Did you think repurposing feces for better digestive health was kind of weird? A team of scientists at the Guangzhou Institutes of Biomedicine and Health decided to take inspiration from the other orifice. Duanqing Pei, a professor of stem cell biology at the research institute, took epithelial cells found in urine and converted them into teeth.
"We have a long-running interest in tooth formation," Pei told ABC News. "We want to use somebody's own cells to generate a tooth." Pei added that if the cells came from somewhere else, they could be rejected by the host's body.
Don't expect your urine to just crystallize into a new set of dentures though. Pei and his colleagues needed to first convert the epithelial cells into induced pluripotent stem cells, iPS cells for short. iPS cells can be grown into many different types of tissues, and it's those iPS cells that eventually turn into new teeth.
Sean Morrison, director of the Children's Research Institute of University of Texas-Southwestern Medical Center, sees larger implications for this research. "Normally, the way you get cells for reprogramming is that you do a biopsy on the skin," he said. "It's not a big deal, but the kids will cry and parents are really reluctant to [let them] do that sort of thing."
It's easier to get a kid to pee in a cup than it is to hold still for a needle. "Doctors are looking for noninvasive ways to get cells from children," said Morrison. "This could represent a better way of getting a child's stem cells."
However, just as there's more than one way to skin a cat, there's more than one way to get iPS cells. Paul Sharpe, head of the craniofacial development and orthodontics department at King's College London, said that urine is an unlikely starting point to get iPS cells. "You can derive a lot of iPS cells from a single hair," he said. "You could make teeth from hair, or even teeth from other teeth."
Sharpe has also been able to synthesize teeth from stem cells, though his work takes a different route. He put epithelial cells collected from the gums of adult humans next to embryonic mouse mesenchymal cells, which later develop into mouse teeth. The two types of cells interacted with each other and formed hybrid mouse/human teeth.
In order to make a good tooth, Sharpe says that it's not the crown but the root that's most important. "You're looking for a periodontal ligament, the soft tissue that attaches the tooth to the bone," he said. "That's the biggest thing, and [Pei] has pretty good roots."
In addition, using urine to get these cells isn't as disgusting as you might think. "Somebody may think that urine is very contaminated," Pei told ABC News. "But from our experience, if you look at midstream urine, it's sterile. We have never encountered any type of bacterial infection."
The peer-reviewed study is published in the journal Cell Regeneration. Pei also serves as the editor in chief of that journal. However, the journal is also managed by Biomed Central, an outside organization. In addition, the journal's other editors contacted peer reviewers whose work was independent of Pei's. Pei told ABC News that he excused himself from any editorial influence over the study.