Stem cells have the potential to revolutionize treatment for a wide array of diseases, such as Alzheimer’s and Parkinson’s, though harvesting enough of them for beneficial use and keeping them viable until they are needed presents significant challenges. So, researchers at the University of Nevada, Las Vegas (UNLV), have developed an efficient technique for taking these cells from a common source—wisdom teeth.
“More and more adults, approximately 5 million throughout the country, have their wisdom teeth, or third molars, removed,” said UNLV biomedical sciences professor Karl Kingsley, PhD, MPH. “Extracting teeth is relatively common among patients undergoing orthodontic treatments. And the majority of those teeth are healthy, containing viable tooth root pulp that offers opportunities for reproducing cells that have been damaged or destroyed by injuries or disease.”
Tooth root pulp includes pluripotent stem cells, which can become any cell in the organism from which they’re drawn, and multipotent stem cells, which change into specific types of cells within that organism. Extracting root pulp often involves drilling into, removing the top of, or shattering the tooth, all of which lead to a low stem-cell recovery rate due to heat, corrosive elements, contaminating enamel particulates, and more.
“Initially, the answer was simple: crack the tooth in half like a nut and remove the pulp,” said James Mah, DDS, director of UNLV’s advanced education program in orthodontics.
With their irregular surfaces and non-uniform shapes, though, cracking teeth usually produces the same shattering effect as a hammer, reducing the number of viable stem cells. The researchers then decided on a technique that scores the tooth to enable a clean break, much like custom cutting glass, and fabricated a device that could do so.
The “Tooth Cracker 5000” uses a clamp to hold the tooth in place for a cutting tool to score the surface, and a blade to crack it, producing a perfectly halved tooth with immediate access to undamaged and uncontaminated root pulp. With it, the researchers tested the fracture rate of 25 teeth and achieved a 100% rate of success.
Next, the researchers needed to test their pulp recovery rates, which typically run around 20% with shattering and drilling methods. They dyed 31 fractured teeth pulp samples to highlight any viable stem cells they contained. Dead cells turned blue when exposed to the dye, and living cells appeared clear. The test showed that 80% of the cells were viable.
“There are potential applications of stem cells for multiple diseases, including cancer, arthritis, and lung disease,” Kingsley said. “The next challenge is reliably collecting the stem cells early enough and storing them successfully so they can be used when needed.”
The number of pluripotent stem cells in teeth decreases dramatically after the age of 30 years, the researchers report, though people can still donate and preserve them just as they donate blood or preserve umbilical cords. When people have their wisdom teeth removed or have a root canal performed, their stem cells could be harvested and stored for future use. So next, the researchers will explore cryogenics.
“There is no standard cryogenesis, or freezing process, for storing stem cells,” said Kingsley. “There are multiple organizations that collect and freeze teeth for future studies and use, but there is no evidence about the long-term effects of cryopreservation. We can’t answer yet just how long the cells will survive.”
A previous study has given the researchers access to a supply of cryogenically stored stem cells, and they have been selecting and thawing a small sample of this collection each year to study their viability. Results so far indicate that rapidly dividing cells have higher rates of viability year after year than slower dividing cells. If this pattern continues, then stem cells could be sorted before the freezing process based on when they might be needed.
“The work Dr. Kingsley and I are doing is part of a paradigm shift,” said Mah. “Our fracturing process could hasten the collection and cryogenesis process, thereby preserving a high stem-cell count that furthers research into how using these cells can aid healing and potentially cure diseases.”
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