American Alligators to serve as tooth replacement models for humans

[drsnehamaheshwari]

American alligators might serve as suitable models to study tooth replacement in human adults, according to a new study in Proceedings of the National Academy of Sciences (May 13, 2013).

To uncover molecular mechanisms of tooth renewal, Cheng-Ming Chuong, MD, PhD, from the University of Southern California and an international team of colleagues studied repetitive tooth formation in American alligators. Because alligators have well-organized teeth with morphological traits similar to those of mammalian teeth — such as secondary palates and implantation in sockets of the dental bones — and are capable of lifelong tooth renewal, the authors reasoned that the long-lived reptiles, which can replace each of their 80 teeth up to 50 times, might serve as models for mammalian tooth replacement.

Through a combination of histological, molecular, and imaging techniques, the researchers found that each alligator tooth is a complex unit of three components in different developmental stages that are structured to facilitate replacement once they are dislodged.

They found that at an early tooth development stage, the alligator dental lamina forms a bulge at its distal tip that houses putative, quiescent stem cells. Molecular analysis revealed that the initiation of the tooth cycle corresponds with the dynamic expression of an array of signaling molecules implicated in tooth development.

According to the authors, the findings might aid efforts to trigger tooth renewal in human adults who have lost teeth or to curb uncontrolled tooth development in people with supernumerary teeth.

        

[drsnehamaheshwari]

Fossil teeth can be used to calculate when a Neanderthal baby was weaned using a new technique developed to study teeth from human infants and monkeys (Nature, May 22, 2013).

Using the technique, the international research team concluded that at least one Neanderthal baby was weaned at much the same age as most modern humans.

The discovery is based in part on knowledge gained from infant and monkey teeth studies at the California National Primate Research Center at the University of California, Davis (UCD).

Just as tree rings record the environment in which a tree grew, traces of barium in the layers of a primate tooth can tell the story of when an infant was exclusively milk-fed, when supplemental food began, and at what age the infant was weaned, according to Katie Hinde, PhD, a professor of human evolutionary biology at Harvard University and an affiliate scientist at the UCD primate center.

Hinde directs the Comparative Lactation Laboratory at Harvard and has conducted a three-year study of lactation, weaning, and behavior among rhesus macaques at UCD. From mineral traces in teeth, the team was able to determine the exact timing of birth, when the infant was fed exclusively on the mother’s milk, and the weaning process. By studying monkey teeth and comparing them with center records, they showed that the technique was accurate almost to the day.

After validating the technique with monkeys, the scientists applied it to human teeth and a Neanderthal tooth. They found that the Neanderthal baby was fed exclusively on the mother’s milk for seven months, followed by seven months of supplementation — a similar pattern to present-day humans. The technique opens up opportunities to further investigate lactation history in fossils and museum collections of primate teeth.

Although there is some variation among human cultures, the accelerated transition to foods other than breast milk is thought to have emerged in our ancestral history due, in part, to more cooperative infant care and access to a more nutritious diet, Hinde said. Shorter lactation periods could mean shorter gaps between pregnancies and a higher rate of reproduction. However, there has been much debate about when our ancestors began accelerated weaning.

 

        

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