The mystery of tooth regeneration may have been solved thanks to research by a team in the UK.
Most reptiles and fish have multiple sets of teeth during their lifetime. However, most mammals, such as humans, have only one set of replacement teeth and some mammals, like mice, have only a single set with no replacement.
This diversity raises an evolutionary question—how did different tooth replacement strategies evolve?—and a developmental one—which mechanisms prevent replacement teeth in animals who’ve lost them?
In their paper in Development, Professor Abigail Tucker and PhD student Elena Popa of King’s College, London, describe why mice don’t have replacement teeth by comparing gene expression in the dental lamina of the mouse and the minipig, which has two sets of teeth.
Wnt signalling is known to be required for tooth replacement in other vertebrates; yet the researchers showed that Wnt activity is absent in a rudimentary form of the dental lamina (RSDL) in mice. This structure forms in the mouse but then disappears, stopping the generation of another set of teeth.
Using sophisticated genetic techniques, the researchers activated Wnt signalling in the mouse RSDL at E15.5 and E16 stages of development, revitalising this structure. Additional teeth were formed as a consequence.
These results demonstrate the potential of the RSDL as a source for replacement teeth in mice, and provide an experimental system suitable for studying the mechanisms behind replacement.
“Why the potential for tooth replacement varies so much across vertebrates is an intriguing question,” Popa said. “Our results show that, although the mouse normally does not form a second replacement set of teeth, it still has the potential to do so given the right signals.”
In addition, they researchers reported that culturing the RSDL in isolation stimulated its tooth-forming potential, suggesting that the first generation of teeth might prevent replacement teeth from developing.
“This is relevant to human tooth replacement, as structures similar to the RSDL have been identified next to the permanent teeth during development,” Professor Tucker said. “In normal development of our teeth, therefore, the second set or permanent teeth may inhibit the generation of a third set of teeth.”