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Growing Teeth and Four More Odd Uses for Urine

Would you buy a wall clock that's powered by pee?

Hirenbhai Bheda displays a wall clock that runs on cow urine in Luni, India.

For those who’ve lost their teeth to accidents and decay, there may be a new way to restore your pearly whites: urine.

Scientists in China have successfully used cells found in human urine to regrow teeth. If that’s not enough of an ick factor, the scientists grew the teeth in mouse kidneys.

The researchers, led by Duanqing Pei at the Chinese Academy of Sciences in Guangzhou, converted cells collected from urine into what’s called pluripotent stem cells, which can become any kind of cell in the body. These stem cells were then mixed with dental tissue from mouse embryos and implanted into mouse kidneys. (Read more about stem cells.)

The entire process took just a few weeks: several days to incubate the stem cells, and then three weeks to grow them in the kidneys, according to the study, published July 30 in the journal Cell Regeneration.

These were not, however, normal teeth. They were probably even less useful than George Washington’s mythical wooden dentures, given that the teeth were soft and misshapen and not actually, you know, attached to a person’s jaw.

In an interview with the BBC, University College London stem cell biologist Chris Mason said urine “is probably one of the worst sources [for teeth]—there are very few cells in the first place and the efficiency of turning them into stem cells is very low.” (Explore a human-body interactive.)

And for the teeth to work, they’d have to be integrated into the gum’s “pulp” of nerves and blood vessels, which would be a “big challenge,” Mason said.

Though human urine hasn’t yet unemployed the tooth fairy, other researchers have come up with some surprising and creative ways to reuse the liters of liquid gold each of us create every day.

Urine as Fuel

At the 2012 Maker Faire for innovators in Lagos, Nigeria, a group of three schoolgirls created a backup generator that could run on human urine. The device uses an electrolytic cell to break down the molecules found in urine and extract pure hydrogen. (Also see “Urine Battery Turns Pee Into Power.”)

The hydrogen is passed through a cylinder of borax to remove any moisture, and then delivered to the generator. The girls used one-way valves to reduce any explosion risks from the hydrogen. One liter of urine can produce up to six hours of electricity.

Other scientists from the Bristol Robotics Laboratory have also been investigating urine fuel cells, only they used microbes to break down the molecules in urine and produce the electricity.

Urine as Medication

Peeing into a cup generally yields a diagnosis, not a pharmaceutical. But when researchers analyzed the urine of menopausal women, they realized they could extract an important—and potentially lucrative—medication for infertility.

As a woman approaches menopause, her ovaries start to become deaf to the monthly siren calls of hormones. The pituitary gland responds by secreting even more hormones, such as follicle-stimulating hormone and luteinizing hormone, which stimulate eggs to mature in the ovary.

Levels of these hormones are often low in infertile women, which gave scientists the brilliant idea to gather urine from perimenopausal women to extract and purify the precious hormones. Thus were born the infertility drugs Menopur and Pergonal.

Urine as Compost

When researchers combined compost with human urine, they found they had created a fertilizer that is superior to compost alone. The trick appears to be the extra nitrogen from the urine, which helps to boost plants’ growth.

Related: Turning Human Poop Into Soil

Although it isn’t as powerful as commercial fertilizers, urine is freely available and a potentially more cost-effective and environmentally friendly fertilizer. (Related: “Human Pee Added to Compost Boosts Crops.”)

Urine as Water

People have been drinking urine for millennia, often for health reasons. But NASA has developed a new filtration system to turn human wastewater like sweat and urine into potable drinking water. The Forward Osmosis Bag (FOB) was designed to give astronauts an extra source of drinking water in space. The FOB, however, can be used outside of zero gravity and, if the technology is scaled up, may help create additional drinking water around the globe.

These ideas are not, of course, the only ways urine can be used—people are inventing new things every day. Even my cat has gotten in on the game, creating inventive works of art on my rug after an inadvertent change of kitty litter brands.