Scientists at Chinese Academy of Sciences in Guangzhou have been working with stem cells in an attempt to grow teeth, and their most recent experiments have been remarkably successful. The team managed to grow completely new human teeth in a rat kidney, but the source of the stem cells is a bit odd. Researchers harvested the cells from urine. Why urine? Because science, that’s why.The study, published in the Cell Regeneration Journal, is careful to call the final product a “tooth-like structure.” They’re not teeth in the way we think of them. Being grown internally, they were softer than normal teeth, and the shape was all wrong. However, all the constituents of a tooth were present and accounted for.Researchers managed this somewhat gross feat by combining the harvested cells (again, from urine) with mouse connective tissue. The cells were induced pluripotent stem cells, which are made from a patient’s own adult somatic cells. The mixture was incubated for two days prior to implantation. Once tucked into the outer layers of a mouse kidney, the cells were encouraged to become dental epithelial tissue, then eventually enamel.The team hopes to improve on the process as a way to grow specific kinds of teeth for use in humans. That will require new techniques to form teeth that can pass for real. Stem cells derived from urine may or may not be part of the research going forward. The principal investigator, Duanqing Pei, noted urine was used because it was the “most convenient source” of stem cells. There are other sources with higher numbers of suitable cells and a lower risk of contamination.The full paper is available online, but it’s probably best you don’t try this at home.