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Researchers have been studying a promising option for male birth control, and we've learned a bit more about how regeneration works in hydras!

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Hank: If I asked you to picture birth control, what pops into your brain? The pill, the patch, IUDs, or maybe hormonal implants? But the thing is, all these options are for biosex females.

For biosex males, there’s really only condoms and vasectomies, where a surgeon shuts the vas deferens tubes that let sperm travel up and out from the testicles.

Even though there’s been a bit of research on safe, reversible male birth control, no product has ever made it out of the lab. And this week in the journal Basic and Clinical Andrology, a group of scientists announced that they've made some progress on a relatively new male contraceptive called Vasalgel.

Vasalgel is a sticky polymer gel that’s injected into the vas deferens tubes, physically blocking sperm so it can’t swim up and mix with the semen. Since semen is still being made, all the sex and fluid stuff works the same. But no sperm means no fertilization, and no pregnancy. It’s also designed to be a reversible contraceptive, so scientists can theoretically break down the gel and flush it out with a second injection of a sodium bicarbonate solution. Plain old baking soda!

Before trying this contraceptive on humans, scientists have been testing its safety and effectiveness in animals, like rats and rabbits, who are known for having lots of sex. And this new study involved injecting Vasalgel into 16 adult male rhesus monkeys at the California National Primate Research Center. They were generally healthy after the treatment and went back to their monkey lives, interacting and mating with fertile females when they were housed together. And even though some were continuously living with females for 2 entire years, not one fathered a baby!

Even with that 100% success rate, Vasalgel is a long way from being safe and ready to go in humans. Sixteen monkeys isn’t that big of a big study, and there were still some side-effects. During one monkey’s surgery, the gel wasn’t injected properly on one side, so the researchers ended up giving him a partial vasectomy.

Another developed a sperm granuloma, which is basically a lump of sperm outside the vas deferens that could become painful. But the researchers looked at other rhesus monkey health data they had collected, too, and found that sperm granulomas seemed to be more common in monkeys with vasectomies than in the group with Vasalgel. Finally, this particular study didn’t try flushing out the Vasalgel, so we still don’t know how reversible it is in primates.

So there’s still a ton more work to do before Vasalgel becomes a widespread birth control option, but it’s off to a promising start. Even though animal sex is interesting, all species reproduce in one way or another. You know what’s really weird though?

Regeneration. And hydra – the squishy tube-shaped freshwater animal, not the mythological sea serpent or Marvel villain – are really, really good at it. Even if you chop them into tiny, shapeless chunks of tissue, they can regrow in just two days – complete with tentacles, a mouth, and a sticky little foot. This superpower raises a bunch of questions, though, like: how can a chunk of tissue know how much to regrow where, without becoming a weird frankenblob with extra tentacles and triple-heads?

Well, researchers from the Israel Institute of Technology published a study in Cell Press this week, which looked at how important the tissue’s physical structure is for regeneration. Hydra have thin, parallel actomyosin fibers running throughout their body, like our muscle tissue.

They can contract these fibers to wiggle around, but it turns out that the alignment of these fibers is really important to help chopped-up tissue reform the right way. See, hydra bodies are really simple: one head and one foot lined up along a single body axis. And regeneration starts pretty simply too -- when a tissue chunk twists and folds into a hollow ball called a spheroid.

The alignment of actomyosin fibers in the spheroid lays out a structure that gets inherited throughout the new hydra’s body. So the researchers wanted to test how different tissue chunk shapes formed spheroids, and how that affects regeneration. Because it can get real bad, real quickly.

Square tissue chunks folded really well, because the actomyosin fibers were stable and aligned, and the outer edges were flexible and could follow those fibers’ lead. On the other hand, slices of hydra shaped like closed rings didn’t fold so well, and formed spheroids with different regions of actomyosin aligned in different ways. So these regenerated hydra were more deformed, and usually had multiple body axes – like two mouths and two feet.

Open rings did even worse – that extra cut made figuring out actomyosin alignment even trickier. But here’s the thing: when the researchers threaded thin platinum wires into these ring-shaped fragments, they were more likely to regenerate correctly, and do it faster – maybe because the actomyosin fibers had more of a guide.

This new research supports the idea that it’s not just chemical signals that matter in growth and development, because physical forces influence cells in lots of ways too. And even though hydra regeneration is a little more extreme, it’s similar to how we humans heal wounds and develop as embryos. So there’s a lot we can learn about ourselves from these squishy little tubes.

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Additionally, we have just launched a podcast that we would like you to be interested in if you are an adult person. Because it is just the scishow staff sitting around talking the way we normally talk, which can include some curse words. I’ll put a link in the description because we can’t say the name of the podcast on SciShow.