Embargoed for Release: Monday, April 21, 2003
Contact:
Bob Kuska, (301) 594-7560
Scientists report for the first time that “baby” teeth, the temporary teeth
that children begin losing around their sixth birthday, contain a rich supply of
stem cells in their dental pulp. The researchers say this unexpected discovery
could have important implications because the stem cells remain alive inside the
tooth for a short time after it falls out of a child’s mouth, suggesting the
cells could be readily harvested for research.
According to the scientists, who published their findings online today in the
Proceedings of the National Academy of Sciences1, the stem cells are unique compared to many “adult”
stem cells in the body. They are long lived, grow rapidly in culture, and, with
careful prompting in the laboratory, have the potential to induce the formation
of specialized dentin, bone, and neuronal cells. If followup studies extend
these initial findings, the scientists speculate they may have identified an
important and easily accessible source of stem cells that possibly could be
manipulated to repair damaged teeth, induce the regeneration of bone, and treat
neural injury or disease.
“Doctors have successfully harvested stem cells from umbilical cord blood for
years,” said Dr. Songtao Shi, a scientist at NIH’s National Institute of Dental
and Craniofacial Research (NIDCR) and the senior author on the paper. “Our
finding is similar in some ways, in that the stem cells in the tooth are likely
latent remnants of an early developmental process.”
Shi and colleagues named the cells SHED, which stands for Stem cells
from human exfoliated deciduous teeth. The term “deciduous
teeth” is the formal name for what most people call colloquially “baby teeth.”
Children normally develop a set of 20 deciduous teeth, which appear after six
months of life and generally are replaced, one tooth at a time, between age 6
and 12.
Shi said the unique acronym was needed to differentiate SHED from stem cells
in adult tissues, such as bone or brain. “Stem cell research has exploded
during the past seven or eight years, yet people still talk in general terms of
postnatal and adult stem cells as though they are one and the same. Postnatal
cells from children may act totally differently than adult stem cells, and we
felt the inherent difference needed to be emphasized,” said Shi.
Today’s finding, as so often happens in science, stems from a chance
interaction. As Shi recounts, it happened one evening when his
then-six-year-old daughter, Julia, asked for help in pulling out a loose baby
tooth. “Once it was out, we sat and looked carefully at the tooth,” recalled
Shi, a pediatric dentist. “I said, ‘Wait a minute, there is some red colored
tissue inside of the tooth,’ so I took the tooth to my laboratory the next day
and examined it. Sure enough, it had beautiful pulp tissue left over.”
A few days later, when another of Julia’s teeth came out, Shi said he was
better prepared. He placed the tooth into a liquid medium used to culture
cells, drove it to the laboratory, and extracted the dental pulp. Soon
thereafter, he succeeded in isolating living stem cells from the tissue, a
discovery that would lead to the collection of more exfoliated teeth from Julia
and other children
The group launched an initial round of studies to determine whether the cells
would grow well in culture. Using dental pulp extracted from the children’s
exfoliated incisors, they discovered that about 12 to 20 stem cells from each
tooth reproducibly had the ability to colonize and grow in culture.
“We also found the SHED behaved much differently than dental pulp stem cells
from permanent teeth, which our group studied previously,” said Dr. Masako
Miura, an NIDCR scientist and a lead author on the study. “They exhibited an
ability to grow much faster and doubled their populations in culture at a
greater rate, suggesting SHED may be in a more immature state than adult stem
cells.”
Interestingly, Muria said she and her colleagues soon found these cells could
be prompted to express proteins on their surface indicative of stem cells that
were in the process of switching into bone and dental pulp cells. This
discovery led to additional followup experiments, led by Dr. Bai Lu of NIH’s
National Institute of Child Health and Human Development (NICHD), to determine
whether SHED also possessed the potential to switch into neural and fat cells.
The groups found, under specific cell culture conditions, the cells responded
accordingly, expressing a variety of proteins indicative of neural and fat
cells.
“These data are just the start,” said Shi. “We're trying to characterize
more fully which cell types can be generated from these stem cells. Can they be
switched into nerve cells only? We need to find this out. We're also
interested in determining the difference between adult dental pulp stem cells
and those in deciduous teeth.”
The NIDCR and NICHD are research components of the federal National
Institutes of Health (NIH), part of the U.S. Department of Health and Human
Services.
1The article is titled, “SHED:
Stem cells from human exfoliated deciduous teeth.” The authors are: Masako
Muira, Stan Gronthos, Mingrui Zhao, Bai Lu, Larry W. Fisher, Pamela Gehron
Robey, and Songtao Shi.