The day a new “biotooth” can be grown in the gap left by a missing tooth as an alternative to having a false one implanted came a step closer recently when UK researchers revealed how they have developed a way to bioengineer new teeth from a person’s own gum cells.
However, it may be some years before what has been achieved in the lab is available to patients sitting in the dentist’s chair. The researchers had to combine the human gum cells with a type of embryonic mouse cell to instruct the gum cells to make teeth. The next challenge is to find a human adult cell that can be coaxed to do the same.
Paul Sharpe, a professor at King’s College London, and colleagues, report their work in the 4 March online before print issue of the Journal of Dental Research.
With an implant, the lack of a natural root structure means eventually the friction from eating, and other jaw movements, cause loss of jaw bone around the implant.
A bioengineered “living” tooth would preserve the health of the surrounding tissue much better than an artificial implant, as Sharpe, an expert in craniofacial development and stem cell biology, explained in 2004, when he and his colleagues received a grant of £0.5m (about $0.8m) to develop a way to use stem cells to make a new tooth:
“Teeth are living, and they are able to respond to a person’s bite. They move and in doing so they maintain the health of the surrounding gums and teeth.”
Natural teeth start forming in the embryo from the interaction of two types of cell: epithelial cells, that make surface lining tissue such as of the skin and gums, and mesenchymal cells, that can develop into a range of different tissues, including bone and cartilage.
In their study background, the authors explain how you can take these embryonic cells individually and recombine them to form normal teeth.
So research has focused on generating immature teeth (teeth primordia) that mimic those in the embryo and can be transplanted as small cell “pellets” into the adult human jaw to grow into functional teeth.
What is remarkable is that even though the cell environments of the embryo and adult jaw are quite different, embryonic immature teeth can deveop normally in the adult mouth.
The challenge to researchers is to find a source of suitable cells that would make the method clinically viable, as Sharpe explains:
“What is required is the identification of adult sources of human epithelial and mesenchymal cells that can be obtained in sufficient numbers to make biotooth formation a viable alternative to dental implants.”
In this study, it looks like they have solved the first half of the problem: how to source human epithelial cells.
Sharpe and colleagues isolated epithelial cells from adult human gum tissue, and then cultured them with mouse embryonic tooth mesenchyme cells.
The gum tissue came from patients at the Dental Institute at King’s College London.
When transplanted into mice, the epithelial-mesenchyme cell combination formed hybrid human-mouse teeth with dentine, enamel, and viable roots.
Sharpe says the study shows that in the lab at least, epithelial cells from adult human tissue are able to respond to the tooth-producing signals from the mouse embryonic tooth mesenchyme cells “in an appropriate way to contribute to tooth crown and root formation and give rise to relevant differentiated cell types”.
“These easily accessible epithelial cells are thus a realistic source for consideration in human biotooth formation,” he concludes.
So the next major challenge, is to find a way to get adult human mesenchymal cells to send tooth-inducing signals, because at the moment, the researchers can only get embryonic mesenchymal cells to do that.
In another recently reported study, teams from the Universities of Southampton and Edinburgh in the UK describe how bone tissue grown from patients’ own stem cells onto a plastic biodegradable scaffolding could soon be helping to heal shattered limbs.
Written by Catharine Paddock PhD