Ten years ago, scientists discovered stem cells in the dental pulp of human teeth. Despite the fact that there are still no FDA-approved therapies using these cells, companies are emerging that charge consumers up to $1,600 to extract and store them. But is there enough scientific evidence to support this type of cellular banking?
"We simply don’t know how useful these cells will be for tissue engineering and regeneritve medicine," said Pamela Robey, a cell biologist at the National Institutes of Health.
Research on dental stem cells is still in its early days. One area of focus is their use in treatments for neurodegenerative diseases. Possibly due to the neural crest origin of dental pulp, "dental stem cells appear to be, based on current data, very potent to neurogenesis," said stem cell biologist George Huang of the Boston University School of Dental Medicine. Indeed, by grafting undifferentiated, untreated stem cells from the dental pulp of rhesus macaques into the hippocampus of immunosuppressed mice, Anthony Chan of Emory University and his colleagues stimulated the growth of new neural cells, many of which formed mature neurons, and initiated a variety of expression changes that promoted proliferation, cell recruitment, and maturation of progenitor cells that persisted for up to 30 days (Stem Cells 26: 2654-2663, 2008). These results suggest that dental stem cells could one day be used to stimulate neuronal growth and repair in the central nervous system.
Another potential application of stem cells extracted specifically from baby teeth — known as stem cells from human exfoliated deciduous teeth (SHED) — is bone reconstruction. A study published in 2008 by Songtao Shi of the University of Southern California (the discoverer of SHED) and his colleagues successfully treated skull injuries in immunocompromised mice by transplanting SHED into the damaged area (Oral Dis. 14:428-34, 2008). The treatment resulted in substantial bone formation, although the newly formed bone did not contain hematopoetic marrow elements, which are common in bone generated by stem cells isolated from bone marrow. Still, the new bone was maintained for at least 6 months after transplantation, suggesting that SHED may be a useful resource for some types of bone regeneration.
For now, such applications, which will require extensive clinical testing and FDA approval to be routinely used in patients, remain in the animal testing phase. But for some autologous treatments — in which a patient is injected with his or her own cells — full FDA approval may not be required; simply registering the therapy and getting patient consent could be enough. The first clinical trial of an autologous treatment using dental stem cells was published last November, in which scientists used progenitor cells extracted from the dental pulp from wisdom teeth to reconstruct the bone surrounding the site from which they were pulled ( Eur. Cell. Mater. 18:75-83, 2009).
"I think that these cells have a lot of potential, and I think they will, at some point, be able to be used," said molecular biologist Eileen Shore of the University of Pennsylvania. "It’s a matter of optimism."
Optimism is exactly what parents like Anne Wakefield are banking on. "I just think that if there is something you can do that in the future might help your children, then one should do it," said Wakefield, who is a customer of dental banking company BioEDEN.
At least four dental stem cell banking companies exist so far, charging anywhere from $575 to more than $1,600 for the initial extraction plus an annual storage fee of around $100 per year. "It’s not a huge sum," said John M. Simpson, the Stem Cell Project director at Consumer Watchdog, but "it just seems an idea to try to cash in on the stem cell craze without any obvious benefits for people being asked to fork over the money."
Indeed, some dental banking companies are not clear about the difference between dental stem cells and other types of stem cells, such as those isolated from umbilical cord blood. "I got an email saying if you were not able to [bank the umbilical cords of] any of your children, there was this option [of dental banking instead]," said Wakefield. "It wasn’t too late to do it." A recent press release from a company called Save-A-Tooth that services dental banking company Store-A-Tooth.com even stated that "…baby teeth and extracted wisdom teeth can be a source of stem cells that are the equivalent to umbilical cord blood stem cells."
In fact, stem cells from cord blood are quite different than those extracted from dental pulp. The predominant cell type isolated from cord blood is hematopoietic stem cells, which give rise to all the blood cell types and are used to treat various blood diseases, such as leukemia, whereas mesenchymal stem cells such as those from teeth most easily give rise to bone, cartilage, and fat tissues.
"Each type of stem cell seems to have a slightly different character," said Robey, stressing that stem cells from umbilical cord blood and teeth "are not equivalent."
After looking over the websites of the four major dental stem cell banking companies, Simpson characterized most of the accessible, background information as "essentially hyping the possibilities more than it should be." "It seems premature to do this based on what we know," he said.
"I think that’s it’s a very exciting time that we can isolate stem cells from different tissues," Robey said, "but we need much more rigorous in vivo studies to show exactly what these cells can do and how useful they will be."
Correction: The original version of this article incorrectly attributed a press release to Store-A-Tooth, when in fact it was released by Save-A-Tooth, a company that services Store-A-Tooth. The Scientist regrets the error.
