Tooth and Bone

By Beth Dunham
Winter 2008

Songtao Shi, D.D.S., Ph.D., knows that tiny stem cells spark big questions and giant possibilities. As associate professor in the USC School of Dentistry’s Center for Craniofacial Molecular Biology, Shi works to understand what stem cells derived from teeth, bone and other tissues can do for patients with dental or craniofacial problems and other diseases.

“We are focusing on how the stem cells link to disease, as well as how we can use them to cure disease,” Shi says. “We want to more closely examine tooth regeneration, disease treatment and cosmetic regeneration involving stem cells.”

Shi’s work has isolated fast-growing, versatile stem cells from periodontal ligaments, and adult and baby teeth. The latter discovery was made with the help of his 6-year-old daughter Julia, who, in 2003, asked him to pull a loose tooth. The red tissue inside sparked a flash of inspiration; Shi rushed the next tooth she lost to the lab and discovered the valuable stem cells inside.

These mesenchymal stem cells—found in dental pulp and also in bone marrow—could help regenerate periodontal tissue, tooth roots and ligaments for dental therapies, and even add structure and firmness to skin during cosmetic procedures, he says. Manipulating mesenchymal stem cells might one day grow new bone for patients born with facial deformities, as well as provide treatment options for other diseases throughout the body.

Shi received his Ph.D. in craniofacial biology from USC in 1994, and he joined the USC faculty in 2006. Trained as a clinician and basic scientific researcher, his experience treating patients before returning to academia reminds him that the research he conducts may benefit countless future patients.

In fact, Shi’s latest study moves beyond dentistry to explore how mesenchymal stem cells in bone marrow play a role in osteoporosis. During osteoporosis, immune system cells mistakenly attack healthy stem cells, impairing their ability to form bone and also increasing bone loss. Shi’s research has found that in mice, an aspirin regimen similar to that of a typical human dose both slows bone loss and promotes bone formation by the stem cells.

“We have opened a door,” Shi says of the possible new use for the common drug. “We hope other scientists can confirm what we’ve found and move the treatment forward.”

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