African fish may hold secret to regrowing teeth

Humans may one day be able to regrow their lost teeth, thanks to a colourful African fish, scientists say.
Working with hundreds of Lake Malawi cichlid, researchers are beginning to understand how the fish maintain their hundreds of teeth throughout their adult lives.
By studying how structures in embryonic fish differentiate into either teeth or taste buds, researchers hope to one day turn on the tooth regeneration mechanism in humans - which, like other mammals - get only two sets of teeth to last a lifetime.
The work, which also involved a study of dental differentiation in mice, shows that the structures responsible for growing new teeth may remain active for longer than previously thought, suggesting that the process might be activated in human adults.

"We have uncovered developmental plasticity between teeth and taste buds, and we are trying to understand the pathways that mediate the fate of cells towards either dental or sensory development," said Todd Streelman, a professor at the Georgia Institute of Technology in Atlanta.
"The potential applications to humans makes this interesting to everybody who has dealt with dental issues at one time or another in their lives," said Streelman.

To understand more about the pathways that lead to the growth and development of teeth, Streelman and first author Ryan Bloomquist from Georgia Tech and Georgia Regents University, studied how teeth and taste buds grow from the same epithelial tissues in embryonic fish.

Unlike humans, fish have no tongues, so their taste buds are mixed in with their teeth, sometimes in adjacent rows.
The Lake Malawi cichlids have adapted their teeth and taste buds to thrive in the unique conditions where they live.
One species eats plankton and needs few teeth because it locates its food visually and swallows it whole. Another species lives on algae which must be scraped or snipped from rocky lake formations, requiring both many more teeth and more taste buds to distinguish food.
The researchers crossed the two closely-related species, and in the second generation of these hybrids, saw substantial variation in the numbers of teeth and taste buds.

By studying the genetic differences in some 300 of these second-generation hybrids, they were able to tease out the genetic components of the variation.
"We were able to map the regions of the genome that control a positive correlation between the densities of each of these structures," Streelman said.
"We were able to demonstrate that a few poorly studied genes were also involved in the development of teeth and taste buds in mice," he said.
The studies in fish and mice suggest the possibility that with the right signals, epithelial tissue in humans might also be able to regenerate new teeth, researchers said.

The study was published in the journal PNAS.