Laser light triggers stem cells to regrow teeth

With a simple, low-power laser, Harvard University scientists have triggered naturally-occurring dental stem cells to regrow teeth in rats. The work is a step toward developing a new form of dental therapy that could be used in people, but also represents a broader shift in thinking about how to trigger the body’s natural regenerative capacity.

In the new research, described in the journal Science Translational Medicine on Wednesday, scientists injured two rat molars, side by side, and then administered the laser treatment to only one tooth. They saw roughly twice the amount of regeneration that occurred on the untreated tooth, after a single, five-minute laser treatment.

 “There have been lots of anecdotal reports that laser treatment can trigger regeneration, but it has been unclear how reproducible it is,” said David Mooney, a professor of bioengineering at Harvard who led the work.

The researchers also began to untangle how the laser treatment worked, by triggering a molecular chain of events within the tissue. Those insights suggest, more broadly, that stem cell therapies may not always require creating cells and grafting them back into the body, but could also include triggering cells in the body to form new tissue using external stimulation.

The portion of the tooth that grew back is called dentin -- a mineralized tissue that forms a layer between the pulp and the outer enamel of the tooth. The new dentin had a different structure than in naturally-occurring teeth, which may be a problem to be refined and studied further.

Mooney said that the basic science described in the paper has the potential to take a relatively short path into the dentist’s office because the treatment can be localized and doesn’t require a powerful laser. The low-power laser the researchers used appeared to trigger no immune response or destruction of tissue. Instead, it caused cells to create molecules called reactive oxygen species that subsequently triggered a boost in a protein called TGF-beta1, which is known to activate stem cells.

Mooney said that one of the scientists who led the work, Praveen Arany, has since moved on to work at the National Institutes of Health, and is focused on translating these insights into a therapy that could be tested in people, as an alternative way to cap teeth and prevent root canals, for example, or to decrease tooth sensitivity to extremes of temperature.

Mooney is also interested in whether a similar approach could be used to stimulate stem cells to regrow other types of tissue.

Dr. Jonathan Garlick, director of the Center for Integrated Tissue Engineering at the Tufts University School of Dental Medicine, who was not involved in the research, said it was a powerful proof-of-concept. Now that it is clear that the laser can trigger regrowth of tooth tissue, he said, it will simply be a matter of refining the technique and learning how to use it to regrow the tissue appropriately -- and making sure that it doesn’t cause any side effects. He added that the technique could eventually find wide use.

“I think it’s very relevant directly in a variety of different tissues that require stimulation and activation of healing and repair -- such as chronic foot ulcers in diabetic patients, bone healing, and bone regeneration,” Garlick said. “I think this has broad applications.”

Low-power laser can be used to induce regrowth of dentin, the hard material in the middle of the tooth, scientists have found out.

Cynicism linked to dementia in new study

Being cynical may hurt your brain health.

People with high levels of cynical distrust may be more likely to develop dementia, according to a new study.

Cynical distrust, which is defined as the belief that others are mainly motivated by selfish concerns, has been associated with other health problems, such as heart disease.

This is the first study to look at the relationship between cynicism and dementia, researchers said.

"These results add to the evidence that people's view on life and personality may have an impact on their health," said study author Anna-Maija Tolppanen, of the University of Eastern Finland in Kuopio.

"Understanding how a personality trait like cynicism affects risk for dementia might provide us with important insights on how to reduce risks for dementia," Tolppanen said.

For the study, 1,449 people with an average age of 71 were given tests for dementia and a questionnaire to measure their level of cynicism.

The questionnaire has been shown to be reliable, and people's scores tend to remain stable over periods of several years.

People are asked how much they agree with statements such as "I think most people would lie to get ahead," "It is safer to trust nobody" and "Most people will use somewhat unfair reasons to gain profit or an advantage rather than lose it."

Based on their scores, participants were grouped in low, moderate and high levels of cynical distrust.

A total of 622 people completed two tests for dementia, with the last one an average of eight years after the study started.

During that time, 46 people were diagnosed with dementia. Once researchers adjusted for other factors that could affect dementia risk, such as high blood pressure, high cholesterol and smoking, people with high levels of cynical distrust were three times more likely to develop dementia than people with low levels of cynicism.

Of the 164 people with high levels of cynicism, 14 people developed dementia, compared to nine of the 212 people with low levels of cynicism.

The study also looked at whether people with high levels of cynicism were more likely to die sooner than people with low levels of cynicism.

A total of 1,146 people were included in this part of the analysis, and 361 people died during the average of 10 years of follow-up.

High cynicism was initially associated with earlier death, but after researchers accounted for factors such as socioeconomic status, behaviours such as smoking and health status, there was no longer any link between cynicism and earlier death.

The study was published in Neurology, the medical journal of the American Academy of Neurology.

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