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Taken from Teeth, Stem Cells Regenerate Tissue

By Michele Garfinkel

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Stem Cells

Researchers have isolated stem cells from the ligament that holds human teeth in place and shown that, in laboratory mice, these cells are able to grow new ligament cells. In particular, they were able to grow a particular type of cell, known as Sharpey's fiber, needed for a tooth to attach to its socket.

The researchers, led by Songtao Shi of the National Institute of Dental and Craniofacial Research in Bethesda, Maryland, had previously shown that the pulp of human teeth contained stem cells capable of producing bony tooth structures.

But isolating the cells that make non-bony material, such as a ligament, proved difficult because a wide variety of cells are present in the tiny bit of tissue that is obtained when a single tooth is extracted.

By using a collection of cells from 25 extracted teeth and creating a large population of colonies of single cells, the researchers were able to observe the growth of bona fide stem cells and then showed that they have some ability to grow tissue appropriately in mice and to repair experimentally-induced periodontal damage in rats.

Although the stem cell transplants were done on only thirteen mice (of which eight were successful) and six rats (of which two were successful), the results are promising because the stem cells regenerated the precise type of tissue that would be necessary for repair of human periodontal disease.

Periodontal disease is common in the United States and throughout the world, and poses a significant public health burden in many areas. Damage that occurs early in the course of disease, such as that caused by gingivitis or moderate periodontitis, can be reversed by aggressive treatment, including root scraping and antibiotic treatments

Advanced periodontal disease, though, is frequently impossible to treat and requires the rebuilding of portions of the tooth and root system with synthetic materials, or by bone or skin grafts.

These treatments have progressed in quality significantly in the past 30 years, but they never really bring the teeth back to their original state, leaving sufferers of the disease with problems eating, distorted jaws, and, the possibility that dental disease will lead to other medical problems, including infections and heart problems.

In order to move this research to studies in people, Shi and his colleagues will next conduct experiments on large animals, including pigs and sheep. In these experiments, they will use the animal’s own stem cells, rather than human ones.

Using stem cells transplantation in adult men and women with advanced periodontal disease will be difficult initially: transplants would have to be done with cells from a donor, or the patient would have to be willing to have a healthy adult tooth extracted, according to Shi.

Ideally, he says, tissue would be saved (“banked”) following the loss of baby teeth as a source of periodontal stem cells later in life, but that is thinking far ahead.

In discussions of the potential applications of stem cell research, periodontal repair rarely makes a list that includes Parkinson disease, Alzheimer’s disease, and cancer. The idea of repairing “bad teeth” is not compelling in the way that curing a degenerative neurological disease is.

Yet periodontal disease is not trivial and its economic burden is likely to increase in the United States as the “baby boomers” age; even those with excellent health insurance frequently lack dental coverage, and the lack of preventative dental care will likely take its toll.

Seo, B.-M. et al. Investigation of Multipotent Postnatal Stem Cells from Human Periodontal Ligament. The Lancet 364, 149-155 (July 10, 2004).

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