happy Friday, sorry about these rats, and double sorry for the below picture which you can save for your records.

Image: Yi et al

[PLOS One]