Lessons from sharks: how we might grow new teeth via stem cells

What if we could grow new teeth from stem cells to replace lost ones or fix others that have big cavities again via tooth stem cells?

While humans and some other animals like dogs have only two sets of teeth — so-called baby and adult teeth — in their lives, other animals aren’t so limited. For instance, alligators and sharks effectively can have a limitless ability to replace lost teeth with new ones.

Learning from sharks on teeth

Over millions of years, billions of sharks have been losing teeth and regrowing new ones such that the bottom of the ocean likely has trillions of shark teeth on it in various layers of sediment. These teeth are not only great from an evolutionary science perspective, but this blanket of old and sometimes fossilized teeth is a striking illustration of how important it is for sharks to be able to readily replace teeth.

How in the world do they do it? Can we learn from that to help our oral health?

Research indicates that the replacement teeth are grown from stem cells present in the mouth. Our human teeth grow that way in the first place too it seems. Then in principle, it’s possible that new, healthy teeth could be grown in the human mouth as replacements if we mastered our understanding of the process and the replacement technology. Also, we could potentially fix (rather than replace) broken or diseased teeth too. This kind of thing would be a really beneficial form of regenerative medicine.

Row by row of new teeth from stem cells

According to this article  by researcher Gareth J. Fraser, sharks don’t replace lost teeth one by one, but instead, rows of “baby” replacements are also available to develop into full-grown replacements:

“Sharks don’t actually regrow teeth one by one but have multiple rows inside their jaw that are constantly regrown. When a tooth on the edge of the jaw drops out, the corresponding tooth in the row behind it moves forward to replace it. The underlying soft tissues anchor and carry each tooth like a conveyor belt.”

These replacement teeth are grown via what I guess we should call “tooth stem cells” or “dental stem cells”, although Fraser with his colleagues Moya Smith and Thimios Mitsiadis called them “odontogenic stem cells” in their 2009 paper on shark teeth growth. Thus, in principle we humans could regrow new teeth from our own stem cells of that type as well.

Since that paper 9 years ago there’s been a lot more research in this area that is somewhat encouraging. Note that some folks are also excited about the potential of stem cells isolated from teeth to be used for non-dental medical applications as well, although the potential of tooth stem cells to make other tissues remains unclear.

A new article in Science Translation Medicine just a couple of months back from a team in China and at U. Penn suggests that regrowth of teeth or of some components of damaged teeth including in humans via stem cells may be possible in the not so distant future. Not all the changes in the treated teeth were particularly large in this study, but the trends are interesting. Here’s the brief summary:

“Dental pulp necrosis is one of the most common pathological conditions that results in tooth loss. However, regeneration of functional dental pulp has proved difficult. In a new study, Xuan et al. implanted ex vivo expanded autologous tooth stem cells from deciduous teeth in two animal models and in human patients. They demonstrated regeneration of dental pulp containing an odontoblast layer, blood vessels, and nerves in the implanted teeth and rescue of sensation to stimuli such as temperature. This work suggests that implantation of tooth stem cells can provide partial recovery of teeth injured by trauma.”

Beyond replacement, it’s probably more practical to try to fix a cavity, for instance, and this could be easier than growing a whole new tooth. With trying to grow a whole new tooth it needs to end up the right size and shape, which are difficult challenges.

Overall this is a promising area of regenerative medicine based on adult stem cells.