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Stem cells in tooth pulp could be used in research

Nebraska Deborah Josefson

Researchers from the United States and Australia have found that deciduous teeth have robust stem cells in their dental pulp. The finding is important, because such teeth may serve as an easily obtainable alternative to embryonic stem cells, the use of which has proved controversial.

Moreover, like umbilical cord blood, they may serve as a ready source of autologous and bankable stem cells, the study says (published online before print in the Proceedings of the National Academy of Science of the United States of America, www.pnas.org).

Stem cells have the ability to differentiate into a wide variety of cell types. Theoretically they can be grown into various organs, as well as into nerve, bone, or haematopoeitic cells.

The researchers, led by Dr Songtao Shi, a paediatric dentist based at the National Institute of Dental and Craniofacial Research, Bethesda, Maryland, isolated stem cells from the baby teeth of children aged seven or eight years. Dr Shi had previously successfully isolated stem cells from adult dental pulp and wondered whether deciduous teeth might prove a better source than the carious teeth of adults (Proceedings of the National Academy of Science of the United States of Americas 2000;97:13625).

The children’s parents were asked to soak the teeth in milk and to place them in the refrigerator to preserve them until they could be delivered to the laboratory the next day. Milk was used as a medium because it provided growth factors capable of temporarily maintaining cell viability. Teeth from seven children were collected, the dental pulp extracted and enzymatically digested, and the cells grown in culture.

Surviving cultured cells were tested for markers of stem cell activity. The researchers found that pulp from incisor teeth had more stem cell activity than molars and that between 12 and 20 cells from deciduous incisors were stem cells. The scientists called these surviving cells "stem cells exfoliated from human deciduous teeth" (SHED) cells.

The investigators then successfully coaxed these cells to differentiate into adipocytes, neural cells, and odontogenic cells by exposing them to various growth factors in culture. Cell type was determined by appearance and immunophenotype.

They also found that the SHED cells survived in vivo when transplanted into the brain and skin of immunocompromised mice. Cells transplanted into the brain took on neural characteristics.

When compared with adult pulp stem cells the SHED cells had a higher replicative rate and greater viability.

The findings have potential clinical applications. SHED cells may one day be used to regenerate native teeth or to secrete dentin, obviating the need for composite bone or metal implants.

Moreover, because deciduous teeth are present though much of childhood they may serve as a readily accessible and bankable source of autologous progenitor cells.